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Neder JA, Santyr G, Zanette B, Kirby M, Pourafkari M, James MD, Vincent SG, Ferguson C, Wang CY, Domnik NJ, Phillips DB, Porszasz J, Stringer WW, O'Donnell DE. Beyond Spirometry: Linking Wasted Ventilation to Exertional Dyspnea in the Initial Stages of COPD. COPD 2024; 21:2301549. [PMID: 38348843 DOI: 10.1080/15412555.2023.2301549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2023] [Accepted: 12/29/2023] [Indexed: 02/15/2024]
Abstract
Exertional dyspnea, a key complaint of patients with chronic obstructive pulmonary disease (COPD), ultimately reflects an increased inspiratory neural drive to breathe. In non-hypoxemic patients with largely preserved lung mechanics - as those in the initial stages of the disease - the heightened inspiratory neural drive is strongly associated with an exaggerated ventilatory response to metabolic demand. Several lines of evidence indicate that the so-called excess ventilation (high ventilation-CO2 output relationship) primarily reflects poor gas exchange efficiency, namely increased physiological dead space. Pulmonary function tests estimating the extension of the wasted ventilation and selected cardiopulmonary exercise testing variables can, therefore, shed unique light on the genesis of patients' out-of-proportion dyspnea. After a succinct overview of the basis of gas exchange efficiency in health and inefficiency in COPD, we discuss how wasted ventilation translates into exertional dyspnea in individual patients. We then outline what is currently known about the structural basis of wasted ventilation in "minor/trivial" COPD vis-à-vis the contribution of emphysema versus a potential impairment in lung perfusion across non-emphysematous lung. After summarizing some unanswered questions on the field, we propose that functional imaging be amalgamated with pulmonary function tests beyond spirometry to improve our understanding of this deeply neglected cause of exertional dyspnea. Advances in the field will depend on our ability to develop robust platforms for deeply phenotyping (structurally and functionally), the dyspneic patients showing unordinary high wasted ventilation despite relatively preserved FEV1.
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Affiliation(s)
- J Alberto Neder
- Respiratory Investigation Unit, Division of Respirology, Department of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, Canada
| | - Giles Santyr
- Translational Medicine Department, Faculty of Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, Canada
| | - Brandon Zanette
- Translational Medicine Department, Faculty of Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, Canada
| | - Miranda Kirby
- Department of Physics, Faculty of Science, Toronto Metropolitan University, Toronto, Canada
| | - Marina Pourafkari
- Department of Radiology and Diagnostic Imaging, Kingston Health Sciences Centre, Kingston, Canada
| | - Matthew D James
- Respiratory Investigation Unit, Division of Respirology, Department of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, Canada
| | - Sandra G Vincent
- Respiratory Investigation Unit, Division of Respirology, Department of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, Canada
| | - Carrie Ferguson
- The Lundquist Institute for Biomedical Innovation, Harbor U.C.L.A Medical Centre, Torrance, CA, USA
| | - Chu-Yi Wang
- The Lundquist Institute for Biomedical Innovation, Harbor U.C.L.A Medical Centre, Torrance, CA, USA
| | - Nicolle J Domnik
- Respiratory Investigation Unit, Division of Respirology, Department of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, Canada
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada
| | - Devin B Phillips
- School of Kinesiology and Health Science, York University, Toronto, Canada
| | - Janos Porszasz
- The Lundquist Institute for Biomedical Innovation, Harbor U.C.L.A Medical Centre, Torrance, CA, USA
| | - William W Stringer
- The Lundquist Institute for Biomedical Innovation, Harbor U.C.L.A Medical Centre, Torrance, CA, USA
| | - Denis E O'Donnell
- Respiratory Investigation Unit, Division of Respirology, Department of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, Canada
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Dominelli PB, Sheel AW. The pulmonary physiology of exercise. ADVANCES IN PHYSIOLOGY EDUCATION 2024; 48:238-251. [PMID: 38205515 DOI: 10.1152/advan.00067.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 12/14/2023] [Accepted: 01/07/2024] [Indexed: 01/12/2024]
Abstract
The pulmonary system is the first and last "line of defense" in terms of maintaining blood gas homeostasis during exercise. Our review provides the reader with an overview of how the pulmonary system responds to acute exercise. We undertook this endeavor to provide a companion article to "Cardiovascular Response to Exercise," which was published in Advances in Physiological Education. Together, these articles provide the readers with a solid foundation of the cardiopulmonary response to acute exercise in healthy individuals. The intended audience of this review is level undergraduate or graduate students and/or instructors for such classes. By intention, we intend this to be used as an educational resource and seek to provide illustrative examples to reinforce topics as well as highlight uncertainty to encourage the reader to think "beyond the textbook." Our treatment of the topic presents "classic" concepts along with new information on the pulmonary physiology of healthy aging.NEW & NOTEWORTHY Our narrative review is written with the student of the pulmonary physiology of exercise in mind, be it a senior undergraduate or graduate student or those simply refreshing their knowledge. We also aim to provide examples where the reader can incorporate real scenarios.
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Affiliation(s)
- Paolo B Dominelli
- Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, Ontario, Canada
| | - A William Sheel
- School of Kinesiology, The University of British Columbia, Vancouver, British Columbia, Canada
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Perdijk O, Azzoni R, Marsland BJ. The microbiome: an integral player in immune homeostasis and inflammation in the respiratory tract. Physiol Rev 2024; 104:835-879. [PMID: 38059886 DOI: 10.1152/physrev.00020.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 11/07/2023] [Accepted: 11/30/2023] [Indexed: 12/08/2023] Open
Abstract
The last decade of microbiome research has highlighted its fundamental role in systemic immune and metabolic homeostasis. The microbiome plays a prominent role during gestation and into early life, when maternal lifestyle factors shape immune development of the newborn. Breast milk further shapes gut colonization, supporting the development of tolerance to commensal bacteria and harmless antigens while preventing outgrowth of pathogens. Environmental microbial and lifestyle factors that disrupt this process can dysregulate immune homeostasis, predisposing infants to atopic disease and childhood asthma. In health, the low-biomass lung microbiome, together with inhaled environmental microbial constituents, establishes the immunological set point that is necessary to maintain pulmonary immune defense. However, in disease perturbations to immunological and physiological processes allow the upper respiratory tract to act as a reservoir of pathogenic bacteria, which can colonize the diseased lung and cause severe inflammation. Studying these host-microbe interactions in respiratory diseases holds great promise to stratify patients for suitable treatment regimens and biomarker discovery to predict disease progression. Preclinical studies show that commensal gut microbes are in a constant flux of cell division and death, releasing microbial constituents, metabolic by-products, and vesicles that shape the immune system and can protect against respiratory diseases. The next major advances may come from testing and utilizing these microbial factors for clinical benefit and exploiting the predictive power of the microbiome by employing multiomics analysis approaches.
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Affiliation(s)
- Olaf Perdijk
- Department of Immunology, School of Translational Science, Monash University, Melbourne, Victoria, Australia
| | - Rossana Azzoni
- Department of Immunology, School of Translational Science, Monash University, Melbourne, Victoria, Australia
| | - Benjamin J Marsland
- Department of Immunology, School of Translational Science, Monash University, Melbourne, Victoria, Australia
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Petersson J, Glenny RW. Gas Exchange in the Lung. Semin Respir Crit Care Med 2023; 44:555-568. [PMID: 37816345 DOI: 10.1055/s-0043-1770060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/12/2023]
Abstract
Gas exchange in the lung depends on tidal breathing, which brings new oxygen to and removes carbon dioxide from alveolar gas. This maintains alveolar partial pressures that promote passive diffusion to add oxygen and remove carbon dioxide from blood in alveolar capillaries. In a lung model without ventilation and perfusion (V̇AQ̇) mismatch, alveolar partial pressures of oxygen and carbon dioxide are primarily determined by inspiratory pressures and alveolar ventilation. Regions with shunt or low ratios worsen arterial oxygenation while alveolar dead space and high lung units lessen CO2 elimination efficiency. Although less common, diffusion limitation might cause hypoxemia in some situations. This review covers the principles of lung gas exchange and therefore mechanisms of hypoxemia or hypercapnia. In addition, we discuss different metrics that quantify the deviation from ideal gas exchange.
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Affiliation(s)
- Johan Petersson
- Section of Anesthesiology and Intensive Care Medicine, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
- Department of Anaesthesiology, Surgical Services and Intensive Care, Karolinska University Hospital, Stockholm, Sweden
| | - Robb W Glenny
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Washington, Seattle, Washington
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington
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Brochu P, Ménard J, Haddad S. Cardiopulmonary parameters and organ blood flows for workers expressed in terms of VO2 for use in physiologically based toxicokinetic modeling. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2022; 85:307-335. [PMID: 34991435 DOI: 10.1080/15287394.2021.2006845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Minute ventilation rates (VE), alveolar ventilation rates (VA), cardiac outputs (Q), liver blood flow (LBF) and kidneys blood flows (KBF) for physiologically based toxicokinetic modeling and occupational health risk assessment in active workers have apparently not been determined. Minute energy expenditure rates (E) and oxygen consumption rates (VO2) in workers during exertions and their aggregate daytime activities are obtained by using open-circuit wearable devices for indirect calorimetry measurements and the doubly labeled water method respectively. Hundreds of E (in kcal/min) and VO2 (in L of O2/min) were previously reported for workers. The oxygen uptake factors of 0.2059 ± 0.0019 and 0.2057 ± 0.0018 L of O2/kcal during postprandial and fasting phases respectively enabled conversion of E into VO2. Equations determined in this study based upon more than 25 000 published measurements enable the calculation of 15 parameters in the same worker only by using the VO2 reflecting workload. These parameters, notably VE, VA, VE/VO2 VA/Q, Q, LBF and KBF were found to be interrelated. Altering one of these changes the order of magnitude of the others. Q, LBF and KBF decrease when supine adults at rest switch to an upright position. This effect of gravity diminished when VO2 increased. The fall in LBF and KBF during exertion might enhance muscle blood flow as reported previously. Taken together these equations and data may improve the accuracy of physiologically based toxicokinetic modeling as well as occupational health assessment studies in active workers exposed to xenobiotics.List of main abbreviations: AVOD: arterioveinous oxygen content difference.BMI: body mass index (in kg/m2).BSA: body surface area (in m2).BTPS: body temperature and saturated with water vapor.Bw: body weight (in kg).E: minute energy expenditure rate (in kcal/min).FGE: organ blood flow factor for the gravitational effect on blood circulation.H: oxygen uptake factor, volume of oxygen (at STPD) consumed to produce 1 kcal of energy expended.KBF: kidneys blood flow (in ml/min).LBF: liver blood flow (in ml/min).PBF: liver or kidneys blood flows expressed in terms of percentages (in %) of Qsup C values: namely PBF = (LBF or KBF/Qsup C) x 100.Q: cardiac output (in L/min or ml/min).Qsup C: cardiac output for the cohort of males or females in supination (in ml/min).STPD: standard temperature and pressure, dry air.sup: values measured when adults are in the supine position.up: values measured when adults are in the upright position.VDphys: physiological dead space at BTPS (in L).VT: tidal volume at BTPS (in L).VA: alveolar ventilation rate at BTPS (in L/min).VA/Q: ventilation-perfusion ratio (unitless).VE: minute ventilation rate at BTPS (in L/min).VO2: oxygen consumption rate (i.e. the oxygen uptake) at STPD (in L/min).VQ: ventilatory equivalent for VO2 (VE at BTPS /VO2 at STPD).
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Affiliation(s)
- Pierre Brochu
- Department of Environmental and Occupational Health, ESPUM, Université de Montréal, Montreal, QC, Canada
| | - Jessie Ménard
- Department of Environmental and Occupational Health, ESPUM, Université de Montréal, Montreal, QC, Canada
- Centre for Public Health Research (CReSP), Université de Montréal, Montréal, QC, Canada
| | - Sami Haddad
- Department of Environmental and Occupational Health, ESPUM, Université de Montréal, Montreal, QC, Canada
- Centre for Public Health Research (CReSP), Université de Montréal, Montréal, QC, Canada
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Licker M, Hagerman A, Jeleff A, Schorer R, Ellenberger C. The hypoxic pulmonary vasoconstriction: From physiology to clinical application in thoracic surgery. Saudi J Anaesth 2021; 15:250-263. [PMID: 34764832 PMCID: PMC8579502 DOI: 10.4103/sja.sja_1216_20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Accepted: 12/28/2020] [Indexed: 11/04/2022] Open
Abstract
More than 70 years after its original report, the hypoxic pulmonary vasoconstriction (HPV) response continues to spark scientific interest on its mechanisms and clinical implications, particularly for anesthesiologists involved in thoracic surgery. Selective airway intubation and one-lung ventilation (OLV) facilitates the surgical intervention on a collapsed lung while the HPV redirects blood flow from the "upper" non-ventilated hypoxic lung to the "dependent" ventilated lung. Therefore, by limiting intrapulmonary shunting and optimizing ventilation-to-perfusion (V/Q) ratio, the fall in arterial oxygen pressure (PaO2) is attenuated during OLV. The HPV involves a biphasic response mobilizing calcium within pulmonary vascular smooth muscles, which is activated within seconds after exposure to low alveolar oxygen pressure and that gradually disappears upon re-oxygenation. Many factors including acid-base balance, the degree of lung expansion, circulatory volemia as well as lung diseases and patient age affect HPV. Anesthetic agents, analgesics and cardiovascular medications may also interfer with HPV during the perioperative period. Since HPV represents the homeostatic mechanism for regional ventilation-to-perfusion matching and in turn, for optimal pulmonary oxygen uptake, a clear understanding of HPV is clinically relevant for all anesthesiologists.
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Affiliation(s)
- Marc Licker
- Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University Hospital of Geneva, CH-1205 GENEVA, Switzerland.,Faculty of Medicine, University of Geneva, Switzerland
| | - Andres Hagerman
- Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University Hospital of Geneva, CH-1205 GENEVA, Switzerland
| | - Alexandre Jeleff
- Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University Hospital of Geneva, CH-1205 GENEVA, Switzerland
| | - Raoul Schorer
- Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University Hospital of Geneva, CH-1205 GENEVA, Switzerland
| | - Christoph Ellenberger
- Department of Anesthesiology, Pharmacology, Intensive Care and Emergency Medicine, University Hospital of Geneva, CH-1205 GENEVA, Switzerland.,Faculty of Medicine, University of Geneva, Switzerland
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Brochu P, Ménard J, Marchand A, Haddad S. Cardiopulmonary values and organ blood flows before and during heat stress: data in nine subjects at rest in the upright position. Can J Physiol Pharmacol 2021; 99:1148-1158. [PMID: 34062083 DOI: 10.1139/cjpp-2021-0044] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Physiological changes associated with thermoregulation can influence the kinetics of chemicals in the human body, such as alveolar ventilation (VA) and redistribution of blood flow to organs. In this study, the influence of heat stress on various physiological parameters was evaluated in nine male volunteers during sessions of exposure to wet blub globe temperatures (WBGT) of 21, 25 and 30°C for four hours. Skin and core temperatures and more than twenty cardiopulmonary parameters were measured. Liver, kidneys, brain, skin and muscles blood flows were also determined based on published measurements. Results show that most subjects (8 out of 9) have been affected by the inhalation of hot and dry air at the WBGT of 30°C. High respiratory rates, superficial tidal volumes and low VA values were notably observed. The skin blood flow has increased by 2.16-fold, whereas the renal blood flow and liver blood flow have decreased by about by 11 and 18% respectively. A complete set of key cardiopulmonary parameters in healthy male adults before and during heat stress was generated for use in PBPK modeling. A toxicokinetic studies are ongoing to evaluate the impact of heat stress on the absorption, biotransformation and excretion rates of volatile xenobiotics.
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Affiliation(s)
- Pierre Brochu
- Université de Montréal, 5622, Environmental and Occupational Health, School of Public Health, Montreal, Quebec, Canada;
| | - Jessie Ménard
- Université de Montréal, 5622, Environmental and Occupational Health, School of Public Health, Montreal, Quebec, Canada.,Centre for Public Health Research (CReSP), Montréal, Quebec, Canada;
| | - Axelle Marchand
- Université de Montréal, 5622, Environmental and Occupational Health, School of Public Health, Montreal, Quebec, Canada.,Centre for Public Health Research (CReSP), Montréal, Quebec, Canada;
| | - Sami Haddad
- Université de Montréal, 5622, Environmental and Occupational Health, School of Public Health, Montreal, Quebec, Canada.,Centre for Public Health Research (CReSP), Montréal, Quebec, Canada;
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Patrician A, Dujić Ž, Spajić B, Drviš I, Ainslie PN. Breath-Hold Diving - The Physiology of Diving Deep and Returning. Front Physiol 2021; 12:639377. [PMID: 34093221 PMCID: PMC8176094 DOI: 10.3389/fphys.2021.639377] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 04/07/2021] [Indexed: 11/13/2022] Open
Abstract
Breath-hold diving involves highly integrative physiology and extreme responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure. With astonishing depth records exceeding 100 m, and up to 214 m on a single breath, the human capacity for deep breath-hold diving continues to refute expectations. The physiological challenges and responses occurring during a deep dive highlight the coordinated interplay of oxygen conservation, exercise economy, and hyperbaric management. In this review, the physiology of deep diving is portrayed as it occurs across the phases of a dive: the first 20 m; passive descent; maximal depth; ascent; last 10 m, and surfacing. The acute risks of diving (i.e., pulmonary barotrauma, nitrogen narcosis, and decompression sickness) and the potential long-term medical consequences to breath-hold diving are summarized, and an emphasis on future areas of research of this unique field of physiological adaptation are provided.
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Affiliation(s)
- Alexander Patrician
- Center for Heart, Lung & Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Željko Dujić
- Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia
| | - Boris Spajić
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Ivan Drviš
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Philip N Ainslie
- Center for Heart, Lung & Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
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Patrician A, Spajić B, Gasho C, Caldwell HG, Dawkins T, Stembridge M, Lovering AT, Coombs GB, Howe CA, Barak O, Drviš I, Dujić Ž, Ainslie PN. Temporal changes in pulmonary gas exchange efficiency when breath-hold diving below residual volume. Exp Physiol 2021; 106:1120-1133. [PMID: 33559974 DOI: 10.1113/ep089176] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 02/04/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? How does deep breath-hold diving impact cardiopulmonary function, both acutely and over the subsequent 2.5 hours post-dive? What is the main finding and its importance? Breath-hold diving, to depths below residual volume, is associated with acute impairments in pulmonary gas exchange, which typically resolve within 2.5 hours. These data provide new insight into the behaviour of the lungs and pulmonary vasculature following deep diving. ABSTRACT Breath-hold diving involves highly integrative and extreme physiological responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure. Over two diving training camps (Study 1 and 2), 25 breath-hold divers (recreational to world-champion) performed 66 dives to 57 ± 20 m (range: 18-117 m). Using the deepest dive from each diver, temporal changes in cardiopulmonary function were assessed using non-invasive pulmonary gas exchange (indexed via the O2 deficit), ultrasound B-line scores, lung compliance and pulmonary haemodynamics at baseline and following the dive. Hydrostatically induced lung compression was quantified in Study 2, using spirometry and lung volume measurement, enabling each dive to be categorized by its residual volume (RV)-equivalent depth. From both studies, pulmonary gas exchange inefficiency - defined as an increase in O2 deficit - was related to the depth of the dive (r2 = 0.345; P < 0.001), with dives associated with lung squeeze symptoms exhibiting the greatest deficits. In Study 1, although B-lines doubled from baseline (P = 0.027), cardiac output and pulmonary artery systolic pressure were unchanged post-dive. In Study 2, dives with lung compression to ≤RV had higher O2 deficits at 9 min, compared to dives that did not exceed RV (24 ± 25 vs. 5 ± 8 mmHg; P = 0.021). The physiological significance of a small increase in estimated lung compliance post-dive (via decreased and increased/unaltered airway resistance and reactance, respectively) remains equivocal. Following deep dives, the current study highlights an integrated link between hydrostatically induced lung compression and transient impairments in pulmonary gas exchange efficiency.
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Affiliation(s)
- Alexander Patrician
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Boris Spajić
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Christopher Gasho
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Hannah G Caldwell
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Tony Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Michael Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, OR, USA
| | - Geoff B Coombs
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Connor A Howe
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Otto Barak
- Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia
| | - Ivan Drviš
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Željko Dujić
- University of Split School of Medicine, Split, Croatia
| | - Philip N Ainslie
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
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Clark AR, Burrowes KS, Tawhai MH. Integrative Computational Models of Lung Structure-Function Interactions. Compr Physiol 2021; 11:1501-1530. [PMID: 33577123 DOI: 10.1002/cphy.c200011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Anatomically based integrative models of the lung and their interaction with other key components of the respiratory system provide unique capabilities for investigating both normal and abnormal lung function. There is substantial regional variability in both structure and function within the normal lung, yet it remains capable of relatively efficient gas exchange by providing close matching of air delivery (ventilation) and blood delivery (perfusion) to regions of gas exchange tissue from the scale of the whole organ to the smallest continuous gas exchange units. This is despite remarkably different mechanisms of air and blood delivery, different fluid properties, and unique scale-dependent anatomical structures through which the blood and air are transported. This inherent heterogeneity can be exacerbated in the presence of disease or when the body is under stress. Current computational power and data availability allow for the construction of sophisticated data-driven integrative models that can mimic respiratory system structure, function, and response to intervention. Computational models do not have the same technical and ethical issues that can limit experimental studies and biomedical imaging, and if they are solidly grounded in physiology and physics they facilitate investigation of the underlying interaction between mechanisms that determine respiratory function and dysfunction, and to estimate otherwise difficult-to-access measures. © 2021 American Physiological Society. Compr Physiol 11:1501-1530, 2021.
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Affiliation(s)
- Alys R Clark
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Kelly S Burrowes
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Merryn H Tawhai
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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Yamamoto S, Hasebe T, Tomita K, Kamei S, Matsumoto T, Imai Y, Takahashi G, Kondo Y, Ito Y, Sakamaki F. Pulmonary perfusion by chest digital dynamic radiography: Comparison between breath-holding and deep-breathing acquisition. J Appl Clin Med Phys 2020; 21:247-255. [PMID: 33104288 PMCID: PMC7700935 DOI: 10.1002/acm2.13071] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/17/2020] [Accepted: 09/29/2020] [Indexed: 12/19/2022] Open
Abstract
Purpose Pulmonary perfusion is an important factor for gas exchange. Chest digital dynamic radiography (DDR) by the deep‐breathing protocol can evaluate pulmonary perfusion in healthy subjects. However, respiratory artifacts may affect DDR in patients with respiratory diseases. We examined the feasibility of a breath‐holding protocol and compared it with the deep‐breathing protocol to reduce respiratory artifacts. Materials and methods A total of 42 consecutive patients with respiratory diseases (32 males; age, 68.6 ± 12.3 yr), including 21 patients with chronic obstructive pulmonary disease, underwent chest DDR through the breath‐holding protocol and the deep‐breathing protocol. Imaging success rate and exposure to radiation were compared. The correlation rate of temporal changes in each pixel value between the lung fields and left cardiac ventricles was analyzed. Results Imaging success rate was higher with the breath‐holding protocol vs the deep‐breathing protocol (97% vs 69%, respectively; P < 0.0001). The entrance surface dose was lower with the breath‐holding protocol (1.09 ± 0.20 vs 1.81 ± 0.08 mGy, respectively; P < 0.0001). The correlation rate was higher with the breath‐holding protocol (right lung field, 41.7 ± 9.3%; left lung field, 44.2 ± 8.9% vs right lung field, 33.4 ± 6.6%; left lung field, 36.0 ± 7.1%, respectively; both lung fields, P < 0.0001). In the lower lung fields, the correlation rate was markedly different (right, 15.3% difference; left, 14.1% difference; both lung fields, P < 0.0001). Conclusion The breath‐holding protocol resulted in high imaging success rate among patients with respiratory diseases, yielding vivid images of pulmonary perfusion.
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Affiliation(s)
- Shota Yamamoto
- Department of Radiology, Tokai University Hachioji Hospital, Tokai University School of Medicine, Hachioji, Tokyo, Japan
| | - Terumitsu Hasebe
- Department of Radiology, Tokai University Hachioji Hospital, Tokai University School of Medicine, Hachioji, Tokyo, Japan
| | - Kosuke Tomita
- Department of Radiology, Tokai University Hachioji Hospital, Tokai University School of Medicine, Hachioji, Tokyo, Japan
| | - Shunsuke Kamei
- Department of Radiology, Tokai University Hachioji Hospital, Tokai University School of Medicine, Hachioji, Tokyo, Japan
| | - Tomohiro Matsumoto
- Department of Radiology, Tokai University Hachioji Hospital, Tokai University School of Medicine, Hachioji, Tokyo, Japan
| | - Yutaka Imai
- Department of Radiology, Tokai University Hachioji Hospital, Tokai University School of Medicine, Hachioji, Tokyo, Japan
| | - Genki Takahashi
- Department of Respiratory Medicine, Tokai University Hachioji Hospital, Tokai University School of Medicine, Hachioji, Tokyo, Japan
| | - Yusuke Kondo
- Department of Respiratory Medicine, Tokai University Hachioji Hospital, Tokai University School of Medicine, Hachioji, Tokyo, Japan
| | - Yoko Ito
- Department of Respiratory Medicine, Tokai University Hachioji Hospital, Tokai University School of Medicine, Hachioji, Tokyo, Japan
| | - Fumio Sakamaki
- Department of Respiratory Medicine, Tokai University Hachioji Hospital, Tokai University School of Medicine, Hachioji, Tokyo, Japan
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12
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Zhang L, Valizadeh H, Alipourfard I, Bidares R, Aghebati-Maleki L, Ahmadi M. Epigenetic Modifications and Therapy in Chronic Obstructive Pulmonary Disease (COPD): An Update Review. COPD 2020; 17:333-342. [PMID: 32558592 DOI: 10.1080/15412555.2020.1780576] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Chronic obstructive pulmonary disease (COPD) that is one of the most prevalent chronic adult diseases and the third leading cause of fatality until 2020. Elastase/anti-elastase hypothesis, chronic inflammation, apoptosis, oxidant-antioxidant balance and infective repair cause pathogenesis of COPD are among the factors at play. Epigenetic changes are post-translational modifications in histone proteins and DNA such as methylation and acetylation as well as dysregulation of miRNAs expression. In this update review, we have examined recent studies on the upregulation or downregulation of methylation in different genes associated with COPD. Dysregulation of HDAC activity which is caused by some factors and miRNAs plays a key role in the suppression and reduction of COPD development. Also, some therapeutic approaches are proposed against COPD by targeting HDAC2 and miRNAs, which have therapeutic effects.
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Affiliation(s)
- Lingzhi Zhang
- Department of Emergency Medicine, Shengjing Hospital of China Medical University, Shenyang, China
| | - Hamed Valizadeh
- Department of Internal Medicine and Pulmonology, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, Iran.,Tuberculosis and Lung Disease Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Iraj Alipourfard
- Faculty of Life Sciences, Center of pharmaceutical sciences, University of Vienna, Vienna, Austria.,Faculty of Sciences, School of Pharmacy, University of Rome Tor Vergata, Roma, Italy
| | - Ramtin Bidares
- Department of Experimental Medicine, Sapienza University, Rome, Italy
| | | | - Majid Ahmadi
- Stem Cell Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.,Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran
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13
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Abstract
The pulmonary blood-gas barrier represents a remarkable feat of engineering. It achieves the exquisite thinness needed for gas exchange by diffusion, the strength to withstand the stresses and strains of repetitive and changing ventilation, and the ability to actively maintain itself under varied demands. Understanding the design principles of this barrier is essential to understanding a variety of lung diseases, and to successfully regenerating or artificially recapitulating the barrier ex vivo. Many classical studies helped to elucidate the unique structure and morphology of the mammalian blood-gas barrier, and ongoing investigations have helped to refine these descriptions and to understand the biological aspects of blood-gas barrier function and regulation. This article reviews the key features of the blood-gas barrier that enable achievement of the necessary design criteria and describes the mechanical environment to which the barrier is exposed. It then focuses on the biological and mechanical components of the barrier that preserve integrity during homeostasis, but which may be compromised in certain pathophysiological states, leading to disease. Finally, this article summarizes recent key advances in efforts to engineer the blood-gas barrier ex vivo, using the platforms of lung-on-a-chip and tissue-engineered whole lungs. © 2020 American Physiological Society. Compr Physiol 10:415-452, 2020.
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Affiliation(s)
- Katherine L. Leiby
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA
- Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Micha Sam Brickman Raredon
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA
- Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Laura E. Niklason
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA
- Yale School of Medicine, Yale University, New Haven, Connecticut, USA
- Department of Anesthesiology, Yale University, New Haven, Connecticut, USA
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14
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Armstrong DA, Chen Y, Dessaint JA, Aridgides DS, Channon JY, Mellinger DL, Christensen BC, Ashare A. DNA Methylation Changes in Regional Lung Macrophages Are Associated with Metabolic Differences. Immunohorizons 2019; 3:274-281. [PMID: 31356157 PMCID: PMC6686200 DOI: 10.4049/immunohorizons.1900042] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 06/05/2019] [Indexed: 12/21/2022] Open
Abstract
A number of pulmonary diseases occur with upper lobe predominance, including cystic fibrosis and smoking-related chronic obstructive pulmonary disease. In the healthy lung, several physiologic and metabolic factors exhibit disparity when comparing the upper lobe of the lung to lower lobe, including differences in oxygenation, ventilation, lymphatic flow, pH, and blood flow. In this study, we asked whether these regional differences in the lung are associated with DNA methylation changes in lung macrophages that could potentially lead to altered cell responsiveness upon subsequent environmental challenge. All analyses were performed using primary lung macrophages collected via bronchoalveolar lavage from healthy human subjects with normal pulmonary function. Epigenome-wide DNA methylation was examined via Infinium MethylationEPIC (850K) array and validated by targeted next-generation bisulfite sequencing. We observed 95 CpG loci with significant differential methylation in lung macrophages, comparing upper lobe to lower lobe (all false discovery rate < 0.05). Several of these genes, including CLIP4, HSH2D, NR4A1, SNX10, and TYK2, have been implicated as participants in inflammatory/immune-related biological processes. Functionally, we identified phenotypic differences in oxygen use, comparing upper versus lower lung macrophages. Our results support a hypothesis that epigenetic changes, specifically DNA methylation, at a multitude of gene loci in lung macrophages are associated with metabolic differences regionally in lung.
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Affiliation(s)
- David A Armstrong
- Department of Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756;
| | - Youdinghuan Chen
- Department of Epidemiology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756.,Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756
| | - John A Dessaint
- Department of Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756
| | - Daniel S Aridgides
- Department of Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756
| | - Jacqueline Y Channon
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756; and
| | - Diane L Mellinger
- Department of Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756
| | - Brock C Christensen
- Department of Epidemiology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756.,Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756.,Department of Community and Family Medicine, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756
| | - Alix Ashare
- Department of Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756; .,Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756; and
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15
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García-Párraga D, Lorenzo T, Wang T, Ortiz JL, Ortega J, Crespo-Picazo JL, Cortijo J, Fahlman A. Deciphering function of the pulmonary arterial sphincters in loggerhead sea turtles ( Caretta caretta). ACTA ACUST UNITED AC 2018; 221:jeb.179820. [PMID: 30348649 DOI: 10.1242/jeb.179820] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 10/14/2018] [Indexed: 10/28/2022]
Abstract
To provide new insight into the pathophysiological mechanisms underlying gas emboli (GE) in bycaught loggerhead sea turtles (Caretta caretta), we investigated the vasoactive characteristics of the pulmonary and systemic arteries, and the lung parenchyma (LP). Tissues were opportunistically excised from recently dead animals for in vitro studies of vasoactive responses to four different neurotransmitters: acetylcholine (ACh; parasympathetic), serotonin (5HT), adrenaline (Adr; sympathetic) and histamine. The significant amount of smooth muscle in the LP contracted in response to ACh, Adr and histamine. The intrapulmonary and systemic arteries contracted under both parasympathetic and sympathetic stimulation and when exposed to 5HT. However, proximal extrapulmonary arterial (PEPA) sections contracted in response to ACh and 5HT, whereas Adr caused relaxation. In sea turtles, the relaxation in the pulmonary artery was particularly pronounced at the level of the pulmonary artery sphincter (PASp), where the vessel wall was highly muscular. For comparison, we also studied tissue response in freshwater sliders turtles (Trachemys scripta elegans). Both PEPA and LP from freshwater sliders contracted in response to 5HT, ACh and also Adr. We propose that in sea turtles, the dive response (parasympathetic tone) constricts the PEPA, LP and PASp, causing a pulmonary shunt and limiting gas uptake at depth, which reduces the risk of GE during long and deep dives. Elevated sympathetic tone caused by forced submersion during entanglement with fishing gear increases the pulmonary blood flow causing an increase in N2 uptake, potentially leading to the formation of blood and tissue GE at the surface. These findings provide potential physiological and anatomical explanations on how these animals have evolved a cardiac shunt pattern that regulates gas exchange during deep and prolonged diving.
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Affiliation(s)
- Daniel García-Párraga
- Fundación Oceanografic de la Comunidad Valenciana, Gran Vía Marques del Turia 19, 46005 Valencia, Spain
| | - Teresa Lorenzo
- Fundación Oceanografic de la Comunidad Valenciana, Gran Vía Marques del Turia 19, 46005 Valencia, Spain
| | - Tobias Wang
- Zoophysiology, Department of Biosciences, Aarhus University, 8000 Aarhus C, Denmark
| | - Jose-Luis Ortiz
- Department of Pharmacology, Faculty of Medicine, University of Valencia, 46010 Valencia, Spain
| | - Joaquín Ortega
- Patología y Sanidad Animal, Departamento PASAPTA, Facultad de Veterinaria, Universidad CEU-Cardenal Herrera, CEU Universities, Moncada, 46018 Valencia, Spain
| | - Jose-Luis Crespo-Picazo
- Fundación Oceanografic de la Comunidad Valenciana, Gran Vía Marques del Turia 19, 46005 Valencia, Spain
| | - Julio Cortijo
- Department of Pharmacology, Faculty of Medicine, University of Valencia, 46010 Valencia, Spain
| | - Andreas Fahlman
- Fundación Oceanografic de la Comunidad Valenciana, Gran Vía Marques del Turia 19, 46005 Valencia, Spain.,Department of Life Science, Texas A&M University-Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412, USA
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16
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Fahlman A, McHugh K, Allen J, Barleycorn A, Allen A, Sweeney J, Stone R, Faulkner Trainor R, Bedford G, Moore MJ, Jensen FH, Wells R. Resting Metabolic Rate and Lung Function in Wild Offshore Common Bottlenose Dolphins, Tursiops truncatus, Near Bermuda. Front Physiol 2018; 9:886. [PMID: 30065656 PMCID: PMC6056772 DOI: 10.3389/fphys.2018.00886] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Accepted: 06/19/2018] [Indexed: 11/16/2022] Open
Abstract
Diving mammals have evolved a suite of physiological adaptations to manage respiratory gases during extended breath-hold dives. To test the hypothesis that offshore bottlenose dolphins have evolved physiological adaptations to improve their ability for extended deep dives and as protection for lung barotrauma, we investigated the lung function and respiratory physiology of four wild common bottlenose dolphins (Tursiops truncatus) near the island of Bermuda. We measured blood hematocrit (Hct, %), resting metabolic rate (RMR, l O2 ⋅ min-1), tidal volume (VT, l), respiratory frequency (fR, breaths ⋅ min-1), respiratory flow (l ⋅ min-1), and dynamic lung compliance (CL, l ⋅ cmH2O-1) in air and in water, and compared measurements with published results from coastal, shallow-diving dolphins. We found that offshore dolphins had greater Hct (56 ± 2%) compared to shallow-diving bottlenose dolphins (range: 30–49%), thus resulting in a greater O2 storage capacity and longer aerobic diving duration. Contrary to our hypothesis, the specific CL (sCL, 0.30 ± 0.12 cmH2O-1) was not different between populations. Neither the mass-specific RMR (3.0 ± 1.7 ml O2 ⋅ min-1 ⋅ kg-1) nor VT (23.0 ± 3.7 ml ⋅ kg-1) were different from coastal ecotype bottlenose dolphins, both in the wild and under managed care, suggesting that deep-diving dolphins do not have metabolic or respiratory adaptations that differ from the shallow-diving ecotypes. The lack of respiratory adaptations for deep diving further support the recently developed hypothesis that gas management in cetaceans is not entirely passive but governed by alteration in the ventilation-perfusion matching, which allows for selective gas exchange to protect against diving related problems such as decompression sickness.
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Affiliation(s)
- Andreas Fahlman
- Fundación Oceanografic de la Comunidad Valenciana, Gran Vía Marques del Turia, Valencia, Spain.,Department of Life Sciences, Texas A&M University-Corpus Christi, Corpus Christi, TX, United States.,Woods Hole Oceanographic Institution, Woods Hole, MA, United States
| | - Katherine McHugh
- Chicago Zoological Society's Sarasota Dolphin Research Program, Mote Marine Laboratory, Sarasota, FL, United States
| | - Jason Allen
- Chicago Zoological Society's Sarasota Dolphin Research Program, Mote Marine Laboratory, Sarasota, FL, United States
| | - Aaron Barleycorn
- Chicago Zoological Society's Sarasota Dolphin Research Program, Mote Marine Laboratory, Sarasota, FL, United States
| | - Austin Allen
- Duke University Marine Lab, Beaufort, NC, United States
| | | | - Rae Stone
- Dolphin Quest, Waikoloa, HI, United States
| | | | - Guy Bedford
- Wildlife Consulting Service, Currumbin, QLD, Australia
| | - Michael J Moore
- Woods Hole Oceanographic Institution, Woods Hole, MA, United States
| | - Frants H Jensen
- Woods Hole Oceanographic Institution, Woods Hole, MA, United States.,Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark
| | - Randall Wells
- Chicago Zoological Society's Sarasota Dolphin Research Program, Mote Marine Laboratory, Sarasota, FL, United States
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17
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Fahlman A, Jensen FH, Tyack PL, Wells RS. Modeling Tissue and Blood Gas Kinetics in Coastal and Offshore Common Bottlenose Dolphins, Tursiops truncatus. Front Physiol 2018; 9:838. [PMID: 30072907 PMCID: PMC6060447 DOI: 10.3389/fphys.2018.00838] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 06/14/2018] [Indexed: 01/07/2023] Open
Abstract
Bottlenose dolphins (Tursiops truncatus) are highly versatile breath-holding predators that have adapted to a wide range of foraging niches from rivers and coastal ecosystems to deep-water oceanic habitats. Considerable research has been done to understand how bottlenose dolphins manage O2 during diving, but little information exists on other gases or how pressure affects gas exchange. Here we used a dynamic multi-compartment gas exchange model to estimate blood and tissue O2, CO2, and N2 from high-resolution dive records of two different common bottlenose dolphin ecotypes inhabiting shallow (Sarasota Bay) and deep (Bermuda) habitats. The objective was to compare potential physiological strategies used by the two populations to manage shallow and deep diving life styles. We informed the model using species-specific parameters for blood hematocrit, resting metabolic rate, and lung compliance. The model suggested that the known O2 stores were sufficient for Sarasota Bay dolphins to remain within the calculated aerobic dive limit (cADL), but insufficient for Bermuda dolphins that regularly exceeded their cADL. By adjusting the model to reflect the body composition of deep diving Bermuda dolphins, with elevated muscle mass, muscle myoglobin concentration and blood volume, the cADL increased beyond the longest dive duration, thus reflecting the necessary physiological and morphological changes to maintain their deep-diving life-style. The results indicate that cardiac output had to remain elevated during surface intervals for both ecotypes, and suggests that cardiac output has to remain elevated during shallow dives in-between deep dives to allow sufficient restoration of O2 stores for Bermuda dolphins. Our integrated modeling approach contradicts predictions from simple models, emphasizing the complex nature of physiological interactions between circulation, lung compression, and gas exchange.
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Affiliation(s)
- Andreas Fahlman
- Global Diving Research, Ottawa, ON, Canada
- Fundación Oceanografic de la Comunidad Valenciana, Valencia, Spain
| | - Frants H. Jensen
- Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark
| | - Peter L. Tyack
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, United Kingdom
| | - Randall S. Wells
- Chicago Zoological Society's Sarasota Dolphin Research Program, Mote Marine Laboratory, Sarasota, FL, United States
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18
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Garcia Párraga D, Moore M, Fahlman A. Pulmonary ventilation-perfusion mismatch: a novel hypothesis for how diving vertebrates may avoid the bends. Proc Biol Sci 2018; 285:20180482. [PMID: 29695441 PMCID: PMC5936736 DOI: 10.1098/rspb.2018.0482] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 03/28/2018] [Indexed: 11/22/2022] Open
Abstract
Hydrostatic lung compression in diving marine mammals, with collapsing alveoli blocking gas exchange at depth, has been the main theoretical basis for limiting N2 uptake and avoiding gas emboli (GE) as they ascend. However, studies of beached and bycaught cetaceans and sea turtles imply that air-breathing marine vertebrates may, under unusual circumstances, develop GE that result in decompression sickness (DCS) symptoms. Theoretical modelling of tissue and blood gas dynamics of breath-hold divers suggests that changes in perfusion and blood flow distribution may also play a significant role. The results from the modelling work suggest that our current understanding of diving physiology in many species is poor, as the models predict blood and tissue N2 levels that would result in severe DCS symptoms (chokes, paralysis and death) in a large fraction of natural dive profiles. In this review, we combine published results from marine mammals and turtles to propose alternative mechanisms for how marine vertebrates control gas exchange in the lung, through management of the pulmonary distribution of alveolar ventilation ([Formula: see text]) and cardiac output/lung perfusion ([Formula: see text]), varying the level of [Formula: see text] in different regions of the lung. Man-made disturbances, causing stress, could alter the [Formula: see text] mismatch level in the lung, resulting in an abnormally elevated uptake of N2, increasing the risk for GE. Our hypothesis provides avenues for new areas of research, offers an explanation for how sonar exposure may alter physiology causing GE and provides a new mechanism for how air-breathing marine vertebrates usually avoid the diving-related problems observed in human divers.
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Affiliation(s)
| | - Michael Moore
- Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Andreas Fahlman
- Fundación Oceanogràfic, Ciudad de las Artes y las Ciencias, 46013 Valencia, Spain
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19
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Some Unanticipated Consequences of Early Cardiac Catheterization. Insights into Pulmonary Pathophysiology. Ann Am Thorac Soc 2018; 15:S9-S11. [PMID: 29461888 DOI: 10.1513/annalsats.201705-394kv] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
One of the most interesting unanticipated findings by André Cournand and Dickinson Richards in their groundbreaking studies of cardiac catheterization was the very low pressure in the normal pulmonary circulation. At the time, in the 1940s, the significance of this was not appreciated. For example, in their speeches at the Nobel Prize ceremony, neither of these laureates referred to the low pressure, although they did discuss other features of the pulmonary circulation. It was up to the cardiologist, William Dock, to point out that these low pressures implied a very uneven distribution of blood flow in the lung, and in particular that in the normal upright lung, the blood flow to the apex would be extremely small. Dock went on to argue that this low blood flow at the top of the lung was responsible for the characteristic apical distribution of adult pulmonary tuberculosis. Since that time, it has been recognized that the low pressures in the pulmonary circulation have many implications in pulmonary pathophysiology. For example, if the vascular pressure is further reduced, such as in hemorrhagic shock, gas exchange is seriously affected because of the development of a large alveolar dead space. Furthermore, if humans are subjected to increased acceleration, such as in a high-performance aircraft, the distribution of blood flow becomes extremely abnormal, with much of the lung being completely unperfused. There are also diseases where distribution in the lung is affected by the uneven distribution of blood flow. These include alpha-1 antitrypsin deficiency and metastatic calcification of the lung.
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20
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Kang W, Clark AR, Tawhai MH. Gravity outweighs the contribution of structure to passive ventilation-perfusion matching in the supine adult human lung. J Appl Physiol (1985) 2017; 124:23-33. [PMID: 29051337 DOI: 10.1152/japplphysiol.00791.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Gravity and matched airway/vascular tree geometries are both hypothesized to be key contributors to ventilation-perfusion (V̇/Q̇) matching in the lung, but their relative contributions are challenging to quantify experimentally. We used a structure-based model to conduct an analysis of the relative contributions of tissue deformation (the "Slinky" effect), other gravitational mechanisms (weight of blood and gravitational gradient in tissue elastic recoil), and matched airway and arterial tree geometry to V̇/Q̇ matching and therefore to total lung oxygen exchange. Our results showed that the heterogeneity in V̇ and Q̇ were lowest and the correlation between V̇ and Q̇ was highest when the only mechanism for V̇/Q̇ matching was either tissue deformation or matched geometry. Heterogeneity in V̇ and Q̇ was highest and their correlation was poorest when all mechanisms were active (that is, at baseline). Eliminating the contribution of matched geometry did not change the correlation between V̇ and Q̇ at baseline. Despite the much larger heterogeneities in V̇ and Q̇ at baseline, the contribution of in-common (to V̇ and Q̇) gravitational mechanisms provided sufficient compensatory V̇/Q̇ matching to minimize the impact on oxygen transfer. In summary, this model predicts that during supine normal breathing under gravitational loading, passive V̇/Q̇ matching is predominantly determined by shared gravitationally induced tissue deformation, compliance distribution, and the effect of the hydrostatic pressure gradient on vessel and capillary size and blood pressures. Contribution from the matching airway and arterial tree geometries in this model is minor under normal gravity in the supine adult human lung. NEW & NOTEWORTHY We use a computational model to systematically analyze contributors to ventilation-perfusion matching in the lung. The model predicts that the multiple effects of gravity are the predominant mechanism in providing passive ventilation-perfusion matching in the supine adult human lung under normal gravitational loads, while geometric matching of airway and arterial trees plays a minor role.
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Affiliation(s)
- W Kang
- Auckland Bioengineering Institute, University of Auckland , Auckland , New Zealand
| | - A R Clark
- Auckland Bioengineering Institute, University of Auckland , Auckland , New Zealand
| | - M H Tawhai
- Auckland Bioengineering Institute, University of Auckland , Auckland , New Zealand
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21
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West JB. The beginnings of cardiac catheterization and the resulting impact on pulmonary medicine. Am J Physiol Lung Cell Mol Physiol 2017; 313:L651-L658. [PMID: 28839102 DOI: 10.1152/ajplung.00133.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 04/11/2017] [Accepted: 04/22/2017] [Indexed: 11/22/2022] Open
Abstract
The early history of cardiac catheterization has many interesting features. First, although it would be natural to assume that the procedure was initiated by cardiologists, two of the three people who shared the Nobel Prize for the discovery were pulmonologists, while the third was a urologist. The primary objective of the pulmonologists André Cournand and Dickinson Richards was to obtain mixed venous blood from the right heart so that they could use the Fick principle to calculate total pulmonary blood flow. Cournand's initial catheterization studies were prompted by his reading of an account by Werner Forssmann, who catheterized himself 12 years before. His bold experiment was one of the most bizarre in medical history. In the earliest studies that followed, Cournand and colleagues first passed catheters into the right atrium, and then into the right ventricle, and finally, the pulmonary artery. At the time, the investigators did not appreciate the significance of the low vascular pressures, nor that what they had done would revolutionize interventional cardiology. Within a year, William Dock predicted that there would be a very low blood flow at the top of the upright lung, and he proposed that this was the cause of the apical localization of pulmonary tuberculosis. The fact that the pulmonary vascular pressures are very low has many implications in lung disease. Cardiac catheterization changed the face of investigative cardiology, and its instigators were awarded the Nobel Prize in 1956.
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Affiliation(s)
- John B West
- Department of Medicine, University of California San Diego, La Jolla, California
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22
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Powell FL. Giants in Chest Medicine: John B. West, MD, PhD, DSc. Chest 2017; 152:10-12. [PMID: 28693761 DOI: 10.1016/j.chest.2016.12.037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 12/14/2016] [Indexed: 11/28/2022] Open
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23
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Ax M, Sanchez-Crespo A, Lindahl SGE, Mure M, Petersson J. The influence of gravity on regional lung blood flow in humans: SPECT in the upright and head-down posture. J Appl Physiol (1985) 2017; 122:1445-1451. [PMID: 28336539 DOI: 10.1152/japplphysiol.00887.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 03/20/2017] [Accepted: 03/20/2017] [Indexed: 11/22/2022] Open
Abstract
Previous studies in humans have shown that gravity has little influence on the distribution of lung blood flow while changing posture from supine to prone. This study aimed to evaluate the maximal influence of posture by comparison of regional lung blood flow in the upright and head-down posture in 8 healthy volunteers, using a tilt table. Regional lung blood flow was marked by intravenous injection of macroaggregates of human albumin labeled with 99mTc or 113mIn, in the upright and head-down posture, respectively, during tidal breathing. Both radiotracers remain fixed in the lung after administration. The distribution of radioactivity was mapped using quantitative single photon emission computed tomography (SPECT) corrected for attenuation and scatter. All images were obtained supine during tidal breathing. A shift from upright to the head-down posture caused a clear redistribution of blood flow from basal to apical regions. We conclude that posture plays a role for the distribution of lung blood flow in upright humans, and that the influence of posture, and thereby gravity, is much greater in the upright and head-down posture than in horizontal postures. However, the results of the study demonstrate that lung structure is the main determinant of regional blood flow and gravity is a secondary contributor to the distribution of lung blood flow in the upright and head-down positions.NEW & NOTEWORTHY Using a dual-isotope quantitative SPECT method, we demonstrated that although a shift in posture redistributes blood flow in the direction of gravity, the results are also consistent with lung structure being a greater determinant of regional blood flow than gravity. To our knowledge, this is the first study to use modern imaging methods to quantify the shift in regional lung blood flow in humans at a change between the upright and head-down postures.
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Affiliation(s)
- M Ax
- Function Perioperative Medicine and Intensive Care, Karolinska University Hospital Solna, Stockholm, Sweden; .,Department of Physiology and Pharmacology, Section of Anesthesiology and Intensive Care Medicine, Karolinska Institutet, Stockholm, Sweden; and
| | - A Sanchez-Crespo
- Department of Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Stockholm, Sweden
| | - S G E Lindahl
- Function Perioperative Medicine and Intensive Care, Karolinska University Hospital Solna, Stockholm, Sweden.,Department of Physiology and Pharmacology, Section of Anesthesiology and Intensive Care Medicine, Karolinska Institutet, Stockholm, Sweden; and
| | - M Mure
- Function Perioperative Medicine and Intensive Care, Karolinska University Hospital Solna, Stockholm, Sweden.,Department of Physiology and Pharmacology, Section of Anesthesiology and Intensive Care Medicine, Karolinska Institutet, Stockholm, Sweden; and
| | - J Petersson
- Function Perioperative Medicine and Intensive Care, Karolinska University Hospital Solna, Stockholm, Sweden.,Department of Physiology and Pharmacology, Section of Anesthesiology and Intensive Care Medicine, Karolinska Institutet, Stockholm, Sweden; and
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24
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Pulmonary microRNA profiling: implications in upper lobe predominant lung disease. Clin Epigenetics 2017; 9:56. [PMID: 28572860 PMCID: PMC5450072 DOI: 10.1186/s13148-017-0355-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 05/16/2017] [Indexed: 12/31/2022] Open
Abstract
Background Numerous pulmonary diseases manifest with upper lobe predominance including cystic fibrosis, smoking-related chronic obstructive pulmonary disease, and tuberculosis. Zonal hypoxia, characteristic of these pulmonary maladies, and oxygen stress in general is known to exert profound effects on various important aspects of cell biology. Lung macrophages are major participants in the pulmonary innate immune response and regional differences in macrophage responsiveness to hypoxia may contribute in the development of lung disease. MicroRNAs are ubiquitous regulators of human biology and emerging evidence indicates altered microRNA expression modulates respiratory disease processes. The objective of this study is to gain insight into the epigenetic and cellular mechanisms influencing regional differences in lung disease by investigating effect of hypoxia on regional microRNA expression in the lung. All studies were performed using primary alveolar macrophages (n = 10) or bronchoalveolar lavage fluid (n = 16) isolated from human subjects. MicroRNA was assayed via the NanoString nCounter microRNA assay. Results Divergent molecular patterns of microRNA expression were observed in alternate lung lobes, specifically noted was disparate expression of miR-93 and miR-4454 in alveolar macrophages along with altered expression of miR-451a and miR-663a in bronchoalveolar lavage fluid. Gene ontology was used to identify potential downstream targets of divergent microRNAs. Targets include cytokines and matrix metalloproteinases, molecules that could have a significant impact on pulmonary inflammation and fibrosis. Conclusions Our findings show variant regional microRNA expression associated with hypoxia in alveolar macrophages and BAL fluid in the lung—upper vs lower lobe. Future studies should address whether these specific microRNAs may act intracellularly, in a paracrine/endocrine manner to direct the innate immune response or may ultimately be involved in pulmonary host-to-pathogen trans-kingdom cross-talk. Electronic supplementary material The online version of this article (doi:10.1186/s13148-017-0355-1) contains supplementary material, which is available to authorized users.
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Akizuki M, Serizawa N, Ueno A, Adachi T, Hagiwara N. Effect of Balloon Pulmonary Angioplasty on Respiratory Function in Patients With Chronic Thromboembolic Pulmonary Hypertension. Chest 2016; 151:643-649. [PMID: 27746200 DOI: 10.1016/j.chest.2016.10.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 09/10/2016] [Accepted: 10/05/2016] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Balloon pulmonary angioplasty (BPA) in chronic thromboembolic pulmonary hypertension (CTEPH) improves hemodynamics and exercise capacity. However, its effect on respiratory function is unclear. Our objective was to investigate the effect of BPA on respiratory function. METHODS We enrolled patients with inoperable CTEPH who underwent BPA primarily in lower lobe arteries (first series) and upper and middle lobe arteries (second series). We compared changes in hemodynamics and respiratory function between different BPA fields. RESULTS Sixty-two BPA sessions were performed in 13 consecutive patients. Mean pulmonary arterial pressure and pulmonary vascular resistance significantly improved from 44 ± 8 to 23 ± 5 mm Hg and 818 ± 383 to 311 ± 117 dyne/s/cm-5. The percent predicted diffusion capacity of lung for carbon monoxide (Dlco) decreased after BPA in the lower lung field (from 60% ± 8% to 54% ± 8%) with no recovery. Percent Dlco increased after BPA in the upper middle lung field (from 53% ± 6% to 58% ± 6%) and continued to improve during the follow-up (from 58% ± 6% to 64% ± 11%). The ventilation/Co2 production (V˙e/V˙co2) slope significantly improved after BPA in the lower lung field (from 51 ± 13 to 41 ± 8) and continued to improve during the follow-up (from 41 ± 8 to 35 ± 7); however, the V˙e/V˙co2 slope remained unchanged after BPA in the upper/middle lung field. Changes in % Dlco and the V˙e/V˙co2 slope differed significantly between lower and upper/middle lung fields. CONCLUSIONS The effect of BPA on respiratory function in patients with CTEPH differed depending on the lung field.
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Affiliation(s)
- Mina Akizuki
- Department of Rehabilitation, Tokyo Women's Medical University, Tokyo, Japan; Department of Internal Medicine and Rehabilitation, Science Disability Science, Tohoku University Graduate School of Medicine, Sendai, Japan.
| | - Naoki Serizawa
- Department of Cardiology, Tokyo Women's Medical University, Tokyo, Japan
| | - Atsuko Ueno
- Department of Cardiology, Tokyo Women's Medical University, Tokyo, Japan
| | - Taku Adachi
- Department of Rehabilitation, Tokyo Women's Medical University, Tokyo, Japan
| | - Nobuhisa Hagiwara
- Department of Cardiology, Tokyo Women's Medical University, Tokyo, Japan
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Johansen T, Venegas JG. 3D mapping of oxygen and CO2 transport rates in the lung: a new imaging tool for use in lung surgery, intensive care and basic research. Expert Rev Respir Med 2016; 10:935-7. [PMID: 27348193 DOI: 10.1080/17476348.2016.1206818] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Troels Johansen
- a Department of Respiratory Diseases , Aarhus University Hospital , Aarhus , Denmark
| | - Jose Gabriel Venegas
- b Department of Anesthesia , Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School , Boston , MA , USA
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A method for mapping regional oxygen and CO2 transfer in the lung. Respir Physiol Neurobiol 2015; 222:29-47. [PMID: 26563454 DOI: 10.1016/j.resp.2015.10.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 10/02/2015] [Accepted: 10/25/2015] [Indexed: 11/22/2022]
Abstract
This paper presents a novel approach to visualizing regional lung function, through quantitative three-dimensional maps of O2 and CO2 transfer rates. These maps describe the contribution of anatomical regions to overall gas exchange and demonstrate how transfer rates of the two gas species' differ regionally. An algorithm for generating such maps is presented, and for illustration, regional gas transfer maps were generated using values of ventilation and perfusion imaged by PET/CT for a healthy subject and an asthmatic patient after bronchoprovocation. In a sensitivity analysis, compartment values of gas transfer showed minor sensitivity to imaging noise in the ventilation and perfusion data, and moderate sensitivity to estimation errors in global lung input values, chiefly global alveolar ventilation, followed by cardiac output and arterial-venous O2 content difference. Gas transfer maps offer an intuitive display of physiologically relevant lung function at a regional level, the potential for an improved understanding of pulmonary gas exchange in health and disease, and potentially a presurgical evaluation tool.
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Gaohua L, Wedagedera J, Small BG, Almond L, Romero K, Hermann D, Hanna D, Jamei M, Gardner I. Development of a Multicompartment Permeability-Limited Lung PBPK Model and Its Application in Predicting Pulmonary Pharmacokinetics of Antituberculosis Drugs. CPT-PHARMACOMETRICS & SYSTEMS PHARMACOLOGY 2015; 4:605-13. [PMID: 26535161 PMCID: PMC4625865 DOI: 10.1002/psp4.12034] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 08/18/2015] [Indexed: 12/20/2022]
Abstract
Achieving sufficient concentrations of antituberculosis (TB) drugs in pulmonary tissue at the optimum time is still a challenge in developing therapeutic regimens for TB. A physiologically based pharmacokinetic model incorporating a multicompartment permeability-limited lung model was developed and used to simulate plasma and pulmonary concentrations of seven drugs. Passive permeability of drugs within the lung was predicted using an in vitro-in vivo extrapolation approach. Simulated epithelial lining fluid (ELF):plasma concentration ratios showed reasonable agreement with observed clinical data for rifampicin, isoniazid, ethambutol, and erythromycin. For clarithromycin, itraconazole and pyrazinamide the observed ELF:plasma ratios were significantly underpredicted. Sensitivity analyses showed that changing ELF pH or introducing efflux transporter activity between lung tissue and ELF can alter the ELF:plasma concentration ratios. The described model has shown utility in predicting the lung pharmacokinetics of anti-TB drugs and provides a framework for predicting pulmonary concentrations of novel anti-TB drugs.
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Affiliation(s)
- L Gaohua
- Simcyp Limited (a Certara company) Sheffield, United Kingdom
| | - J Wedagedera
- Simcyp Limited (a Certara company) Sheffield, United Kingdom
| | - B G Small
- Simcyp Limited (a Certara company) Sheffield, United Kingdom
| | - L Almond
- Simcyp Limited (a Certara company) Sheffield, United Kingdom
| | - K Romero
- Critical Path Institute Tucson, Arizona, USA
| | - D Hermann
- Certara USA, Inc. Princeton, New Jersey, USA
| | - D Hanna
- Critical Path Institute Tucson, Arizona, USA
| | - M Jamei
- Simcyp Limited (a Certara company) Sheffield, United Kingdom
| | - I Gardner
- Simcyp Limited (a Certara company) Sheffield, United Kingdom
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Ishii M, Hamedani H, Clapp JT, Kadlecek SJ, Xin Y, Gefter WB, Rossman MD, Rizi RR. Oxygen-weighted Hyperpolarized (3)He MR Imaging: A Short-term Reproducibility Study in Human Subjects. Radiology 2015; 277:247-58. [PMID: 26110668 DOI: 10.1148/radiol.2015142038] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To determine whether hyperpolarized helium 3 magnetic resonance (MR) imaging to measure alveolar partial pressure of oxygen (Pao2) shows sufficient test-retest repeatability and between-cohort differences to be used as a reliable technique for detection of alterations in gas exchange in asymptomatic smokers. MATERIALS AND METHODS The protocol was approved by the local institutional review board and was HIPAA compliant. Informed consent was obtained from all subjects. Two sets of MR images were obtained 10 minutes apart in 25 subjects: 10 nonsmokers (five men, five women; mean ± standard deviation age, 50 years ± 6) and 15 smokers (seven women, eight men; mean age, 50 years ± 8). A mixed-effects model was developed to identify the regional repeatability of Pao2 measurements as an intraclass correlation coefficient. Ten smokers were matched with the 10 nonsmokers on the basis of signal-to-noise ratio (SNR). Three separate models were generated: one for nonsmokers, one for the SNR-matched smokers, and one for the five remaining smokers, who were imaged with a significantly higher SNR. RESULTS Short-term back-to-back regional reproducibility was assessed by using intraclass correlation coefficients, which were 0.67 and 0.65 for SNR case-matched nonsmokers and smokers, respectively. Repeatability was a strong function of SNR; a 50% increase in SNR in the remaining smokers improved the intraclass correlation coefficient to 0.82. Although repeatability was not significantly different between the SNR-matched cohorts (P = .44), the smoker group showed higher spatial and temporal variability in Pao2. CONCLUSION The short-term test-retest repeatability of hyperpolarized gas MR imaging of regional Pao2 was good. Asymptomatic smokers exhibited greater spatial and temporal variability in Pao2 than did the nonsmokers, which suggests that this parameter allows detection of small functional alterations associated with smoking.
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Affiliation(s)
- Masaru Ishii
- From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104
| | - Hooman Hamedani
- From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104
| | - Justin T Clapp
- From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104
| | - Stephen J Kadlecek
- From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104
| | - Yi Xin
- From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104
| | - Warren B Gefter
- From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104
| | - Milton D Rossman
- From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104
| | - Rahim R Rizi
- From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104
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Wang LW, Kwan BCH, Glanville AR. Regional differences in ventilation-perfusion ratio may help explain the differential diagnosis in interstitial lung disease. Intern Med J 2015; 45:365-7. [PMID: 25735587 DOI: 10.1111/imj.12694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2014] [Accepted: 09/04/2014] [Indexed: 11/26/2022]
Affiliation(s)
- L W Wang
- St Vincent's Hospital, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales, Australia
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Hamedani H, Shaghaghi H, Kadlecek SJ, Xin Y, Han B, Siddiqui S, Rajaei J, Ishii M, Rossman M, Rizi RR. Vertical gradients in regional alveolar oxygen tension in supine human lung imaged by hyperpolarized 3He MRI. NMR IN BIOMEDICINE 2014; 27:1439-50. [PMID: 25395184 PMCID: PMC5033039 DOI: 10.1002/nbm.3227] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 09/22/2014] [Accepted: 09/22/2014] [Indexed: 06/04/2023]
Abstract
The purpose of this study was to evaluate whether regional alveolar oxygen tension (P(A)O2) vertical gradients imaged with hyperpolarized (3)He can identify smoking-induced pulmonary alterations. These gradients are compared with common clinical measurements including pulmonary function tests (PFTs), the six minute walk test, and the St. George's Respiratory Questionnaire. 8 healthy non-smokers, 12 asymptomatic smokers, and 7 symptomatic subjects with chronic obstructive pulmonary disease (COPD) underwent two sets of back-to-back P(A)O2 imaging acquisitions in the supine position in two opposite directions (top to bottom and bottom to top), followed by clinically standard pulmonary tests. The whole-lung mean, standard deviation (DP(A)O2) and vertical gradients of P(A)O2 along the slices were extracted, and the results were compared with clinically derived metrics. Statistical tests were performed to analyze the differences between cohorts. The anterior-posterior vertical gradients and DP(A)O2 effectively differentiated all three cohorts (p < 0.05). The average vertical gradient P(A)O2 in healthy subjects was -1.03 ± 0.51 Torr/cm toward lower values in the posterior/dependent regions. The directional gradient was absent in smokers (0.36 ± 1.22 Torr/cm) and was in the opposite direction in COPD subjects (2.18 ± 1.54 Torr/cm). The vertical gradients correlated with smoking history (p = 0.004); body mass index (p = 0.037), PFT metrics (forced expiratory volume in 1 s, p = 0.025; residual volume/total lung capacity percent predicted, p = 0.033) and with distance walked in 6 min (p = 0.009). Regional P(A)O2 data indicate that cigarette smoke induces physiological alterations that are not being detected by the most widely used physiological tests.
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Affiliation(s)
- Hooman Hamedani
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Hoora Shaghaghi
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Stephen J. Kadlecek
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Yi Xin
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Biao Han
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Sarmad Siddiqui
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Jennia Rajaei
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Masaru Ishii
- Departments of Otolaryngology-Head and Neck Surgery, Johns Hopkins University, Baltimore, MD, United States
| | - Milton Rossman
- Department of Pulmonary and Critical Care, Johns Hopkins University of Pennsylvania, Philadelphia, PA, Baltimore, MD, United States
| | - Rahim R. Rizi
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
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Petersson J, Glenny RW. Gas exchange and ventilation-perfusion relationships in the lung. Eur Respir J 2014; 44:1023-41. [PMID: 25063240 DOI: 10.1183/09031936.00037014] [Citation(s) in RCA: 178] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
This review provides an overview of the relationship between ventilation/perfusion ratios and gas exchange in the lung, emphasising basic concepts and relating them to clinical scenarios. For each gas exchanging unit, the alveolar and effluent blood partial pressures of oxygen and carbon dioxide (PO2 and PCO2) are determined by the ratio of alveolar ventilation to blood flow (V'A/Q') for each unit. Shunt and low V'A/Q' regions are two examples of V'A/Q' mismatch and are the most frequent causes of hypoxaemia. Diffusion limitation, hypoventilation and low inspired PO2 cause hypoxaemia, even in the absence of V'A/Q' mismatch. In contrast to other causes, hypoxaemia due to shunt responds poorly to supplemental oxygen. Gas exchanging units with little or no blood flow (high V'A/Q' regions) result in alveolar dead space and increased wasted ventilation, i.e. less efficient carbon dioxide removal. Because of the respiratory drive to maintain a normal arterial PCO2, the most frequent result of wasted ventilation is increased minute ventilation and work of breathing, not hypercapnia. Calculations of alveolar-arterial oxygen tension difference, venous admixture and wasted ventilation provide quantitative estimates of the effect of V'A/Q' mismatch on gas exchange. The types of V'A/Q' mismatch causing impaired gas exchange vary characteristically with different lung diseases.
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Affiliation(s)
- Johan Petersson
- Section of Anaesthesiology and Intensive Care Medicine, Dept of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden Dept of Anaesthesiology, Surgical Services and Intensive Care, Karolinska University Hospital, Stockholm, Sweden
| | - Robb W Glenny
- Dept of Medicine, Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, WA, USA Dept of Physiology and Biophysics, University of Washington, Seattle, WA, USA
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Kinsey CM, Estepar RSJ, Zhao Y, Yu X, Diao N, Heist RS, Wain JC, Mark EJ, Washko G, Christiani DC. Invasive adenocarcinoma of the lung is associated with the upper lung regions. Lung Cancer 2014; 84:145-50. [PMID: 24598367 PMCID: PMC4004700 DOI: 10.1016/j.lungcan.2014.02.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 02/03/2014] [Indexed: 01/15/2023]
Abstract
OBJECTIVES We postulated that ventilation-perfusion (V/Q) relationships within the lung might influence where lung cancer occurs. To address this hypothesis we evaluated the location of lung adenocarcinoma, by both tumor lobe and superior-inferior regional distribution, and associated variables such as emphysema. MATERIALS AND METHODS One hundred fifty-nine cases of invasive adenocarcinoma and adenocarcinoma with lepidic features were visually evaluated to identify lobar or regional tumor location. Regions were determined by automated division of the lungs into three equal volumes: (upper region, middle region, or lower region). Automated densitometry was used to measure radiographic emphysema. RESULTS The majority of invasive adenocarcinomas occurred in the upper lobes (69%), with 94% of upper lobe adenocarcinomas occurring in the upper region of the lung. The distribution of adenocarcinoma, when classified as upper or lower lobe, was not different between invasive adenocarcinoma and adenocarcinoma with lepidic features (formerly bronchioloalveolar cell carcinoma, P = 0.08). Regional distribution of tumor was significantly different between invasive adenocarcinoma and adenocarcinoma with lepidic features (P = 0.001). Logistic regression analysis with the outcome of invasive adenocarcinoma histology was used to adjust for confounders. Tumor region continued to be a significant predictor (OR 8.5, P = 0.008, compared to lower region), whereas lobar location of tumor was not (P = 0.09). In stratified analysis, smoking was not associated with region of invasive adenocarcinoma occurrence (P = 0.089). There was no difference in total emphysema scores between invasive adenocarcinoma cases occurring in each of the three regions (P = 0.155). There was also no difference in the distribution of region of adenocarcinoma occurrence between quartiles of emphysema (P = 0.217). CONCLUSION Invasive adenocarcinoma of the lung is highly associated with the upper lung regions. This association is not related to smoking, history of COPD, or total emphysema. The regional distribution of invasive adenocarcinoma may be due to V/Q relationships or other local factors.
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Affiliation(s)
- C Matthew Kinsey
- Division of Pulmonary and Critical Care, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington VT 05405, United States
| | - Raul San Jose Estepar
- Department of Environmental Health and Epidemiology, Harvard School of Public Health, 665 Huntington Ave, Boston, MA 02115, United States; Department of Radiology, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, United States
| | - Yang Zhao
- Department of Epidemiology and Biostatistics, School of Public Health, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Xiaojin Yu
- Department of Epidemiology and Biostatistics, School of Public Health, Southeast University, Nanjing, Jiangsu, China
| | - Nancy Diao
- Department of Environmental Health and Epidemiology, Harvard School of Public Health, 665 Huntington Ave, Boston, MA 02115, United States
| | - Rebecca Suk Heist
- Division of Hematology and Oncology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, United States
| | - John C Wain
- Division of Thoracic Surgery, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, United States
| | - Eugene J Mark
- Department of Pathology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, United States
| | - George Washko
- Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, United States
| | - David C Christiani
- Pulmonary and Critical Care Unit, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, United States; Departments of Environmental Health and Epidemiology, Harvard School of Public Health, 665 Huntington Ave, Boston, MA 02115, United States.
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Ben-Tal A, Tawhai MH. Integrative approaches for modeling regulation and function of the respiratory system. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2013; 5:687-99. [PMID: 24591490 PMCID: PMC4048368 DOI: 10.1002/wsbm.1244] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 08/02/2013] [Accepted: 08/05/2013] [Indexed: 11/08/2022]
Abstract
Mathematical models have been central to understanding the interaction between neural control and breathing. Models of the entire respiratory system-which comprises the lungs and the neural circuitry that controls their ventilation-have been derived using simplifying assumptions to compartmentalize each component of the system and to define the interactions between components. These full system models often rely-through necessity-on empirically derived relationships or parameters, in addition to physiological values. In parallel with the development of whole respiratory system models are mathematical models that focus on furthering a detailed understanding of the neural control network, or of the several functions that contribute to gas exchange within the lung. These models are biophysically based, and rely on physiological parameters. They include single-unit models for a breathing lung or neural circuit, through to spatially distributed models of ventilation and perfusion, or multicircuit models for neural control. The challenge is to bring together these more recent advances in models of neural control with models of lung function, into a full simulation for the respiratory system that builds upon the more detailed models but remains computationally tractable. This requires first understanding the mathematical models that have been developed for the respiratory system at different levels, and which could be used to study how physiological levels of O2 and CO2 in the blood are maintained.
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Affiliation(s)
- Alona Ben-Tal
- Institute of Natural and Mathematical Sciences, Massey University, Albany, Auckland, New Zealand
| | - Merryn H. Tawhai
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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Glenny RW, Robertson HT. Spatial distribution of ventilation and perfusion: mechanisms and regulation. Compr Physiol 2013; 1:375-95. [PMID: 23737178 DOI: 10.1002/cphy.c100002] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
With increasing spatial resolution of regional ventilation and perfusion, it has become more apparent that ventilation and blood flow are quite heterogeneous in the lung. A number of mechanisms contribute to this regional variability, including hydrostatic gradients, pleural pressure gradients, lung compressibility, and the geometry of the airway and vascular trees. Despite this marked heterogeneity in both ventilation and perfusion, efficient gas exchange is possible through the close regional matching of the two. Passive mechanisms, such as the shared effect of gravity and the matched branching of vascular and airway trees, create efficient gas exchange through the strong correlation between ventilation and perfusion. Active mechanisms that match local ventilation and perfusion play little if no role in the normal healthy lung but are important under pathologic conditions.
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Affiliation(s)
- Robb W Glenny
- Department of Medicine, University of Washington, USA.
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Abstract
Efficient gas exchange in the lung depends on the matching of ventilation and perfusion. However, the human lung is a readily deformable structure and as a result gravitational stresses generate gradients in both ventilation and perfusion. Nevertheless, the lung is capable of withstanding considerable change in the applied gravitational load before pulmonary gas exchange becomes impaired. The postural changes that are part of the everyday existence for most bipedal species are well tolerated, as is the removal of gravity (weightlessness). Increases in the applied gravitational load result only in a large impairment in pulmonary gas exchange above approximately three times that on the ground, at which point the matching of ventilation to perfusion is so impaired that efficient gas exchange is no longer possible. Much of the tolerance of the lung to alterations in gravitation stress comes from the fact that ventilation and perfusion are inextricably coupled. Deformations in the lung that alter ventilation necessarily alter perfusion, thus maintaining a degree of matching and minimizing the disruption in ventilation to perfusion ratio and thus gas exchange.
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Affiliation(s)
- G Kim Prisk
- Departments of Medicine and Radiology, University of California, San Diego, USA.
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Abstract
Local driving pressures and resistances within the pulmonary vascular tree determine the distribution of perfusion in the lung. Unlike other organs, these local determinants are significantly influenced by regional hydrostatic and alveolar pressures. Those effects on blood flow distribution are further magnified by the large vertical height of the human lung and the relatively low intravascular pressures in the pulmonary circulation. While the distribution of perfusion is largely due to passive determinants such as vascular geometry and hydrostatic pressures, active mechanisms such as vasoconstriction induced by local hypoxia can also redistribute blood flow. This chapter reviews the determinants of regional lung perfusion with a focus on vascular tree geometry, vertical gradients induced by gravity, the interactions between vascular and surrounding alveolar pressures, and hypoxic pulmonary vasoconstriction. While each of these determinants of perfusion distribution can be examined in isolation, the distribution of blood flow is dynamically determined and each component interacts with the others so that a change in one region of the lung influences the distribution of blood flow in other lung regions.
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Affiliation(s)
- Robb Glenny
- Departments of Medicine, University of Washington, Seattle, Washington, USA.
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Lilburn DML, Hughes-Riley T, Six JS, Stupic KF, Shaw DE, Pavlovskaya GE, Meersmann T. Validating excised rodent lungs for functional hyperpolarized xenon-129 MRI. PLoS One 2013; 8:e73468. [PMID: 24023683 PMCID: PMC3758272 DOI: 10.1371/journal.pone.0073468] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 07/21/2013] [Indexed: 12/15/2022] Open
Abstract
Ex vivo rodent lung models are explored for physiological measurements of respiratory function with hyperpolarized (hp) (129)Xe MRI. It is shown that excised lung models allow for simplification of the technical challenges involved and provide valuable physiological insights that are not feasible using in vivo MRI protocols. A custom designed breathing apparatus enables MR images of gas distribution on increasing ventilation volumes of actively inhaled hp (129)Xe. Straightforward hp (129)Xe MRI protocols provide residual lung volume (RV) data and permit for spatially resolved tracking of small hp (129)Xe probe volumes during the inhalation cycle. Hp (129)Xe MRI of lung function in the excised organ demonstrates the persistence of post mortem airway responsiveness to intravenous methacholine challenges. The presented methodology enables physiology of lung function in health and disease without additional regulatory approval requirements and reduces the technical and logistical challenges with hp gas MRI experiments. The post mortem lung functional data can augment histological measurements and should be of interest for drug development studies.
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Affiliation(s)
- David M. L. Lilburn
- Sir Peter Mansfield Magnetic Resonance Centre, School of Clinical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Theodore Hughes-Riley
- Sir Peter Mansfield Magnetic Resonance Centre, School of Clinical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Joseph S. Six
- Sir Peter Mansfield Magnetic Resonance Centre, School of Clinical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Karl F. Stupic
- Sir Peter Mansfield Magnetic Resonance Centre, School of Clinical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Dominick E. Shaw
- Nottingham Respiratory Research Unit, Nottingham City Hospital, Nottingham, United Kingdom
| | - Galina E. Pavlovskaya
- Sir Peter Mansfield Magnetic Resonance Centre, School of Clinical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Thomas Meersmann
- Sir Peter Mansfield Magnetic Resonance Centre, School of Clinical Sciences, University of Nottingham, Nottingham, United Kingdom
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Hahn G, Just A, Hellige G, Dittmar J, Quintel M. How absolute EIT reflects the dependence of unilateral lung aeration on hyper-gravity and weightlessness? Physiol Meas 2013; 34:1063-74. [DOI: 10.1088/0967-3334/34/9/1063] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Glenny RW, Bauer C, Hofmanninger J, Lamm WJ, Krueger MA, Beichel RR. Heterogeneity and matching of ventilation and perfusion within anatomical lung units in rats. Respir Physiol Neurobiol 2013; 189:594-606. [PMID: 23942308 DOI: 10.1016/j.resp.2013.07.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 07/24/2013] [Accepted: 07/30/2013] [Indexed: 11/30/2022]
Abstract
Prior studies exploring the spatial distributions of ventilation and perfusion have partitioned the lung into discrete regions not constrained by anatomical boundaries and may blur regional differences in perfusion and ventilation. To characterize the anatomical heterogeneity of regional ventilation and perfusion, we administered fluorescent microspheres to mark regional ventilation and perfusion in five Sprague-Dawley rats and then using highly automated computer algorithms, partitioned the lungs into regions defined by anatomical structures identified in the images. The anatomical regions ranged in size from the near-acinar to the lobar level. Ventilation and perfusion were well correlated at the smallest anatomical level. Perfusion and ventilation heterogeneity were relatively less in rats compared to data previously published in larger animals. The more uniform distributions may be due to a smaller gravitational gradient and/or the fewer number of generations in the distribution trees before reaching the level of gas exchange, making regional matching of ventilation and perfusion less extensive in small animals.
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Burrowes KS, Clark AR, Tawhai MH. Blood flow redistribution and ventilation-perfusion mismatch during embolic pulmonary arterial occlusion. Pulm Circ 2012; 1:365-76. [PMID: 22140626 PMCID: PMC3224428 DOI: 10.4103/2045-8932.87302] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Acute pulmonary embolism causes redistribution of blood in the lung, which impairs ventilation/perfusion matching and gas exchange and can elevate pulmonary arterial pressure (PAP) by increasing pulmonary vascular resistance (PVR). An anatomically-based multi-scale model of the human pulmonary circulation was used to simulate pre- and post-occlusion flow, to study blood flow redistribution in the presence of an embolus, and to evaluate whether reduction in perfused vascular bed is sufficient to increase PAP to hypertensive levels, or whether other vasoconstrictive mechanisms are necessary. A model of oxygen transfer from air to blood was included to assess the impact of vascular occlusion on oxygen exchange. Emboli of 5, 7, and 10 mm radius were introduced to occlude increasing proportions of the vasculature. Blood flow redistribution was calculated after arterial occlusion, giving predictions of PAP, PVR, flow redistribution, and micro-circulatory flow dynamics. Because of the large flow reserve capacity (via both capillary recruitment and distension), approximately 55% of the vasculature was occluded before PAP reached clinically significant levels indicative of hypertension. In contrast, model predictions showed that even relatively low levels of occlusion could cause localized oxygen deficit. Flow preferentially redistributed to gravitationally non-dependent regions regardless of occlusion location, due to the greater potential for capillary recruitment in this region. Red blood cell transit times decreased below the minimum time for oxygen saturation (<0.25 s) and capillary pressures became high enough to initiate cell damage (which may result in edema) only after ~80% of the lung was occluded.
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Affiliation(s)
- K S Burrowes
- Department of Computer Science, University of Oxford, United Kingdom
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Robertson HT, Buxton RB. Imaging for lung physiology: what do we wish we could measure? J Appl Physiol (1985) 2012; 113:317-27. [PMID: 22582217 DOI: 10.1152/japplphysiol.00146.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The role of imaging as a tool for investigating lung physiology is growing at an accelerating pace. Looking forward, we wished to identify unresolved issues in lung physiology that might realistically be addressed by imaging methods in development or imaging approaches that could be considered. The role of imaging is framed in terms of the importance of good spatial and temporal resolution and the types of questions that could be addressed as these technical capabilities improve. Recognizing that physiology is fundamentally a quantitative science, a recurring emphasis is on the need for imaging methods that provide reliable measurements of specific physiological parameters. The topics included necessarily reflect our perspective on what are interesting questions and are not meant to be a comprehensive review. Nevertheless, we hope that this essay will be a spur to physiologists to think about how imaging could usefully be applied in their research and to physical scientists developing new imaging methods to attack challenging questions imaging could potentially answer.
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Affiliation(s)
- H Thomas Robertson
- Department of Medicine, University of Washington, Seattle, WA 98195, USA.
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Weiskopf RB, Feiner J, Toy P, Twiford J, Shimabukuro D, Lieberman J, Looney MR, Lowell CA, Gropper MA. Fresh and stored red blood cell transfusion equivalently induce subclinical pulmonary gas exchange deficit in normal humans. Anesth Analg 2012; 114:511-9. [PMID: 22262647 DOI: 10.1213/ane.0b013e318241fcd5] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Transfusion can cause severe acute lung injury, although most transfusions do not seem to induce complications. We tested the hypothesis that transfusion can cause mild pulmonary dysfunction that has not been noticed clinically and is not sufficiently severe to fit the definition of transfusion-related acute lung injury. METHODS We studied 35 healthy, normal volunteers who donated 1 U of blood 4 weeks and another 3 weeks before 2 study days separated by 1 week. On study days, 2 U of blood were withdrawn while maintaining isovolemia, followed by transfusion with either the volunteer's autologous fresh red blood cells (RBCs) removed 2 hours earlier or their autologous stored RBCs (random order). The following week, each volunteer was studied again, transfused with the RBCs of the other storage duration. The primary outcome variable was the change in alveolar to arterial difference in oxygen partial pressure (AaDo(2)) from before to 60 minutes after transfusion with fresh or older RBCs. RESULTS Fresh RBCs and RBCs stored for 24.5 days equally (P = 0.85) caused an increase of AaDo(2) (fresh: 2.8 mm Hg [95% confidence interval: 0.8-4.8; P = 0.007]; stored: 3.0 mm Hg [1.4-4.7; P = 0.0006]). Concentrations of all measured cytokines, except for interleukin-10 (P = 0.15), were less in stored leukoreduced (LR) than stored non-LR packed RBCs; however, vascular endothelial growth factor was the only measured in vivo cytokine that increased more after transfusion with LR than non-LR stored packed RBCs. Vascular endothelial growth factor was the only cytokine tested with in vivo concentrations that correlated with AaDo(2). CONCLUSION RBC transfusion causes subtle pulmonary dysfunction, as evidenced by impaired gas exchange for oxygen, supporting our hypothesis that lung impairment after transfusion includes a wide spectrum of physiologic derangements and may not require an existing state of altered physiology. These data do not support the hypothesis that transfusion of RBCs stored for >21 days is more injurious than that of fresh RBCs.
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Affiliation(s)
- Richard B Weiskopf
- Department of Anesthesia & Perioperative Care, University of California, San Francisco, Box 0648, San Francisco, CA 94143-0648, USA.
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Tawhai MH, Clark AR, Burrowes KS. Computational models of the pulmonary circulation: Insights and the move towards clinically directed studies. Pulm Circ 2011; 1:224-38. [PMID: 22034608 PMCID: PMC3198640 DOI: 10.4103/2045-8932.83452] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Biophysically-based computational models provide a tool for integrating and explaining experimental data, observations, and hypotheses. Computational models of the pulmonary circulation have evolved from minimal and efficient constructs that have been used to study individual mechanisms that contribute to lung perfusion, to sophisticated multi-scale and -physics structure-based models that predict integrated structure-function relationships within a heterogeneous organ. This review considers the utility of computational models in providing new insights into the function of the pulmonary circulation, and their application in clinically motivated studies. We review mathematical and computational models of the pulmonary circulation based on their application; we begin with models that seek to answer questions in basic science and physiology and progress to models that aim to have clinical application. In looking forward, we discuss the relative merits and clinical relevance of computational models: what important features are still lacking; and how these models may ultimately be applied to further increasing our understanding of the mechanisms occurring in disease of the pulmonary circulation.
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Affiliation(s)
- Merryn H Tawhai
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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Amen EM, Becker EM, Truebel H. Analysis of V/Q-matching—a safety “biomarker” in pulmonary drug development? Biomarkers 2011; 16 Suppl 1:S5-10. [DOI: 10.3109/1354750x.2011.585243] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Brochu P, Brodeur J, Krishnan K. Derivation of cardiac output and alveolar ventilation rate based on energy expenditure measurements in healthy males and females. J Appl Toxicol 2011; 32:564-80. [DOI: 10.1002/jat.1651] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Revised: 12/03/2010] [Accepted: 12/03/2010] [Indexed: 11/09/2022]
Affiliation(s)
- Pierre Brochu
- Ministère du Développement durable, de l'Environnement et des Parcs, Direction du suivi et de l'état de l'environnement, Service des avis et expertises scientifiques, gouvernement du Québec, édifice Marie-Guyart; 7; e; étage, 675, boulevard René-Lévesque Est; Québec; QC; G1R 5V7; Canada
| | - Jules Brodeur
- Département de santé environnementale et santé au travail, Faculté de médecine; Université de Montréal; C.P. 6128, succursale Centre-Ville; Montréal; QC; H3C 3J7; Canada
| | - Kannan Krishnan
- Département de santé environnementale et santé au travail, Faculté de médecine; Université de Montréal; C.P. 6128, succursale Centre-Ville; Montréal; QC; H3C 3J7; Canada
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Capelli C, Carlo C, Cautero M, Michela C, Pogliaghi S, Silvia P. Algorithms, modelling and VO₂ kinetics. Eur J Appl Physiol 2010; 111:331-42. [PMID: 20195628 DOI: 10.1007/s00421-010-1396-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/07/2010] [Indexed: 12/01/2022]
Abstract
This article summarises the pros and cons of different algorithms developed for estimating breath-by-breath (B-by-B) alveolar O(2) transfer (VO 2A) in humans. VO 2A is the difference between O(2) uptake at the mouth and changes in alveolar O(2) stores (∆ VO(2s)), which for any given breath, are equal to the alveolar volume change at constant FAO2/FAiO2 ∆VAi plus the O(2) alveolar fraction change at constant volume [V Ai-1(F Ai - F Ai-1) O2, where V (Ai-1) is the alveolar volume at the beginning of a breath. Therefore, VO 2A can be determined B-by-B provided that V (Ai-1) is: (a) set equal to the subject's functional residual capacity (algorithm of Auchincloss, A) or to zero; (b) measured (optoelectronic plethysmography, OEP); (c) selected according to a procedure that minimises B-by-B variability (algorithm of Busso and Robbins, BR). Alternatively, the respiratory cycle can be redefined as the time between equal FO(2) in two subsequent breaths (algorithm of Grønlund, G), making any assumption of V (Ai-1) unnecessary. All the above methods allow an unbiased estimate of VO2 at steady state, albeit with different precision. Yet the algorithms "per se" affect the parameters describing the B-by-B kinetics during exercise transitions. Among these approaches, BR and G, by increasing the signal-to-noise ratio of the measurements, reduce the number of exercise repetitions necessary to study VO2 kinetics, compared to A approach. OEP and G (though technically challenging and conceptually still debated), thanks to their ability to track ∆VO(2s) changes during the early phase of exercise transitions, appear rather promising for investigating B-by-B gas exchange.
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Affiliation(s)
- Carlo Capelli
- Department of Visual and Neurological Sciences, School of Exercise and Sports Sciences, University of Verona, Via Felice Casorati 43, 37131, Verona, Italy.
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