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Lindahl SGE. Using the prone position could help to combat the development of fast hypoxia in some patients with COVID-19. Acta Paediatr 2020; 109:1539-1544. [PMID: 32484966 PMCID: PMC7301016 DOI: 10.1111/apa.15382] [Citation(s) in RCA: 17] [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] [Received: 05/12/2020] [Revised: 05/20/2020] [Accepted: 05/27/2020] [Indexed: 02/05/2023]
Abstract
The world is facing an explosive COVID‐19 pandemic. Some cases rapidly develop deteriorating lung function, which causes deep hypoxaemia and requires urgent treatment. Many centres have started treating patients in the prone position, and oxygenation has improved considerably in some cases. Questions have been raised regarding the mechanisms behind this. The mini review provides some insights into the role of supine and prone body positions and summarises the latest understanding of the responsible mechanisms. The scope for discussion is outside the neonatal period and entirely based on experimental and clinical experiences related to adults. The human respiratory system is a complex interplay of many different variables. Therefore, this mini review has prioritised previous and ongoing research to find explanations based on three scientific areas: gravity, lung structure and fractal geometry and vascular regulation. It concludes that gravity is one of the variables responsible for ventilation/perfusion matching but in concert with lung structure and fractal geometry, ventilation and regulation of lung vascular tone. Since ventilation distribution does not change between supine and prone positions, the higher expression of nitric oxide in dorsal lung vessels than in ventral vessels is likely to be the most important mechanism behind enhanced oxygenation in the prone position.
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2
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Cieri RL. Pulmonary Smooth Muscle in Vertebrates: A Comparative Review of Structure and Function. Integr Comp Biol 2019; 59:10-28. [DOI: 10.1093/icb/icz002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Abstract
Although the airways of vertebrates are diverse in shape, complexity, and function, they all contain visceral smooth muscle. The morphology, function, and innervation of this tissue in airways is reviewed in actinopterygians, lungfish, amphibians, non-avian reptiles, birds, and mammals. Smooth muscle was likely involved in tension regulation ancestrally, and may serve to assist lung emptying in fishes and aquatic amphibians, as well as maintain internal lung structure. In certain non-avian reptiles and anurans antagonistic smooth muscle fibers may contribute to intrapulmonary gas mixing. In mammals and birds, smooth muscle regulates airway caliber, and may be important in controlling the distribution of ventilation at rest and exercise, or during thermoregulatory and vocal hyperventilation. Airway smooth muscle is controlled by the autonomic nervous system: cranial cholinergic innervation generally causes excitation, cranial non-adrenergic, non-cholinergic innervation causes inhibition, and spinal adrenergic (SA) input causes species-specific, often heterogeneous contractions and relaxations.
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Affiliation(s)
- Robert L Cieri
- School of Biological Sciences, The University of Utah, 247 South 1400 East, 201 South Biology, Salt Lake City, UT 84112, USA
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3
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Kruger SJ, Nagle SK, Couch MJ, Ohno Y, Albert M, Fain SB. Functional imaging of the lungs with gas agents. J Magn Reson Imaging 2016; 43:295-315. [PMID: 26218920 PMCID: PMC4733870 DOI: 10.1002/jmri.25002] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 06/26/2015] [Indexed: 12/22/2022] Open
Abstract
This review focuses on the state-of-the-art of the three major classes of gas contrast agents used in magnetic resonance imaging (MRI)-hyperpolarized (HP) gas, molecular oxygen, and fluorinated gas--and their application to clinical pulmonary research. During the past several years there has been accelerated development of pulmonary MRI. This has been driven in part by concerns regarding ionizing radiation using multidetector computed tomography (CT). However, MRI also offers capabilities for fast multispectral and functional imaging using gas agents that are not technically feasible with CT. Recent improvements in gradient performance and radial acquisition methods using ultrashort echo time (UTE) have contributed to advances in these functional pulmonary MRI techniques. The relative strengths and weaknesses of the main functional imaging methods and gas agents are compared and applications to measures of ventilation, diffusion, and gas exchange are presented. Functional lung MRI methods using these gas agents are improving our understanding of a wide range of chronic lung diseases, including chronic obstructive pulmonary disease, asthma, and cystic fibrosis in both adults and children.
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Affiliation(s)
- Stanley J. Kruger
- Department of Medical Physics, University of Wisconsin – Madison, WI, U.S.A
| | - Scott K. Nagle
- Department of Medical Physics, University of Wisconsin – Madison, WI, U.S.A
- Department of Radiology, University of Wisconsin – Madison, WI, U.S.A
- Department of Pediatrics, University of Wisconsin – Madison, WI, U.S.A
| | - Marcus J. Couch
- Thunder Bay Regional Research Institute, Thunder Bay, ON, Canada
- Biotechnology Program, Lakehead University, Thunder Bay, ON, Canada
| | - Yoshiharu Ohno
- Department of Radiology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Mitchell Albert
- Thunder Bay Regional Research Institute, Thunder Bay, ON, Canada
- Department of Chemistry, Lakehead University, Thunder Bay, ON, Canada
| | - Sean B. Fain
- Department of Medical Physics, University of Wisconsin – Madison, WI, U.S.A
- Department of Radiology, University of Wisconsin – Madison, WI, U.S.A
- Department of Biomedical Engineering, University of Wisconsin – Madison, WI, U.S.A
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Siev M, Motamedinia P, Leavitt D, Fakhoury M, Barcohana K, Hoenig D, Smith AD, Okeke Z. Does Peak Inspiratory Pressure Increase in the Prone Position? An Analysis Related to Body Mass Index. J Urol 2015; 194:1302-6. [PMID: 25983193 DOI: 10.1016/j.juro.2015.05.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/05/2015] [Indexed: 11/30/2022]
Abstract
PURPOSE Percutaneous nephrolithotomy is commonly performed with the patient prone. There is concern that the prone position, especially in obese patients, negatively affects ventilation due to the restriction of chest compliance and respiratory mechanics. We analyzed the change in airway resistance between supine and prone positioning of patients undergoing percutaneous nephrolithotomy. MATERIALS AND METHODS We retrospectively reviewed the intraoperative respiratory parameters of 101 patients who underwent prone percutaneous nephrolithotomy. Peak inspiratory pressure was assessed with the patient supine, at several time points after being turned prone and at the end of the case. The change in peak inspiratory pressure with time was calculated. Results were stratified based on body mass index and data were compared using the paired t-test and Spearman ρ. RESULTS Of 101 patients 50 (50%) were obese (body mass index 30 kg/m(2) or greater). Median body mass index was 25.6 kg/m(2) in the nonobese cohort and 38.3 kg/m(2) in the obese cohort. Average peak inspiratory pressure while supine and prone was 18.0 and 18.5 cm H2O in the nonobese cohort, and 25.5 and 26.6 cm H2O, respectively, in the obese cohort. Obese patients had significantly higher peak inspiratory pressure in the supine and the prone positions relative to nonobese patients (p <0.0001). However, there was no change in peak inspiratory pressure from the supine to the prone position in either cohort. CONCLUSIONS Obese patients have higher baseline peak inspiratory pressure regardless of position. However, prone positioning does not impact peak inspiratory pressure in either cohort. It remains a safe and viable option.
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Affiliation(s)
- Michael Siev
- Smith Institute for Urology and Department of Anesthesia (KB), NorthShore-LIJ Health System, New Hyde Park, New York
| | - Piruz Motamedinia
- Smith Institute for Urology and Department of Anesthesia (KB), NorthShore-LIJ Health System, New Hyde Park, New York
| | - David Leavitt
- Smith Institute for Urology and Department of Anesthesia (KB), NorthShore-LIJ Health System, New Hyde Park, New York
| | - Mathew Fakhoury
- Smith Institute for Urology and Department of Anesthesia (KB), NorthShore-LIJ Health System, New Hyde Park, New York
| | - Kevin Barcohana
- Smith Institute for Urology and Department of Anesthesia (KB), NorthShore-LIJ Health System, New Hyde Park, New York
| | - David Hoenig
- Smith Institute for Urology and Department of Anesthesia (KB), NorthShore-LIJ Health System, New Hyde Park, New York
| | - Arthur D Smith
- Smith Institute for Urology and Department of Anesthesia (KB), NorthShore-LIJ Health System, New Hyde Park, New York
| | - Zeph Okeke
- Smith Institute for Urology and Department of Anesthesia (KB), NorthShore-LIJ Health System, New Hyde Park, New York.
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Pennati F, Salito C, Baroni G, Woods J, Aliverti A. Comparison between multivolume CT-based surrogates of regional ventilation in healthy subjects. Acad Radiol 2014; 21:1268-75. [PMID: 25126974 DOI: 10.1016/j.acra.2014.05.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 05/22/2014] [Accepted: 05/27/2014] [Indexed: 01/14/2023]
Abstract
RATIONALE AND OBJECTIVES The assessment of regional ventilation is of critical importance when investigating lung function during disease progression and planning of pulmonary interventions. Recently, different computed tomography (CT)-based parameters have been proposed as surrogates of lung ventilation. The aim of the present study was to compare these parameters, namely variations of density (ΔHU), specific volume (sVol), and specific gas volume (ΔSVg) between different lung volumes, in relation to their topographic distribution within the lung. MATERIALS AND METHODS Ten healthy volunteers were scanned via high-resolution CT at residual volume (RV) and total lung capacity (TLC); ΔHU, sVol, and ΔSVg were mapped voxel by voxel after registering TLC onto RV. Variations of the three parameters along the vertical and horizontal directions were analyzed. RESULTS Along the vertical direction (from ventral to dorsal regions), a strong dependence on gravity was found in ΔHU and sVol, with greater values in the dorsal regions of the lung (P < .001), whereas ΔSVg was more homogeneously distributed within the lung. Conversely, along the caudocranial direction (from lung bases to apexes) where no gravitational gradient is present, the three parameters behaved similarly, with lower values at the apices. CONCLUSIONS ΔHU, sVol, and ΔSVg behave differently along the gravity direction. As the greater amount of air delivered to the dependent portion of the lung supplies a larger number of alveoli, the amount of gas delivered to alveoli compared to the mass of tissue is not gravity dependent. The minimization of gravity dependence in the distribution of ventilation when using ΔSVg suggests that this parameter is more reliable to discriminate healthy from pathologic regions.
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Affiliation(s)
- Francesca Pennati
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, P.zza L. da Vinci, 32, 20133 Milano, Italy
| | - Caterina Salito
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, P.zza L. da Vinci, 32, 20133 Milano, Italy
| | - Guido Baroni
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, P.zza L. da Vinci, 32, 20133 Milano, Italy
| | - Jason Woods
- Pulmonary Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Andrea Aliverti
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, P.zza L. da Vinci, 32, 20133 Milano, Italy.
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6
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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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Ax M, Karlsson LL, Sanchez-Crespo A, Lindahl SGE, Linnarsson D, Mure M, Petersson J. Regional lung ventilation in humans during hypergravity studied with quantitative SPECT. Respir Physiol Neurobiol 2013; 189:558-64. [PMID: 24004984 DOI: 10.1016/j.resp.2013.08.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2013] [Revised: 07/23/2013] [Accepted: 08/15/2013] [Indexed: 11/28/2022]
Abstract
Recently we challenged the view that arterial desaturation during hypergravity is caused by redistribution of blood flow to dependent lung regions by demonstrating a paradoxical redistribution of blood flow towards non-dependent regions. We have now quantified regional ventilation in 10 healthy supine volunteers at normal and three times normal gravity (1G and 3G). Regional ventilation was measured with Technegas ((99m)Tc) and quantitative single photon emission computed tomography (SPECT). Hypergravity caused arterial desaturation, mean decrease 8%, p<0.05 vs. 1G. The ratio for mean ventilation per voxel for non-dependent and dependent lung regions was 0.81±0.12 during 1G and 1.63±0.35 during 3G (mean±SD), p<0.0001. Thus, regional ventilation was shifted from dependent to non-dependent regions. We suggest that arterial desaturation during hypergravity is caused by quantitatively different redistributions of blood flow and ventilation. To our knowledge, this is the first study presenting high-resolution measurements of regional ventilation in humans breathing normally during hypergravity.
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Affiliation(s)
- M Ax
- Department of Anesthesiology and Intensive Care, Karolinska University Hospital Solna, 171 76 Stockholm, Sweden; Department of Physiology and Pharmacology, Section of Anesthesiology and Intensive Care Medicine, Karolinska Institutet, 171 77 Stockholm, Sweden.
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Choi S, Hoffman EA, Wenzel SE, Tawhai MH, Yin Y, Castro M, Lin CL. Registration-based assessment of regional lung function via volumetric CT images of normal subjects vs. severe asthmatics. J Appl Physiol (1985) 2013; 115:730-42. [PMID: 23743399 DOI: 10.1152/japplphysiol.00113.2013] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The purpose of this work was to explore the use of image registration-derived variables associated with computed tomographic (CT) imaging of the lung acquired at multiple volumes. As an evaluation of the utility of such an imaging approach, we explored two groups at the extremes of population ranging from normal subjects to severe asthmatics. A mass-preserving image registration technique was employed to match CT images at total lung capacity (TLC) and functional residual capacity (FRC) for assessment of regional air volume change and lung deformation between the two states. Fourteen normal subjects and thirty severe asthmatics were analyzed via image registration-derived metrics together with their pulmonary function test (PFT) and CT-based air-trapping. Relative to the normal group, the severely asthmatic group demonstrated reduced air volume change (consistent with air trapping) and more isotropic deformation in the basal lung regions while demonstrating increased air volume change associated with increased anisotropic deformation in the apical lung regions. These differences were found despite the fact that both PFT-derived TLC and FRC in the two groups were nearly 100% of predicted values. Data suggest that reduced basal-lung air volume change in severe asthmatics was compensated by increased apical-lung air volume change and that relative increase in apical-lung air volume change in severe asthmatics was accompanied by enhanced anisotropic deformation. These data suggest that CT-based deformation, assessed via inspiration vs. expiration scans, provides a tool for distinguishing differences in lung mechanics when applied to the extreme ends of a population range.
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Affiliation(s)
- Sanghun Choi
- Department of Mechanical and Industrial Engineering
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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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Swan AJ, Clark AR, Tawhai MH. A computational model of the topographic distribution of ventilation in healthy human lungs. J Theor Biol 2012; 300:222-31. [PMID: 22326472 PMCID: PMC3308631 DOI: 10.1016/j.jtbi.2012.01.042] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 01/25/2012] [Accepted: 01/27/2012] [Indexed: 11/24/2022]
Abstract
The topographic distribution of ventilation in the lungs is determined by the interaction of several factors, including lung shape, airway tree geometry, posture, and tissue deformation. Inter-species differences in lung structure-function and technical difficulty in obtaining high resolution imaging of the upright human lung means that it is not straightforward to experimentally determine the contribution of each of these factors to ventilation distribution. We present a mathematical model for predicting the topological distribution of inhaled air in the upright healthy human lung, based on anatomically structured model geometries and biophysical equations for model function. Gravitational deformation of the lung tissue is predicted using a continuum model. Airflow is simulated in anatomically based conducting airways coupled to geometrically simplified terminal acinar units with varying volume-dependent compliances. The predicted ventilation distribution is hence governed by local tissue density and elastic recoil pressure, airway resistance and acinar compliance. Results suggest that there is significant spatial variation in intrinsic tissue properties in the lungs. The model confirms experimental evidence that in the healthy lungs tissue compliance has a far greater effect than airway resistance on the spatial distribution of ventilation, and hence a realistic description of tissue deformation is essential in models of ventilation.
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Affiliation(s)
- Annalisa J Swan
- Auckland Bioengineering Institute, University of Auckland, 70 Symonds St, Auckland, New Zealand
| | - Alys R Clark
- Auckland Bioengineering Institute, University of Auckland, 70 Symonds St, Auckland, New Zealand
| | - Merryn H Tawhai
- Auckland Bioengineering Institute, University of Auckland, 70 Symonds St, Auckland, New Zealand
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Kaushik SS, Cleveland ZI, Cofer GP, Metz G, Beaver D, Nouls J, Kraft M, Auffermann W, Wolber J, McAdams HP, Driehuys B. Diffusion-weighted hyperpolarized 129Xe MRI in healthy volunteers and subjects with chronic obstructive pulmonary disease. Magn Reson Med 2010; 65:1154-65. [PMID: 21413080 DOI: 10.1002/mrm.22697] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 09/13/2010] [Accepted: 10/03/2010] [Indexed: 01/24/2023]
Abstract
Given its greater availability and lower cost, (129) Xe apparent diffusion coefficient (ADC) MRI offers an alternative to (3) He ADC MRI. To demonstrate the feasibility of hyperpolarized (129) Xe ADC MRI, we present results from healthy volunteers (HV), chronic obstructive pulmonary disease (COPD) subjects, and age-matched healthy controls (AMC). The mean parenchymal ADC was 0.036 ± 0.003 cm(2) sec(-1) for HV, 0.043 ± 0.006 cm(2) sec(-1) for AMC, and 0.056 ± 0.008 cm(2) sec(-1) for COPD subjects with emphysema. In healthy individuals, but not the COPD group, ADC decreased significantly in the anterior-posterior direction by ∼ 22% (P = 0.006, AMC; 0.0059, HV), likely because of gravity-induced tissue compression. The COPD group exhibited a significantly larger superior-inferior ADC reduction (∼ 28%) than the healthy groups (∼ 24%) (P = 0.00018, HV; P = 3.45 × 10(-5) , AMC), consistent with smoking-related tissue destruction in the superior lung. Superior-inferior gradients in healthy subjects may result from regional differences in xenon concentration. ADC was significantly correlated with pulmonary function tests (forced expiratory volume in 1 sec, r = -0.77, P = 0.0002; forced expiratory volume in 1 sec/forced vital capacity, r = -0.77, P = 0.0002; diffusing capacity of carbon monoxide in the lung/alveolar volume (V(A) ), r = -0.77, P = 0.0002). In healthy groups, ADC increased with age by 0.0002 cm(2) sec(-1) year(-1) (r = 0.56, P = 0.02). This study shows that (129) Xe ADC MRI is clinically feasible, sufficiently sensitive to distinguish HV from subjects with emphysema, and detects age- and posture-dependent changes.
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Affiliation(s)
- S Sivaram Kaushik
- Department of Radiology, Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina 27710, USA
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Sá RC, Cronin MV, Henderson AC, Holverda S, Theilmann RJ, Arai TJ, Dubowitz DJ, Hopkins SR, Buxton RB, Prisk GK. Vertical distribution of specific ventilation in normal supine humans measured by oxygen-enhanced proton MRI. J Appl Physiol (1985) 2010; 109:1950-9. [PMID: 20930129 DOI: 10.1152/japplphysiol.00220.2010] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Specific ventilation (SV) is the ratio of fresh gas entering a lung region divided by its end-expiratory volume. To quantify the vertical (gravitationally dependent) gradient of SV in eight healthy supine subjects, we implemented a novel proton magnetic resonance imaging (MRI) method. Oxygen is used as a contrast agent, which in solution changes the longitudinal relaxation time (T1) in lung tissue. Thus alterations in the MR signal resulting from the regional rise in O(2) concentration following a sudden change in inspired O(2) reflect SV-lung units with higher SV reach a new equilibrium faster than those with lower SV. We acquired T1-weighted inversion recovery images of a sagittal slice of the supine right lung with a 1.5-T MRI system. Images were voluntarily respiratory gated at functional residual capacity; 20 images were acquired with the subject breathing air and 20 breathing 100% O(2), and this cycle was repeated five times. Expired tidal volume was measured simultaneously. The SV maps presented an average spatial fractal dimension of 1.13 ± 0.03. There was a vertical gradient in SV of 0.029 ± 0.012 cm(-1), with SV being highest in the dependent lung. Dividing the lung vertically into thirds showed a statistically significant difference in SV, with SV of 0.42 ± 0.14 (mean ± SD), 0.29 ± 0.10, and 0.24 ± 0.08 in the dependent, intermediate, and nondependent regions, respectively (all differences, P < 0.05). This vertical gradient in SV is consistent with the known gravitationally induced deformation of the lung resulting in greater lung expansion in the dependent lung with inspiration. This SV imaging technique can be used to quantify regional SV in the lung with proton MRI.
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Affiliation(s)
- Rui Carlos Sá
- Department of Medicine, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0852, USA.
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13
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Appelberg J, Janson C, Lindberg E, Pavlenko T, Hedenstierna G. Lung aeration during sleep in patients with obstructive sleep apnoea. Clin Physiol Funct Imaging 2010; 30:301-7. [PMID: 20497447 DOI: 10.1111/j.1475-097x.2010.00941.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Previous studies have indicated that patients with obstructive sleep apnoea (OSA) have altered ventilation and lung volumes awake and the results suggest that this may be a determinant of severity of desaturations during sleep. However, little is known about regional lung aeration during sleep in patients with OSA. METHODS Twelve patients with OSA were included in the study. Computed tomography was used to study regional lung aeration during wakefulness and sleep. Lung aeration was calculated in ml gas/g lung tissue in four different regions of interest (ROI(1-4)), along the border of the lung from ventral to dorsal. RESULTS Lung aeration in the dorsal (dependent) lung region (ROI(4)) was lower during sleep compared to wakefulness 0.78 +/- 0.19 versus 0.88 +/- 0.19 (mean +/- SD) ml gas/g lung tissue (P = 0.005). Associations were found between awake expiratory reserve volume and change in lung aeration from wakefulness to sleep in ROI(4) (r = -0.69; P = 0.012). In addition, the change in lung aeration in the dorsal region correlated to sleep time (r = 0.69; P = 0.014) but not to time in supine position. The difference in lung aeration between inspiration and expiration (i.e. ventilation), was larger in the ventral lung region when expressed as ml gas per g lung tissue. In two patients it was noted that, during on-going obstructive apnoea, lung aeration tended to be increased rather than decreased. CONCLUSIONS Aeration in the dorsal lung region is reduced during sleep in patients with OSA. The decrease is related to lung volume awake and to sleep time.
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Affiliation(s)
- Jonas Appelberg
- Department of Clinical Physiology, Sundsvall Hospital, Sundsvall, Sweden.
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Harris RS, Winkler T, Musch G, Vidal Melo MF, Schroeder T, Tgavalekos N, Venegas JG. The prone position results in smaller ventilation defects during bronchoconstriction in asthma. J Appl Physiol (1985) 2009; 107:266-74. [PMID: 19443742 DOI: 10.1152/japplphysiol.91386.2008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effect of body posture on regional ventilation during bronchoconstriction is unknown. In five subjects with asthma, we measured spirometry, low-frequency (0.15-Hz) lung elastance, and resistance and regional ventilation by intravenous (13)NN-saline positron emission tomography before and after nebulized methacholine. The subjects were imaged prone on 1 day and supine on another, but on both days the methacholine was delivered while prone. From the residual (13)NN after washout, ventilation defective areas were defined, and their location, volume, ventilation, and fractional gas content relative to the rest of the lung were calculated. Independent of posture, all subjects developed ventilation defective areas. Although ventilation within these areas was similarly reduced in both postures, their volume was smaller in prone than supine (25 vs. 41%, P < 0.05). The geometric center of the ventilation defective areas was gravitationally dependent relative to that of the lung in both postures. Mean lung fractional gas content was greater in the prone position before methacholine and did not increase as much as in the supine position after methacholine. In the prone position at baseline, areas that became ventilation defects had lower gas content than the rest of the lung. In both positions at baseline, there was a gradient of gas content in the vertical direction. In asthma, the size and location of ventilation defects is affected by body position and likely affected by small differences in lung expansion during bronchoconstriction.
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Affiliation(s)
- R Scott Harris
- Department of Medicine, Pulmonary and Critical Care Unit, Bulfinch 148, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
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15
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Petersson J, Rohdin M, Sánchez-Crespo A, Nyrén S, Jacobsson H, Larsson SA, Lindahl SG, Linnarsson D, Neradilek B, Polissar NL, Glenny RW, Mure M. Regional lung blood flow and ventilation in upright humans studied with quantitative SPECT. Respir Physiol Neurobiol 2009; 166:54-60. [DOI: 10.1016/j.resp.2009.01.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Revised: 01/27/2009] [Accepted: 01/30/2009] [Indexed: 10/21/2022]
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Abstract
Prone positioning of patients during anaesthesia is required to provide operative access for a wide variety of surgical procedures. It is associated with predictable changes in physiology but also with a number of complications, and safe use of the prone position requires an understanding of both issues. We have reviewed the development of the prone position and its variants and the physiological changes which occur on prone positioning. The complications associated with this position and the published techniques for various practical procedures in this position will be discussed. The aim of this review is to identify the risks associated with prone positioning and how these risks may be anticipated and minimized.
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Affiliation(s)
- H Edgcombe
- Royal Berkshire NHS Foundation Trust, London Road, Reading RG1 5AN, UK
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17
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Prisk GK, Yamada K, Henderson AC, Arai TJ, Levin DL, Buxton RB, Hopkins SR. Pulmonary perfusion in the prone and supine postures in the normal human lung. J Appl Physiol (1985) 2007; 103:883-94. [PMID: 17569767 PMCID: PMC2399900 DOI: 10.1152/japplphysiol.00292.2007] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Prone posture increases cardiac output and improves pulmonary gas exchange. We hypothesized that, in the supine posture, greater compression of dependent lung limits regional blood flow. To test this, MRI-based measures of regional lung density, MRI arterial spin labeling quantification of pulmonary perfusion, and density-normalized perfusion were made in six healthy subjects. Measurements were made in both the prone and supine posture at functional residual capacity. Data were acquired in three nonoverlapping 15-mm sagittal slices covering most of the right lung: central, middle, and lateral, which were further divided into vertical zones: anterior, intermediate, and posterior. The density of the entire lung was not different between prone and supine, but the increase in lung density in the anterior lung with prone posture was less than the decrease in the posterior lung (change: +0.07 g/cm(3) anterior, -0.11 posterior; P < 0.0001), indicating greater compression of dependent lung in supine posture, principally in the central lung slice (P < 0.0001). Overall, density-normalized perfusion was significantly greater in prone posture (7.9 +/- 3.6 ml.min(-1).g(-1) prone, 5.1 +/- 1.8 supine, a 55% increase; P < 0.05) and showed the largest increase in the posterior lung as it became nondependent (change: +71% posterior, +58% intermediate, +31% anterior; P = 0.08), most marked in the central lung slice (P < 0.05). These data indicate that central posterior portions of the lung are more compressed in the supine posture, likely by the heart and adjacent structures, than are central anterior portions in the prone and that this limits regional perfusion in the supine posture.
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Affiliation(s)
- G Kim Prisk
- Department of Medicine, University of California, San Diego, La Jolla, California 92093-0931, USA.
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von Ungern-Sternberg BS, Hammer J, Frei FJ, Jordi Ritz EM, Schibler A, Erb TO. Prone equals prone? Impact of positioning techniques on respiratory function in anesthetized and paralyzed healthy children. Intensive Care Med 2007; 33:1771-7. [PMID: 17558496 DOI: 10.1007/s00134-007-0670-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2006] [Accepted: 04/19/2007] [Indexed: 10/23/2022]
Abstract
OBJECTIVES Although the prone position is effectively used to improve oxygenation, its impact on functional residual capacity is controversial. Different techniques of body positioning might be an important confounding factor. The aim of this study was to determine the impact of two different prone positioning techniques on functional residual capacity and ventilation distribution in anesthetized, preschool-aged children. DESIGN Functional residual capacity and lung clearance index, a measure of ventilation homogeneity, were calculated using a sulfur-hexafluoride multibreath washout technique. After intubation, measurements were taken in the supine position and, in random order, in the flat prone position and the augmented prone position (gel pads supporting the pelvis and the upper thorax). SETTING Pediatric anesthesia unit of university hospital. PATIENTS AND PARTICIPANTS Thirty preschool children without cardiopulmonary disease undergoing elective surgery. MEASUREMENTS AND RESULTS Mean (range) age was 48.5 (24-80) months, weight 17.2 (10.5-26.9) kg, functional residual capacity (mean +/- SD) 22.9+/- 6.2 ml.kg (-1) in the supine position and 23.3 +/- 5.6 ml.kg (-1) in the flat prone position, while lung clearance indices were 8.1 +/- 2.3 vs. 7.9 +/- 2.3, respectively. In contrast, functional residual capacity increased to 27.6 +/- 6.5 ml.kg (-1) (p< 0.001) in the augmented prone position while at the same time the lung clearance index decreased to 6.7 +/- 0.9 (p< 0.001). CONCLUSIONS Functional residual capacity and ventilation distribution were similar in the supine and flat prone positions, while these parameters improved significantly in the augmented prone position, suggesting that the technique of prone positioning has major implications for pulmonary function.
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Petersson J, Rohdin M, Sánchez-Crespo A, Nyrén S, Jacobsson H, Larsson SA, Lindahl SGE, Linnarsson D, Neradilek B, Polissar NL, Glenny RW, Mure M. Posture primarily affects lung tissue distribution with minor effect on blood flow and ventilation. Respir Physiol Neurobiol 2007; 156:293-303. [PMID: 17169620 DOI: 10.1016/j.resp.2006.11.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 10/13/2006] [Accepted: 11/01/2006] [Indexed: 11/30/2022]
Abstract
We used quantitative single photon emission computed tomography to estimate the proportion of the observed redistribution of blood flow and ventilation that is due to lung tissue shift with a change in posture. Seven healthy volunteers were studied awake, breathing spontaneously. Regional blood flow and ventilation were marked using radiotracers that remain fixed in the lung after administration. The radiotracers were administered in prone or supine at separate occasions, at both occasions followed by imaging in both postures. Images showed greater blood flow and ventilation to regions dependent at the time of imaging, regardless of posture at radiotracer administration. The results suggest that a shift in lung parenchyma has a major influence on the imaged distributions. We conclude that a change from the supine to the prone posture primarily causes a change in the vertical distribution of lung tissue. The effect on the vertical distribution of blood flow and ventilation within the lung parenchyma is much less.
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Affiliation(s)
- Johan Petersson
- Department of Anesthesiology and Intensive Care Medicine, Karolinska University Hospital Solna, 171 76 Stockholm, Sweden.
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Regli A, Habre W, Saudan S, Mamie C, Erb TO, von Ungern-Sternberg BS. Impact of Trendelenburg positioning on functional residual capacity and ventilation homogeneity in anaesthetised children. Anaesthesia 2007; 62:451-5. [PMID: 17448055 DOI: 10.1111/j.1365-2044.2007.05030.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Trendelenburg positioning, a head-down tilt, is routinely used in anaesthesia when inserting a central venous catheter to increase the calibre of the jugular or subclavian veins and to prevent an air embolism. We investigated the impact of Trendelenburg positioning on functional residual capacity and ventilation homogeneity as well as the potential reversibility of these changes by repositioning and/or a recruitment manoeuvre in children with congenital heart disease. Functional residual capacity and ventilation homogeneity were assessed in 20 anaesthetised children between the ages of 3 months and 8 years who required central venous catheterisation before undergoing cardiac surgery. Functional residual capacity was measured (1) in the supine position, (2) in the Trendelenburg position, (3) after repositioning supine and (4) after a recruitment manoeuvre to total lung capacity which was performed by manually elevating the airway pressure to 40 cmH(2)O for ten consecutive breaths. Adopting the Trendelenburg position led to a significant decrease in functional residual capacity (median [range]- 12 (6-21)%) and increase in lung clearance index (12 (2-19)%). Baseline values were not reached after repositioning supine in any patient until after a standardised recruitment manoeuvre was performed.
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Affiliation(s)
- A Regli
- Department of Anaesthesia, Pharmacology and Intensive Care, University Hospitals of Geneva, Geneva, Switzerland
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21
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Anzueto A, Guntapalli K. Adjunctive therapy to mechanical ventilation: surfactant therapy, liquid ventilation, and prone position. Clin Chest Med 2007; 27:637-54; abstract ix. [PMID: 17085252 DOI: 10.1016/j.ccm.2006.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Acute lung injury and acute respiratory distress syndrome are associated with significant morbidity and mortality in critically ill patients. Although lung protective mechanical ventilation is the only therapy shown to reduce mortality and development of organ failure, several biologic pathways have been identified and provided an opportunity for therapeutic interventions. No pharmacologic or adjunctive treatments are available. Clinical studies demonstrated that prone position results in significant and clinically relevant improvement in oxygenation and ventilation, which persist when patients are returned to supine position; the beneficial response is not limited to patients turned early in disease course. Few complications are associated with prone ventilation. Clinical experience suggests that prone ventilation may protect the lung from potential detrimental effects of mechanical ventilation. Further studies are needed.
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Affiliation(s)
- Antonio Anzueto
- University of Texas Health Science Center, San Antonio, TX 78229, USA.
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22
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Krieg S, Alison JA, McCarren B, Cowell S. Position affects distribution of ventilation in the lungs of older people: an experimental study. ACTA ACUST UNITED AC 2007; 53:179-84. [PMID: 17725475 DOI: 10.1016/s0004-9514(07)70025-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
QUESTION What is the effect of sitting and side-lying on the distribution of ventilation during tidal breathing in healthy older people? DESIGN Randomised, within-participant, experimental study. PARTICIPANTS Ten healthy people more than 65 years old. INTERVENTION Tidal breathing during sitting and right side-lying. OUTCOME MEASURES Distribution of ventilation as a percentage of total counts using Technetium-99m Technegas lung ventilation imaging. RESULTS In sitting, the ratio of the distribution of ventilation to apical: middle: basal regions was 1: 3.5: 3.3 in the right lung, and 1: 2.9: 2.3 in the left lung. In right side-lying, 32% (95% CI 22 to 43) more ventilation was distributed to the right lung than to the left lung. The ratio of the distribution of ventilation to apical: middle: basal regions was 1: 2.8: 2.2 in the right lung, and 1: 2.4: 1.9 in the left lung. CONCLUSIONS In both sitting and right side-lying, ventilation was distributed more to the middle than to the basal region, which may be related to age-associated changes in the respiratory system.
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Affiliation(s)
- Sally Krieg
- The University of Sydney, Lidcombe, NSW, 1825, Australia
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Petersson J, Sánchez-Crespo A, Larsson SA, Mure M. Physiological imaging of the lung: single-photon-emission computed tomography (SPECT). J Appl Physiol (1985) 2007; 102:468-76. [PMID: 16990505 DOI: 10.1152/japplphysiol.00732.2006] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Emission tomography provides three-dimensional, quantitative images of the distribution of radiotracers used to mark physiological, metabolic, or pathological processes. Quantitative single photon emission computed tomography (SPECT) requires correction for the image-degrading effects due to photon attenuation and scatter. Phantom experiments have shown that radioactive concentrations can be assessed within some percentage of the true value when relevant corrections are applied. SPECT is widely spread, and radiotracers are available that are easy to use and comparably inexpensive. Compared with other methods, SPECT suffers from a lower spatial resolution, and the time required for image acquisition is longer than for some alternative methods. In contrast to some other methods, SPECT allows simultaneous imaging of more than one process, e.g., both regional blood flow and ventilation, for the whole lung. SPECT has been used to explore the influence of posture and clinical interventions on the spatial distribution of lung blood flow and ventilation. Lung blood flow is typically imaged using macroaggregates of albumin. Both radioactive gases and particulate aerosols labeled with radioactivity have been used for imaging of regional ventilation. However, all radiotracers are not equally suited for quantitative measurements; all have specific advantages and limitations. With SPECT, both blood flow and ventilation can be marked with radiotracers that remain fixed in the lung tissue, which allows tracer administration during conditions different from those at image registration. All SPECT methods have specific features that result from the used radiotracer, the manner in which it is administered, and how images are registered and analyzed.
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Affiliation(s)
- Johan Petersson
- Department of Anesthesiology and Intensive Care, Karolinska University Hospital, Solna, 171 76 Stockholm, Sweden.
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Robertson HT, Kreck TC, Krueger MA. The spatial and temporal heterogeneity of regional ventilation: Comparison of measurements by two high-resolution methods. Respir Physiol Neurobiol 2005; 148:85-95. [PMID: 15964251 DOI: 10.1016/j.resp.2005.05.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2005] [Revised: 05/09/2005] [Accepted: 05/11/2005] [Indexed: 11/22/2022]
Abstract
High-resolution estimates of ventilation distribution in normal animals utilizing deposition of fluorescent microsphere aerosol (FMS technique) demonstrate substantial ventilation heterogeneity, but this finding has not been confirmed by an independent method. Five supine anesthetized sheep were used to compare the spatial and temporal heterogeneity of regional ventilation measured by both the FMS technique and by a ventilation model utilizing the data from computed tomography images of xenon gas washin (CT/Xe technique). An aerosol containing 1 microm fluorescent microspheres (FMS) was administered via a mechanical ventilator delivering a 2-s end-inspiration hold during each breath. Following the aerosol administration, sequential CT images of a transverse lung slice were acquired during each end-inspiration hold during washin of a 65% Xenon/35% oxygen gas mixture (CT/Xe technique). Four paired FMS and CT/Xe measurements were done at 30 min intervals, after which the animals were sacrificed. The lungs were extracted, air-dried and sliced in 1cm transverse sections. The lung section corresponding to the CT image was cut into 1 cm3 cubes, with notation of spatial coordinates. The individual cubes were soaked in solvent and the four fluorescent signals were measured with a fluorescence spectrophotometer. The color signals were normalized by the mean signal for all pieces and taken as the FMS estimate of ventilation heterogeneity. The CT images were clustered into 1 cm3 voxels and the rate of increase in voxel density was used to calculate voxel ventilation utilizing the model of . The regional ventilation voxel measurements were normalized by the mean value to give a CT/Xe estimate of ventilation heterogeneity comparable to the normalized FMS measurements. The overall of heterogeneity of ventilation at the 1 cm3 level of resolution was comparable by both techniques, with substantial differences among animals (coefficient of variation ranging from 37% to 74%). The repeated within-animal measurements by both techniques gave consistent values. Both techniques showed comparable large-scale distribution of regional ventilation in the caudal lobes of the supine animals. There were appreciable differences in the temporal variability of ventilation among animals. This study provides an independent confirmation of the scale-dependent heterogeneity of ventilation described by previous FMS aerosol studies of ventilation heterogeneity.
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Affiliation(s)
- H Thomas Robertson
- University of Washington, Departments of Medicine and Physiology and Biophysics, Box 356522,University Hospital, Seattle, WA 98195-6522, USA.
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25
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Ahlberg NE, Hoppe F, Kelter U, Svensson L. A COMPUTED TOMOGRAPHIC STUDY OF VOLUME AND X-RAY ATTENUATION OF THE LUNGS OF BEAGLES IN VARIOUS BODY POSITIONS. ACTA ACUST UNITED AC 2005. [DOI: 10.1111/j.1740-8261.1985.tb01115.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
The pleural space separating the lung and chest wall of mammals contains a small amount of liquid that lubricates the pleural surfaces during breathing. Recent studies have pointed to a conceptual understanding of the pleural space that is different from the one advocated some 30 years ago in this journal. The fundamental concept is that pleural surface pressure, the result of the opposing recoils of the lung and chest wall, is the major determinant of the pressure in the pleural liquid. Pleural liquid is not in hydrostatic equilibrium because the vertical gradient in pleural liquid pressure, determined by the vertical gradient in pleural surface pressure, does not equal the hydrostatic gradient. As a result, a viscous flow of pleural liquid occurs in the pleural space. Ventilatory and cardiogenic motions serve to redistribute pleural liquid and minimize contact between the pleural surfaces. Pleural liquid is a microvascular filtrate from parietal pleural capillaries in the chest wall. Homeostasis in pleural liquid volume is achieved by an adjustment of the pleural liquid thickness to the filtration rate that is matched by an outflow via lymphatic stomata.
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Affiliation(s)
- Stephen J Lai-Fook
- Center for Biomedical Engineering, Wenner-Gren Research Laboratory, Univ. of Kentucky, Lexington, KY 40506-0070, USA.
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Rohdin M, Petersson J, Mure M, Glenny RW, Lindahl SGE, Linnarsson D. Protective effect of prone posture against hypergravity-induced arterial hypoxaemia in humans. J Physiol 2003; 548:585-91. [PMID: 12598589 PMCID: PMC2342857 DOI: 10.1113/jphysiol.2002.035956] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Patients with acute respiratory distress syndrome have increased lung tissue weight and therefore an increased hydrostatic pressure gradient down the lung. Also, they have a better arterial oxygenation in prone (face down) than in supine (face up) posture. We hypothesized that this effect of the direction of gravity also existed in healthy humans, when increased hydrostatic gradients were induced by hypergravity. Ten healthy subjects were studied in a human centrifuge while exposed to 1 or 5 G in anterio-posterior (supine) or posterio-anterior (prone) direction. We measured blood gases using remote-controlled sampling and gas exchange by mass spectrometry. Hypergravity led to marked impairments of arterial oxygenation in both postures and more so in supine posture. At 5 G, the arterial oxygen saturation was 84.6 +/- 1.2 % (mean +/- S.E.M.) in supine and 89.7 +/- 1.4 % in prone posture (P < 0.001 for supine vs. prone). Ventilation and alveolar PO2 were increased at 5 G and did not differ between postures. The alveolar-to-arterial PO2 difference increased at 5 G to 8.0 +/- 0.2 kPa and 6.6 +/- 0.3 kPa in supine and prone postures (P = 0.003). Arterial oxygenation was less impaired in prone during hypergravity due to a better-preserved alveolo-arterial oxygen transport. We speculate that mammals have developed a cardiopulmonary structure that favours function with the gravitational vector in the posterio-anterior direction.
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Affiliation(s)
- M Rohdin
- Section of Environmental Physiology, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
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28
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Nitz J, Burke B. A study of the facilitation of respiration in myotonic dystrophy. PHYSIOTHERAPY RESEARCH INTERNATIONAL 2003; 7:228-38. [PMID: 12528578 DOI: 10.1002/pri.262] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND AND PURPOSE Dystrophia myotonica or myotonic dystrophy is a progressive neuromuscular disorder in which patients demonstrate an irregular respiratory pattern and are particularly subject to cardiopulmonary compromise. The aim of the present study was to investigate the effects of both proprioceptive neuromuscular facilitation (PNF) and staged basal expansion (SBE) breathing exercises in subjects with myotonic dystrophy in two different positions: high support sitting and left side-lying. METHOD A randomized, double-blind study design was used. Seven non-congenital myotonic dystrophy subjects took part in the study. Six 'treatment' levels were applied to each subject: resting in high support sitting; resting in left side-lying; PNF of deep breathing in high support sitting; PNF of deep breathing in left side-lying; SBE in high support sitting and SBE in left side-lying. The outcome measures employed were arterial oxygen saturation (SpO2) and heart rate, as measured by oximetry and thoraco-abdominal motion (TAM), and respiratory rate, as measured by a pneumograph. RESULTS The PNF technique was found to be the main contributor to improvement in SpO2 for subjects with myotonic dystrophy, where a 2.2% increase was found in the high support sitting position and a 2.6% increase was found in the left side-lying position. There was an increase of between 377% and 556% in TAM during application of both treatment techniques, in either the high support sitting or left side-lying positions. Respiratory rate declined between 15% and 30% immediately after treatment application and heart rate dropped slightly by between 0.2% and 4.1%. CONCLUSION The present study provides objective evidence that application of these respiratory physiotherapy interventions elicits an improvement in respiratory function in subjects with myotonic dystrophy. Further research into the physiological effects of these techniques could explore the mechanisms responsible for improvement in respiratory indices.
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Affiliation(s)
- Jennifer Nitz
- Department of Physiotherapy, School of Health and Rehabilitation Sciences, University of Queensland, Australia
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29
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Musch G, Layfield JDH, Harris RS, Melo MFV, Winkler T, Callahan RJ, Fischman AJ, Venegas JG. Topographical distribution of pulmonary perfusion and ventilation, assessed by PET in supine and prone humans. J Appl Physiol (1985) 2002; 93:1841-51. [PMID: 12381773 DOI: 10.1152/japplphysiol.00223.2002] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Using positron emission tomography (PET) and intravenously injected (13)N(2), we assessed the topographical distribution of pulmonary perfusion (Q) and ventilation (V) in six healthy, spontaneously breathing subjects in the supine and prone position. In this technique, the intrapulmonary distribution of (13)N(2), measured during a short apnea, is proportional to regional Q. After resumption of breathing, regional specific alveolar V (sVA, ventilation per unit of alveolar gas volume) can be calculated from the tracer washout rate. The PET scanner imaged 15 contiguous, 6-mm-thick, slices of lung. Vertical gradients of Q and sVA were computed by linear regression, and spatial heterogeneity was assessed from the squared coefficient of variation (CV(2)). Both CV and CV were corrected for the estimated contribution of random imaging noise. We found that 1) both Q and V had vertical gradients favoring dependent lung regions, 2) vertical gradients were similar in the supine and prone position and explained, on average, 24% of Q heterogeneity and 8% of V heterogeneity, 3) CV was similar in the supine and prone position, and 4) CV was lower in the prone position. We conclude that, in recumbent, spontaneously breathing humans, 1) vertical gradients favoring dependent lung regions explain a significant fraction of heterogeneity, especially of Q, and 2) although Q does not seem to be systematically more homogeneous in the prone position, differences in individual behaviors may make the prone position advantageous, in terms of V-to-Q matching, in selected subjects.
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Affiliation(s)
- Guido Musch
- Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
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Rodríguez-Nieto MJ, Peces-Barba G, González Mangado N, Paiva M, Verbanck S. Similar ventilation distribution in normal subjects prone and supine during tidal breathing. J Appl Physiol (1985) 2002; 92:622-6. [PMID: 11796673 DOI: 10.1152/japplphysiol.00574.2001] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Multiple-breath washout (MBW) tests, with end-expiratory lung volume at functional residual capacity (FRC) and 90% O(2), 5% He, and 5% SF(6) as an inspired gas mixture, were performed in healthy volunteers in supine and prone postures. The semilog plot of MBW N(2) concentrations was evaluated in terms of its curvilinearity. The MBW N(2) normalized slope analysis yielded indexes of acinar and conductive ventilation heterogeneity (Verbanck S, Schuermans D, Van Muylem A, Paiva M, Noppen M, and Vincken W. J App Physiol 83: 1907-1916, 1997). Also, the difference between SF(6) and He normalized phase III slopes was computed in the first MBW expiration. Only MBW tests with similar FRC in the prone and supine postures (P > 0.1; n = 8) were considered. Prone and supine postures did not reveal any significant differences in curvilinearity, N(2) normalized slope-derived indexes of conductive or acinar ventilation heterogeneity, nor SF(6)-He normalized phase III slope difference in the first MBW expiration (P > 0.1 for all). The absence of significant changes in any of the MBW indexes suggests that ventilation heterogeneity is similar in the supine and prone postures of normal subjects breathing near FRC.
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Affiliation(s)
- M J Rodríguez-Nieto
- Laboratorio de Fisiopatología Respiratoria, Fundación Jiménez Díaz, Madrid 28040, Spain
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31
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Chang H, Lai-Fook SJ, Domino KB, Schimmel C, Hildebrandt J, Robertson HT, Glenny RW, Hlastala MP. Spatial distribution of ventilation and perfusion in anesthetized dogs in lateral postures. J Appl Physiol (1985) 2002; 92:745-62. [PMID: 11796689 DOI: 10.1152/japplphysiol.00377.2001] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We aimed to assess the influence of lateral decubitus postures and positive end-expiratory pressure (PEEP) on the regional distribution of ventilation and perfusion. We measured regional ventilation (VA) and regional blood flow (Q) in six anesthetized, mechanically ventilated dogs in the left (LLD) and right lateral decubitus (RLD) postures with and without 10 cmH(2)O PEEP. Q was measured by use of intravenously injected 15-microm fluorescent microspheres, and VA was measured by aerosolized 1-microm fluorescent microspheres. Fluorescence was analyzed in lung pieces approximately 1.7 cm(3) in volume. Multiple linear regression analysis was used to evaluate three-dimensional spatial gradients of Q, VA, the ratio VA/Q, and regional PO(2) (Pr(O(2))) in both lungs. In the LLD posture, a gravity-dependent vertical gradient in Q was observed in both lungs in conjunction with a reduced blood flow and Pr(O(2)) to the dependent left lung. Change from the LLD to the RLD or 10 cmH(2)O PEEP increased local VA/Q and Pr(O(2)) in the left lung and minimized any role of hypoxia. The greatest reduction in individual lung volume occurred to the left lung in the LLD posture. We conclude that lung distortion caused by the weight of the heart and abdomen is greater in the LLD posture and influences both Q and VA, and ultimately gas exchange. In this respect, the smaller left lung was the most susceptible to impaired gas exchange in the LLD posture.
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Affiliation(s)
- Hung Chang
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, USA
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32
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Grönkvist MJ, Emery MJ, Gustafsson PM. Mechanisms of ventilation inhomogeneity during vital capacity breaths standing and supine. RESPIRATION PHYSIOLOGY 2002; 129:345-55. [PMID: 11788137 DOI: 10.1016/s0034-5687(01)00318-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Overall inhomogeneity of ventilation distribution, as measured by single-breath vital capacity (VC) washout (SBW) is known to be greater supine vs. standing. To establish the underlying mechanisms 13 healthy males performed VC SBW of 4% SF(6) and He, standing and supine, with or without a 10 sec breathhold (BH). Overall inhomogeneity, as indicated by normalized phase III slopes, was >50% greater supine (SF(6) 13.1 x 10(-3); He 10.7 x 10(-3) L(-1)) than standing (SF(6) 8.6 x 10(-3); He 6.4 x 10(-3) L(-1); P<0.001). The (SF(6)-He) slope, an index of intraacinar inhomogeneity, did not change with posture. Breathholding, assumed to eliminate convective dependent inhomogeneity within and/or between small lung units, produced twice as great reduction of inhomogeneity when supine vs. standing. After BH inhomogeneity remained significantly greater supine vs. standing. In conclusion, at least two events seem to underlie the increased inhomogeneity when supine: (1) a substantially increased convection dependent non-uniformity between well-separated lung regions; and (2) a somewhat increased convection dependent non-uniformity within and/or between peripherally located lung units.
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Affiliation(s)
- Mikael J Grönkvist
- Department of Defense Medicine, Swedish Defense Research Agency, Man-System-Interaction, P.O. Box 13 400, S-580 13 Linköping, Sweden.
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33
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Abstract
In summary, the many studies done on PPV show that the technique improves oxygenation most of the time. The mechanisms behind this effect are probably numerous and have yet to be elucidated completely. In addition, PPV is a safe procedure that rarely worsens a patient's respiratory status or causes other complications and is thus a welcome additional therapeutic option when treating patients with ARDS. Despite the recent large, randomized, controlled trial showing no improvement in mortality rate or organ dysfunction overall, there is evidence suggesting that PPV may be of most benefit in more severely ill patients. Further studies will be useful.
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Affiliation(s)
- Nicholas S Ward
- Rhode Island Hospital, Brown University School of Medicine, Providence, Rhode Island, USA
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34
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Tucker B, Jenkins S. The effect of breathing exercises with body positioning on regional lung ventilation. THE AUSTRALIAN JOURNAL OF PHYSIOTHERAPY 2001; 42:219-227. [PMID: 11676653 DOI: 10.1016/s0004-9514(14)60389-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
This review discusses the distribution of ventilation in the normal adult lung and includes the influence of quiet and deep breathing on regional ventilation. The effects of breathing at low lung volumes; inspiratory flow rate; posture; age; and body weight on ventilation are also described. A selection of breathing exercises are examined with regard to their ability to influence regional ventilation. There is no evidence that breathing control (diaphragmatic breathing exercises) improves regional ventilation to the dependent zones of the lungs. Limited evidence does suggest that thoracic expansion exercises, whereby respiratory muscles are voluntarily contracted to alter regional chest wall expansion, can improve underlying ventilation. However, there remains a paucity of evidence regarding the effects of breathing exercises on regional ventilation.
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Affiliation(s)
- Beatrice Tucker
- School of Physiotherapy, Curtin University of Technology, Shenton Park, WA, 6008, Australia
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35
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Gustafsson PM, Eiken O, Grönkvist M. Effects of hypergravity and anti-G suit pressure on intraregional ventilation distribution during VC breaths. J Appl Physiol (1985) 2001; 91:637-44. [PMID: 11457775 DOI: 10.1152/jappl.2001.91.2.637] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effects of increased gravity in the head-to-foot direction (+G(z)) and pressurization of an anti-G suit (AGS) on total and intraregional intra-acinar ventilation inhomogeneity were explored in 10 healthy male subjects. They performed vital capacity (VC) single-breath washin/washouts of SF(6) and He in +1, +2, or +3 G(z) in a human centrifuge, with an AGS pressurized to 0, 6, or 12 kPa. The phase III slopes for SF(6) and He over 25-75% of the expired VC were used as markers of total ventilation inhomogeneity, and the (SF(6) -- He) slopes were used as indicators of intraregional intra-acinar inhomogeneity. SF(6) and He phase III slopes increased proportionally with increasing gravity, but the (SF(6) -- He) slopes remained unchanged. AGS pressurization did not change SF(6) or He slopes significantly but resulted in increased (SF(6) -- He) slope differences at 12 kPa. In conclusion, hypergravity increases overall but not intraregional intra-acinar inhomogeneity during VC breaths. AGS pressurization provokes increased intraregional intra-acinar ventilation inhomogeneity, presumably reflecting the consequences of basilar pulmonary vessel engorgement in combination with compression of the basilar lung regions.
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Affiliation(s)
- P M Gustafsson
- Swedish Defense Research Agency, Aviation Medicine, S-580 13 Linköping, Sweden.
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36
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Mure M, Domino KB, Lindahl SG, Hlastala MP, Altemeier WA, Glenny RW. Regional ventilation-perfusion distribution is more uniform in the prone position. J Appl Physiol (1985) 2000; 88:1076-83. [PMID: 10710406 DOI: 10.1152/jappl.2000.88.3.1076] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The arterial blood PO(2) is increased in the prone position in animals and humans because of an improvement in ventilation (VA) and perfusion (Q) matching. However, the mechanism of improved VA/Q is unknown. This experiment measured regional VA/Q heterogeneity and the correlation between VA and Q in supine and prone positions in pigs. Eight ketamine-diazepam-anesthetized, mechanically ventilated pigs were studied in supine and prone positions in random order. Regional VA and Q were measured using fluorescent-labeled aerosols and radioactive-labeled microspheres, respectively. The lungs were dried at total lung capacity and cubed into 603-967 small ( approximately 1.7-cm(3)) pieces. In the prone position the homogeneity of the ventilation distribution increased (P = 0.030) and the correlation between VA and Q increased (correlation coefficient = 0.72 +/- 0.08 and 0.82 +/- 0.06 in supine and prone positions, respectively, P = 0.03). The homogeneity of the VA/Q distribution increased in the prone position (P = 0.028). We conclude that the improvement in VA/Q matching in the prone position is secondary to increased homogeneity of the VA distribution and increased correlation of regional VA and Q.
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Affiliation(s)
- M Mure
- Department of Anesthesiology and Intensive Care, Karolinska Hospital and Institute, SE-171 76 Stockholm, Sweden
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37
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Abstract
Prone positioning to improve oxygenation in acute lung injury was first reported over 20 years ago. Although this and several subsequent studies have shown that prone positioning improved oxygenation in the majority of patients, it has failed to become common practice in intensive care units. This paper reviews the mechanism by which prone positioning improves oxygenation and the clinical studies of its use to date.
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Affiliation(s)
- A Tobin
- Intensive Care, St Vincent's Hospital, Melbourne, Victoria
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38
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Hlastala MP, Chornuk MA, Self DA, Kallas HJ, Burns JW, Bernard S, Polissar NL, Glenny RW. Pulmonary blood flow redistribution by increased gravitational force. J Appl Physiol (1985) 1998; 84:1278-88. [PMID: 9516194 DOI: 10.1152/jappl.1998.84.4.1278] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
This study was undertaken to assess the influence of gravity on the distribution of pulmonary blood flow (PBF) using increased inertial force as a perturbation. PBF was studied in unanesthetized swine exposed to -Gx (dorsal-to-ventral direction, prone position), where G is the magnitude of the force of gravity at the surface of the Earth, on the Armstrong Laboratory Centrifuge at Brooks Air Force Base. PBF was measured using 15-micron fluorescent microspheres, a method with markedly enhanced spatial resolution. Each animal was exposed randomly to -1, -2, and -3 Gx. Pulmonary vascular pressures, cardiac output, heart rate, arterial blood gases, and PBF distribution were measured at each G level. Heterogeneity of PBF distribution as measured by the coefficient of variation of PBF distribution increased from 0.38 +/- 0.05 to 0.55 +/- 0.11 to 0.72 +/- 0.16 at -1, -2, and -3 Gx, respectively. At -1 Gx, PBF was greatest in the ventral and cranial and lowest in the dorsal and caudal regions of the lung. With increased -Gx, this gradient was augmented in both directions. Extrapolation of these values to 0 G predicts a slight dorsal (nondependent) region dominance of PBF and a coefficient of variation of 0.22 in microgravity. Analysis of variance revealed that a fixed component (vascular structure) accounted for 81% and nonstructure components (including gravity) accounted for the remaining 19% of the PBF variance across the entire experiment (all 3 gravitational levels). The results are inconsistent with the predictions of the zone model.
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Affiliation(s)
- M P Hlastala
- Department of Physiology and Biophysics, University of Washington, Seattle 98195, USA
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39
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Affiliation(s)
- N R Webster
- Anaesthesia and Intensive Care, University of Aberdeen, UK
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40
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Treppo S, Mijailovich SM, Venegas JG. Contributions of pulmonary perfusion and ventilation to heterogeneity in V(A)/Q measured by PET. J Appl Physiol (1985) 1997; 82:1163-76. [PMID: 9104853 DOI: 10.1152/jappl.1997.82.4.1163] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
To estimate the contributions of the heterogeneity in regional perfusion (Q) and alveolar ventilation (V A) to that of ventilation-perfusion ratio (V A/Q), we have refined positron emission tomography (PET) techniques to image local distributions of Q and V A per unit of gas volume content (sQ and sV A, respectively) and V A/Q in dogs. sV A was assessed in two ways: 1) the washout of 13NN tracer after equilibration by rebreathing (sV A(i)), and 2) the ratio of an apneic image after a bolus intravenous infusion of 13NN-saline solution to an image collected during a steady-state intravenous infusion of the same solution (sV A(p)). SV A(p) was systematically higher than sV A(i) in all animals, and there was a high spatial correlation between sQ and sV A(p) in both body positions (mean correlation was 0.69 prone and 0.81 supine) suggesting that ventilation to well-perfused units was higher than to those poorly perfused. In the prone position, the spatial distributions of sQ, sV A(p), and V A/Q were fairly uniform with no significant gravitational gradients; however, in the supine position, these variables were significantly more heterogeneous, mostly because of significant gravitational gradients (15, 5.5, and -10%/cm, respectively) accounting for 73, 33, and 66% of the corresponding coefficient of variation (CV)2 values. We conclude that, in the prone position, gravitational forces in blood and lung tissues are largely balanced out by dorsoventral differences in lung structure. In the supine position, effects of gravity and structure become additive, resulting in substantial gravitational gradients in sQ and sV A(p), with the higher heterogeneity in V A/Q caused by a gravitational gradient in sQ, only partially compensated by that in sV A.
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Affiliation(s)
- S Treppo
- Department of Anesthesia, Massachusetts General Hospital, and Harvard Medical School, Boston 02114, USA
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41
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Morrell NW, Nijran KS, Biggs T, Seed WA. Magnitude and time course of acute hypoxic pulmonary vasoconstriction in man. RESPIRATION PHYSIOLOGY 1995; 100:271-81. [PMID: 7481117 DOI: 10.1016/0034-5687(95)00002-u] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Acute hypoxic pulmonary vasoconstriction has an established role in the preservation of ventilation-perfusion balance. To further characterize this homeostatic response in man we have attempted to measure both the time course and magnitude of blood flow diversion from single hypoxic lobes. Lobar hypoxia (mean PO2 38 +/- 1.5(SEM)mmHg, mean PCO2 39.9 +/- 0.9 mmHg) was induced by inflating catheter-tip balloons in left upper lobe bronchi during fibreoptic bronchoscopy under local anaesthesia in 8 normal subjects. An index of lobar blood flow was obtained by acquiring dynamic scintigraphic lung images during a continuous intravenous infusion of the short-lived radioisotope krypton-81m dissolved in 5% glucose solution. In 3 subjects blood flow to the occluded lobes was monitored while the lobes were maintained under hyperoxic conditions (mean PO2 127.8 +/- 31.5 mmHg, mean PCO2 40.2 +/- 1.3 mmHg). Under hypoxic conditions the blood flow to the occluded lobes fell to 53% of baseline after 5 min with a mean time constant of 151 +/- 24.8 sec. Under hyperoxic conditions there was no significant change from baseline blood flow. We conclude that this technique has allowed us to monitor both the dynamic and steady state responses of the pulmonary circulation to lobar hypoxia in man.
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Affiliation(s)
- N W Morrell
- Department of Medicine, Charing Cross and Westminster Medical School, Charing Cross Hospital, London, UK
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42
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Abstract
Recordings were made from phrenic, abdominal and intercostal nerves following electrical stimulation of the vestibular nerve to test for the presence of vestibulo-respiratory connections in cats that were decerebrate, paralyzed, and artificially ventilated. Short stimulus trains (2 or 3 shocks) at intensities < or = 125 microA typically elicited responses bilaterally in all of the respiratory nerves; the onset latency of the evoked activity was < 15 ms from the effective shock. The mean peak-to-peak amplitudes of integrated vestibulo-respiratory responses were 15% of the average amplitude of spontaneous respiratory-related discharges in the case of the phrenic nerve and 100% in the case of the abdominal nerve. The vestibulo-respiratory reflexes, as well as vestibulo-sympathetic responses recorded from the splanchnic nerve, could be abolished by injections of the excitotoxin kainic acid confined primarily to the medial and adjacent inferior vestibular nuclei. The physiological role of vestibulo-respiratory connections is yet to be determined, but possible functions include adjustments of respiration during changes in posture, assistance in venous return to the heart during movements that might lead to orthostatic hypotension, and direct participation in the execution of specific movements and the maintenance of some postures.
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Affiliation(s)
- B J Yates
- Laboratory of Neurophysiology, Rockefeller University, New York, NY 10021
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43
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Uren NG, Davies SW, Agnew JE, Irwin AG, Jordan SL, Hilson AJ, Lipkin DP. Reduction of mismatch of global ventilation and perfusion on exercise is related to exercise capacity in chronic heart failure. BRITISH HEART JOURNAL 1993; 70:241-6. [PMID: 8398494 PMCID: PMC1025303 DOI: 10.1136/hrt.70.3.241] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
BACKGROUND The inability to match lung perfusion to ventilation because of a reduced cardiac output on exercise contributes to reduced exercise capacity in chronic heart failure. OBJECTIVE To quantify ventilation to perfusion matching at rest and at peak exercise in patients with chronic heart failure and relate this to haemodynamic and ventilatory variables of exercise capacity. DESIGN Eight men in New York Heart Association class II underwent maximal bicycle ergometry with expired gas analysis. MAIN OUTCOME MEASURES On separate days, ventilation and perfusion gamma camera imaging was performed at rest, and at 80% of previous peak exercise heart rate during bicycle ergometry. The vertical distribution of mismatch between ventilation and perfusion (V/Q) was estimated from subtracted profiles of activity (ventilation and perfusion) to derive a numerical index of global mismatch. RESULTS Maximal mean (SD) oxygen consumption on bicycle ergometry was 16.0 (4.5) ml min-1 kg-1. There was a reduction in the global V/Q mismatch index from 23.96 (5.90) to 14.88 (7.90) units (p < 0.01) at rest and at peak exercise. Global V/Q mismatch index at peak exercise correlated negatively with maximal minute ventilation (R = -0.90, p < 0.01) and with maximal mean arterial pressure (R = -0.79, p < 0.05), although no relation was seen with maximal oxygen consumption. The reduction in global V/Q mismatch index from rest to peak exercise correlated with maximal oxygen consumption (R = 0.88, p < 0.01), and with maximal minute ventilation (R = 0.87, p < 0.01). CONCLUSIONS During exercise in patients with chronic heart failure, there is a reduction in the global V/Q mismatch index. A lower global V/Q mismatch index at peak exercise is associated with higher maximal ventilation. The reduction in global V/Q mismatch index on exercise correlates well with maximal exercise capacity. This may imply that the inability to perfuse adequately all regions of lung on exercise and match this to ventilation is a factor determining exercise capacity in chronic heart failure.
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Affiliation(s)
- N G Uren
- Department of Cardiology, Royal Free Hospital, London
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44
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Abstract
We describe positional changes in oxygenation in two patients with respiratory failure due to massive pulmonary embolism. In both patients, oxygenation improved when the "sick" lung was dependent and deteriorated when the "healthy" lung was in the dependent position. These positional changes are different from previously reported changes in unilateral pulmonary disease. We speculate that a combination of unilateral pulmonary embolism and mechanical ventilation was responsible for the improvement in gas exchange when the "sick" lung was placed in the dependent position. The relative contribution of these two components to the development of this phenomenon is unclear.
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Affiliation(s)
- M S Badr
- Pulmonary Section, University of Wisconsin Hospitals and Clinics, Madison
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45
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O'Doherty MJ, Thomas SH, Page CJ, Bradbeer C, Nunan TO, Bateman NT. Does inhalation of pentamidine in the supine position increase deposition in the upper part of the lung? Chest 1990; 97:1343-8. [PMID: 2347219 DOI: 10.1378/chest.97.6.1343] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
To assess the effect of posture on the distribution of nebulized pentamidine isethionate deposition in the lung, ten patients with AIDS were studied. Two nebulizer systems, System 22 Mizer (MedicAid) and Respirgard II (Marquest) were modified by adding 40 cm of corrugated tubing (volume 150 ml) to allow the patients to be studied in both the sitting and supine posture. Modification of the nebulizers caused a reduction in lung deposition in the sitting position for the System 22 Mizer but increased deposition in the Respirgard II compared with the unmodified apparatus. The ratio of upper to lower zone deposition (corrected for 133Xe distribution) was increased in the supine position for both devices (p less than 0.01). The best upper zone deposition was achieved with the unmodified System 22 Mizer in the sitting position. Respirgard II had the lowest nonpulmonary deposition and the lowest incidence of adverse effects. The supine position was associated with a redistribution of deposition to the upper zones. To attempt to reduce upper zone recurrence of Pneumocystis carinii pneumonia, the supine posture is suggested for less efficient nebulizer devices, ie, the Respirgard II, but for more efficient systems, ie, System 22 Mizer, the sitting position is probably suitable. This postulate needs to be confirmed by a clinical trial.
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Affiliation(s)
- M J O'Doherty
- Department of Nuclear Medicine, Rayne Institute, St. Thomas' Hospital, London, England
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46
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Lung compression: a mechanism for orthopnoea? Lancet 1990; 335:1069. [PMID: 1970376 DOI: 10.1016/0140-6736(90)92639-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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47
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Vassilyadi M, Michel RP. Effect of methylprednisolone on nitrogen dioxide (NO2)-induced pulmonary edema in guinea pigs. Toxicol Appl Pharmacol 1989; 97:256-66. [PMID: 2493689 DOI: 10.1016/0041-008x(89)90330-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The treatment of nitrogen dioxide (NO2)-induced lung edema is controversial. In addition, mechanisms and patterns of interstitial edema formation in this form of increased permeability edema are unclear. To ascertain if methylprednisolone (MP) is effective in the therapy of NO2-induced edema, we exposed 108 unaesthetized guinea pigs, in groups of 12, to 277-448 ppm.hr NO2: in 60, we administered MP just before, and in 48 immediately after exposure. In each group, half the animals were randomly assigned to receive 30 mg/kg MP ip, and the other half saline. Mortality rates and lung water with wet weight/dry weight (W/D) ratios were calculated. Alveolar edema, periarterial interstitial edema, and NO2-induced bronchiolitis were graded semiquantitatively by light microscopy from freeze-substituted middle (ML) and lower lobes (LL). We found NO2 produced an exposure-dependent increase in lung water (R = 0.70, p less than 0.01). Treatment with MP preexposure produced a fourfold reduction mortality, and and a significant fall in W/D ratios and in alveolar and interstitial edema. No difference in the degree of acute bronchiolitis was found between treated and untreated animals, although ML had significantly more inflammation than LL. Treatment with MP immediately after NO2 was ineffective since mortality rates, W/D ratios, and alveolar and interstitial edema were not lower in the treated animals; there was significantly more intestitial edema in the middle lobes of the latter. Both LL and ML had equally abundant alveolar edema, but LL had significantly more interstitial edema, supporting our previous findings that in NO2-induced edema interstitial fluid accumulation follows alveolar flooding, with interlobar discrepancies probably due to differences in lung volume or in ventilation.
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Affiliation(s)
- M Vassilyadi
- Lyman Duff Laboratories, Department of Pathology, McGill University Montréal, Québec, Canada
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48
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Orphanidou D, Hughes JM, Myers MJ, Al-Suhali AR, Henderson B. Tomography of regional ventilation and perfusion using krypton 81m in normal subjects and asthmatic patients. Thorax 1986; 41:542-51. [PMID: 3491441 PMCID: PMC460388 DOI: 10.1136/thx.41.7.542] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Single photon emission computed tomography, a rotating gamma camera, and continuous inhalation or infusion of krypton 81m (half life 13 seconds) were used to measure regional ventilation (V), perfusion (Q), and ventilation-perfusion (V/Q) ratios in five normal subjects in supine, prone, and lateral decubitus postures and in three asthmatic patients (supine posture only) before and after inhalation of 2.5 mg nebulised salbutamol. Vertical and horizontal gradients of V, Q, and V/Q were examined at three levels in each lung in regions of 1.9 cm3 size. In normal subjects V and Q increased along the axis of gravity in all postures and at all levels in the lung except for V in the prone position. Smaller horizontal gradients were found with an increase in V and Q from caudal to cranial--again except in the prone posture, where the gradient was slightly reversed. Constraint to outward motion of the ventral chest and abdominal wall is the most likely explanation for the different behaviour in the prone posture. In chronic asthma the vertical gradients of V and V/Q were the reverse of normal, but the Q gradient was normal. Bronchodilator treatment did not affect the vertical or horizontal gradients significantly, but analysis of individual regions showed that, relatively, V/Q worsened in 42% of them; this was associated in two thirds with an increase in fractional Q. After inhalation of beta agonist local vasodilatation may influence V/Q ratios in some units more than bronchodilatation.
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49
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Hughes JM. Regional lung function: physiology and clinical applications. CLINICAL PHYSIOLOGY (OXFORD, ENGLAND) 1985; 5 Suppl 3:19-31. [PMID: 3995885 DOI: 10.1111/j.1475-097x.1985.tb00598.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The current status of tests of regional lung function has been reviewed from the physiological and clinical standpoint. Recent technical innovations include the use of single photon and positron emission computerized tomography (SPECT and PET). For PET work, neon-19 (t 1/2 17 sec) has been introduced as a ventilation tracer, and fluorine-18 deoxyglucose as a marker of glucose metabolism. Indium-111 labelled neutrophils have been studied. Physiological measurements of the distribution of blood flow and ventilation are concentrating on non-gravitational influences such as the pattern of force generation by the respiratory muscles and vasomotor tone. Ventilation and perfusion imaging of the lung with the gamma camera has established itself as an essential screening test for the diagnosis of pulmonary embolic disease. Inhalation of a radio-labelled aerosol of small particle size (1 micron) may be an acceptable substitute for a radioactive gas ventilation scan. Mucociliary clearance has been investigated with radionuclide techniques. Measurements of regional lung water have been replaced by tracers sensitive to alterations of epithelial (inhaled 99Tcm-DTPA) or endothelial (i.v. 113Inm-transferrin) permeability. New techniques using positron emission tomography, such as measurements of extravascular lung density, regional ventilation (19Ne) and regional glucose metabolism (18F-deoxyglucose) have been discussed briefly.
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50
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Amis TC, Jones HA, Hughes JM. Effect of posture on inter-regional distribution of pulmonary perfusion and VA/Q ratios in man. RESPIRATION PHYSIOLOGY 1984; 56:169-82. [PMID: 6463424 DOI: 10.1016/0034-5687(84)90101-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Using a gamma camera regional pulmonary perfusion per unit alveolar volume (Q/VA) and ventilation-perfusion ratios (VA/Q) were measured in fourteen normal male volunteers in upright, supine, lateral decubitus, prone and prone suspended postures with inhalation and intravenous infusion of radioactive 81Krm (half-life 13 sec) and inhalation of radioactive 85Krm (half-life 4.4 h). In the vertical axis, Q/VA increased from upper to lower lung regions in upright, lateral decubitus, prone and prone suspended postures but was uniform in supine and within the dependent lung in decubitus postures. Horizontally, Q/VA decreased from cranial to caudal in lateral decubitus, prone suspended, and near the diaphragm in supine. Vertically, VA/Q decreased from upper to lower in all postures except in supine and within the dependent decubitus lung where it increased. VA/Q tended to increase from cranial to caudal in horizontal postures. The effects of gravity on Q/VA and VA/Q vertical distributions are modified when FRC is low (supine, lower decubitus lung) because perfusion is more uniformly distributed. Horizontal gradients of Q/VA and VA/Q are more pronounced under conditions of high local lung volume but also occur in postures where FRC is low.
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