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Roth CJ, Yoshihara L, Wall WA. A simplified parametrised model for lung microstructures capable of mimicking realistic geometrical and mechanical properties. Comput Biol Med 2017; 89:104-114. [PMID: 28800439 DOI: 10.1016/j.compbiomed.2017.07.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 07/27/2017] [Accepted: 07/28/2017] [Indexed: 11/16/2022]
Abstract
The respiratory zone of mammalian lungs contains several millions of so-called alveoli. The geometrical and mechanical properties of this microstructure are crucial for respiration and influence the macroscopic behaviour of the entire organ in health and disease. Hence, if computational models are sought to gain more insight into lung behaviour, predict lung states in certain scenarios or suggest better treatment options in early stages of respiratory dysfunction, an adequate representation of this microstructure is essential. However, investigating the real alveolar architecture requires complex medical-imaging methods and would be computationally extremely expensive. Even worse, there is currently no way of obtaining the real patient-specific microstructure in vivo. Hence, we present a fast and easy to compute parametrised model of lung microstructures based on tetrakaidecahedra which can represent both geometrical and mechanical properties of the parenchyma. We show that gas transport pathways and stress and strain distributions are comparable to real alveolar microstructures and even capable of capturing variations present in biology. The created parametrised lung microstructure models can be utilized in finite element simulations to study, e.g., alveolar flow phenomena, particle deposition, or alveolar stresses and strains during mechanical ventilation. Due to the simpler geometry of the parametrised microgeometries compared to imaging-based microstructures, remarkable savings in CPU time can be achieved. We show that our model requires a minimum of 10% of the computational time for computing the same strain state in structural mechanics simulations compared to imaging-based alveolar microstructures.
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Affiliation(s)
- Christian J Roth
- Institute for Computational Mechanics, Technical University of Munich, Boltzmannstrasse 15, 85748, Garching b. München, Germany
| | - Lena Yoshihara
- Institute for Computational Mechanics, Technical University of Munich, Boltzmannstrasse 15, 85748, Garching b. München, Germany.
| | - Wolfgang A Wall
- Institute for Computational Mechanics, Technical University of Munich, Boltzmannstrasse 15, 85748, Garching b. München, Germany
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Loring SH, Topulos GP, Hubmayr RD. Transpulmonary Pressure: The Importance of Precise Definitions and Limiting Assumptions. Am J Respir Crit Care Med 2017; 194:1452-1457. [PMID: 27606837 DOI: 10.1164/rccm.201512-2448cp] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Recent studies applying the principles of respiratory mechanics to respiratory disease have used inconsistent and mutually exclusive definitions of the term "transpulmonary pressure." By the traditional definition, transpulmonary pressure is the pressure across the whole lung, including the intrapulmonary airways, (i.e., the pressure difference between the opening to the pulmonary airway and the pleural surface). However, more recently transpulmonary pressure has also been defined as the pressure across only the lung tissue (i.e., the pressure difference between the alveolar space and the pleural surface), traditionally known as the "elastic recoil pressure of the lung." Multiple definitions of the same term, and failure to recognize their underlying assumptions, have led to different interpretations of lung physiology and conclusions about appropriate therapy for patients. It is our view that many current controversies in the physiological interpretation of disease are caused by the lack of consistency in the definitions of these common physiological terms. In this article, we discuss the historical uses of these terms and recent misconceptions that may have resulted when these terms were confused. These misconceptions include assertions that normal pleural pressure must be negative (subatmospheric) and that a pressure in the pleural space may not be substantially positive when a subject is relaxed with an open airway. We urge specificity and uniformity when using physiological terms to define the physical state of the lungs, the chest wall, and the integrated respiratory system.
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Affiliation(s)
- Stephen H Loring
- 1 Department of Anesthesia, Critical Care, and Pain Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts
| | - George P Topulos
- 2 Department of Anesthesia, Perioperative and Pain Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts; and
| | - Rolf D Hubmayr
- 3 Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minnesota
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Narendra DK, Hess DR, Sessler CN, Belete HM, Guntupalli KK, Khusid F, Carpati CM, Astiz ME, Raoof S. Update in Management of Severe Hypoxemic Respiratory Failure. Chest 2017; 152:867-879. [PMID: 28716645 DOI: 10.1016/j.chest.2017.06.039] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Revised: 06/17/2017] [Accepted: 06/25/2017] [Indexed: 02/07/2023] Open
Abstract
Mortality related to severe-moderate and severe ARDS remains high. We searched the literature to update this topic. We defined severe hypoxemic respiratory failure as Pao2/Fio2 < 150 mm Hg (ie, severe-moderate and severe ARDS). For these patients, we support setting the ventilator to a tidal volume of 4 to 8 mL/kg predicted body weight (PBW), with plateau pressure (Pplat) ≤ 30 cm H2O, and initial positive end-expiratory pressure (PEEP) of 10 to 12 cm H2O. To promote alveolar recruitment, we propose increasing PEEP in increments of 2 to 3 cm provided that Pplat remains ≤ 30 cm H2O and driving pressure does not increase. A fluid-restricted strategy is recommended, and nonrespiratory causes of hypoxemia should be considered. For patients who remain hypoxemic after PEEP optimization, neuromuscular blockade and prone positioning should be considered. Profound refractory hypoxemia (Pao2/Fio2 < 80 mm Hg) after PEEP titration is an indication to consider extracorporeal life support. This may necessitate early transfer to a center with expertise in these techniques. Inhaled vasodilators and nontraditional ventilator modes may improve oxygenation, but evidence for improved outcomes is weak.
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Affiliation(s)
- Dharani Kumari Narendra
- Section of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Baylor College of Medicine, Houston, TX
| | - Dean R Hess
- Massachusetts General Hospital and Harvard Medical School, Boston, MA
| | - Curtis N Sessler
- Division of Pulmonary Diseases and Critical Care Medicine, Virginia Commonwealth University Health System, Richmond, VA
| | - Habtamu M Belete
- Department of Medicine, Lenox Hill and Northwell Hofstra School of Medicine, New York, NY
| | - Kalpalatha K Guntupalli
- Section of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Baylor College of Medicine, Houston, TX
| | - Felix Khusid
- Respiratory Therapy and Pulmonary Physiology Center, New York Presbyterian Brooklyn Methodist Hospital, Brooklyn, NY
| | | | - Mark Elton Astiz
- Departments of Internal Medicine and Critical Care Medicine, Lenox Hill Hospital, New York, NY
| | - Suhail Raoof
- Division of Pulmonary Medicine, Lenox Hill Hospital, and Hofstra Northwell School of Medicine, New York, NY.
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Xie J, Jin F, Pan C, Liu S, Liu L, Xu J, Yang Y, Qiu H. The effects of low tidal ventilation on lung strain correlate with respiratory system compliance. Crit Care 2017; 21:23. [PMID: 28159013 PMCID: PMC5291981 DOI: 10.1186/s13054-017-1600-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Accepted: 01/04/2017] [Indexed: 02/23/2023] Open
Abstract
BACKGROUND The effect of alterations in tidal volume on mortality of acute respiratory distress syndrome (ARDS) is determined by respiratory system compliance. We aimed to investigate the effects of different tidal volumes on lung strain in ARDS patients who had various levels of respiratory system compliance. METHODS Nineteen patients were divided into high (Chigh group) and low (Clow group) respiratory system compliance groups based on their respiratory system compliance values. We defined compliance ≥0.6 ml/(cmH2O/kg) as Chigh and compliance <0.6 ml/(cmH2O/kg) as Clow. End-expiratory lung volumes (EELV) at various tidal volumes were measured by nitrogen wash-in/washout. Lung strain was calculated as the ratio between tidal volume and EELV. The primary outcome was that lung strain is a function of tidal volume in patients with various levels of respiratory system compliance. RESULTS The mean baseline EELV, strain and respiratory system compliance values were 1873 ml, 0.31 and 0.65 ml/(cmH2O/kg), respectively; differences in all of these parameters were statistically significant between the two groups. For all participants, a positive correlation was found between the respiratory system compliance and EELV (R = 0.488, p = 0.034). Driving pressure and strain increased together as the tidal volume increased from 6 ml/kg predicted body weight (PBW) to 12 ml/kg PBW. Compared to the Chigh ARDS patients, the driving pressure was significantly higher in the Clow patients at each tidal volume. Similar effects of lung strain were found for tidal volumes of 6 and 8 ml/kg PBW. The "lung injury" limits for driving pressure and lung strain were much easier to exceed with increases in the tidal volume in Clow patients. CONCLUSIONS Respiratory system compliance affected the relationships between tidal volume and driving pressure and lung strain in ARDS patients. These results showed that increasing tidal volume induced lung injury more easily in patients with low respiratory system compliance. TRIAL REGISTRATION Clinicaltrials.gov identifier NCT01864668 , Registered 21 May 2013.
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Affiliation(s)
- Jianfeng Xie
- Department of Critical Care Medicine, Nanjing ZhongDa Hospital, School of Medicine, Southeast University, 87 Dingjiaqiao Road, Gulou District, Nanjing, Jiangsu 210009 China
| | - Fang Jin
- Department of Critical Care Medicine, Nanjing ZhongDa Hospital, School of Medicine, Southeast University, 87 Dingjiaqiao Road, Gulou District, Nanjing, Jiangsu 210009 China
| | - Chun Pan
- Department of Critical Care Medicine, Nanjing ZhongDa Hospital, School of Medicine, Southeast University, 87 Dingjiaqiao Road, Gulou District, Nanjing, Jiangsu 210009 China
| | - Songqiao Liu
- Department of Critical Care Medicine, Nanjing ZhongDa Hospital, School of Medicine, Southeast University, 87 Dingjiaqiao Road, Gulou District, Nanjing, Jiangsu 210009 China
| | - Ling Liu
- Department of Critical Care Medicine, Nanjing ZhongDa Hospital, School of Medicine, Southeast University, 87 Dingjiaqiao Road, Gulou District, Nanjing, Jiangsu 210009 China
| | - Jingyuan Xu
- Department of Critical Care Medicine, Nanjing ZhongDa Hospital, School of Medicine, Southeast University, 87 Dingjiaqiao Road, Gulou District, Nanjing, Jiangsu 210009 China
| | - Yi Yang
- Department of Critical Care Medicine, Nanjing ZhongDa Hospital, School of Medicine, Southeast University, 87 Dingjiaqiao Road, Gulou District, Nanjing, Jiangsu 210009 China
| | - Haibo Qiu
- Department of Critical Care Medicine, Nanjing ZhongDa Hospital, School of Medicine, Southeast University, 87 Dingjiaqiao Road, Gulou District, Nanjing, Jiangsu 210009 China
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Abstract
Ventilator-induced lung injury (VILI) results from mechanical disruption of blood-gas barrier and consequent edema and releases of inflammatory mediators. A transpulmonary pressure (PL) of 17 cmH2O increases baby lung volume to its anatomical limit, predisposing to VILI. Viscoelastic property of lung makes pulmonary mechanics time dependent so that stress (PL) increases with respiratory rate. Alveolar inhomogeneity in acute respiratory distress syndrome acts as a stress riser, multiplying global stress at regional level experienced by baby lung. Limitation of stress (PL) rather than strain (tidal volume [VT]) is the safe strategy of mechanical ventilation to prevent VILI. Driving pressure is the noninvasive surrogate of lung strain, but its relations to PL is dependent on the chest wall compliance. Determinants of lung stress (VT, driving pressure, positive end-expiratory pressure, and inspiratory flow) can be quantified in terms of mechanical power, and a safe threshold can be determined, which can be used in decision-making between safe mechanical ventilation and extracorporeal lung support.
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Affiliation(s)
- Ubaidur Rahaman
- Department of Critical Care Medicine, King Saud Medical City, Riyadh, Saudi Arabia
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56
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Current Concepts of ARDS: A Narrative Review. Int J Mol Sci 2016; 18:ijms18010064. [PMID: 28036088 PMCID: PMC5297699 DOI: 10.3390/ijms18010064] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 12/18/2016] [Accepted: 12/23/2016] [Indexed: 01/20/2023] Open
Abstract
Acute respiratory distress syndrome (ARDS) is characterized by the acute onset of pulmonary edema of non-cardiogenic origin, along with bilateral pulmonary infiltrates and reduction in respiratory system compliance. The hallmark of the syndrome is refractory hypoxemia. Despite its first description dates back in the late 1970s, a new definition has recently been proposed. However, the definition remains based on clinical characteristic. In the present review, the diagnostic workup and the pathophysiology of the syndrome will be presented. Therapeutic approaches to ARDS, including lung protective ventilation, prone positioning, neuromuscular blockade, inhaled vasodilators, corticosteroids and recruitment manoeuvres will be reviewed. We will underline how a holistic framework of respiratory and hemodynamic support should be provided to patients with ARDS, aiming to ensure adequate gas exchange by promoting lung recruitment while minimizing the risk of ventilator-induced lung injury. To do so, lung recruitability should be considered, as well as the avoidance of lung overstress by monitoring transpulmonary pressure or airway driving pressure. In the most severe cases, neuromuscular blockade, prone positioning, and extra-corporeal life support (alone or in combination) should be taken into account.
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57
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Henderson WR, Molgat-Seon Y, Vos W, Lipson R, Ferreira F, Kirby M, Holsbeke CV, Dominelli PB, Griesdale DEG, Sekhon M, Coxson HO, Mayo J, Sheel AW. Functional respiratory imaging, regional strain, and expiratory time constants at three levels of positive end expiratory pressure in an ex vivo pig model. Physiol Rep 2016; 4:e13059. [PMID: 27923979 PMCID: PMC5357821 DOI: 10.14814/phy2.13059] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 10/28/2016] [Accepted: 11/05/2016] [Indexed: 12/24/2022] Open
Abstract
Heterogeneity in regional end expiratory lung volume (EELV) may lead to variations in regional strain (ε). High ε levels have been associated with ventilator-associated lung injury (VALI). While both whole lung and regional EELV may be affected by changes in positive end-expiratory pressure (PEEP), regional variations are not revealed by conventional respiratory system measurements. Differential rates of deflation of adjacent lung units due to regional variation in expiratory time constants (τE) may create localized regions of ε that are significantly greater than implied by whole lung measures. We used functional respiratory imaging (FRI) in an ex vivo porcine lung model to: (i) demonstrate that computed tomography (CT)-based imaging studies can be used to assess global and regional values of ε and τE and, (ii) demonstrate that the manipulation of PEEP will cause measurable changes in total and regional ε and τE values. Our study provides three insights into lung mechanics. First, image-based measurements reveal egional variation that cannot be detected by traditional methods such as spirometry. Second, the manipulation of PEEP causes global and regional changes in R, E, ε and τE values. Finally, regional ε and τE were correlated in several lobes, suggesting the possibility that regional τE could be used as a surrogate marker for regional ε.
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Affiliation(s)
- William R Henderson
- Division of Critical Care Medicine, Vancouver General Hospital, Vancouver, British Columbia, Canada
| | | | | | | | | | - Miranda Kirby
- Radiology, The University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Paolo B Dominelli
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Donald E G Griesdale
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Mypinder Sekhon
- Division of Critical Care Medicine Vancouver General Hospital, Vancouver, British Columbia, Canada
| | - Harvey O Coxson
- Centre for Heart Lung Innovation St Paul's Hospital University of British Columbia, Vancouver, British Columbia, Canada
| | - John Mayo
- Department of Radiology Vancouver General Hospital University of British Columbia, Vancouver, British Columbia, Canada
| | - A William Sheel
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
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58
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Henderson WR, Dominelli PB, Molgat-Seon Y, Lipson R, Griesdale DEG, Sekhon M, Ayas N, Sheel AW. Effect of tidal volume and positive end-expiratory pressure on expiratory time constants in experimental lung injury. Physiol Rep 2016; 4:4/5/e12737. [PMID: 26997633 PMCID: PMC4823592 DOI: 10.14814/phy2.12737] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
We utilized a multicompartment model to describe the effects of changes in tidal volume (VT) and positive end‐expiratory pressure (PEEP) on lung emptying during passive deflation before and after experimental lung injury. Expiratory time constants (τE) were determined by partitioning the expiratory flow–volume (V˙EV) curve into multiple discrete segments and individually calculating τE for each segment. Under all conditions of PEEP and VT, τE increased throughout expiration both before and after injury. Segmented τE values increased throughout expiration with a slope that was different than zero (P < 0. 01). On average, τE increased by 45.08 msec per segment. When an interaction between injury status and τE segment was included in the model, it was significant (P < 0.05), indicating that later segments had higher τE values post injury than early τE segments. Higher PEEP and VT values were associated with higher τE values. No evidence was found for an interaction between injury status and VT, or PEEP. The current experiment confirms previous observations that τE values are smaller in subjects with injured lungs when compared to controls. We are the first to demonstrate changes in the pattern of τE before and after injury when examined with a multiple compartment model. Finally, increases in PEEP or VT increased τE throughout expiration, but did not appear to have effects that differed between the uninjured and injured state.
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Affiliation(s)
- William R Henderson
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Paolo B Dominelli
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Yannick Molgat-Seon
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Donald E G Griesdale
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada Department of Anesthesiology, Pharmacology & Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Mypinder Sekhon
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Najib Ayas
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - A William Sheel
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
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Henderson WR, Molgat-Seon Y, Dominelli PB, Brasher PMA, Griesdale DEG, Foster GE, Yacyshyn A, Ayas NT, Sheel AW. Gas density alters expiratory time constants before and after experimental lung injury. Exp Physiol 2016; 100:1217-28. [PMID: 26289254 DOI: 10.1113/ep085205] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 08/17/2015] [Indexed: 01/10/2023]
Abstract
NEW FINDINGS What is the central question of this study? Does the induction of a model of lung injury affect the expiratory time constant (τE) in terms of either total duration or morphology? Does ventilation with gases of different densities alter the duration or morphology of τE either before or after injury? What is the main finding and its importance? The use of sulfur hexafluoride in ventilating gas mixtures lengthens total expiratory time constants before and after lung injury compared with both nitrogen and helium mixtures. Sulfur hexafluoride mixtures also decrease the difference and variability of τE between fast- and slow-emptying compartments before and after injury when compared with nitrogen and helium mixtures. Acute lung injury is characterized by regional heterogeneity of lung resistance and elastance that may lead to regional heterogeneity of expiratory time constants (τE). We hypothesized that increasing airflow resistance by using inhaled sulfur hexafluoride (SF6) would lengthen time constants and decrease their heterogeneity in an experimental model of lung injury when compared with nitrogen or helium mixtures. To overcome the limitations of a single-compartment model, we employed a multisegment model of expiratory gas flow. An experimental model of lung injury was created using intratracheal injection of sodium polyacrylate in anaesthetized and mechanically ventilated female Yorkshire-cross pigs (n = 7). The animals were ventilated with 50% O2 and the remaining 50% as nitrogen (N2), helium (He) or sulfur hexafluoride (SF6). Values for τE decreased with injury and were more variable after injury than before (P < 0.001). Values for τE increased throughout expiration both before and after injury, and the rate of increase in τE was lessened by SF6 (P < 0.001 when compared with N2 both before and after injury). Altering the inhaled gas density did not affect indices of oxygenation, dead space or shunt. The use of SF6 in ventilating gas mixtures lengthens total expiratory time constants before and after lung injury compared with both N2 and He mixtures. Importantly, SF6 mixtures also decrease the difference and variability of τE between fast- and slow-emptying compartments before and after injury when compared with N2 and He mixtures.
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Affiliation(s)
- William R Henderson
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.,School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Yannick Molgat-Seon
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Paolo B Dominelli
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Penelope M A Brasher
- Centre for Clinical Epidemiology & Evaluation, Vancouver Coastal Health Research Institute, Vancouver, British Columbia, Canada
| | - Donald E G Griesdale
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Glen E Foster
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Alexandra Yacyshyn
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Najib T Ayas
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - A William Sheel
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
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60
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Abstract
BACKGROUND Acute respiratory distress syndrome (ARDS) is characterized by a noncardiogenic pulmonary edema with bilateral chest X-ray opacities and reduction in lung compliance, and the hallmark of the syndrome is hypoxemia refractory to oxygen therapy. Severe hypoxemia (PaO2/FiO2 < 100 mmHg), which defines severe ARDS, can be found in 20-30 % of the patients and is associated with the highest mortality rate. Although the standard supportive treatment remains mechanical ventilation (noninvasive and invasive), possible adjuvant therapies can be considered. We performed an up-to-date clinical review of the possible available strategies for ARDS patients with severe hypoxemia. MAIN RESULTS In summary, in moderate-to-severe ARDS or in the presence of other organ failure, noninvasive ventilatory support presents a high risk of failure: in those cases the risk/benefit of delayed mechanical ventilation should be evaluated carefully. Tailoring mechanical ventilation to the individual patient is fundamental to reduce the risk of ventilation-induced lung injury (VILI): it is mandatory to apply a low tidal volume, while the optimal level of positive end-expiratory pressure should be selected after a stratification of the severity of the disease, also taking into account lung recruitability; monitoring transpulmonary pressure or airway driving pressure can help to avoid lung overstress. Targeting oxygenation of 88-92 % and tolerating a moderate level of hypercapnia are a safe choice. Neuromuscular blocking agents (NMBAs) are useful to maintain patient-ventilation synchrony in the first hours; prone positioning improves oxygenation in most cases and promotes a more homogeneous distribution of ventilation, reducing the risk of VILI; both treatments, also in combination, are associated with an improvement in outcome if applied in the acute phase in the most severe cases. The use of extracorporeal membrane oxygenation (ECMO) in severe ARDS is increasing worldwide, but because of a lack of randomized trials is still considered a rescue therapy. CONCLUSION Severe ARDS patients should receive a holistic framework of respiratory and hemodynamic support aimed to ensure adequate gas exchange while minimizing the risk of VILI, by promoting lung recruitment and setting protective mechanical ventilation. In the most severe cases, NMBAs, prone positioning, and ECMO should be considered.
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Affiliation(s)
- Davide Chiumello
- Dipartimento di Anestesia, Rianimazione ed Emergenza-Urgenza, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, Via F. Sforza 35, Milan, Italy.
- Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
| | - Matteo Brioni
- Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy
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Koulouras V, Papathanakos G, Papathanasiou A, Nakos G. Efficacy of prone position in acute respiratory distress syndrome patients: A pathophysiology-based review. World J Crit Care Med 2016; 5:121-36. [PMID: 27152255 PMCID: PMC4848155 DOI: 10.5492/wjccm.v5.i2.121] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2015] [Revised: 01/11/2016] [Accepted: 03/07/2016] [Indexed: 02/06/2023] Open
Abstract
Acute respiratory distress syndrome (ARDS) is a syndrome with heterogeneous underlying pathological processes. It represents a common clinical problem in intensive care unit patients and it is characterized by high mortality. The mainstay of treatment for ARDS is lung protective ventilation with low tidal volumes and positive end-expiratory pressure sufficient for alveolar recruitment. Prone positioning is a supplementary strategy available in managing patients with ARDS. It was first described 40 years ago and it proves to be in alignment with two major ARDS pathophysiological lung models; the "sponge lung" - and the "shape matching" -model. Current evidence strongly supports that prone positioning has beneficial effects on gas exchange, respiratory mechanics, lung protection and hemodynamics as it redistributes transpulmonary pressure, stress and strain throughout the lung and unloads the right ventricle. The factors that individually influence the time course of alveolar recruitment and the improvement in oxygenation during prone positioning have not been well characterized. Although patients' response to prone positioning is quite variable and hard to predict, large randomized trials and recent meta-analyses show that prone position in conjunction with a lung-protective strategy, when performed early and in sufficient duration, may improve survival in patients with ARDS. This pathophysiology-based review and recent clinical evidence strongly support the use of prone positioning in the early management of severe ARDS systematically and not as a rescue maneuver or a last-ditch effort.
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62
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Donoso A, Arriagada D, Contreras D, Ulloa D, Neumann M. [Respiratory monitoring of pediatric patients in the Intensive Care Unit]. BOLETIN MEDICO DEL HOSPITAL INFANTIL DE MEXICO 2016; 73:149-165. [PMID: 29421202 DOI: 10.1016/j.bmhimx.2016.02.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 01/29/2016] [Accepted: 02/02/2016] [Indexed: 06/08/2023] Open
Abstract
Respiratory monitoring plays an important role in the care of children with acute respiratory failure. Therefore, its proper use and correct interpretation (recognizing which signals and variables should be prioritized) should help to a better understanding of the pathophysiology of the disease and the effects of therapeutic interventions. In addition, ventilated patient monitoring, among other determinations, allows to evaluate various parameters of respiratory mechanics, know the status of the different components of the respiratory system and guide the adjustments of ventilatory therapy. In this update, the usefulness of several techniques of respiratory monitoring including conventional respiratory monitoring and more recent methods are described. Moreover, basic concepts of mechanical ventilation, their interpretation and how the appropriate analysis of the information obtained can cause an impact on the clinical management of the patient are defined.
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Affiliation(s)
| | | | - Dina Contreras
- Hospital Clínico Metropolitano La Florida, Santiago, Chile
| | - Daniela Ulloa
- Hospital Clínico Metropolitano La Florida, Santiago, Chile
| | - Megan Neumann
- Hospital Clínico Metropolitano La Florida, Santiago, Chile
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63
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Blankman P, Hasan D, Bikker IG, Gommers D. Lung stress and strain calculations in mechanically ventilated patients in the intensive care unit. Acta Anaesthesiol Scand 2016; 60:69-78. [PMID: 26192561 PMCID: PMC6191648 DOI: 10.1111/aas.12589] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Revised: 04/18/2015] [Accepted: 06/08/2015] [Indexed: 11/28/2022]
Abstract
Background Stress and strain are parameters to describe respiratory mechanics during mechanical ventilation. Calculations of stress require invasive and difficult to perform esophageal pressure measurements. The hypothesis of the present study was: Can lung stress be reliably calculated based on non‐invasive lung volume measurements, during a decremental Positive end‐expiratory pressure (PEEP) trial in mechanically ventilated patients with different diseases? Methods Data of 26 pressure‐controlled ventilated patients admitted to the ICU with different lung conditions were retrospectively analyzed: 11 coronary artery bypass graft (CABG), 9 neurology, and 6 lung disorders. During a decremental PEEP trial (from 15 to 0 cmH2O in three steps) end‐expiratory lung volume (EELV) measurements were performed at each PEEP step, without interruption of mechanical ventilation. Strain, specific elastance, and stress were calculated for each PEEP level. Elastance was calculated as delta PEEP divided by delta PEEP volume, whereas specific elastance is elastance times the FRC. Stress was calculated as specific elastance times the strain. Global strain was divided into dynamic (tidal volume) and static (PEEP) strain. Results Strain calculations based on FRC showed mainly changes in static component, whereas calculations based on EELV showed changes in both the static and dynamic component of strain. Stress calculated from EELV measurements was 24.0 ± 2.7 and 13.1 ± 3.8 cmH2O in the lung disorder group at 15 and 5 cmH2O PEEP. For the normal lungs, the stress values were 19.2 ± 3.2 and 10.9 ± 3.3 cmH2O, respectively. These values are comparable to earlier publications. Specific elastance calculations were comparable in patients with neurologic and lung disorders, and lower in the CABG group due to recruitment in this latter group. Conclusion Stress and strain can reliably be calculated at the bedside based on non‐invasive EELV measurements during a decremental PEEP trial in patients with different diseases.
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Affiliation(s)
- P. Blankman
- Department of Adult Intensive Care; Erasmus MC Rotterdam; Rotterdam The Netherlands
| | - D. Hasan
- Department of Adult Intensive Care; Erasmus MC Rotterdam; Rotterdam The Netherlands
| | - I. G. Bikker
- Department of Adult Intensive Care; Erasmus MC Rotterdam; Rotterdam The Netherlands
| | - D. Gommers
- Department of Adult Intensive Care; Erasmus MC Rotterdam; Rotterdam The Netherlands
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Casserly B, McCool FD, Saunders J, Selvakumar N, Levy MM. End-Expiratory Volume and Oxygenation: Targeting PEEP in ARDS Patients. Lung 2015; 194:35-41. [PMID: 26645226 DOI: 10.1007/s00408-015-9823-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 11/03/2015] [Indexed: 10/22/2022]
Abstract
INTRODUCTION Changes in end-expiratory lung volume (∆EELV) in response to changes in PEEP (∆PEEP) have not been reported in mechanically ventilated patients with ARDS. The purpose of this study was to determine the utility of measurements of ∆EELV in determining optimal PEEP in ARDS patients. METHODS Nine patients with ARDS were prospectively recruited. ∆EELV was measured using magnetometers during serial decremental PEEP trials. Changes in PaO2 (∆PaO2) were simultaneously measured. Static respiratory system compliance (CRS), ∆PaO2/∆PEEP, and ∆EELV/∆PEEP were calculated at each level of PEEP. RESULTS For the group, ∆EELV decreased by 1.09 ± 0.13 L (mean ± SD) as PEEP was reduced from 20 to 0 cm H2O with the greatest changes in ∆EELV occurring over the mid range of the decremental PEEP curve. Optimal values for CRS, ∆EELV/∆PEEP, and ∆PaO2/∆PEEP could be identified for each patient and occurred at PEEP levels ranging from 10 to 17.5 cm H2O. There was a significant correlation (r = 0.712, p = 0.047) between ∆PaO2/∆PEEP and ∆EELV/∆PEEP. CONCLUSIONS ∆EELV can be measured from a decremental PEEP curve. Since ∆EELV is highly correlated with ∆PaO2, measures of ∆PaO2/∆PEEP may provide a surrogate for measures of ∆EELV/∆PEEP. Combining measures of ∆EELV/∆PEEP with measures of CRS may provide a novel means of determining optimal PEEP in patients with ARDS.
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Affiliation(s)
- Brian Casserly
- Pulmonary, Critical Care, and Sleep Medicine, Mid-Western Regional Hospital, Dooradoyle, Limerick, Ireland. .,University Hospital Limerick, Dooradoyle, Limerick, Ireland.
| | - F Dennis McCool
- Division of Pulmonary, Critical Care and Sleep Medicine, The Memorial Hospital of Rhode Island, 111 Brewster Street, Pawtucket, RI, USA
| | - Jean Saunders
- Director of Statistical Consulting Unit, University of Limerick, Limerick, Ireland
| | | | - Mitchell M Levy
- Division of Pulmonary, Critical Care and Sleep Medicine, Rhode Island Hospital, 593 Eddy Street, Providence, RI, USA
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Intraoperative protective mechanical ventilation for prevention of postoperative pulmonary complications: a comprehensive review of the role of tidal volume, positive end-expiratory pressure, and lung recruitment maneuvers. Anesthesiology 2015; 123:692-713. [PMID: 26120769 DOI: 10.1097/aln.0000000000000754] [Citation(s) in RCA: 249] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Postoperative pulmonary complications are associated with increased morbidity, length of hospital stay, and mortality after major surgery. Intraoperative lung-protective mechanical ventilation has the potential to reduce the incidence of postoperative pulmonary complications. This review discusses the relevant literature on definition and methods to predict the occurrence of postoperative pulmonary complication, the pathophysiology of ventilator-induced lung injury with emphasis on the noninjured lung, and protective ventilation strategies, including the respective roles of tidal volumes, positive end-expiratory pressure, and recruitment maneuvers. The authors propose an algorithm for protective intraoperative mechanical ventilation based on evidence from recent randomized controlled trials.
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Abstract
BACKGROUND Acute hypoxaemia de novo or on a background of chronic hypoxaemia is a common reason for admission to intensive care and for provision of mechanical ventilation. Various refinements of mechanical ventilation or adjuncts are employed to improve patient outcomes. Mortality from acute respiratory distress syndrome, one of the main contributors to the need for mechanical ventilation for hypoxaemia, remains approximately 40%. Ventilation in the prone position may improve lung mechanics and gas exchange and could improve outcomes. OBJECTIVES The objectives of this review are (1) to ascertain whether prone ventilation offers a mortality advantage when compared with traditional supine or semi recumbent ventilation in patients with severe acute respiratory failure requiring conventional invasive artificial ventilation, and (2) to supplement previous systematic reviews on prone ventilation for hypoxaemic respiratory failure in an adult population. SEARCH METHODS We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 1), Ovid MEDLINE (1950 to 31 January 2014), EMBASE (1980 to 31 January 2014), the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (1982 to 31 January 2014) and Latin American Caribbean Health Sciences Literature (LILACS) (1992 to 31 January 2014) in Ovid MEDLINE for eligible randomized controlled trials. We also searched for studies by handsearching reference lists of relevant articles, by contacting colleagues and by handsearching published proceedings of relevant journals. We applied no language constraints, and we reran the searches in CENTRAL, MEDLINE, EMBASE, CINAHL and LILACS in June 2015. We added five new studies of potential interest to the list of "Studies awaiting classification" and will incorporate them into formal review findings during the review update. SELECTION CRITERIA We included randomized controlled trials (RCTs) that examined the effects of prone position versus supine/semi recumbent position during conventional mechanical ventilation in adult participants with acute hypoxaemia. DATA COLLECTION AND ANALYSIS Two review authors independently reviewed all trials identified by the search and assessed them for suitability, methods and quality. Two review authors extracted data, and three review authors reviewed the data extracted. We analysed data using Review Manager software and pooled included studies to determine the risk ratio (RR) for mortality and the risk ratio or mean difference (MD) for secondary outcomes; we also performed subgroup analyses and sensitivity analyses. MAIN RESULTS We identified nine relevant RCTs, which enrolled a total of 2165 participants (10 publications). All recruited participants suffered from disorders of lung function causing moderate to severe hypoxaemia and requiring mechanical ventilation, so they were fairly comparable, given the heterogeneity of specific disease diagnoses in intensive care. Risk of bias, although acceptable in the view of the review authors, was inevitable: Blinding of participants and carers to treatment allocation was not possible (face-up vs face-down).Primary analyses of short- and longer-term mortality pooled from six trials demonstrated an RR of 0.84 to 0.86 in favour of the prone position (PP), but findings were not statistically significant: In the short term, mortality for those ventilated prone was 33.4% (363/1086) and supine 38.3% (395/1031). This resulted in an RR of 0.84 (95% confidence interval (CI) 0.69 to 1.02) marginally in favour of PP. For longer-term mortality, results showed 41.7% (462/1107) for prone and 47.1% (490/1041) for supine positions, with an RR of 0.86 (95% CI 0.72 to 1.03). The quality of the evidence for both outcomes was rated as low as a result of important potential bias and serious inconsistency.Subgroup analyses for mortality identified three groups consistently favouring PP: those recruited within 48 hours of meeting entry criteria (five trials; 1024 participants showed an RR of 0.75 (95% CI 0.59 to 94)); those treated in the PP for 16 or more hours per day (five trials; 1005 participants showed an RR of 0.77 (95% CI 0.61 to 0.99)); and participants with more severe hypoxaemia at trial entry (six trials; 1108 participants showed an RR of 0.77 (95% CI 0.65 to 0.92)). The quality of the evidence for these outcomes was rated as moderate as a result of potentially important bias.Prone positioning appeared to influence adverse effects: Pressure sores (three trials; 366 participants) with an RR of 1.37 (95% CI 1.05 to 1.79) and tracheal tube obstruction with an RR of 1.78 (95% CI 1.22 to 2.60) were increased with prone ventilation. Reporting of arrhythmias was reduced with PP, with an RR of 0.64 (95% CI 0.47 to 0.87). AUTHORS' CONCLUSIONS We found no convincing evidence of benefit nor harm from universal application of PP in adults with hypoxaemia mechanically ventilated in intensive care units (ICUs). Three subgroups (early implementation of PP, prolonged adoption of PP and severe hypoxaemia at study entry) suggested that prone positioning may confer a statistically significant mortality advantage. Additional adequately powered studies would be required to confirm or refute these possibilities of subgroup benefit but are unlikely, given results of the most recent study and recommendations derived from several published subgroup analyses. Meta-analysis of individual patient data could be useful for further data exploration in this regard. Complications such as tracheal obstruction are increased with use of prone ventilation. Long-term mortality data (12 months and beyond), as well as functional, neuro-psychological and quality of life data, are required if future studies are to better inform the role of PP in the management of hypoxaemic respiratory failure in the ICU.
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Affiliation(s)
- Roxanna Bloomfield
- Intensive Care Unit and Department of Anaesthesia, Aberdeen Royal Infirmary, Foresterhill, Aberdeen, Scotland, UK, AB25 2ZN
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Impact of Chest Wall Modifications and Lung Injury on the Correspondence Between Airway and Transpulmonary Driving Pressures. Crit Care Med 2015; 43:e287-95. [PMID: 26186478 DOI: 10.1097/ccm.0000000000001036] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
OBJECTIVE Recent interest has arisen in airway driving pressure (DP(AW)), the quotient of tidal volume (V(T)), and respiratory system compliance (C(RS)), which could serve as a direct and easily measured marker for ventilator-induced lung injury risk. We aimed to test the correspondence between DP(AW) and transpulmonary driving pressure (DP(TP))-the quotient of V(T) and lung compliance (C(L)), in response to intra-abdominal hypertension and changes in positive end-expiratory pressure during different models of lung pathology. DESIGN Well-controlled experimental setting that allowed reversible modification of chest wall compliance (C(CW)) in a variety of models of lung pathology. SETTING Large animal laboratory of a university-affiliated hospital. SUBJECTS Ten deeply anesthetized swine. INTERVENTIONS Application of intra-abdominal pressures of 0 and 20 cm H2O at positive end-expiratory pressure of 1 and 10 cm H2O, under volume-controlled mechanical ventilation in the settings of normal lungs (baseline), unilateral whole-lung atelectasis, and unilateral and bilateral lung injuries caused by saline lavage. MEASUREMENTS AND MAIN RESULTS Pulmonary mechanics including esophageal pressure and calculations of DP(AW), DP(TP), C(RS), C(L), and C(CW). When compared with normal intra-abdominal pressures, intra-abdominal hypertension increased DP(AW), during both "normal lung conditions" (p < 0.0001) and "unilateral atelectasis" (p = 0.0026). In contrast, DP(TP) remained virtually unaffected by changes in positive end-expiratory pressure or intra-abdominal pressures in both conditions. During unilateral lung injury, both DPA(W) and DP(TP) were increased by the presence of intra-abdominal hypertension (p < 0.0001 and p = 0.0222, respectively). During bilateral lung injury, intra-abdominal hypertension increased both DP(AW) (at positive end-expiratory pressure of 1 cm H2O, p < 0.0001; and at positive end-expiratory pressure of 10 cm H2O, p = 0.0091) and DP(TP) (at positive end-expiratory pressure of 1 cm H2O, p = 0.0510; and at positive end-expiratory pressure of 10 cm H2O, p = 0.0335). CONCLUSIONS Our data indicate that DP(AW) is influenced by reductions in chest wall compliance and by underlying lung properties. As with other measures of pulmonary mechanics that are based on unmodified P(AW), caution is advised in attempting to attribute hazard or safety to any specific absolute value of DP(AW).
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Liu Q, Gao YH, Hua DM, Li W, Cheng Z, Zheng H, Chen RC. Functional residual capacity in beagle dogs with and without acute respiratory distress syndrome. J Thorac Dis 2015; 7:1459-66. [PMID: 26380772 DOI: 10.3978/j.issn.2072-1439.2015.08.20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 07/08/2015] [Indexed: 11/14/2022]
Abstract
BACKGROUND Traditionally, the choice of tidal volume for mechanical ventilation was based on body weight (BW) and usually, predicted BW was used to correct actual BW inter-individual variations in obesity and muscle weight. The method of selecting tidal volume depended on the fact that normal lung volumes, especially functional residual capacity (FRC), were mainly determined by height (indirectly by predicted BW), sex and age in healthy persons. However, FRCs in patients with acute respiratory distress syndrome (ARDS) might not abide by the same rule and be significantly different from each other in patients with the same height and sex. We hypothesized that FRC was determined by body length (surrogate for predicted BW) and age in healthy male beagle dogs but not in lung injured ones. METHODS A total of 24 dogs were recruited and ARDS model was induced by intravenous injection of oleic acid. FRC was measured by chest computer tomography. Blood gas analysis, extra vascular lung water and respiratory system mechanics were tested at baseline and post-lung injury. Age, body length and actual BW were also recorded before experiments. RESULTS After lung injury, FRC decreased sharply from baseline (414±84) to (214±70) mL. For healthy lungs, FRC could be estimated by the following formula: FRC =21.86 × age (months) + 20.55 × body length (cm) - 1,337.98 (P<0.05), while for injured lungs, the formula of multiple linear regression was invalid (P=0.305). CONCLUSIONS FRC was linearly related to body length in healthy dogs but not in lung injured ones. The traditional view of setting tidal volume based on predicted BW should be challenged cautiously.
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Affiliation(s)
- Qi Liu
- 1 Department of Respiratory and Critical Medicine, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China ; 2 Respiratory Mechanics Lab, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 3 Department of Radiology, the First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 4 Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Yong-Hua Gao
- 1 Department of Respiratory and Critical Medicine, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China ; 2 Respiratory Mechanics Lab, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 3 Department of Radiology, the First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 4 Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Dong-Ming Hua
- 1 Department of Respiratory and Critical Medicine, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China ; 2 Respiratory Mechanics Lab, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 3 Department of Radiology, the First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 4 Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Wen Li
- 1 Department of Respiratory and Critical Medicine, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China ; 2 Respiratory Mechanics Lab, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 3 Department of Radiology, the First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 4 Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Zhe Cheng
- 1 Department of Respiratory and Critical Medicine, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China ; 2 Respiratory Mechanics Lab, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 3 Department of Radiology, the First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 4 Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Hui Zheng
- 1 Department of Respiratory and Critical Medicine, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China ; 2 Respiratory Mechanics Lab, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 3 Department of Radiology, the First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 4 Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Rong-Chang Chen
- 1 Department of Respiratory and Critical Medicine, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China ; 2 Respiratory Mechanics Lab, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 3 Department of Radiology, the First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510182, China ; 4 Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
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High-frequency oscillation ventilation for hypercapnic failure of conventional ventilation in pulmonary acute respiratory distress syndrome. Crit Care 2015; 19:201. [PMID: 25929255 PMCID: PMC4438528 DOI: 10.1186/s13054-015-0935-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 04/20/2015] [Indexed: 11/10/2022] Open
Abstract
Introduction High-frequency oscillation ventilation (HFOV) is regarded as particularly lung protective. Recently, HFOV has been shown to be not beneficial for acute respiratory distress syndrome (ARDS) patients in general. Due to its special physical effects, it could be beneficial, however, in inhomogeneous ARDS. This study evaluates the effect of HFOV on PaCO2 removal in hypercapnic patients with ARDS of pulmonary origin. Methods Between October 2010 and June 2014 patients with ARDS of pulmonary origin with PaO2/FiO2 ratio >60 mmHg, but respiratory acidosis (pH <7.26) under optimized protective ventilation were switched to HFOV, using moderate airway pressure (adopting the mean airway pressure of the prior ventilation). Data from these patients were analyzed retrospectively; PaCO2 and pH before, 1 h and 24 h after the start of HFOV were compared. Results Twenty-six patients with PaO2/FiO2 ratio 139 ± 49 and respiratory acidosis (PaCO2 68 ± 12 mmHg) were put on HFOV after 17 ± 22 h of conventional ventilation. Mean airway pressure was 19 cm H2O (15 to 28). PaCO2 decreased significantly: after 1 hour the mean difference was −14 ± 10 mmHg; P <0.01 and after 24 hours −17 ± 12 mmHg; P <0.01; n = 24. CO2 clearance improved in all but two patients; in those, extracorporeal lung support was initiated. Oxygenation remained unchanged after 1 h and slightly increased after 24 h. No complications related to HFOV were observed. Twenty-two patients improved and could be weaned from HFOV. Twenty patients (77%) were alive on day 30. Conclusions HFOV could be a useful alternative in patients with ARDS of pulmonary origin with hypercapnic failure of lung-protective conventional ventilation. Electronic supplementary material The online version of this article (doi:10.1186/s13054-015-0935-4) contains supplementary material, which is available to authorized users.
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Modulation of stress versus time product during mechanical ventilation influences inflammation as well as alveolar epithelial and endothelial response in rats. Anesthesiology 2015; 122:106-16. [PMID: 25141026 DOI: 10.1097/aln.0000000000000415] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
BACKGROUND Mechanical ventilation can lead to lung biotrauma when mechanical stress exceeds safety thresholds. The authors investigated whether the duration of mechanical stress, that is, the impact of a stress versus time product (STP), influences biotrauma. The authors hypothesized that higher STP levels are associated with increased inflammation and with alveolar epithelial and endothelial cell injury. METHODS In 46 rats, Escherichia coli lipopolysaccharide (acute lung inflammation) or saline (control) was administered intratracheally. Both groups were protectively ventilated with inspiratory-to-expiratory ratios 1:2, 1:1, or 2:1 (n = 12 each), corresponding to low, middle, and high STP levels (STPlow, STPmid, and STPhigh, respectively). The remaining 10 animals were not mechanically ventilated. RESULTS In animals with mild acute lung inflammation, but not in controls: (1) messenger RNA expression of interleukin-6 was higher in STPhigh (28.1 ± 13.6; mean ± SD) and STPlow (28.9 ± 16.0) versus STPmid (7.4 ± 7.5) (P < 0.05); (2) expression of the receptor for advanced glycation end-products was increased in STPhigh (3.6 ± 1.6) versus STPlow (2.3 ± 1.1) (P < 0.05); (3) alveolar edema was decreased in STPmid (0 [0 to 0]; median, Q1 to Q3) compared with STPhigh (0.8 [0.6 to 1]) (P < 0.05); and (4) expressions of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 were higher in STPlow (3.0 ± 1.8) versus STPhigh (1.2 ± 0.5) and STPmid (1.4 ± 0.7) (P < 0.05), respectively. CONCLUSIONS In the mild acute lung inflammation model used herein, mechanical ventilation with inspiratory-to-expiratory of 1:1 (STPmid) minimized lung damage, whereas STPhigh increased the gene expression of biological markers associated with inflammation and alveolar epithelial cell injury and STPlow increased markers of endothelial cell damage.
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Di Marco F, Bonacina D, Vassena E, Arisi E, Apostolo A, Banfi C, Centanni S, Agostoni P, Fumagalli R. The Effects of Anesthesia, Muscle Paralysis, and Ventilation on the Lung Evaluated by Lung Diffusion for Carbon Monoxide and Pulmonary Surfactant Protein B. Anesth Analg 2015; 120:373-80. [DOI: 10.1213/ane.0000000000000496] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Müller-Redetzky HC, Felten M, Hellwig K, Wienhold SM, Naujoks J, Opitz B, Kershaw O, Gruber AD, Suttorp N, Witzenrath M. Increasing the inspiratory time and I:E ratio during mechanical ventilation aggravates ventilator-induced lung injury in mice. Crit Care 2015; 19:23. [PMID: 25888164 PMCID: PMC4336519 DOI: 10.1186/s13054-015-0759-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 01/20/2015] [Indexed: 11/10/2022] Open
Abstract
Introduction Lung-protective ventilation reduced acute respiratory distress syndrome (ARDS) mortality. To minimize ventilator-induced lung injury (VILI), tidal volume is limited, high plateau pressures are avoided, and positive end-expiratory pressure (PEEP) is applied. However, the impact of specific ventilatory patterns on VILI is not well defined. Increasing inspiratory time and thereby the inspiratory/expiratory ratio (I:E ratio) may improve oxygenation, but may also be harmful as the absolute stress and strain over time increase. We thus hypothesized that increasing inspiratory time and I:E ratio aggravates VILI. Methods VILI was induced in mice by high tidal-volume ventilation (HVT 34 ml/kg). Low tidal-volume ventilation (LVT 9 ml/kg) was used in control groups. PEEP was set to 2 cm H2O, FiO2 was 0.5 in all groups. HVT and LVT mice were ventilated with either I:E of 1:2 (LVT 1:2, HVT 1:2) or 1:1 (LVT 1:1, HVT 1:1) for 4 hours or until an alternative end point, defined as mean arterial blood pressure below 40 mm Hg. Dynamic hyperinflation due to the increased I:E ratio was excluded in a separate group of animals. Survival, lung compliance, oxygenation, pulmonary permeability, markers of pulmonary and systemic inflammation (leukocyte differentiation in lung and blood, analyses of pulmonary interleukin-6, interleukin-1β, keratinocyte-derived chemokine, monocyte chemoattractant protein-1), and histopathologic pulmonary changes were analyzed. Results LVT 1:2 or LVT 1:1 did not result in VILI, and all individuals survived the ventilation period. HVT 1:2 decreased lung compliance, increased pulmonary neutrophils and cytokine expression, and evoked marked histologic signs of lung injury. All animals survived. HVT 1:1 caused further significant worsening of oxygenation, compliance and increased pulmonary proinflammatory cytokine expression, and pulmonary and blood neutrophils. In the HVT 1:1 group, significant mortality during mechanical ventilation was observed. Conclusion According to the “baby lung” concept, mechanical ventilation-associated stress and strain in overinflated regions of ARDS lungs was simulated by using high tidal-volume ventilation. Increase of inspiratory time and I:E ratio significantly aggravated VILI in mice, suggesting an impact of a “stress/strain × time product” for the pathogenesis of VILI. Thus increasing the inspiratory time and I:E ratio should be critically considered. Electronic supplementary material The online version of this article (doi:10.1186/s13054-015-0759-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Holger C Müller-Redetzky
- Department of Infectious Diseases and Pulmonary Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
| | - Matthias Felten
- Department of Infectious Diseases and Pulmonary Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
| | - Katharina Hellwig
- Department of Infectious Diseases and Pulmonary Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
| | - Sandra-Maria Wienhold
- Department of Infectious Diseases and Pulmonary Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
| | - Jan Naujoks
- Department of Infectious Diseases and Pulmonary Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
| | - Bastian Opitz
- Department of Infectious Diseases and Pulmonary Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
| | - Olivia Kershaw
- Department of Veterinary Pathology, Freie Universität Berlin, Berlin, Germany.
| | - Achim D Gruber
- Department of Veterinary Pathology, Freie Universität Berlin, Berlin, Germany.
| | - Norbert Suttorp
- Department of Infectious Diseases and Pulmonary Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
| | - Martin Witzenrath
- Department of Infectious Diseases and Pulmonary Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
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Wu MY, Lin PJ, Tseng YH, Kao KC, Hsiao HL, Huang CC. Venovenous extracorporeal life support for posttraumatic respiratory distress syndrome in adults: the risk of major hemorrhages. Scand J Trauma Resusc Emerg Med 2014; 22:56. [PMID: 25273618 PMCID: PMC4189614 DOI: 10.1186/s13049-014-0056-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Accepted: 09/07/2014] [Indexed: 02/05/2023] Open
Abstract
Background The aim of this retrospective study is to investigate the therapeutic benefits and the bleeding risks of venovenous extracorporeal life support (VV-ECLS) when used for adult posttraumatic respiratory distress syndrome (posttraumatic ARDS). Materials and methods Twenty adult trauma patients (median age: 38 years, median injury severity score: 35) treated with VV-ECLS in a level I trauma center between January 2004 and June 2013 were enrolled in this study. The indication of VV-ECLS for posttraumatic ARDS was refractory hypoxemia (PaO2/FiO2 ratio ≤ 70 mmHg) under advanced mechanical ventilation. To minimize potential complications, a protocol-guided VV-ECLS was adopted. Results Sixteen patients were weaned off VV-ECLS, and of these patients fourteen survived. Medians of the trauma-to-ECLS time, the pre-ECLS mechanical ventilation, and the ECLS duration in all patients were 64, 45, and 144 hours respectively. The median PaO2/FiO2 ratio was improved significantly soon after VV-ECLS, from 56 to 106 mmHg (p < 0.001). However, seven major hemorrhages occurred during VV-ECLS, of which three were lethal. The multivariate analysis revealed that the occurrence of major hemorrhages during VV-ECLS was independently related to the trauma-to-ECLS time < 24 hours (OR: 20; p = 0.02; 95% CI: 2–239; c-index: 0.81). Conclusions Despite an effective respiratory support, VV-ECLS should be cautiously administered to patients who develop advanced ARDS soon after major trauma. Electronic supplementary material The online version of this article (doi:10.1186/s13049-014-0056-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | - Chung-Chi Huang
- Department of Thoracic Medicine, Chang Gung Memorial Hospital and Chang Gung University, 5, Fushing Street, Gueishan Shiang, Taoyuan 333, Taiwan.
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BLANKMAN P, VAN DER KREEFT SM, GOMMERS D. Tidal ventilation distribution during pressure-controlled ventilation and pressure support ventilation in post-cardiac surgery patients. Acta Anaesthesiol Scand 2014; 58:997-1006. [PMID: 25039666 DOI: 10.1111/aas.12367] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2014] [Indexed: 11/25/2022]
Abstract
BACKGROUND Inhomogeneous ventilation is an important contributor to ventilator-induced lung injury. Therefore, this study examines homogeneity of lung ventilation by means of electrical impedance tomography (EIT) measurements during pressure-controlled ventilation (PCV) and pressure support ventilation (PSV) using the same ventilation pressures. METHODS Twenty mechanically ventilated patients were studied after cardiac surgery. On arrival at the intensive care unit, ventilation distribution was measured with EIT just above the diaphragm for 15 min. After awakening, PCV was switched to PSV and EIT measurements were again recorded. RESULTS Tidal impedance variation, a measure of tidal volume, increased during PSV compared with PCV, despite using the same ventilation pressures (P = 0.045). The distribution of tidal ventilation to the dependent lung region was more pronounced during PSV compared with PCV, especially during the first half of the inspiration. An even distribution of tidal ventilation between the dependent and non-dependent lung regions was seen during PCV at lower tidal volumes (< 8 ml/kg) and PSV at higher tidal volumes (≥ 8 ml/kg). In addition, the distribution of tidal ventilation was predominantly distributed to the dependent lung during PSV at low tidal volumes. CONCLUSION In post-cardiac surgery patients, PSV showed improved ventilation of the dependent lung region due to the contribution of the diaphragm activity, which is even more pronounced during lower assist levels.
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Affiliation(s)
- P. BLANKMAN
- Department of Adult Intensive Care; Erasmus MC; Rotterdam The Netherlands
| | | | - D. GOMMERS
- Department of Adult Intensive Care; Erasmus MC; Rotterdam The Netherlands
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Bodenstein M, Boehme S, Wang H, Duenges B, Markstaller K. Hints for cyclical recruitment of atelectasis during ongoing mechanical ventilation in lavage and oleic acid lung injury detected by SpO₂ oscillations and electrical impedance tomography. Exp Lung Res 2014; 40:427-38. [PMID: 25153803 DOI: 10.3109/01902148.2014.944719] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE OF THE STUDY Detection of cyclical recruitment of atelectasis after induction of lavage (LAV) or oleic acid injury (OAI) in mechanically ventilated pigs. Primary hypothesis is that oxygen oscillations within the respiratory cycle can be detected by SpO₂ recordings (direct hint). SpO₂ oscillations reflect shunt oscillations that can only be explained by cyclical recruitment of atelectasis. Secondary hypothesis is that electrical impedance tomography (EIT) depicts specific regional changes of lung aeration and of pulmonary mechanical properties (indirect hint). MATERIALS AND METHODS Three groups (each n = 7) of mechanically ventilated pigs were investigated applying above mentioned methods before and repeatedly after induction of lung injury: (1) sham treated animals (SHAM), (2) LAV, and (3) OAI. RESULTS Early oxygen oscillations occurred in the LAV group (mean calculated amplitude: 73.8 mmHg reflecting shunt oscillation of 11.2% in mean). In the OAI group oxygen oscillations occurred hours after induction of lung injury (mean calculated amplitude: 57.1 mmHg reflecting shunt oscillations of 8.4% in mean). The SHAM group had no relevant oxygen oscillations (<30 mmHg, shunt oscillations < 1.5%). Synchronously to oxygen oscillations, EIT depicted (1) a decrease of ventilation in dorsal areas, (2) an increase in ventral areas, (3) a decrease of especially dependent expiratory impedance, 3) an increase in late inspiratory flow especially in the dependant areas, (4) an increase in the speed of peak expiratory flow (PEF), and (5) a decrease of dorsal late expiratory flow. CONCLUSIONS SpO2 and EIT recordings detect events that are interpreted as cyclical recruitment of atelectasis.
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Affiliation(s)
- Marc Bodenstein
- 1Department of Anaesthesiology, University Medical Center Mainz, Mainz, Germany
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Stress et strain : application au cours du syndrome de détresse respiratoire aiguë. MEDECINE INTENSIVE REANIMATION 2014. [DOI: 10.1007/s13546-014-0906-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Wellman TJ, Winkler T, Costa EL, Musch G, Harris RS, Zheng H, Venegas JG, Vidal Melo MF. Effect of local tidal lung strain on inflammation in normal and lipopolysaccharide-exposed sheep*. Crit Care Med 2014; 42:e491-500. [PMID: 24758890 PMCID: PMC4123638 DOI: 10.1097/ccm.0000000000000346] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
OBJECTIVES Regional tidal lung strain may trigger local inflammation during mechanical ventilation, particularly when additional inflammatory stimuli are present. However, it is unclear whether inflammation develops proportionally to tidal strain or only above a threshold. We aimed to 1) assess the relationship between regional tidal strain and local inflammation in vivo during the early stages of lung injury in lungs with regional aeration heterogeneity comparable to that of humans and 2) determine how this strain-inflammation relationship is affected by endotoxemia. DESIGN Interventional animal study. SETTING Experimental laboratory and PET facility. SUBJECTS Eighteen 2- to 4-month-old sheep. INTERVENTIONS Three groups of sheep (n = 6) were mechanically ventilated to the same plateau pressure (30-32 cm H2O) with high-strain (VT = 18.2 ± 6.5 mL/kg, positive end-expiratory pressure = 0), high-strain plus IV lipopolysaccharide (VT = 18.4 ± 4.2 mL/kg, positive end-expiratory pressure = 0), or low-strain plus lipopolysaccharide (VT = 8.1 ± 0.2 mL/kg, positive end-expiratory pressure = 17 ± 3 cm H2O). At baseline, we acquired respiratory-gated PET scans of inhaled NN to measure tidal strain from end-expiratory and end-inspiratory images in six regions of interest. After 3 hours of mechanical ventilation, dynamic [F]fluoro-2-deoxy-D-glucose scans were acquired to quantify metabolic activation, indicating local neutrophilic inflammation, in the same regions of interest. MEASUREMENTS AND MAIN RESULTS Baseline regional tidal strain had a significant effect on [F]fluoro-2-deoxy-D-glucose net uptake rate Ki in high-strain lipopolysaccharide (p = 0.036) and on phosphorylation rate k3 in high-strain (p = 0.027) and high-strain lipopolysaccharide (p = 0.004). Lipopolysaccharide exposure increased the k3-tidal strain slope three-fold (p = 0.009), without significant lung edema. The low-strain lipopolysaccharide group showed lower baseline regional tidal strain (0.33 ± 0.17) than high-strain (1.21 ± 0.62; p < 0.001) or high-strain lipopolysaccharide (1.26 ± 0.44; p < 0.001) and lower k3 (p < 0.001) and Ki (p < 0.05) than high-strain lipopolysaccharide. CONCLUSIONS Local inflammation develops proportionally to regional tidal strain during early lung injury. The regional inflammatory effect of strain is greatly amplified by IV lipopolysaccharide. Tidal strain enhances local [F]fluoro-2-deoxy-D-glucose uptake primarily by increasing the rate of intracellular [F]fluoro-2-deoxy-D-glucose phosphorylation.
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Affiliation(s)
- Tyler J. Wellman
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Tilo Winkler
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Eduardo L.V. Costa
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Guido Musch
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - R. Scott Harris
- Pulmonary and Critical Care Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Hui Zheng
- Biostatistics Center, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Jose G. Venegas
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Marcos F. Vidal Melo
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
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Does prone positioning improve oxygenation and reduce mortality in patients with acute respiratory distress syndrome? Can Respir J 2014; 21:213-5. [PMID: 24927376 DOI: 10.1155/2014/472136] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The emergence of computed tomography imaging more than 25 years ago led to characterization of acute respiratory distress syndrome (ARDS) as areas of relatively normal lung parenchyma juxtaposed with areas of dense consolidation and atelectasis. Given that this heterogeneity is often dorsally distributed, investigators questioned whether care for ARDS patients in the prone position would lead to improved mortality outcomes. This clinical review discusses the physiological rationale and clinical evidence supporting prone positioning in treating ARDS, in addition to its complications and contraindications.
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Blankman P, Hasan D, Erik G, Gommers D. Detection of 'best' positive end-expiratory pressure derived from electrical impedance tomography parameters during a decremental positive end-expiratory pressure trial. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2014; 18:R95. [PMID: 24887391 PMCID: PMC4095609 DOI: 10.1186/cc13866] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Accepted: 05/01/2014] [Indexed: 01/21/2023]
Abstract
Introduction This study compares different parameters derived from electrical impedance tomography (EIT) data to define ‘best’ positive end-expiratory pressure (PEEP) during a decremental PEEP trial in mechanically-ventilated patients. ‘Best’ PEEP is regarded as minimal lung collapse and overdistention in order to prevent ventilator-induced lung injury. Methods A decremental PEEP trial (from 15 to 0 cm H2O PEEP in 4 steps) was performed in 12 post-cardiac surgery patients on the ICU. At each PEEP step, EIT measurements were performed and from this data the following were calculated: tidal impedance variation (TIV), regional compliance, ventilation surface area (VSA), center of ventilation (COV), regional ventilation delay (RVD index), global inhomogeneity (GI index), and intratidal gas distribution. From the latter parameter we developed the ITV index as a new homogeneity parameter. The EIT parameters were compared with dynamic compliance and the PaO2/FiO2 ratio. Results Dynamic compliance and the PaO2/FiO2 ratio had the highest value at 10 and 15 cm H2O PEEP, respectively. TIV, regional compliance and VSA had a maximum value at 5 cm H2O PEEP for the non-dependent lung region and a maximal value at 15 cm H2O PEEP for the dependent lung region. GI index showed the lowest value at 10 cm H2O PEEP, whereas for COV and the RVD index this was at 15 cm H2O PEEP. The intratidal gas distribution showed an equal contribution of both lung regions at a specific PEEP level in each patient. Conclusion In post-cardiac surgery patients, the ITV index was comparable with dynamic compliance to indicate ‘best’ PEEP. The ITV index can visualize the PEEP level at which ventilation of the non-dependent region is diminished, indicating overdistention. Additional studies should test whether application of this specific PEEP level leads to better outcome and also confirm these results in patients with acute respiratory distress syndrome.
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Kaniaris E, Vaporidi K, Vergadi E, Theodorakis EE, Kondili E, Lagoudaki E, Tsatsanis C, Georgopoulos D. Genetic and pharmacologic inhibition of Tpl2 kinase is protective in a mouse model of ventilator-induced lung injury. Intensive Care Med Exp 2014; 2:15. [PMID: 26266915 PMCID: PMC4513004 DOI: 10.1186/2197-425x-2-15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 03/26/2014] [Indexed: 12/17/2022] Open
Abstract
Background Mechanical stress induced by injurious ventilation leads to pro-inflammatory cytokine production and lung injury. The extracellular-signal-regulated-kinase, ERK1/2, participates in the signaling pathways activated upon mechanical stress in the lungs to promote the inflammatory response. Tumor progression locus 2 (Tpl2) is a MAP3kinase that activates ERK1/2 upon cytokine or TLR signaling, to induce pro-inflammatory cytokine production. The role of Tpl2 in lung inflammation, and specifically in the one caused by mechanical stress has not been investigated. The aim of the study was to examine if genetic or pharmacologic inhibition of Tpl2 could ameliorate ventilator-induced lung injury. Methods Adult male wild-type and Tpl2-deficient mice were ventilated with normal or high tidal volume for 4 h. Additional wild-type mice were treated with a Tpl2 inhibitor either before or 30 min after initiation of high tidal ventilation. Non-ventilated mice of both genotypes served as controls. The development of lung injury was evaluated by measuring lung mechanics, arterial blood gases, concentrations of proteins, IL-6, and MIP-2 in bronchoalveolar lavage fluid (BALF) and by lung histology. Data were compared by Kruskal-Wallis non-parametric test and significance was defined as p < 0.05. Results Mechanical ventilation with normal tidal volume induced a mild increase of IL-6 in BALF in both strains. High tidal volume ventilation induced lung injury in wild-type mice, characterized by decreased lung compliance, increased concentrations of proteins, IL-6 and MIP-2 in BALF, and inflammatory cell infiltration on histology. All indices of lung injury were ameliorated in Tpl2-deficient mice. Wild-type mice treated with the Tpl2 inhibitor, either prior of after the initiation of high tidal volume ventilation were protected from the development of lung injury, as indicated by preserved lung compliance and lower BALF concentrations of proteins and IL-6, than similarly ventilated, untreated wild-type mice. Conclusions Genetic and pharmacologic inhibition of Tpl2 is protective in a mouse model of ventilator-induced lung injury, ameliorating both high-permeability pulmonary edema and lung inflammation.
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Affiliation(s)
- Evangelos Kaniaris
- Department of Intensive Care Medicine, Experimental Intensive Care Medicine Laboratory, University of Crete, School of Medicine, Heraklio, Crete, 71003, Greece,
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Cruces P, Donoso A, Valenzuela J, Díaz F. Respiratory and hemodynamic effects of a stepwise lung recruitment maneuver in pediatric ARDS: a feasibility study. Pediatr Pulmonol 2013; 48:1135-43. [PMID: 23255291 DOI: 10.1002/ppul.22729] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 10/17/2012] [Indexed: 11/06/2022]
Abstract
BACKGROUND Little is known about the efficacy and safety of recruitment maneuvers (RMs) in pediatric patients with acute respiratory distress syndrome (ARDS). We therefore assessed the effects on gas exchange and lung mechanics and the possible detrimental effects of a sequential lung RMs and decremental positive end-expiratory pressure (PEEP) titration in pediatric ARDS patients. METHODS We enrolled patients <15 years of age with ARDS, progressive hypoxemia, <72 hr of mechanical ventilation, and hemodynamic stability. A step-wise RM and decremental PEEP trial were performed. Safety was evaluated as the occurrence of hypotension and low pulse oxymeter oxygen saturation during the maneuver and development of airleaks after. Efficacy was evaluated as changes in lung compliance (Cdyn ) and gas exchange 1, 12, and 24 hr after the RM. RESULTS We included 25 patients, of median age 5 (1-16) months, median weight 7.0 (4.1-9.2) kg, median PaO2 /FIO2 117 (96-139), and median Cdyn 0.48 (0.41-0.68) ml/cmH2 O/kg at baseline. Thirty RM were performed, with all completed successfully. No airleaks developed. Mild hypotension was detected during four procedures. Following RM, Cdyn , and PaO2 /FIO2 increased significantly (P < 0.01 each), without changes in PaCO2 (P = 0.4). A >25% improvement in lung function (Cdyn or PaO2 /FIO2 ) was observed after 90% of the RM procedures. Gas exchange worsening over the next 24 hr resulted in HFOV use in 36% of patients, while the remaining subjects sustained improvements in oxygenation at 12 and 24 hr. The 28-day mortality rate was 16%. CONCLUSIONS Sequential RMs were safe and well tolerated in hemodynamically stable children with ARDS. RMs and a decremental PEEP trial may improve lung function in pediatric patients with ARDS and severe hypoxemia.
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Affiliation(s)
- Pablo Cruces
- Área de Cuidados Críticos, Hospital Padre Hurtado, Santiago, Chile; Department of Pediatrics, Facultad de Medicina Clínica Alemana Universidad del Desarrollo, Santiago, Chile
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Intraoperative ventilatory strategies to prevent postoperative pulmonary complications: a meta-analysis. Curr Opin Anaesthesiol 2013; 26:126-33. [PMID: 23385321 DOI: 10.1097/aco.0b013e32835e1242] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
PURPOSE OF REVIEW It is uncertain whether patients undergoing short-lasting mechanical ventilation for surgery benefit from lung-protective intraoperative ventilatory settings including the use of lower tidal volumes, higher levels of positive end-expiratory pressure (PEEP) and/or recruitment maneuvers. We meta-analyzed trials testing the effect of lung-protective intraoperative ventilatory settings on the incidence of postoperative pulmonary complications. RECENT FINDINGS Eight articles (1669 patients) were included. Meta-analysis showed a decrease in lung injury development [risk ratio (RR) 0.40; 95% confidence interval (CI) 0.22-0.70; I 0%; number needed to treat (NNT) 37], pulmonary infection (RR 0.64; 95% CI 0.43-0.97; I 0%; NNT 27) and atelectasis (RR 0.67; 95% CI 0.47-0.96; I 48%; NNT 31) in patients receiving intraoperative mechanical ventilation with lower tidal volumes. Meta-analysis also showed a decrease in lung injury development (RR 0.29; 95% CI 0.14-0.60; I 0%; NNT 29), pulmonary infection (RR 0.62; 95% CI 0.40-0.96; I 15%; NNT 33) and atelectasis (RR 0.61; 95% CI 0.41-0.91; I 0%; NNT 29) in patients ventilated with higher levels of PEEP, with or without recruitment maneuvers. SUMMARY Lung-protective intraoperative ventilatory settings have the potential to protect against postoperative pulmonary complications.
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Our favorite unproven ideas for future critical care. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2013; 17 Suppl 1:S9. [PMID: 23514590 PMCID: PMC3603478 DOI: 10.1186/cc11507] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The future of critical care medicine will be shaped not only by the evidence-validated foundations of science, but also by innovations based on unproven and, in many cases, untested concepts and thoughtful visions of scientists and clinicians familiar with the complex problems actually faced in clinical practice. Clinical investigations and trials often lag behind collective experience and impressions, in a well-intentioned and necessary quest to determine the fallacy or validity of ongoing practice. Progress made in this way can be painfully slow, and imperfect theory may prove difficult to challenge. On occasion, an innovative paradigm shift fostered by a novel approach can reorient the forces of academic investigation toward generating an evidence base upon which such concepts and interpretations can find scientific justification. This discussion presents a selected set of ideas to improve the future practice of critical care - each having a defensible rationale, but unconfirmed validity.
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Hess DR, Kondili D, Burns E, Bittner EA, Schmidt UH. A 5-year observational study of lung-protective ventilation in the operating room: a single-center experience. J Crit Care 2013; 28:533.e9-15. [PMID: 23369521 DOI: 10.1016/j.jcrc.2012.11.014] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 11/19/2012] [Accepted: 11/20/2012] [Indexed: 11/25/2022]
Abstract
PURPOSE We assessed the evolution of lung-protective ventilation strategies during anesthesia and identified factors associated with the selection of a nonprotective ventilation strategy. METHODS This retrospective observational study covered a 5-year period from March 2006 to March 2011. It included 45575 adult patients who underwent intubation de novo in the operating room. We considered a tidal volume (VT) greater than 10 mL/kg of ideal body weight (IBW) and/or positive end-expiratory pressure (PEEP) less than 5 cm H2O as not lung protective. We evaluated the use of nonprotective ventilation strategies over time in men and women, by American Society of Anesthesiologists classification, and for elective vs emergent surgery. RESULTS Over the duration of the study, there was a significant reduction in the percentage of patients receiving a VT greater than 10 mL/kg IBW (28.5%-16.3%, P < .001), zero PEEP (27.5%-18.2%, P < .001), and VT greater than 10 mL/kg IBW with PEEP less than 5 cm H2O (13.4%-8.0%, P < .001). The odds of receiving nonprotective ventilation were greater for women than for men, in the first year compared with the last year, and for elective compared with emergent surgery. CONCLUSION Although use of nonprotective ventilation decreased over time, an important percentage of patients continue to receive nonprotective ventilation.
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Affiliation(s)
- Dean R Hess
- Respiratory Care, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
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Bortolotto SJ, Makic MBF. Understanding advanced modes of mechanical ventilation. Crit Care Nurs Clin North Am 2013; 24:443-56. [PMID: 22920468 DOI: 10.1016/j.ccell.2012.06.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Approaches to mechanical ventilation (MV) are consistently changing and the level of ventilator sophistication provides opportunities to improve pulmonary support for critically ill patients. Advanced MV modes are used in the treatment of patients with complex pulmonary conditions. To achieve optimal patient outcomes MV modes that best meet the needs of patient's evolving pulmonary conditions are necessary. It's essential for nurses to integrate pulmonary MV knowledge in the care of critically ill patients. The purpose of this article is to describe the evidence supporting lung protective modes of MV used in the care of critically ill adults.
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Bae HB, Li M, Lee SH, Jeong CW, Kim SJ, Kim HS, Chung SS, Kwak SH. Propofol attenuates pulmonary injury induced by collapse and reventilation of lung in rabbits. Inflammation 2013; 36:680-8. [PMID: 23321722 DOI: 10.1007/s10753-012-9592-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Propofol is an anesthetic drug with antioxidant and anti-inflammatory properties. We previously found that propofol attenuated lipopolysaccharide-induced acute lung injury in rabbits. This study was performed to evaluate the effects of propofol on lung injury caused by collapse and reventilation in rabbits. The wet/dry weight ratio of the lung, lung injury scores, percentage of polymorphonuclear leukocytes, albumin concentration, malondialdehyde, and interleukin-8 levels in bronchoalveolar lavage fluid were significantly increased in both lungs of the reventilation group. The degree of increase in these parameters was more significant in the right (reventilated) than in the left (non-reventilated) lung. Propofol attenuated these changes. These findings suggest that reventilation of a collapsed lung can cause injury in the contralateral non-reventilated lung as well as the reventilated lung. Propofol may provide a beneficial effect on lung injury induced by collapse and reventilation of the lung.
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Affiliation(s)
- Hong-Beom Bae
- Department of Anesthesiology and Pain Medicine, Chonnam National University, Medical School, Gwangju 501-757, South Korea
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Zannin E, Dellaca RL, Kostic P, Pompilio PP, Larsson A, Pedotti A, Hedenstierna G, Frykholm P. Optimizing positive end-expiratory pressure by oscillatory mechanics minimizes tidal recruitment and distension: an experimental study in a lavage model of lung injury. Crit Care 2012; 16:R217. [PMID: 23134702 PMCID: PMC3672594 DOI: 10.1186/cc11858] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 10/23/2012] [Indexed: 11/29/2022] Open
Abstract
Introduction It is well established that during mechanical ventilation of patients with acute respiratory distress syndrome cyclic recruitment/derecruitment and overdistension are potentially injurious for lung tissues. We evaluated whether the forced oscillation technique (FOT) could be used to guide the ventilator settings in order to minimize cyclic lung recruitment/derecruitment and cyclic mechanical stress in an experimental model of acute lung injury. Methods We studied six pigs in which lung injury was induced by bronchoalveolar lavage. The animals were ventilated with a tidal volume of 6 ml/kg. Forced oscillations at 5 Hz were superimposed on the ventilation waveform. Pressure and flow were measured at the tip and at the inlet of the endotracheal tube respectively. Respiratory system reactance (Xrs) was computed from the pressure and flow signals and expressed in terms of oscillatory elastance (EX5). Positive end-expiratory pressure (PEEP) was increased from 0 to 24 cm H2O in steps of 4 cm H2O and subsequently decreased from 24 to 0 in steps of 2 cm H2O. At each PEEP step CT scans and EX5 were assessed at end-expiration and end-inspiration. Results During deflation the relationship between both end-expiratory and end-inspiratory EX5 and PEEP was a U-shaped curve with minimum values at PEEP = 13.4 ± 1.0 cm H2O (mean ± SD) and 13.0 ± 1.0 cm H2O respectively. EX5 was always higher at end-inspiration than at end-expiration, the difference between the average curves being minimal at 12 cm H2O. At this PEEP level, CT did not show any substantial sign of intra-tidal recruitment/derecruitment or expiratory lung collapse. Conclusions Using FOT it was possible to measure EX5 both at end-expiration and at end-inspiration. The optimal PEEP strategy based on end-expiratory EX5 minimized intra-tidal recruitment/derecruitment as assessed by CT, and the concurrent attenuation of intra-tidal variations of EX5 suggests that it may also minimize tidal mechanical stress.
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Lipes J, Bojmehrani A, Lellouche F. Low Tidal Volume Ventilation in Patients without Acute Respiratory Distress Syndrome: A Paradigm Shift in Mechanical Ventilation. Crit Care Res Pract 2012; 2012:416862. [PMID: 22536499 PMCID: PMC3318889 DOI: 10.1155/2012/416862] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Revised: 01/07/2012] [Accepted: 01/09/2012] [Indexed: 01/11/2023] Open
Abstract
Protective ventilation with low tidal volume has been shown to reduce morbidity and mortality in patients suffering from acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Low tidal volume ventilation is associated with particular clinical challenges and is therefore often underutilized as a therapeutic option in clinical practice. Despite some potential difficulties, data have been published examining the application of protective ventilation in patients without lung injury. We will briefly review the physiologic rationale for low tidal volume ventilation and explore the current evidence for protective ventilation in patients without lung injury. In addition, we will explore some of the potential reasons for its underuse and provide strategies to overcome some of the associated clinical challenges.
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Affiliation(s)
- Jed Lipes
- Institut Universitaire de Cardiologie et de Pneumologie de Quebec, Université Laval, Quebec, QC, Canada G1V 4G5
- Department of Adult Critical Care, Jewish General Hospital, McGill University, Montreal, QC, Canada H3T 1E2
| | - Azadeh Bojmehrani
- Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Quebec, Université Laval, Quebec, QC, Canada G1V 4G5
| | - Francois Lellouche
- Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Quebec, Université Laval, Quebec, QC, Canada G1V 4G5
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