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Zeng C, Zhu M, Motta-Ribeiro G, Lagier D, Hinoshita T, Zang M, Grogg K, Winkler T, Vidal Melo MF. Dynamic lung aeration and strain with positive end-expiratory pressure individualized to maximal compliance versus ARDSNet low-stretch strategy: a study in a surfactant depletion model of lung injury. Crit Care 2023; 27:307. [PMID: 37537654 PMCID: PMC10401825 DOI: 10.1186/s13054-023-04591-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 07/26/2023] [Indexed: 08/05/2023] Open
Abstract
BACKGROUND Positive end-expiratory pressure (PEEP) individualized to a maximal respiratory system compliance directly implies minimal driving pressures with potential outcome benefits, yet, raises concerns on static and dynamic overinflation, strain and cyclic recruitment. Detailed accurate assessment and understanding of these has been hampered by methodological limitations. We aimed to investigate the effects of a maximal compliance-guided PEEP strategy on dynamic lung aeration, strain and tidal recruitment using current four-dimensional computed tomography (CT) techniques and analytical methods of tissue deformation in a surfactant depletion experimental model of acute respiratory distress syndrome (ARDS). METHODS ARDS was induced by saline lung lavage in anesthetized and mechanically ventilated healthy sheep (n = 6). Animals were ventilated in a random sequence with: (1) ARDSNet low-stretch protocol; (2) maximal compliance PEEP strategy. Lung aeration, strain and tidal recruitment were acquired with whole-lung respiratory-gated high-resolution CT and quantified using registration-based techniques. RESULTS Relative to the ARDSNet low-stretch protocol, the maximal compliance PEEP strategy resulted in: (1) improved dynamic whole-lung aeration at end-expiration (0.456 ± 0.064 vs. 0.377 ± 0.101, P = 0.019) and end-inspiration (0.514 ± 0.079 vs. 0.446 ± 0.083, P = 0.012) with reduced non-aerated and increased normally-aerated lung mass without associated hyperinflation; (2) decreased aeration heterogeneity at end-expiration (coefficient of variation: 0.498 ± 0.078 vs. 0.711 ± 0.207, P = 0.025) and end-inspiration (0.419 ± 0.135 vs. 0.580 ± 0.108, P = 0.014) with higher aeration in dorsal regions; (3) tidal aeration with larger inspiratory increases in normally-aerated and decreases in poorly-aerated areas, and negligible in hyperinflated lung (Aeration × Strategy: P = 0.026); (4) reduced tidal strains in lung regions with normal-aeration (Aeration × Strategy: P = 0.047) and improved regional distributions with lower tidal strains in middle and ventral lung (Region-of-interest [ROI] × Strategy: P < 0.001); and (5) less tidal recruitment in middle and dorsal lung (ROI × Strategy: P = 0.044) directly related to whole-lung tidal strain (r = 0.751, P = 0.007). CONCLUSIONS In well-recruitable ARDS models, a maximal compliance PEEP strategy improved end-expiratory/inspiratory whole-lung aeration and its homogeneity without overinflation. It further reduced dynamic strain in middle-ventral regions and tidal recruitment in middle-dorsal areas. These findings suggest the maximal compliance strategy minimizing whole-lung dynamically quantified mechanisms of ventilator-induced lung injury with less cyclic recruitment and no additional overinflation in large heterogeneously expanded and recruitable lungs.
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Affiliation(s)
- Congli Zeng
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA.
| | - Min Zhu
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Gabriel Motta-Ribeiro
- Biomedical Engineering Program, Alberto Luiz Coimbra Institute for Graduate Studies and Research in Engineering, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - David Lagier
- Department of Cardiovascular Anesthesiology and Critical Care Medicine, University Hospital Timone, Marseille, France
| | | | - Mingyang Zang
- Department of Biomedical Engineering, Columbia University, New York, NY, USA
| | - Kira Grogg
- Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Tilo Winkler
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Marcos F Vidal Melo
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
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Saxena D, Singh P, Dixit A, Arya B, Bhandari M, Sanwatsarkar S. Does Pulmonary Artery Systolic Pressure as Estimated by Transthoracic Echocardiography Alter the Effect of Positive End-Expiratory Pressure on Arterial Blood Gases and Hemodynamics in Morbidly Obese Patients? Anesth Essays Res 2017; 11:1013-1017. [PMID: 29284866 PMCID: PMC5735441 DOI: 10.4103/aer.aer_73_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Background Positive end-expiratory pressure (PEEP) at the time of induction increases oxygenation by preventing lung atelectasis. However, PEEP may not prove beneficial in all cases. Factors affecting the action of PEEP have not been elucidated well and remain controversial. Pulmonary vasculature has direct bearing on the action of PEEP as has been proven in the previous studies. Thus, this prospective study was planned to evaluate the action of PEEP on the basis of pulmonary artery systolic pressure (PASP) which is noninvasive and easily measured by transthoracic echocardiography. Materials and Methods Seventy morbidly obese patients, the American Society of Anesthesiologists Grade II, or III, aged 20-65 years with body mass index >40 kg/m2, scheduled for elective laparoscopic bariatric surgery were included. Patients who denied consent, those undergoing emergency and/or open surgery and those requiring >2 attempts for intubation were excluded from the study. Ten patients had to be excluded. Thus, a total of sixty patients participated in the study. Thirty patients received no PEEP at the time of induction while other thirty patients were given a PEEP of 10 cm of H2O. Serial ABG samples were taken preoperatively, at the time of intubation, 5 min after intubation, and 10 min after intubation. Patients were then divided into four groups on the basis of PASP value of ≤30 mm Hg with and without PEEP or >30 mm Hg with and without PEEP. Primary Outcome The primary outcome was the effect of PEEP of 10 cm of H2 O on ABG and hemodynamics in morbidly obese patients. Secondary Outcome The secondary outcome was the effect of PASP on the action of PEEP in morbidly obese patients undergoing laparoscopic surgery. Results Patients having PASP of >30 mm Hg had significant improvement in oxygenation on PEEP application (270.11 ± 119.26 mm Hg) as compared to those without PEEP (157.57 ± 109.29 mm Hg) just after intubation. The increase in oxygenation remained significant at all time intervals. Patients with PASP ≤30 mm Hg did not show significant improvement in oxygenation with PEEP application (177.09 ± 85.85 mm Hg as compared to 226.27 ± 92.42 mm Hg without PEEP). Hemodynamic parameters did not show statistically significant alterations. Conclusion Morbidly obese patients who have PASP >30 mm Hg benefit most from the PEEP. Thus, PASP which is an easily measurable noninvasive parameter can be used as a criterion for selecting patients who benefit from PEEP application.
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Affiliation(s)
- Dipti Saxena
- Department of Anesthesiology, Sri Aurobindo Institute of Medical Sciences, MOHAK Hi-Tech Hospital, Indore, Madhya Pradesh, India
| | - Priyank Singh
- Department of Anesthesiology, Sri Aurobindo Institute of Medical Sciences, MOHAK Hi-Tech Hospital, Indore, Madhya Pradesh, India
| | - Atul Dixit
- Department of Anesthesiology, Sri Aurobindo Institute of Medical Sciences, MOHAK Hi-Tech Hospital, Indore, Madhya Pradesh, India
| | - Bipin Arya
- Department of Anesthesiology, Sri Aurobindo Institute of Medical Sciences, MOHAK Hi-Tech Hospital, Indore, Madhya Pradesh, India
| | - Mohit Bhandari
- Department of Bariatric and Metabolic Surgeries, MOHAK Hi-Tech Hospital, Indore, Madhya Pradesh, India
| | - Sadhana Sanwatsarkar
- Department of Anesthesiology, Sri Aurobindo Institute of Medical Sciences, MOHAK Hi-Tech Hospital, Indore, Madhya Pradesh, India
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Retamal J, Bugedo G, Larsson A, Bruhn A. High PEEP levels are associated with overdistension and tidal recruitment/derecruitment in ARDS patients. Acta Anaesthesiol Scand 2015; 59:1161-9. [PMID: 26061818 DOI: 10.1111/aas.12563] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 04/28/2015] [Accepted: 04/30/2015] [Indexed: 01/14/2023]
Abstract
BACKGROUND Positive end-expiratory pressure (PEEP) improves gas exchange and respiratory mechanics, and it may decrease tissue injury and inflammation. The mechanisms of this protective effect are not fully elucidated. Our aim was to determine the intrinsic effects of moderate and higher levels of PEEP on tidal recruitment/derecruitment, hyperinflation, and lung mechanics, in patients with acute respiratory distress syndrome (ARDS). METHODS Nine patients with ARDS of mainly pulmonary origin were ventilated sequential and randomly using two levels of PEEP: 9 and 15 cmH2 O, and studied with dynamic computed tomography at a fix transversal lung region. Tidal recruitment/derecruitment and hyperinflation were determined as non-aerated tissue and hyperinflated tissue variation between inspiration and expiration, expressed as percentage of total weight. We also assessed the maximal amount of non-aerated and hyperinflated tissue weight. RESULTS PEEP 15 cmH2 O was associated with decrease in non-aerated tissue in all the patients (P < 0.01). However, PEEP 15 cmH2 O did not decrease tidal recruitment/derecruitment compared to PEEP 9 cmH2 O (P = 1). In addition, PEEP 15 cmH2 O markedly increased maximal hyperinflation (P < 0.01) and tidal hyperinflation (P < 0.05). Lung compliance decreased with PEEP 15 cmH2 O (P < 0.001). CONCLUSION In this series of patients with ARDS of mainly pulmonary origin, application of high levels of PEEP did not decrease tidal recruitment/derecruitment, but instead consistently increased tidal and maximal hyperinflation.
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Affiliation(s)
- J. Retamal
- Facultad de Medicina; Departamento de Medicina Intensiva; Pontificia Universidad Católica de Chile; Santiago Chile
- Hedenstierna Laboratory; Surgical Science Department; Uppsala University; Uppsala Sweden
| | - G. Bugedo
- Facultad de Medicina; Departamento de Medicina Intensiva; Pontificia Universidad Católica de Chile; Santiago Chile
| | - A. Larsson
- Hedenstierna Laboratory; Surgical Science Department; Uppsala University; Uppsala Sweden
| | - A. Bruhn
- Facultad de Medicina; Departamento de Medicina Intensiva; Pontificia Universidad Católica de Chile; Santiago Chile
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Marumo CK, Otsuki DA, Fantoni DT, Margarido CB, Ambrósio AM, Pelosi P, Auler JOC. Hemodynamic effects of PEEP in a porcine model of HCl-induced mild acute lung injury. Acta Anaesthesiol Scand 2009; 53:190-202. [PMID: 19094174 DOI: 10.1111/j.1399-6576.2008.01842.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Positive end-expiratory pressure (PEEP) and sustained inspiratory insufflations (SI) during acute lung injury (ALI) are suggested to improve oxygenation and respiratory mechanics. We aimed to investigate the hemodynamic effects of PEEP with and without alveolar recruiting maneuver in a mild ALI model induced by inhalation of hydrochloric acid. METHODS Thirty-two pigs were randomly allocated into four groups (Control-PEEP, Control-SI, ALI-PEEP and ALI-SI). ALI was induced by intratracheal instillation of hydrochloric acid. PEEP values were progressively increased and decreased from 5, 10, 15 and 20 cmH2O in all groups. Three SIs maneuvers of 30 cmH2O for 20 s were applied to the assignable groups between each PEEP level. Transesophageal echocardiography (TEE), global hemodynamics, oxygenation indexes and gastric tonometry were measured 5 min after the maneuvers had been concluded and at each established value of PEEP (5, 10, 15 and 20 cmH2O). RESULTS The cardiac index, ejection fraction and end-diastolic volume of right ventricle were significantly (P < 0.001) decreased with PEEP in both Control and ALI groups. Left ventricle echocardiography showed a significant decrease in end-diastolic volume at 20 cmH2O of PEEP (P < 0.001). SIs did not exert any significant hemodynamic effects either early (after 5 min) or late (after 3 h). CONCLUSIONS In a mild ALI model induced by inhalation of hydrochloric acid, significant hemodynamic impairment characterized by cardiac function deterioration occurred during PEEP increment, but SI, probably due to low applied values (30 cmH2O), did not exert further negative hemodynamic effects. PEEP should be used cautiously in ALI caused by acid gastric content inhalation.
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Affiliation(s)
- C K Marumo
- Laboratory of Medical Investigation LIM08, Faculdade de Medicina, Universidade de São Paulo, Brazil
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Abstract
PURPOSE OF REVIEW Bedside assessment of lung recruitment is critical for setting mechanical ventilation during acute respiratory distress syndrome. We review recent findings on this topic and attempt to provide a clinical approach to estimating lung recruitment. RECENT FINDINGS Because of intrinsic limitations in considering single parameters of gas exchange as tools to estimate lung recruitment, investigators have combined different respiratory variables, including respiratory mechanics, to enhance the likelihood of predicting lung recruitment. Confusions on interpreting the physiologic rationale of gas-exchange variations as associated with lung recruitment are still widespread. Techniques of lung imaging, in particular computed-tomography scanning, are still the most applied for reference measurement. Dynamic computed-tomography scanning may allow continuous monitoring of the effects of mechanical ventilation on lung parenchyma. Among the new techniques proposed, electric impedance and positron emission tomography are the most promising. Despite progress, computed-tomography scanning still represents the best technique to measure lung recruitment in clinical practice. SUMMARY Two approaches should be considered to estimate lung recruitment: the use of computed-tomography scanning and indices combining different respiratory variables. Future studies, especially on lung-perfusion distribution, are warranted to improve our knowledge of the pathophysiology of lung recruitment.
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Affiliation(s)
- Pietro Caironi
- Istituto di Anestesiologia e Rianimazione, Dipartimento di Anestesia, Rianimazione, e Terapia del Dolore, Fondazione IRCCS - Ospedale Maggiore Policlinico, Mangiagalli, Regina Elena di Milano, Università degli Studi di Milano, Milan, Italy
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Luecke T, Meinhardt JP, Herrmann P, Weiss A, Quintel M, Pelosi P. Oleic acid vs saline solution lung lavage-induced acute lung injury: effects on lung morphology, pressure-volume relationships, and response to positive end-expiratory pressure. Chest 2006; 130:392-401. [PMID: 16899837 DOI: 10.1378/chest.130.2.392] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
OBJECTIVE To compare two lung injury models (oleic acid [OA] and saline solution washout [SW]) regarding lung morphology, regional inflation, and recruitment during static pressure-volume (PV) curves, and the effects of positive end-expiratory pressure (PEEP) below and above the lower inflection point (Pflex). METHODS Fourteen adult pigs underwent OA or SW lung injury. Lung volumes were measured using CT. PV curves were obtained with simultaneous CT scanning at lung apex and base. Fractional inflation and recruitment were compared to data on PEEP above and below Pflex. RESULTS Severity of lung injury was comparable. At zero PEEP, SW showed an increased amount of edema and poorly aerated lung volume, recruitment during inspiration, and a better oxygenation response with PEEP. Whole-lung PV curves were similar in both models, reflecting changes in alveolar inflation or deflation. On the inspiratory PV limb, recruitment and inflation were on the same line, while there was a substantial difference between deflation and derecruitment on the expiratory limb. PEEP-induced recruitment at lung apex and base was at or above the derecruitment line on the expiratory limb and showed no relationship to the whole-lung expiratory PV curve. CONCLUSIONS The following conclusions were made: (1) OA and SW models are comparable in mechanics but not in lung injury characteristics; (2) neither inspiratory nor expiratory whole-lung PV curves are useful to select PEEP in order to optimize recruitment; and (3) after recruitment, there is no difference in derecruitment between the models at high PEEP, while more collapse occurs at lower PEEP in the basal sections of SW lungs.
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Affiliation(s)
- Thomas Luecke
- Department of Anesthesiology and Critical Care Medicine, University Hospital of Mannheim, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Theodor-Kutzer Ufer, Germany.
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Simon BA, Easley RB, Grigoryev DN, Ma SF, Ye SQ, Lavoie T, Tuder RM, Garcia JGN. Microarray analysis of regional cellular responses to local mechanical stress in acute lung injury. Am J Physiol Lung Cell Mol Physiol 2006; 291:L851-61. [PMID: 16782753 DOI: 10.1152/ajplung.00463.2005] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Human acute lung injury is characterized by heterogeneous tissue involvement, leading to the potential for extremes of mechanical stress and tissue injury when mechanical ventilation, required to support critically ill patients, is employed. Our goal was to establish whether regional cellular responses to these disparate local mechanical conditions could be determined as a novel approach toward understanding the mechanism of development of ventilator-associated lung injury. We utilized cross-species genomic microarrays in a unilateral model of ventilator-associated lung injury in anesthetized dogs to assess regional cellular responses to local mechanical conditions that potentially contribute pathogenic mechanisms of injury. Highly significant regional differences in gene expression were observed between lung apex/base regions as well as between gravitationally dependent/nondependent regions of the base, with 367 and 1,544 genes differentially regulated between these regions, respectively. Major functional groupings of differentially regulated genes included inflammation and immune responses, cell proliferation, adhesion, signaling, and apoptosis. Expression of genes encoding both acute lung injury-associated inflammatory cytokines and protective acute response genes were markedly different in the nondependent compared with the dependent regions of the lung base. We conclude that there are significant differences in the local responses to stress within the lung, and consequently, insights into the cellular responses that contribute to ventilator-associated lung injury development must be sought in the context of the mechanical heterogeneity that characterizes this syndrome.
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Affiliation(s)
- Brett A Simon
- Department of Anesthesiology and Critical Medicine, Tower 711, Johns Hopkins Hospital, Baltimore, MD 21287-8711, USA.
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Abstract
Alveolar recruitment is one of the primary goals of respiratory care for acute lung injury. It is aimed at improving pulmonary gas exchange and, even more important, at protecting the lungs from ventilator-induced trauma. This review addresses the concept of alveolar recruitment for lung protection in acute lung injury. It provides reasons for why atelectasis and atelectrauma should be avoided; it analyses current and future approaches on how to achieve and preserve alveolar recruitment; and it discusses the possibilities of detecting alveolar recruitment and derecruitment. The latter is of particular clinical relevance because interventions aimed at lung recruitment are often undertaken without simultaneous verification of their effectiveness.
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Affiliation(s)
- G Mols
- Department of Anaesthesia and Critical Care Medicine, University of Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany.
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Luecke T, Pelosi P. Clinical review: Positive end-expiratory pressure and cardiac output. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2005; 9:607-21. [PMID: 16356246 PMCID: PMC1414045 DOI: 10.1186/cc3877] [Citation(s) in RCA: 247] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In patients with acute lung injury, high levels of positive end-expiratory pressure (PEEP) may be necessary to maintain or restore oxygenation, despite the fact that 'aggressive' mechanical ventilation can markedly affect cardiac function in a complex and often unpredictable fashion. As heart rate usually does not change with PEEP, the entire fall in cardiac output is a consequence of a reduction in left ventricular stroke volume (SV). PEEP-induced changes in cardiac output are analyzed, therefore, in terms of changes in SV and its determinants (preload, afterload, contractility and ventricular compliance). Mechanical ventilation with PEEP, like any other active or passive ventilatory maneuver, primarily affects cardiac function by changing lung volume and intrathoracic pressure. In order to describe the direct cardiocirculatory consequences of respiratory failure necessitating mechanical ventilation and PEEP, this review will focus on the effects of changes in lung volume, factors controlling venous return, the diastolic interactions between the ventricles and the effects of intrathoracic pressure on cardiac function, specifically left ventricular function. Finally, the hemodynamic consequences of PEEP in patients with heart failure, chronic obstructive pulmonary disease and acute respiratory distress syndrome are discussed.
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Affiliation(s)
- Thomas Luecke
- Section Head, Critical Care, Department of Anesthesiology and Critical Care Medicine, University Hospital of Mannheim, Germany
| | - Paolo Pelosi
- Associate Professor in Anaesthesia and Intensive Care, Dipartimento di Scienze Cliniche e Biologiche, Università degli Studi dell'Insubria, Varese, Italy
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Halbertsma FJJ, van der Hoeven JG. Lung recruitment during mechanical positive pressure ventilation in the PICU: what can be learned from the literature? Anaesthesia 2005; 60:779-90. [PMID: 16029227 DOI: 10.1111/j.1365-2044.2005.04187.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A literature review was conducted to assess the evidence for recruitment manoeuvres used in conventional mechanical positive pressure ventilation. A total of 61 studies on recruitment manoeuvres were identified: 13 experimental, 31 ICU, 6 PICU and 12 anaesthesia studies. Recruitment appears to be a continuous process during inspiration and expiration and is determined by peak inspiratory pressure (PIP) and positive end expiratory pressure (PEEP). Single or repeated recruitment manoeuvres may result in a statistically significant increase in oxygenation; however, this is short lasting and clinically irrelevant, especially in late ARDS and pneumonia. Temporary PIP elevation may be effective but only after PEEP loss (for example disconnection and tracheal suctioning). Continuous PEEP elevation and prone positioning can increase P(a)O2 significantly. Adverse haemodynamic or barotrauma effects are reported in various studies. No data exist on the effect of recruitment manoeuvres on mortality, morbidity, length of stay or duration of mechanical ventilation. Although recruitment manoeuvres can improve oxygenation, they can potentially increase lung injury, which eventually determines outcome. Based on the presently available literature, prone position and sufficient PEEP as part of a lung protective ventilation strategy seem to be the safest and most effective recruitment manoeuvres. As paediatric physiology is essentially different from adult, paediatric studies are needed to determine the role of recruitment manoeuvres in the PICU.
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Affiliation(s)
- F J J Halbertsma
- Department of Paediatric Intensive Care, University Medical Centre Nijmegen St. Radboud, PB 9101, 6500 HB Nijmegen, the Netherlands.
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Luecke T, Herrmann P, Kraincuk P, Pelosi P. Computed tomography scan assessment of lung volume and recruitment during high-frequency oscillatory ventilation. Crit Care Med 2005; 33:S155-62. [PMID: 15753722 DOI: 10.1097/01.ccm.0000155916.47455.df] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE This review describes how computed tomography has increased our understanding of the pathophysiology of acute respiratory distress syndrome. It summarizes current knowledge about lung volume changes and alveolar recruitment during high-frequency oscillatory ventilation (HFOV) assessed by computed tomography (CT), outlines potential problems when comparing HFOV with conventional ventilation (CV) as a result of the different pressure-time profiles, and describes future research directions. DATA SOURCE CT allows accurate assessment of total lung volumes and differentiation between overinflated, normally aerated, poorly aerated, and nonaerated lung regions. It allows for classification of different patterns of consolidation and may be predictive for the potential for recruitment. DATA SUMMARY Experimental data suggest that HFOV at mean airway pressures (mPaw) set according to a static PV curve leads to effective lung recruitment but results in overall lung volumes that are considerably higher than those predicted from the PV relationship. In saline-lavaged sheep, similar changes in total lung volumes and subvolumes were observed during HFOV and CV. One single study specifically assessed lung volume recruitment during HFOV as compared with CV in eight patients with acute respiratory distress syndrome from pneumonia or sepsis. After 48 hrs on HFOV, total ventilated lung volume was significantly increased, whereas only a minor increase in overinflated lung volume was observed. These changes correlated with a significant improvement in gas exchange. CONCLUSION CT is a valuable tool to quantify recruitment and overinflation during HFOV. Additional studies are needed to better characterize the specific effects of HFOV on lung volume and morphology.
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Affiliation(s)
- Thomas Luecke
- Department of Anesthesiology, University Hospital of Mannheim, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany
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Roth H, Luecke T, Deventer B, Joachim A, Herrmann P, Quintel M. Pulmonary gas distribution during ventilation with different inspiratory flow patterns in experimental lung injury -- a computed tomography study. Acta Anaesthesiol Scand 2004; 48:851-61. [PMID: 15242429 DOI: 10.1111/j.1399-6576.2004.00430.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND There is still controversy about the optimal inspiratory flow pattern for ventilation of patients with acute lung injury. The aim of this study was to compare the effects of pressure-controlled ventilation (PCV) with a decelerating inspiratory flow with volume-controlled ventilation (VCV) with constant inspiratory flow on pulmonary gas distribution (PGD) in experimentally induced ARDS. METHODS Sixteen adult sheep were randomized to be ventilated with PCV or VCV after surfactant depletion by repeated bronchoalveolar lavage. Positive end-expiratory pressure (PEEP) was increased in a stepwise manner from zero end-expiratory pressure (ZEEP) to 7, 14 and 21 cm H(2)O in hourly intervals. Respiratory rate, inspiration-to-expiration ratio and tidal volume were kept constant. Central hemodynamics, gas exchange and airway pressures were measured. Electron beam computed tomographic (EBCT) scans of the entire lungs were performed at baseline (preinjury) and each level of end-expiratory pressure during an inspiratory and expiratory hold maneuver. The lungs were three-dimensionally reconstructed and volumetric assessments were made separating the lungs into four subvolumes classified as overinflated, normally aerated, poorly aerated and nonaerated. RESULTS Pressure-controlled ventilation led to a decrease in peak airway pressure and an increase in mean airway pressure. No differences between groups were found regarding plateau pressures, hemodynamics and gas exchange. Recruitment, defined as a decrease in expiratory lung volume classified as nonaerated, was similar in both groups and predominantly associated with PEEP. Overinflated lung volumes were increased with PCV. CONCLUSIONS In this model of acute lung injury, ventilation with decelerating inspiratory flow had no beneficial effects on PGD when compared with ventilation with constant inspiratory flow, while the increase in overinflated lung volumes may raise concerns regarding potential ventilator-associated lung injury.
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Affiliation(s)
- H Roth
- Department of Anesthesiology and Critical Care, University Hospital of Mannheim, Faculty of Clinical Medicine, University of Heidelberg, Heidelberg, Germany
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