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Hanson A, Göthberg S, Nilsson K, Hedenstierna G. Recruitment and PEEP level influences long-time aeration in saline-lavaged piglets: an experimental model. Paediatr Anaesth 2012; 22:1072-9. [PMID: 22340954 DOI: 10.1111/j.1460-9592.2012.03817.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To evaluate aeration/ventilation in saline-lavaged piglets during a 3-h follow-up after a recruitment maneuver (RM)/PEEP titration compared with PEEP 10 cmH2O without a RM. BACKGROUND Lung recruitment and PEEP titration are used to find a PEEP preventing repetitive opening/collapsing of lung. METHODS Twenty-one lung-lavaged piglets, mean age 7 weeks and mean weight 10 kg; a RM-group and a PEEP10-group, were ventilated at PEEP 5 cmH2O (baseline) followed by zero PEEP ventilation. In the RM-group, tidal elimination of CO2 and dynamic compliance (Cdyn) guided recruitment and PEEP titration, respectively. A final 3-h ventilation followed using PEEP 2 cmH2O above the first decline of Cdyn and end-inspiratory pressure (EIP) for a target tidal volume (VT) of 10 ml · kg(-1). In the PEEP10-group, PEEP 10 cmH2O without a RM was used during the final 3-h ventilation. CT scans and blood gases were repeated every 30 min. Airway pressures, Cdyn and hemodynamics were continuously recorded. RESULTS Aeration improved without differences between groups. The RM-group PEEP level of 10 ± 0.6 cmH2O did not differ from the PEEP10-group. Compared to baseline EIP was lower in the RM-group after 3-h ventilation. In both groups, driving pressure (DP) was lower and Cdyn higher than baseline. In the RM-group, final EIP and DP were lower and Cdyn higher than in the PEEP10-group. CONCLUSIONS Both RM/PEEP titration and PEEP elevation resulted in improved aeration without differences between groups at the end point. Lung aeration was achieved at lower EIP and DP and higher Cdyn in the RM-group than in the PEEP10-group.
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Affiliation(s)
- Angela Hanson
- The Department of Paediatric Anaesthesia and Intensive Care, The Queen Silvia Children's Hospital, University of Gothenburg, Göteborg, Sweden.
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Hua S, Zhang X, Zhang S, Xu J, Feng Z. Effects of different ventilation strategies on lung injury in newborn rabbits. Pediatr Pulmonol 2012; 47:1103-12. [PMID: 22451169 DOI: 10.1002/ppul.22541] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 01/11/2012] [Indexed: 11/12/2022]
Abstract
BACKGROUND The results from experimental and clinical studies have shown that mechanical ventilation (MV) and/or hyperoxia may aggravate a pre-existing lung injury, or even cause lung injury in healthy lungs, despite the fact that it might be the only life-saving intervention available to a patient. The present study was designed to investigate the roles of MV and hyperoxia in the pathogenesis of lung injury. METHODS Newborn New Zealand white rabbits were randomly assigned to an unventilated air control group or to one of the 2 × 3 × 3 ventilation strategies using a factorial design. The experimental groups were assigned different fractions of inspired oxygen (FiO(2)), peak inspiratory pressures (PIP), and respiratory times (RT). The lung wet-to-dry ratio (W/D), lung histopathology scores, and cells in the bronchoalveolar lavage fluid (BALF) were analyzed for each group. The apoptosis levels were studied by immunohistochemistry and a terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) assay. RESULTS Different ventilation regimes induced alterations in microvascular permeability, differential histopathological grading, WBC and/or neutrophil and/or lymphocyte influx, and apoptosis levels; moreover, there were significant correlations and interaction effects between these indices. CONCLUSIONS Our data demonstrate that different ventilation regimes can induce lung injury and that the interaction effects of the FiO(2), the PIP and the RT may play crucial roles in the pathogenesis of lung injury.
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Affiliation(s)
- Shaodong Hua
- Department of Pediatrics, BaYi Children's Hospital of The General Military Hospital of Beijing PLA, Beijing, PR China
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Jauncey-Cooke J, Bogossian F, Hough JL, Schibler A, Davies MW, Grant CA, Gibbons K, East CE. Lung recruitment manoeuvres for reducing respiratory morbidity in mechanically ventilated neonates. Hippokratia 2012. [DOI: 10.1002/14651858.cd009969] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
| | - Fiona Bogossian
- School of Nursing and Midwifery; The University of Queensland; Herston Australia
| | - Judith L Hough
- Mater Medical Research Institute; South Brisbane Queensland Australia 4101
| | - Andreas Schibler
- Mater Children's Hospital; Paediatric Intensive Care Unit; Raymond Terrace South Brisbane Queensland Australia 4101
| | - Mark W Davies
- Department of Paediatrics & Child Health, The University of Queensland; Grantley Stable Neonatal Unit, Royal Brisbane and Women's Hospital; Butterfield St Herston Brisbane Queensland Australia 4029
| | - Caroline A Grant
- Mater Children's Hospital; Paediatric Intensive Care Unit; Raymond Terrace South Brisbane Queensland Australia 4101
| | - Kristen Gibbons
- Mater Medical Research Institute; Clinical Research Support Unit; Level 3, Quarters Building Raymond Terrace South Brisbane Queensland Australia 4101
| | - Christine E East
- School of Nursing and Midwifery, Monash University / Southern Health; School of Nursing and Midwifery, University of Queensland; 246 Clayton Rd Clayton Victoria Australia 3168
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Schwenninger D, Runck H, Schumann S, Haberstroh J, Guttmann J. Locally measured shear moduli of pulmonary tissue and global lung mechanics in mechanically ventilated rats. J Appl Physiol (1985) 2012; 113:273-80. [PMID: 22628379 DOI: 10.1152/japplphysiol.01620.2011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study was aimed at measuring shear moduli in vivo in mechanically ventilated rats and comparing them to global lung mechanics. Wistar rats (n = 28) were anesthetized, tracheally intubated, and mechanically ventilated in supine position. The animals were randomly assigned to the healthy control or the lung injury group where lung injury was induced by bronchoalveolar lavage. The respiratory system elastance E(rs) was analyzed based on the single compartment resistance/elastance lung model using multiple linear regression analysis. The shear modulus (G) of alveolar parenchyma was studied using a newly developed endoscopic system with adjustable pressure at the tip that was designed to induce local mechanostimulation. The data analysis was then carried out with an inverse finite element method. G was determined at continuous positive airway pressure (CPAP) levels of 15, 17, 20, and 30 mbar. The resulting shear moduli of lungs in healthy animals increased from 3.3 ± 1.4 kPa at 15 mbar CPAP to 5.8 ± 2.4 kPa at 30 mbar CPAP (P = 0.012), whereas G was ~2.5 kPa at all CPAP levels for the lung-injured animals. Regression analysis showed a negative correlation between G and relative E(rs) in the control group (r = -0.73, P = 0.008 at CPAP = 20 mbar) and no significant correlation in the lung injury group. These results suggest that the locally measured G were inversely associated with the elastance of the respiratory system. Rejecting the study hypothesis the researchers concluded that low global respiratory system elastance is related to high local resistance against tissue deformation.
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Affiliation(s)
- David Schwenninger
- Division of Experimental Anaesthesiology, University Medical Center Freiburg, Hugstetter Strasse 55, Freiburg, Germany.
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Eslami S, Abu-Hanna A, Schultz MJ, de Jonge E, de Keizer NF. Evaluation of consulting and critiquing decision support systems: effect on adherence to a lower tidal volume mechanical ventilation strategy. J Crit Care 2011; 27:425.e1-8. [PMID: 22172793 DOI: 10.1016/j.jcrc.2011.07.082] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 07/01/2011] [Accepted: 07/29/2011] [Indexed: 01/22/2023]
Abstract
PURPOSE Our hypothesis was that both styles are effective to decrease tidal volume (V(T)) but that critiquing comprises the most effective strategy. The purpose of this study is to test this hypothesis by measuring the effect of an active computerized decision support system, in 2 communication styles, consulting and critiquing, on adherence to V(T) recommendations. MATERIALS AND METHODS We developed and implemented an active computerized decision support system (CDSS) working in a consulting style that always shows the preferred V(T) and in a critiquing style that shows the preferred V(T) only if V(T) is above the desired threshold. A prospective, off-on-off-on study evaluated the system's performance in a mixed medical-surgical intensive care unit of a university hospital. RESULTS Four thousand seven hundred sixty-four patient-day mechanical ventilation from 757 patients were analyzed. The percentage of ventilation time in excess of 6 and 8 mL/kg predicted body weight decreased significantly after intervening with the consulting style (12% reduction and P < .001; 22% reduction and P < .001) and again increased after stopping the CDSS (11% increase and P < .001; 29% increase and P < .001). With the critiquing CDSS, the percentage of ventilation time in excess of 6 and 8 mL/kg predicted body weight again decreased significantly (6% reduction and P < .001; 15% reduction and P < .001). CONCLUSIONS The use of a CDSS in both communication styles improved the use of lower V(T)s for ventilated patients. When decision support was not sustained, adherence to low V(T) fell back to its original value. Interestingly, the consulting style had a slightly larger effect. This may stem from the high frequency of showing reminders in this style and the relatively simple underlying guideline where its display implies the associated action of lowering V(T). The consulting style, however, was more interruptive for clinicians, calling upon the need to strike a balance between effect and intrusiveness.
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Affiliation(s)
- Saeid Eslami
- Department of Medical Informatics, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
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Lung aeration during ventilation after recruitment guided by tidal elimination of carbon dioxide and dynamic compliance was better than after end-tidal carbon dioxide targeted ventilation: a computed tomography study in surfactant-depleted piglets. Pediatr Crit Care Med 2011; 12:e362-8. [PMID: 21263364 DOI: 10.1097/pcc.0b013e31820aba6e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To test the hypothesis that tidal elimination of carbon dioxide and dynamic compliance guided lung recruitment and positive end-expiratory pressure titration in surfactant-depleted piglets result in improved aeration (repeated computed tomography scans) and reduced ventilation pressures compared to those of a control group with conventional end-tidal carbon dioxide targeted ventilation. DESIGN Prospective animal investigation. SETTING Clinical physiology research laboratory. SUBJECTS Seventeen saline-lavaged piglets. INTERVENTIONS The piglets were initially ventilated at an end-inspiratory pressure of 20 cm H2O, a positive end-expiratory pressure of 5 cm H2O, and a tidal volume of 10 mL kg for an end-tidal carbon dioxide target of 30-45 torr followed by 5 mins of ventilation without positive end-expiratory pressure. After this, the control group was ventilated for the same end-tidal carbon dioxide target during the study period. In the recruitment group, the protocol started with an increase of the positive end-expiratory pressure to 15 cm H2O. The end-inspiratory pressure was then increased in steps of 3 cm H2O to a tidal elimination of carbon dioxide peak/plateau in one recruitment group and further increased in two steps in a second recruitment group. A downward positive end-expiratory pressure titration was followed by continuous dynamic compliance monitoring. The "open lung positive end-expiratory pressure" was set 2 cm H2O above the positive end-expiratory pressure at the first dynamic compliance decline and used for a final "open lung ventilation" period. MEASUREMENTS AND MAIN RESULTS The recruitment groups showed better aeration, lower ventilatory pressure amplitude, and better dynamic compliance than the control group at the end of the study. Recruitment using airway pressures above the tidal elimination of carbon dioxide peak/plateau did not improve aeration. Using end-tidal carbon dioxide targeted ventilation in the control group restored aeration after the ventilation without positive end-expiratory pressure, but no recruitment or improvement of dynamic compliance was measured. CONCLUSIONS Aeration was significantly better after recruitment and positive end-expiratory pressure titration than in a control group managed by "conventional" end-tidal carbon dioxide targeted ventilation. An increase of the end-inspiratory pressure above the tidal elimination of carbon dioxide peak/plateau did not result in an increased amount of normally aerated lung. A recruitment maneuver resulted in a lower ventilatory amplitude for achieving a target tidal volume and better dynamic compliance at the end of the study period compared to those of the control group.
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Reiss LK, Kowallik A, Uhlig S. Recurrent recruitment manoeuvres improve lung mechanics and minimize lung injury during mechanical ventilation of healthy mice. PLoS One 2011; 6:e24527. [PMID: 21935418 PMCID: PMC3174196 DOI: 10.1371/journal.pone.0024527] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 08/12/2011] [Indexed: 11/18/2022] Open
Abstract
INTRODUCTION Mechanical ventilation (MV) of mice is increasingly required in experimental studies, but the conditions that allow stable ventilation of mice over several hours have not yet been fully defined. In addition, most previous studies documented vital parameters and lung mechanics only incompletely. The aim of the present study was to establish experimental conditions that keep these parameters within their physiological range over a period of 6 h. For this purpose, we also examined the effects of frequent short recruitment manoeuvres (RM) in healthy mice. METHODS Mice were ventilated at low tidal volume V(T) = 8 mL/kg or high tidal volume V(T) = 16 mL/kg and a positive end-expiratory pressure (PEEP) of 2 or 6 cm H(2)O. RM were performed every 5 min, 60 min or not at all. Lung mechanics were followed by the forced oscillation technique. Blood pressure (BP), electrocardiogram (ECG), heart frequency (HF), oxygen saturation and body temperature were monitored. Blood gases, neutrophil-recruitment, microvascular permeability and pro-inflammatory cytokines in bronchoalveolar lavage (BAL) and blood serum as well as histopathology of the lung were examined. RESULTS MV with repetitive RM every 5 min resulted in stable respiratory mechanics. Ventilation without RM worsened lung mechanics due to alveolar collapse, leading to impaired gas exchange. HF and BP were affected by anaesthesia, but not by ventilation. Microvascular permeability was highest in atelectatic lungs, whereas neutrophil-recruitment and structural changes were strongest in lungs ventilated with high tidal volume. The cytokines IL-6 and KC, but neither TNF nor IP-10, were elevated in the BAL and serum of all ventilated mice and were reduced by recurrent RM. Lung mechanics, oxygenation and pulmonary inflammation were improved by increased PEEP. CONCLUSIONS Recurrent RM maintain lung mechanics in their physiological range during low tidal volume ventilation of healthy mice by preventing atelectasis and reduce the development of pulmonary inflammation.
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Affiliation(s)
- Lucy Kathleen Reiss
- Institute of Pharmacology and Toxicology, Medical Faculty of RWTH Aachen University, Aachen, Germany.
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Bickenbach J, Biener I, Czaplik M, Nolte K, Dembinski R, Marx G, Rossaint R, Fries M. Neurological outcome after experimental lung injury. Respir Physiol Neurobiol 2011; 179:174-80. [PMID: 21855657 DOI: 10.1016/j.resp.2011.08.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2011] [Revised: 07/29/2011] [Accepted: 08/01/2011] [Indexed: 10/17/2022]
Abstract
We examined the influences of acute lung injury and hypoxia on neurological outcome. Functional performance was assessed using a neurocognitive test and a neurologic deficit score (NDS) five days before. On experimental day, mechanically ventilated pigs were randomized to hypoxia only (HO group, n=5) or to acute lung injury (ALI group, n=5). Hemodynamics, respiratory mechanics, systemic cytokines and further physiologic variables were obtained at baseline, at the time of ALI, 2, 4 and 8h thereafter. Subsequently, injured lungs were recruited and animals weaned from the ventilator. Neurocognitive testing was re-examined for five days. Then, brains were harvested for neurohistopathology. After the experiment, neurocognitive performance was significantly worsened and the NDS increased in the ALI group. Histopathology revealed no significant differences. Oxygenation was comparable between groups although significantly higher inspiratory pressures occured after ALI. Cytokines showed a trend towards higher levels after ALI. Neurocognitive compromise after ALI seems due to a more pronounced inflammatory response and complex mechanical ventilation.
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Krebs J, Pelosi P, Tsagogiorgas C, Haas J, Yard B, Rocco PRM, Luecke T. Time course of lung inflammatory and fibrogenic responses during protective mechanical ventilation in healthy rats. Respir Physiol Neurobiol 2011; 178:323-8. [PMID: 21787886 DOI: 10.1016/j.resp.2011.07.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 07/08/2011] [Accepted: 07/10/2011] [Indexed: 01/22/2023]
Abstract
This study aimed to assess pulmonary inflammatory and fibrogenic responses and their impact on lung mechanics and histology in healthy rats submitted to protective mechanical ventilation for different experimental periods. Eighteen Wistar rats were randomized to undergo open lung-mechanical ventilation (OL-MV) for 1, 6 or 12 h. Following a recruitment maneuver, a decremental PEEP trial was performed and PEEP set according to the minimal respiratory system static elastance. Respiratory system, lung, and chest-wall elastance and gas-exchange were maintained throughout the 12 h experimental period. Histological lung injury score remained low at 1 and 6 h, but was higher at 12 h due to overinflation. A moderate inflammatory response was observed with a distinct peak at 6h. Compared to unventilated controls, type I procollagen mRNA expression was decreased at 1 and 12h, while type III procollagen expression decreased throughout the 12h experimental period. In conclusion, OL-MV in healthy rats yielded overinflation after 6 h even though respiratory elastance and gas-exchange were preserved for up to 12 h.
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Affiliation(s)
- Joerg Krebs
- Department of Anaesthesiology and Critical Care Medicine, University Hospital Mannheim, Faculty of Medicine, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68165 Mannheim, Germany
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Roy SK, Kendrick D, Sadowitz BD, Gatto L, Snyder K, Satalin JM, Golub LM, Nieman G. Jack of all trades: pleiotropy and the application of chemically modified tetracycline-3 in sepsis and the acute respiratory distress syndrome (ARDS). Pharmacol Res 2011; 64:580-9. [PMID: 21767646 DOI: 10.1016/j.phrs.2011.06.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Sepsis is a disease process that has humbled the medical profession for centuries with its resistance to therapy, relentless mortality, and pathophysiologic complexity. Despite 30 years of aggressive, concerted, well-resourced efforts the biomedical community has been unable to reduce the mortality of sepsis from 30%, nor the mortality of septic shock from greater than 50%. In the last decade only one new drug for sepsis has been brought to the market, drotrecogin alfa-activated (Xigris™), and the success of this drug has been limited by patient safety issues. Clearly a new agent is desperately needed. The advent of recombinant human immune modulators held promise but the outcomes of clinical trials using biologics that target single immune mediators have been disappointing. The complex pathophysiology of the systemic inflammatory response syndrome (SIRS) is self-amplifying and redundant at multiple levels. In this review we argue that perhaps pharmacologic therapy for sepsis will only be successful if it addresses this pathophysiologic complexity; the drug would have to be pleiotropic, working on many components of the inflammatory cascade at once. In this context, therapy that targets any single inflammatory mediator will not adequately address the complexity of SIRS. We propose that chemically modified tetracycline-3, CMT-3 (or COL-3), a non-antimicrobial modified tetracycline with pleiotropic anti-inflammatory properties, is an excellent agent for the management of sepsis and its associated complication of the acute respiratory distress syndrome (ARDS). The purpose of this review is threefold: (1) to examine the shortcomings of current approaches to treatment of sepsis and ARDS in light of their pathophysiology, (2) to explore the application of COL-3 in ARDS and sepsis, and finally (3) to elucidate the mechanisms of COL-3 that may have potential therapeutic benefit in ARDS and sepsis.
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Affiliation(s)
- Shreyas K Roy
- Department of Surgery, Upstate University Hospital, 750 East Adams Street, Syracuse, NY 13210, USA.
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Abstract
Ventilator-induced lung injury (VILI) consists of tissue damage and a biological response resulting from the application of inappropriate mechanical forces to the lung parenchyma. The current paradigm attributes VILI to overstretching due to very high-volume ventilation (volutrauma) and cyclic changes in aeration due to very low-volume ventilation (atelectrauma); however, this model cannot explain some research findings. In the present review, we discuss the relevance of cyclic deformation of lung tissue as the main determinant of VILI. Parenchymal stability resulting from the interplay of respiratory parameters such as tidal volume, positive end-expiratory pressure or respiratory rate can explain the results of different clinical trials and experimental studies that do not fit with the classic volutrauma/atelectrauma model. Focusing on tissue deformation could lead to new bedside monitoring and ventilatory strategies.
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Affiliation(s)
- Guillermo M Albaiceta
- Intensive Care Unit, Hospital Universitario Central de Asturias, Departamento de Biología Funcional, Universidad de Oviedo, Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Celestino Villamil s/n, 33006 Oviedo, Spain
- CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Spain
| | - Lluis Blanch
- CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Spain
- Critical Care Center, Hospital de Sabadell, Corporació Parc Taulí, Insitut Universitari Fundació Parc Tauli, Universitat Autònoma de Barcelona, Parc Taulí s/n, 08208 Sabadell, Spain
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Seah AS, Grant KA, Aliyeva M, Allen GB, Bates JHT. Quantifying the roles of tidal volume and PEEP in the pathogenesis of ventilator-induced lung injury. Ann Biomed Eng 2011; 39:1505-16. [PMID: 21203845 DOI: 10.1007/s10439-010-0237-6] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Accepted: 12/21/2010] [Indexed: 11/28/2022]
Abstract
Management of patients with acute lung injury (ALI) rests on achieving a balance between the gas exchanging benefits of mechanical ventilation and the exacerbation of tissue damage in the form of ventilator-induced lung injury (VILI). Optimizing this balance requires an injury cost function relating injury progression to the measurable pressures, flows, and volumes delivered during mechanical ventilation. With this in mind, we mechanically ventilated naive, anesthetized, paralyzed mice for 4 h using either a low or high tidal volume (Vt) with either moderate or zero positive end-expiratory pressure (PEEP). The derecruitability of the lung was assessed every 15 min in terms of the degree of increase in lung elastance occurring over 3 min following a recruitment maneuver. Mice could be safely ventilated for 4 h with either a high Vt or zero PEEP, but when both conditions were applied simultaneously the lung became increasingly unstable, demonstrating worsening injury. We were able to mimic these data using a computational model of dynamic recruitment and derecruitment that simulates the effects of progressively increasing surface tension at the air-liquid interface, suggesting that the VILI in our animal model progressed via a vicious cycle of alveolar leak, degradation of surfactant function, and increasing tissue stress. We thus propose that the task of ventilating the injured lung is usefully understood in terms of the Vt-PEEP plane. Within this plane, non-injurious combinations of Vt and PEEP lie within a "safe region", the boundaries of which shrink as VILI develops.
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Affiliation(s)
- Adrian S Seah
- Department of Surgery, Fletcher Allen Health Care, Burlington, VT 05405, USA
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A recruitment maneuver increases oxygenation after intubation of hypoxemic intensive care unit patients: a randomized controlled study. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2010; 14:R76. [PMID: 20426859 PMCID: PMC2887199 DOI: 10.1186/cc8989] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2009] [Revised: 02/10/2010] [Accepted: 04/28/2010] [Indexed: 12/28/2022]
Abstract
Introduction Tracheal intubation and anaesthesia promotes lung collapse and hypoxemia. In acute lung injury patients, recruitment maneuvers (RMs) increase lung volume and oxygenation, and decrease atelectasis. The aim of this study was to evaluate the efficacy and safety of RMs performed immediately after intubation. Methods This randomized controlled study was conducted in two 16-bed medical-surgical intensive care units within the same university hospital. Consecutive patients requiring intubation for acute hypoxemic respiratory failure were included. Patients were randomized to undergo a RM immediately (within 2 minutes) after intubation, consisting of a continuous positive airway pressure (CPAP) of 40 cmH2O over 30 seconds (RM group), or not (control group). Blood gases were sampled and blood samples taken for culture before, within 2 minutes, 5 minutes, and 30 minutes after intubation. Haemodynamic and respiratory parameters were continuously recorded throughout the study. Positive end expiratory pressure (PEEP) was set at 5 cmH2O throughout. Results The control (n = 20) and RM (n = 20) groups were similar in terms of age, disease severity, diagnosis at time of admission, and PaO2 obtained under 10-15 L/min oxygen flow immediately before (81 ± 15 vs 83 ± 35 mmHg, P = 0.9), and within 2 minutes after, intubation under 100% FiO2 (81 ± 15 vs 83 ± 35 mmHg, P = 0.9). Five minutes after intubation, PaO2 obtained under 100% FiO2 was significantly higher in the RM group compared with the control group (93 ± 36 vs 236 ± 117 mmHg, P = 0.008). The difference remained significant at 30 minutes with 110 ± 39 and 180 ± 79 mmHg, respectively, for the control and RM groups. No significant difference in haemodynamic conditions was observed between groups at any time. Following tracheal intubation, 15 patients had positive blood cultures, showing microorganisms shared with tracheal aspirates, with no significant difference in the incidence of culture positivity between groups. Conclusions Recruitment maneuver following intubation in hypoxemic patients improved short-term oxygenation, and was not associated with increased adverse effects. Trial registration NCT01014299
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Saad SM, Neumann A, Acosta EJ. A dynamic compression–relaxation model for lung surfactants. Colloids Surf A Physicochem Eng Asp 2010. [DOI: 10.1016/j.colsurfa.2009.07.046] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Schumann S, Kirschbaum A, Schliessmann SJ, Wagner G, Goebel U, Priebe HJ, Guttmann J. Low pulmonary artery flush perfusion pressure combined with high positive end-expiratory pressure reduces oedema formation in isolated porcine lungs. Physiol Meas 2010; 31:261-72. [PMID: 20086272 DOI: 10.1088/0967-3334/31/2/011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Flush perfusion of the pulmonary artery with organ protection solution is a standard procedure before lung explantation. However, rapid flush perfusion may cause pulmonary oedema which is deleterious in the lung transplantation setting. In this study we tested the hypotheses that high pulmonary perfusion pressure contributes to the development of pulmonary oedema and positive end-expiratory pressure (PEEP) counteracts oedema formation. We expected oedema formation to increase weight and decrease compliance of the lungs on the basis of a decrease in alveolar volume as fluid replaces alveolar air spaces. The pulmonary artery of 28 isolated porcine lungs was perfused with a low-potassium dextrane solution at low (mean 27 mmHg) or high (mean 40 mmHg) pulmonary artery pressure (PAP) during mechanical ventilation at low (4 cmH(2)O) or high (8 cmH(2)O) PEEP, respectively. Following perfusion and storage, relative increases in lung weight were smaller (p < 0.05) during perfusion at low PAP (62 +/- 32% and 42 +/- 26%, respectively) compared to perfusion at high PAP (133 +/- 54% and 87 +/- 30%, respectively). Compared to all other PAP-PEEP combinations, increases in lung weight were smallest (44 +/- 9% and 27 +/- 12%, respectively), nonlinear intratidal lung compliance was largest (46% and 17% respectively, both p < 0.05) and lung histology showed least infiltration of mononuclear cells in the alveolar septa, and least alveolar destruction during the combination of low perfusion pressure and high PEEP. The findings suggest that oedema formation during pulmonary artery flush perfusion in isolated and ventilated lungs can be reduced by choosing low perfusion pressure and high PEEP. PAP-PEEP titration to minimize pulmonary oedema should be based on lung mechanics and PAP monitoring.
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Affiliation(s)
- Stefan Schumann
- Department of Anaesthesiology, Division of Experimental Anaesthesiology, University Medical Centre Freiburg, Germany.
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Jauncey-Cooke JI, Bogossian F, East CE. Lung protective ventilation strategies in paediatrics-A review. Aust Crit Care 2010; 23:81-8. [PMID: 20047842 DOI: 10.1016/j.aucc.2009.11.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2008] [Revised: 11/03/2009] [Accepted: 11/10/2009] [Indexed: 10/20/2022] Open
Abstract
Ventilator Associated Lung Injury (VALI) is an iatrogenic phenomena that significantly impacts on the morbidity and mortality of critically ill patients. The hazards associated with mechanical ventilation are becoming increasingly understood courtesy of a large body of research. Barotrauma, volutrauma and biotrauma all play a role in VALI. Concomitant to this growth in understanding is the development of strategies to reduce the deleterious impact of mechanical ventilation. The majority of the research is based upon adult populations but with careful extrapolation this review will focus on paediatrics. This review article describes the physiological basis of VALI and discusses the various lung protective strategies that clinicians can employ to minimise its incidence and optimise outcomes for paediatric patients.
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Affiliation(s)
- Jacqui I Jauncey-Cooke
- The University of Queensland, School of Nursing and Midwifery, Herston, Australia; Clinical Nurse, PICU, Mater Children's Hospital, South Brisbane, Queensland, Australia.
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Eslami S, de Keizer NF, Abu-Hanna A, de Jonge E, Schultz MJ. Effect of a clinical decision support system on adherence to a lower tidal volume mechanical ventilation strategy. J Crit Care 2009; 24:523-9. [DOI: 10.1016/j.jcrc.2008.11.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Revised: 10/14/2008] [Accepted: 11/23/2008] [Indexed: 11/26/2022]
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Hanson A, Göthberg S, Nilsson K, Larsson LE, Hedenstierna G. VTCO2 and dynamic compliance-guided lung recruitment in surfactant-depleted piglets: a computed tomography study. Pediatr Crit Care Med 2009; 10:687-92. [PMID: 19451840 DOI: 10.1097/pcc.0b013e3181a703cc] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Using computed tomography (CT) as reference, our primary objectives were to test if maximal tidal elimination of carbon dioxide (VTCO2) could be used as a marker of "optimal recruitment," indicating maximal available lung tissue for gas exchange and if a decrease in dynamic compliance (Cdyn) indicated the beginning of lung collapse during a downward positive end-expiratory pressure (PEEP) titration. DESIGN Prospective laboratory animal investigation. SETTING Clinical physiology research laboratory. SUBJECTS Six piglets undergoing lung lavage. INTERVENTIONS Saline-lavaged piglets were initially ventilated without PEEP at a tidal volume (VT) of 10 mL/kg followed by baseline ventilation at end-inspiratory pressure (EIP) 25 cm H2O and PEEP 6 cm H2O. PEEP was increased to 12 or 15 cm H2O. Then EIP was increased in steps of 5 cm H2O and the EIP where VTCO2 peaked or leveled off was assumed to define optimally recruited lungs. A downward PEEP titration followed from 12 or 15 to 4 cm H2O in steps of 1 cm H2O. First decline of Cdyn was assumed to define onset of lung collapse. VTCO2 and Cdyn were continuously recorded and CT scans iterated for each change of ventilation. "Open-lung PEEP" was set 2 cm H2O above PEEP at the first Cdyn decline and was used for a final period of "open-lung ventilation." MEASUREMENTS AND MAIN RESULTS CT images showed recruited lungs at peak VTCO2 and that a minimal amount of normally aerated lung was added by further increase in EIP. Cdyn declined just before CT scans indicated lung collapse. Compared with baseline, the target VT of 10 mL/kg was achieved at lower EIP and pressure amplitude (EIP-PEEP) during the final open-lung ventilation with more normally aerated and fewer collapsed lungs. Cdyn was doubled after recruitment. CONCLUSIONS The lung recruitment maneuver was effective and lungs optimally recruited at maximal VTCO2. A fall in Cdyn indicated lung collapse during downward PEEP titration as confirmed by CT.
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Affiliation(s)
- Angela Hanson
- Department of Paediatric Anaesthesia and Intensive Care, The Queen Silvia Children's Hospital, University of Gothenburg, Göteborg, Sweden.
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69
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Zosky GR, Cannizzaro V, Hantos Z, Sly PD. Protective mechanical ventilation does not exacerbate lung function impairment or lung inflammation following influenza A infection. J Appl Physiol (1985) 2009; 107:1472-8. [DOI: 10.1152/japplphysiol.00393.2009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The degree to which mechanical ventilation induces ventilator-associated lung injury is dependent on the initial acute lung injury (ALI). Viral-induced ALI is poorly studied, and this study aimed to determine whether ALI induced by a clinically relevant infection is exacerbated by protective mechanical ventilation. Adult female BALB/c mice were inoculated with 104.5 plaque-forming units of influenza A/Mem/1/71 in 50 μl of medium or medium alone. This study used a protective ventilation strategy, whereby mice were anesthetized, tracheostomized, and mechanically ventilated for 2 h. Lung mechanics were measured periodically throughout the ventilation period using a modification of the forced oscillation technique to obtain measures of airway resistance and coefficients of tissue damping and tissue elastance. Thoracic gas volume was measured and used to obtain specific airway resistance, tissue damping, and tissue elastance. At the end of the ventilation period, a bronchoalveolar lavage sample was collected to measure inflammatory cells, macrophage inflammatory protein-2, IL-6, TNF-α, and protein leak. Influenza infection caused significant increases in inflammatory cells, protein leak, and deterioration in lung mechanics that were not exacerbated by mechanical ventilation, in contrast to previous studies using bacterial and mouse-specific viral infection. This study highlighted the importance of type and severity of lung injury in determining outcome following mechanical ventilation.
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Affiliation(s)
- Graeme R. Zosky
- Division of Clinical Science, Telethon Institute for Child Health Research, Centre for Child Health Research, University of Western Australia, Subiaco, Western Australia, Australia
| | - Vincenzo Cannizzaro
- Division of Clinical Science, Telethon Institute for Child Health Research, Centre for Child Health Research, University of Western Australia, Subiaco, Western Australia, Australia
| | - Zoltan Hantos
- Division of Clinical Science, Telethon Institute for Child Health Research, Centre for Child Health Research, University of Western Australia, Subiaco, Western Australia, Australia
| | - Peter D. Sly
- Division of Clinical Science, Telethon Institute for Child Health Research, Centre for Child Health Research, University of Western Australia, Subiaco, Western Australia, Australia
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Alveolar dynamics in acute lung injury: heterogeneous distension rather than cyclic opening and collapse. Crit Care Med 2009; 37:2604-11. [PMID: 19623041 DOI: 10.1097/ccm.0b013e3181a5544d] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVES : To analyze alveolar dynamics in healthy and acid-injured lungs of ventilated mice. Protective ventilation is potentially lifesaving in patients with acute lung injury. However, optimization of ventilation strategies is hampered by an incomplete understanding of the effects of mechanical ventilation at the alveolar level. DESIGN : In anesthetized and ventilated Balb/c mice, subpleural alveoli were visualized by darkfield intravital microscopy and optical coherence tomography. SETTING : Animal research laboratory. SUBJECTS : Male Balb/c mice. INTERVENTIONS : Lung injury was induced by intratracheal instillation of hydrochloric acid. In control animals and mice with lung injury, ventilation pressures were varied between 0 and 24 cm H2O at baseline, 60 mins, and 120 mins, and alveolar distension and cyclic opening and collapse of alveolar clusters were analyzed. MEASUREMENTS AND MAIN RESULTS : In normal lungs, alveolar clusters distend with increasing ventilation pressure in a sigmoid relationship. Although an increase in ventilation pressure from 0 to 24 cm H2O increases alveolar size by 41.5 +/- 2.3% in normal lungs, alveolar distension is reduced to 20.6 +/- 2.2% 120 mins after induction of lung injury by acid aspiration. Cyclic opening and collapse of alveolar clusters are neither observed in normal nor acid-injured lungs. Alveolar compliance is highest in small and distensible alveolar clusters, which are also most prone to acid-induced injury. CONCLUSIONS : Over the applied pressure range, volume changes in control and acid-injured mouse lungs result predominantly from alveolar distension rather than cyclic opening and collapse of alveolar clusters. Preferential loss of compliance in small alveolar clusters redistributes tidal volume to larger alveoli, which increases spatial heterogeneity in alveolar inflation and may promote alveolar overdistension.
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71
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Comparison of two in vivo microscopy techniques to visualize alveolar mechanics. J Clin Monit Comput 2009; 23:323-32. [DOI: 10.1007/s10877-009-9200-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 08/18/2009] [Indexed: 10/20/2022]
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Jauncey-Cooke JI, Bogossian F, East CE. Lung recruitment--a guide for clinicians. Aust Crit Care 2009; 22:155-62. [PMID: 19679490 DOI: 10.1016/j.aucc.2009.06.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Revised: 05/12/2009] [Accepted: 06/04/2009] [Indexed: 12/31/2022] Open
Abstract
Recruitment manoeuvres play an important role in minimising ventilator associated lung injury (VALI) particularly when lung protective ventilation strategies are employed and as such clinicians should consider their application. This paper provides evidence-based recommendations for clinical practice with regard to alveolar recruitment. It includes recommendations for timing of recruitment, strategies of recruitment and methods of measuring the efficacy of recruitment manoeuvres and contributes to knowledge about the risks associated with recruitment manoeuvres. There are a range of methods for recruiting alveoli, most notably by manipulating positive end expiratory pressure (PEEP) and peak inspiratory pressure (PIP) with consensus as to the most effective not yet determined. A number of studies have demonstrated that improvement in oxygenation is rarely sustained following a recruitment manoeuvre and it is questionable whether improved oxygenation should be the clinician's goal. Transient haemodynamic compromise has been noted in a number of studies with a few studies reporting persistent, harmful sequelae to recruitment manoeuvres. No studies have been located that assess the impact of recruitment manoeuvres on length of ventilation, length of stay, morbidity or mortality. Recruitment manoeuvres restore end expiratory lung volume by overcoming threshold opening pressures and are most effective when applied after circuit disconnection and airway suction. Whether this ultimately improves outcomes in adult or paediatric populations is unknown.
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73
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Broden CC. Acute renal failure and mechanical ventilation: reality or myth? Crit Care Nurse 2009; 29:62-75; quiz 76. [PMID: 19339448 DOI: 10.4037/ccn2009267] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Affiliation(s)
- Caroline C Broden
- US Army Nurse Corps at William Beaumont Army Medical Center, El Paso, Texas, USA.
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Pássaro CP, Silva PL, Rzezinski AF, Abrantes S, Santiago VR, Nardelli L, Santos RS, Barbosa CML, Morales MM, Zin WA, Amato MBP, Capelozzi VL, Pelosi P, Rocco PRM. Pulmonary lesion induced by low and high positive end-expiratory pressure levels during protective ventilation in experimental acute lung injury. Crit Care Med 2009; 37:1011-7. [DOI: 10.1097/ccm.0b013e3181962d85] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Albert S, Kubiak B, Nieman G. Protective Mechanical Ventilation: Lessons Learned From Alveolar Mechanics. Intensive Care Med 2009. [DOI: 10.1007/978-0-387-77383-4_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
All original research contributions published in Critical Care in 2007 in the field of respirology and critical care medicine are summarized in this article. Fifteen papers were grouped in the following categories: acute lung injury and acute respiratory distress syndrome, mechanical ventilation, ventilator-induced lung injury, imaging, and other topics.
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Affiliation(s)
- Lorenzo Del Sorbo
- Department of Anesthesia and Intensive Care, University of Turin, Corso Dogliotti 14, 10126, Turin, Italy
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Ko SC, Zhang H, Haitsma JJ, Cheng KC, Li CF, Slutsky AS. Effects of PEEP levels following repeated recruitment maneuvers on ventilator-induced lung injury. Acta Anaesthesiol Scand 2008; 52:514-21. [PMID: 18261196 DOI: 10.1111/j.1399-6576.2008.01581.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Different levels of positive end-expiratory pressure (PEEP) with and without a recruitment maneuver (RM) may have a significant impact on ventilator-induced lung injury but this issue has not been well addressed. METHODS Anesthetized rats received hydrochloric acid (HCl, pH 1.5) aspiration, followed by mechanical ventilation with a tidal volume of 6 ml/kg. The animals were randomized into four groups of 10 each: (1) high PEEP at 6 cm H(2)O with an RM by applying peak airway pressure at 30 cm H(2)O for 10 s every 15 min; (2) low PEEP at 2 cm H(2)O with RM; (3) high PEEP alone; and (4) low PEEP alone. RESULTS The mean arterial pressure and the amounts of fluid infused were similar in the four groups. Application of the higher PEEP improved oxygenation compared with the lower PEEP groups (P<0.05). The lung compliance was better reserved, and the systemic cytokine responses and lung wet to dry ratio were lower in the high PEEP than in the low PEEP group for a given RM (P<0.05). CONCLUSIONS The use of a combination of periodic RM and the higher PEEP had an additive effect in improving oxygenation and pulmonary mechanics and attenuation of inflammation.
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Affiliation(s)
- S-C Ko
- The Keenan Research Centre in the Li Ka Shing Knowledge Institute of St Michael's Hospital, Toronto, ON, Canada
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Namati E, Thiesse J, de Ryk J, McLennan G. Alveolar dynamics during respiration: are the pores of Kohn a pathway to recruitment? Am J Respir Cell Mol Biol 2007; 38:572-8. [PMID: 18096874 DOI: 10.1165/rcmb.2007-0120oc] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The change in alveolar size and number during the full breathing cycle in mammals remains unanswered, yet these descriptors are fundamental for understanding alveolar-based diseases and for improving ventilator management. Genetic and environmental mouse models are used increasingly to evaluate the evolution of disease in the peripheral lung; however, little is known regarding alveolar structure and function in the fresh, intact lung. Therefore, we have developed an optical confocal process to evaluate alveolar dynamics in the fresh intact mouse lung and as an initial experiment, have evaluated mouse alveolar dynamics during a single respiratory cycle immediately after passive lung deflation. We observe that alveoli become smaller and more numerous at the end of inspiration, and propose that this is direct evidence for alveolar recruitment in the mouse lung. The findings reported support a new hypothesis that requires recruitable secondary (daughter) alveoli to inflate via primary (mother) alveoli rather than from a conducting airway.
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Affiliation(s)
- Eman Namati
- Internal Medicine, University of Iowa, 200 Hawkins Drive, C325 GH, Iowa City, IA 52242, USA
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79
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Pavone L, Albert S, DiRocco J, Gatto L, Nieman G. Alveolar instability caused by mechanical ventilation initially damages the nondependent normal lung. Crit Care 2007; 11:R104. [PMID: 17877789 PMCID: PMC2556747 DOI: 10.1186/cc6122] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Revised: 09/06/2007] [Accepted: 09/18/2007] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Septic shock is often associated with acute respiratory distress syndrome, a serious clinical problem exacerbated by improper mechanical ventilation. Ventilator-induced lung injury (VILI) can exacerbate the lung injury caused by acute respiratory distress syndrome, significantly increasing the morbidity and mortality. In this study, we asked the following questions: what is the effect of the lung position (dependent lung versus nondependent lung) on the rate at which VILI occurs in the normal lung? Will positive end-expiratory pressure (PEEP) slow the progression of lung injury in either the dependent lung or the nondependent lung? MATERIALS AND METHODS Sprague-Dawley rats (n = 19) were placed on mechanical ventilation, and the subpleural alveolar mechanics were measured with an in vivo microscope. Animals were placed in the lateral decubitus position, left lung up to measure nondependent alveolar mechanics and left lung down to film dependent alveolar mechanics. Animals were ventilated with a high peak inspiratory pressure of 45 cmH2O and either a low PEEP of 3 cmH2O or a high PEEP of 10 cmH2O for 90 minutes. Animals were separated into four groups based on the lung position and the amount of PEEP: Group I, dependent + low PEEP (n = 5); Group II, nondependent + low PEEP (n = 4); Group III, dependent + high PEEP (n = 5); and Group IV, nondependent + high PEEP (n = 5). Hemodynamic and lung function parameters were recorded concomitant with the filming of alveolar mechanics. Histological assessment was performed at necropsy to determine the presence of lung edema. RESULTS VILI occurred earliest (60 min) in Group II. Alveolar instability eventually developed in Groups I and II at 75 minutes. Alveoli in both the high PEEP groups were stable for the entire experiment. There were no significant differences in arterial PO2 or in the degree of edema measured histologically among experimental groups. CONCLUSION This open-chest animal model demonstrates that the position of the normal lung (dependent or nondependent) plays a role on the rate of VILI.
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Affiliation(s)
- Lucio Pavone
- Upstate Medical University, Department of Surgery, 750 E Adams Street, Syracuse, NY 13210 USA
| | - Scott Albert
- Upstate Medical University, Department of Surgery, 750 E Adams Street, Syracuse, NY 13210 USA
| | - Joseph DiRocco
- Upstate Medical University, Department of Surgery, 750 E Adams Street, Syracuse, NY 13210 USA
| | - Louis Gatto
- Department of Biology, Cortland College, P.O. Box 2000 Cortland, NY 13045 USA
| | - Gary Nieman
- Upstate Medical University, Department of Surgery, 750 E Adams Street, Syracuse, NY 13210 USA
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80
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Pavone LA, Albert S, Carney D, Gatto LA, Halter JM, Nieman GF. Injurious mechanical ventilation in the normal lung causes a progressive pathologic change in dynamic alveolar mechanics. Crit Care 2007; 11:R64. [PMID: 17565688 PMCID: PMC2206429 DOI: 10.1186/cc5940] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 04/04/2007] [Accepted: 06/12/2007] [Indexed: 01/11/2023] Open
Abstract
INTRODUCTION Acute respiratory distress syndrome causes a heterogeneous lung injury, and without protective mechanical ventilation a secondary ventilator-induced lung injury can occur. To ventilate noncompliant lung regions, high inflation pressures are required to 'pop open' the injured alveoli. The temporal impact, however, of these elevated pressures on normal alveolar mechanics (that is, the dynamic change in alveolar size and shape during ventilation) is unknown. In the present study we found that ventilating the normal lung with high peak pressure (45 cmH(2)0) and low positive end-expiratory pressure (PEEP of 3 cmH(2)O) did not initially result in altered alveolar mechanics, but alveolar instability developed over time. METHODS Anesthetized rats underwent tracheostomy, were placed on pressure control ventilation, and underwent sternotomy. Rats were then assigned to one of three ventilation strategies: control group (n = 3, P control = 14 cmH(2)O, PEEP = 3 cmH(2)O), high pressure/low PEEP group (n = 6, P control = 45 cmH(2)O, PEEP = 3 cmH(2)O), and high pressure/high PEEP group (n = 5, P control = 45 cmH(2)O, PEEP = 10 cmH(2)O). In vivo microscopic footage of subpleural alveolar stability (that is, recruitment/derecruitment) was taken at baseline and than every 15 minutes for 90 minutes following ventilator adjustments. Alveolar recruitment/derecruitment was determined by measuring the area of individual alveoli at peak inspiration (I) and end expiration (E) by computer image analysis. Alveolar recruitment/derecruitment was quantified by the percentage change in alveolar area during tidal ventilation (%I - E Delta). RESULTS Alveoli were stable in the control group for the entire experiment (low %I - E Delta). Alveoli in the high pressure/low PEEP group were initially stable (low %I - E Delta), but with time alveolar recruitment/derecruitment developed. The development of alveolar instability in the high pressure/low PEEP group was associated with histologic lung injury. CONCLUSION A large change in lung volume with each breath will, in time, lead to unstable alveoli and pulmonary damage. Reducing the change in lung volume by increasing the PEEP, even with high inflation pressure, prevents alveolar instability and reduces injury. We speculate that ventilation with large changes in lung volume over time results in surfactant deactivation, which leads to alveolar instability.
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Affiliation(s)
- Lucio A Pavone
- Department of Surgery, SUNY Upstate Medical University, 750 East Adams St Syracuse, NY 13210, USA
| | - Scott Albert
- Department of Surgery, SUNY Upstate Medical University, 750 East Adams St Syracuse, NY 13210, USA
| | - David Carney
- Memorial Health University Medical Center, 4700 Waters Ave Savannah, GA 31404, USA
| | - Louis A Gatto
- Department of Biological Sciences, SUNY Cortland, P.O. Box 2000 Cortland, NY 13045, USA
| | - Jeffrey M Halter
- Department of Surgery, SUNY Upstate Medical University, 750 East Adams St Syracuse, NY 13210, USA
| | - Gary F Nieman
- Department of Surgery, SUNY Upstate Medical University, 750 East Adams St Syracuse, NY 13210, USA
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