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Introduction The mechanism of fast inspiratory flow rate (V.sub.I') induced lung injury is unclear. As fast V.sub.I' increases hysteresis, a measure of surface tension at the air-liquid interface, surfactant release or function may be important. This experimental study examines the contribution of impaired surfactant release or function to dynamic-VILI. Methods Isolated perfused lungs from male Sprague Dawley rats were randomly allocated to four groups: a long or short inspiratory time (Ti = 0.5 s; slow V.sub.I' or Ti = 0.1 s; fast V.sub.I') at PEEP of 2 or 10 cmH.sub.2O. Tidal volume was constant (7 ml/kg), with f = 60 breath/min. Forced impedance mechanics (tissue elastance (Htis), tissue resistance (Gtis) and airway resistance (Raw) were measured at 30, 60 and 90 min following which the lung was lavaged for surfactant phospholipids (PL) and disaturated PL (DSP). Results Fast V.sub.I' resulted in a stiffer lung. Concurrently, PL and DSP were decreased in both tubular myelin rich and poor fractions. Phospholipid decreases were similar with PEEP. In a subsequent cohort, laser confocal microscopy-based assessment demonstrated increased cellular injury with increased V.sub.I' at both 30 and 90 min ventilation. Conclusion Rapid V.sub.I' may contribute to ventilator induced lung injury (VILI) through reduced surfactant release and/or more rapid reuptake despite unchanged tidal stretch., Author(s): Andrew D. Bersten [sup.1] [sup.2] , Malgorzata Krupa [sup.2] , Kim Griggs [sup.2] , Dani-Louise Dixon [sup.1] [sup.2] Author Affiliations: (1) grid.414925.f, 0000 0000 9685 0624, Intensive and Critical [...]

Purpose Mechanical ventilation is a well-established therapy for patients with acute respiratory failure. However, up to 35% of mortality in acute respiratory distress syndrome may be attributed to ventilation-induced lung injury (VILI). We previously demonstrated the efficacy of the synthetic tripeptide feG for preventing and ameliorating acute pancreatitis-associated lung injury. However, as the mechanisms of induction of injury during mechanical ventilation may differ, we aimed to investigate the effect of feG in a rodent model of VILI, with or without secondary challenge, as a preventative treatment when administered before injury (prophylactic), or as a therapeutic treatment administered following initiation of injury (therapeutic). Methods Lung injury was assessed following prophylactic or therapeutic intratracheal feG administration in a rodent model of ventilation-induced lung injury, with or without secondary intratracheal lipopolysaccharide challenge. Results Prophylactic feG administration resulted in significant improvements in arterial blood oxygenation and respiratory mechanics, and decreased lung oedema, bronchoalveolar lavage protein concentration, histological tissue injury scores, blood vessel activation, bronchoalveolar lavage cell infiltration and lung myeloperoxidase activity in VILI, both with and without lipopolysaccharide. Therapeutic feG administration similarly ameliorated the severity of tissue damage and encouraged the resolution of injury. feG associated decreases in endothelial adhesion molecules may indicate a mechanism for these effects. Conclusions This study supports the potential for feG as a pharmacological agent in the prevention or treatment of lung injury associated with mechanical ventilation., Author(s): Alison S. F. Elder [sup.1], Andrew D. Bersten [sup.1] [sup.2], Gino T. P. Saccone [sup.3], Claudine S. Bonder [sup.4], Dani-Louise Dixon [sup.1] [sup.2] Author Affiliations: (1) grid.1014.4, 0000 0004 [...]

Background: Since publication of the 2012 Berlin definition of acute respiratory distress syndrome (ARDS), several developments have supported the need for an expansion of the definition, including the use of high-flow nasal oxygen, the expansion of the use of pulse oximetry in place of arterial blood gases, the use of ultrasound for chest imaging, and the need for applicability in resource-limited settings. Methods: A consensus conference of 32 critical care ARDS experts was convened, had six virtual meetings (June 2021 to March 2022), and subsequently obtained input from members of several critical care societies. The goal was to develop a definition that would 1) identify patients with the currently accepted conceptual framework for ARDS, 2) facilitate rapid ARDS diagnosis for clinical care and research, 3) be applicable in resource-limited settings, 4) be useful for testing specific therapies, and 5) be practical for communication to patients and caregivers. Results: The committee made four main recommendations: 1) include high-flow nasal oxygen with a minimum flow rate of ⩾30 L/min; 2) use PaO2:FiO2 ⩽ 300 mm Hg or oxygen saturation as measured by pulse oximetry SpO2:FiO2 ⩽ 315 (if oxygen saturation as measured by pulse oximetry is ⩽97%) to identify hypoxemia; 3) retain bilateral opacities for imaging criteria but add ultrasound as an imaging modality, especially in resource-limited areas; and 4) in resource-limited settings, do not require positive end-expiratory pressure, oxygen flow rate, or specific respiratory support devices. Conclusions: We propose a new global definition of ARDS that builds on the Berlin definition. The recommendations also identify areas for future research, including the need for prospective assessments of the feasibility, reliability, and prognostic validity of the proposed global definition. [ABSTRACT FROM AUTHOR]

Author(s): Shailesh Bihari [sup.1] [sup.2], John G. Laffey [sup.3] [sup.4], Andrew D. Bersten [sup.1] [sup.2] Author Affiliations: (1) grid.1014.4, 0000000403672697, Department of Critical Care Medicine, Flinders University, , Bedford Park, [...]

A letter published in the American Journal of Respiratory & Critical Care Medicine discusses a recent study on lung injury in pigs. The study found that using positive end-expiratory pressure (PEEP) to minimize overdistension resulted in a high amount of lung collapse and increased mortality. The authors suggest that airway closure, rather than alveolar collapse, may be a more important factor in these findings. They propose that reporting airway opening pressure in future studies would help clarify these concerns. [Extracted from the article]