The effects of airway pressure release ventilation on respiratory mechanics in extrapulmonary lung injury

Abstract

BackgroundLung injury is often studied without consideration for pathologic changes in the chest wall. In order to reduce the incidence of lung injury using preemptive mechanical ventilation, it is important to recognize the influence of altered chest wall mechanics on disease pathogenesis. In this study, we hypothesize that airway pressure release ventilation (APRV) may be able to reduce the chest wall elastance associated with an extrapulmonary lung injury model as compared with low tidal volume (LVt) ventilation.MethodsFemale Yorkshire pigs were anesthetized and instrumented. Fecal peritonitis was established, and the superior mesenteric artery was clamped for 30 min to induce an ischemia/reperfusion injury. Immediately following injury, pigs were randomized into (1) LVt (n = 3), positive end-expiratory pressure (PEEP) 5 cmH2O, Vt 6 cc kg−1, FiO2 21 %, and guided by the ARDSnet protocol or (2) APRV (n = 3), PHigh 16–22 cmH2O, PLow 0 cmH2O, THigh 4.5 s, TLow set to terminate the peak expiratory flow at 75 %, and FiO2 21 %. Pigs were monitored continuously for 48 h. Lung samples and bronchoalveolar lavage fluid were collected at necropsy.ResultsLVt resulted in mild acute respiratory distress syndrome (ARDS) (PaO2/FiO2 = 226.2 ± 17.1 mmHg) whereas APRV prevented ARDS (PaO2/FiO2 = 465.7 ± 66.5 mmHg; p < 0.05). LVt had a reduced surfactant protein A concentration and increased histologic injury as compared with APRV. The plateau pressure in APRV (34.3 ± 0.9 cmH2O) was significantly greater than LVt (22.2 ± 2.0 cmH2O; p < 0.05) yet transpulmonary pressure between groups was similar (p > 0.05). This was because the pleural pressure was significantly lower in LVt (7.6 ± 0.5 cmH2O) as compared with APRV (17.4 ± 3.5 cmH2O; p < 0.05). Finally, the elastance of the lung, chest wall, and respiratory system were all significantly greater in LVt as compared with APRV (all p < 0.05).ConclusionsAPRV preserved surfactant and lung architecture and maintenance of oxygenation. Despite the greater plateau pressure and tidal volumes in the APRV group, the transpulmonary pressure was similar to that of LVt. Thus, the majority of the plateau pressure in the APRV group was distributed as pleural pressure in this extrapulmonary lung injury model. APRV maintained a normal lung elastance and an open, homogeneously ventilated lung without increasing lung stress.

Prevention and treatment of acute lung injury with time-controlled adaptive ventilation: physiologically informed modification of airway pressure release ventilation

“…Time controlled-PEEP (TC-PEEP) is adaptive (not arbitrary) because it is determined in real-time according to compliance, which is measured in the preceding breath by the slope of the expiratory flow curve (Slope FE ) (red arrowhead on right) ( Fig. 6) inspiratory duration effectively opens the lung; therefore, alveolar heterogeneity and regional strain were not eliminated [26,82,83]. To normalize the alveolar duct to alveolar volume distribution in the acutely injured lung, it is necessary to use a combination of an extended time at inspiration (CPAP phase) and short expiratory duration (Release phase) ( Fig.…”

“…5a, top and 7). Figure 7 presents gross lung photographs and the corresponding lung compliance (C RS ), tidal volume (Vt), and driving pressure (ΔP) calculated from a previously published paper [82]. The animal model utilized was a clinically applicable porcine peritoneal sepsis and gut ischemia/ reperfusion (PS + I/R) ARDS model [83].…”

A Physiologically Informed Strategy to Effectively Open, Stabilize, and Protect the Acutely Injured Lung

“…Our group has investigated the physiological impact of the TCAV method in both mechanistic and efficacy animal studies (Roy et al, 2012;Emr et al, 2013;Roy S.K. et al, 2013;Kollisch-Singule et al, 2014a,b, 2015aSmith et al, 2015;Silva et al, 2018) and in a meta-analysis of data on SICU patients (Andrews et al, 2013). In addition, the TCAV method is the primary ventilator strategy used at the R Adam Cowley Shock Trauma Center in Baltimore, with well over 1,000,000 h of ventilator time.…”

“…Indeed, our work in translational animal models and a meta-analysis of data on surgical intensive care unit (SICU) patients has shown that our time-controlled adaptive ventilation (TCAV) method, using airway pressure release ventilation (APRV) mode, is highly effective at keeping the lung open and stable, significantly reducing morbidity in translational animal models and reducing the ARDS incidence and mortality rates of SICU patients at high risk of developing ARDS (Roy et al, 2012;Andrews et al, 2013;Emr et al, 2013;Roy S.K. et al, 2013;Kollisch-Singule et al, 2014a,b, 2015aNieman et al, Nieman et al, 2015, 2017aSmith et al, 2015;Jain et al, 2016Jain et al, , 2017Satalin et al, 2018;Silva et al, 2018;Mahajan et al, 2019).…”

Physiology in Medicine: Understanding dynamic alveolar physiology to minimize ventilator-induced lung injury

“…The failure of HFOV to reduce mortality may be due to a misdistribution of ventilation in the heterogeneously injured lung (29). A very specific strategy of personalized APRV (30) has been shown to be effective at stabilizing alveoli (35,36) and protecting from the development of ARDS in a clinically applicable porcine model (34,51,52). In a meta-analysis this personalized APRV strategy significantly reduced ARDS incidence and mortality in a surgical intensive care unit (8), but it has not been tested in a prospective clinical trial.…”