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Purpose Experimental animal models of acute respiratory distress syndrome (ARDS) have shown that the updated airway pressure release ventilation (APRV) methodologies may significantly improve oxygenation, maximize lung recruitment, and attenuate lung injury, without circulatory depression. This led us to hypothesize that early application of APRV in patients with ARDS would allow pulmonary function to recover faster and would reduce the duration of mechanical ventilation as compared with low tidal volume lung protective ventilation (LTV). Methods A total of 138 patients with ARDS who received mechanical ventilation for <48 h between May 2015 to October 2016 while in the critical care medicine unit (ICU) of the West China Hospital of Sichuan University were enrolled in the study. Patients were randomly assigned to receive APRV ( n  = 71) or LTV ( n  = 67). The settings for APRV were: high airway pressure (P high ) set at the last plateau airway pressure (P plat ), not to exceed 30 cmH 2 O) and low airway pressure ( P low ) set at 5 cmH 2 O; the release phase (T low ) setting adjusted to terminate the peak expiratory flow rate to ≥ 50%; release frequency of 10–14 cycles/min. The settings for LTV were: target tidal volume of 6 mL/kg of predicted body weight; P plat not exceeding 30 cmH 2 O; positive end-expiratory pressure (PEEP) guided by the PEEP–FiO 2 table according to the ARDSnet protocol. The primary outcome was the number of days without mechanical ventilation from enrollment to day 28. The secondary endpoints included oxygenation, P plat , respiratory system compliance, and patient outcomes. Results Compared with the LTV group, patients in the APRV group had a higher median number of ventilator-free days {19 [interquartile range (IQR) 8–22] vs. 2 (IQR 0–15); P  < 0.001}. This finding was independent of the coexisting differences in chronic disease. The APRV group had a shorter stay in the ICU ( P  = 0.003). The ICU mortality rate was 19.7% in the APRV group versus 34.3% in the LTV group ( P  = 0.053) and was associated with better oxygenation and respiratory system compliance, lower P plat , and less sedation requirement during the first week following enrollment ( P  < 0.05, repeated-measures analysis of variance). Conclusions Compared with LTV, early application of APRV in patients with ARDS improved oxygenation and respiratory system compliance, decreased P plat and reduced the duration of both mechanical ventilation and ICU stay.

Objective The aim of this study was to investigate the physiological impact of airway pressure release ventilation (APRV) on patients with early moderate-to-severe acute respiratory distress syndrome (ARDS) by electrical impedance tomography (EIT). Methods In this single-center prospective physiological study, adult patients with early moderate-to-severe ARDS mechanically ventilated with APRV were assessed by EIT shortly after APRV (T0), and 6 h (T1), 12 h (T2), and 24 h (T3) after APRV initiation. Regional ventilation and perfusion distribution, dead space (%), shunt (%), and ventilation/perfusion matching (%) based on EIT measurement at different time points were compared. Additionally, clinical variables related to respiratory and hemodynamic condition were analyzed. Results Twelve patients were included in the study. After APRV, lung ventilation and perfusion were significantly redistributed to dorsal region. One indicator of ventilation distribution heterogeneity is the global inhomogeneity index, which decreased gradually [0.61 (0.55–0.62) to 0.50 (0.42–0.53), p  < 0.001]. The other is the center of ventilation, which gradually shifted towards the dorsal region (43.31 ± 5.07 to 46.84 ± 4.96%, p  = 0.048). The dorsal ventilation/perfusion matching increased significantly from T0 to T3 (25.72 ± 9.01 to 29.80 ± 7.19%, p  = 0.007). Better dorsal ventilation (%) was significantly correlated with higher PaO 2 /FiO 2 (r = 0.624, p  = 0.001) and lower PaCO 2 (r = -0.408, p  = 0.048). Conclusions APRV optimizes the distribution of ventilation and perfusion, reducing lung heterogeneity, which potentially reduces the risk of ventilator-induced lung injury.

Background Airway pressure release ventilation (APRV) is widely available on mechanical ventilators and has been proposed as an early intervention to prevent lung injury or as a rescue therapy in the management of refractory hypoxemia. Driving pressure ( Δ P ) has been identified in numerous studies as a key indicator of ventilator-induced-lung-injury that needs to be carefully controlled. Δ P delivered by the ventilator in APRV is not directly measurable in dynamic conditions, and there is no “gold standard” method for its estimation. Methods We used a computational simulator matched to data from 90 patients with acute respiratory distress syndrome (ARDS) to evaluate the accuracy of three “at-the-bedside” methods for estimating ventilator Δ P during APRV. Results Levels of Δ P delivered by the ventilator in APRV were generally within safe limits, but in some cases exceeded levels specified by protective ventilation strategies. A formula based on estimating the intrinsic positive end expiratory pressure present at the end of the APRV release provided the most accurate estimates of Δ P . A second formula based on assuming that expiratory flow, volume and pressure decay mono-exponentially, and a third method that requires temporarily switching to volume-controlled ventilation, also provided accurate estimates of true Δ P . Conclusions Levels of Δ P delivered by the ventilator during APRV can potentially exceed levels specified by standard protective ventilation strategies, highlighting the need for careful monitoring. Our results show that Δ P delivered by the ventilator during APRV can be accurately estimated at the bedside using simple formulae that are based on readily available measurements.

Background Airway pressure release ventilation (APRV) has become increasingly popular for the management of acute respiratory distress syndrome (ARDS); however, its clinical impact remains a topic of debate. Furthermore, there is a gap between the guidelines and the actual clinical practices in mechanical ventilation management for ARDS. This survey aimed to explore the utilization of APRV and mechanical ventilation strategies for ARDS in Chinese intensive care unit (ICU) clinicians. Methods A comprehensive 34‐item survey was distributed online platforms amongst ICU clinicians across mainland China from June to August 2019. Results A total of 420 valid responses were collected, with 57.4% (241) originating from academic hospitals and 42.6% (179) from non‐academic hospitals. Of the respondents, 98.6% (414) recognized the significance of low tidal volume ventilation for ARDS prognosis, 85.2% adhered to a tidal volume below 8 mL/kg predicted body weight, and most (46.4%) selected the initial positive end‐expiratory pressure within the range of 5–10 cmH2O based on experience. Among the respondents, 62.1% (261) reported familiarity with APRV and 41.9% (176) had implemented APRV. Of those who had utilized APRV, 93.2% (164) believed in its effectiveness for ARDS patients and 69.3% (122) advocated for early application of APRV. Substantial variations were noted regarding APRV initiation settings and the preservation of spontaneous breathing during APRV. Academic hospitals exhibited higher usage rates of lung recruitment, neuromuscular blockade, prone ventilation, and acquaintance with and utilization of APRV compared to non‐academic hospitals (all p values ≤ 0.001). Conclusions Our findings highlight opportunities for improvement in mechanical ventilation management for ARDS, particularly in non‐academic hospitals. Additionally, a significant proportion of clinicians demonstrated limited knowledge of APRV, and there was a lack of consensus on its application. Further training and larger‐scale clinical trials are required to validate the efficacy and utilization of APRV in managing ARDS.

Background Conventional Mechanical ventilation modes used for individuals suffering from acute respiratory distress syndrome have the potential to exacerbate lung injury through regional alveolar overinflation and/or repetitive alveolar collapse with shearing, known as atelectrauma. Animal studies have demonstrated that airway pressure release ventilation (APRV) offers distinct advantages over conventional mechanical ventilation modes. However, the methodologies for implementing APRV vary widely, and the findings from clinical studies remain controversial. This study (APRVplus trial), aims to assess the impact of an early pathophysiology-driven APRV ventilation approach compared to a low tidal volume ventilation (LTV) strategy on the prognosis of patients with moderate to severe ARDS. Methods The APRVplus trial is a prospective, multicenter, randomized clinical trial, building upon our prior single-center study, to enroll 840 patients from at least 35 hospitals in China. This investigation plans to compare the early pathophysiology-driven APRV ventilation approach with the control intervention of LTV lung-protective ventilation. The primary outcome measure will be all-cause mortality at 28 days after randomization in the intensive care units (ICU). Secondary outcome measures will include assessments of oxygenation, and physiology parameters at baseline, as well as on days 1, 2, and 3. Additionally, clinical outcomes such as ventilator-free days at 28 days, duration of ICU and hospital stay, ICU and hospital mortality, and the occurrence of adverse events will be evaluated. Trial ethics and dissemination The research project has obtained approval from the Ethics Committee of West China Hospital of Sichuan University (2019-337). Informed consent is required. The results will be submitted for publication in a peer-reviewed journal and presented at one or more scientific conferences. Trial registration The study was registered at Clinical Trials.gov (NCT03549910) on June 8, 2018.

Background Trauma has been identified as one of the risk factors for acute respiratory distress syndrome. Respiratory support can be further complicated by comorbidities of trauma such as primary or secondary lung injury. Conventional ventilation strategies may not be suitable for all trauma-related acute respiratory distress syndrome. Airway pressure release ventilation has emerged as a potential rescue method for patients with acute respiratory distress syndrome and hypoxemia refractory to conventional mechanical ventilation. However, there is a lack of research on the use of airway pressure release ventilation in children with trauma-related acute respiratory distress syndrome. We report a case of airway pressure release ventilation applied to a child with falling injury, severe acute respiratory distress syndrome, hemorrhagic shock, and bilateral hemopneumothorax. We hope this case report presents a potential option for trauma-related acute respiratory distress syndrome and serves as a basis for future research. Case presentation A 15-year-old female with falling injury who developed severe acute respiratory distress syndrome, hemorrhagic shock, and bilateral hemopneumothorax was admitted to the surgical intensive care unit. She presented refractory hypoxemia despite the treatment of conventional ventilation with deep analgesia, sedation, and muscular relaxation. Lung recruitment was ineffective and prone positioning was contraindicated. Her oxygenation significantly improved after the use of airway pressure release ventilation. She was eventually extubated after 12 days of admission and discharged after 42 days of hospitalization. Conclusion Airway pressure release ventilation may be considered early in the management of trauma patients with severe acute respiratory distress syndrome when prone position ventilation cannot be performed and refractory hypoxemia persists despite conventional ventilation and lung recruitment maneuvers.

Background In pressure-controlled (PC) ventilation, tidal volume ( V T ) and transpulmonary pressure ( P L ) result from the addition of ventilator pressure and the patient’s inspiratory effort. PC modes can be classified into fully, partially, and non-synchronized modes, and the degree of synchronization may result in different V T and P L despite identical ventilator settings. This study assessed the effects of three PC modes on V T , P L , inspiratory effort (esophageal pressure–time product, PTP es ), and airway occlusion pressure, P 0.1 . We also assessed whether P 0.1 can be used for evaluating patient effort. Methods Prospective, randomized, crossover physiologic study performed in 14 spontaneously breathing mechanically ventilated patients recovering from acute respiratory failure (1 subsequently withdrew). PC modes were fully (PC-CMV), partially (PC-SIMV), and non-synchronized (PC-IMV using airway pressure release ventilation) and were applied randomly; driving pressure, inspiratory time, and set respiratory rate being similar for all modes. Airway, esophageal pressure, P 0.1 , airflow, gas exchange, and hemodynamics were recorded. Results V T was significantly lower during PC-IMV as compared with PC-SIMV and PC-CMV (387 ± 105 vs 458 ± 134 vs 482 ± 108 mL, respectively; p  < 0.05). Maximal P L was also significantly lower (13.3 ± 4.9 vs 15.3 ± 5.7 vs 15.5 ± 5.2 cmH 2 O, respectively; p  < 0.05), but PTP es was significantly higher in PC-IMV (215.6 ± 154.3 vs 150.0 ± 102.4 vs 130.9 ± 101.8 cmH 2 O × s × min −1 , respectively; p  < 0.05), with no differences in gas exchange and hemodynamic variables. PTP es increased by more than 15% in 10 patients and by more than 50% in 5 patients. An increased P 0.1 could identify high levels of PTP es . Conclusions Non-synchronized PC mode lowers V T and P L in comparison with more synchronized modes in spontaneously breathing patients but can increase patient effort and may need specific adjustments. Clinical Trial Registration Clinicaltrial.gov # NCT02071277

Purpose To compare characteristics and clinical outcomes of patients receiving airway pressure release ventilation (APRV) or biphasic positive airway pressure (BIPAP) to assist-control ventilation (A/C) as their primary mode of ventilatory support. The objective was to estimate if patients ventilated with APRV/BIPAP have a lower mortality. Methods Secondary analysis of an observational study in 349 intensive care units from 23 countries. A total of 234 patients were included who were ventilated only with APRV/BIPAP and 1,228 patients who were ventilated only with A/C. A case-matched analysis according to a propensity score was used to make comparisons between groups. Results In logistic regression analysis, the most important factor associated with the use of APRV/BIPAP was the country (196 of 234 patients were from German units). Patients with coma or congestive heart failure as the reason to start mechanical ventilation, pH <7.15 prior to mechanical ventilation, and patients who developed respiratory failure (SOFA score >2) after intubation with or without criteria of acute respiratory distress syndrome were less likely to be ventilated with APRV/BIPAP. In the case-matched analysis there were no differences in outcomes, including mortality in the intensive care unit, days of mechanical ventilation or weaning, rate of reintubation, length of stay in the intensive care unit or hospital, and mortality in the hospital. Conclusions In this study, the APRV/BIPAP ventilation mode is being used widely across many causes of respiratory failure, but only in selected geographic areas. In our patient population we could not demonstrate any improvement in outcomes with APRV/BIPAP compared with assist-control ventilation.

Introduction Morbidly obese patients occasionally have respiratory problems owing to hypoventilation. Airway pressure release ventilation is one of the ventilation settings often used for respiratory management of acute respiratory distress syndrome. However, previous reports indicating that airway pressure release ventilation may become a therapeutic measure as ventilator management in morbid obesity with respiratory failure is limited. We report a case of markedly improved oxygenation in a morbidly obese patient after airway pressure release ventilation application. Case report A 50s-year-old Asian man (body mass index 41 kg/m 2 ) presented with breathing difficulties. The patient had respiratory failure with a PaO 2 /F I O 2 ratio of approximately 100 and severe atelectasis in the left lung, and ventilator management was initiated. Although the patient was managed on a conventional ventilate mode, oxygenation did not improve. On day 11, we changed the ventilation setting to airway pressure release ventilation, which showed marked improvement in oxygenation with a PaO 2 /F I O 2 ratio of approximately 300. We could reduce sedative medication and apply respiratory rehabilitation. The patient was weaned from the ventilator on day 29 and transferred to another hospital for further rehabilitation on day 31. Conclusion Airway pressure release ventilation ventilator management in morbidly obese patients may contribute to improving oxygenation and become one of the direct therapeutic measures in the early stage of critical care.

Acute respiratory distress syndrome (ARDS) is associated with a heterogeneous pattern of injury throughout the lung parenchyma that alters regional alveolar opening and collapse time constants. Such heterogeneity leads to atelectasis and repetitive alveolar collapse and expansion (RACE). The net effect is a progressive loss of lung volume with secondary ventilator-induced lung injury (VILI). Previous concepts of ARDS pathophysiology envisioned a two-compartment system: a small amount of normally aerated lung tissue in the non-dependent regions (termed “baby lung”); and a collapsed and edematous tissue in dependent regions. Based on such compartmentalization, two protective ventilation strategies have been developed: (1) a “protective lung approach” (PLA), designed to reduce overdistension in the remaining aerated compartment using a low tidal volume; and (2) an “open lung approach” (OLA), which first attempts to open the collapsed lung tissue over a short time frame (seconds or minutes) with an initial recruitment maneuver, and then stabilize newly recruited tissue using titrated positive end-expiratory pressure (PEEP). A more recent understanding of ARDS pathophysiology identifies regional alveolar instability and collapse (i.e., hidden micro-atelectasis) in both lung compartments as a primary VILI mechanism. Based on this understanding, we propose an alternative strategy to ventilating the injured lung, which we term a “stabilize lung approach” (SLA). The SLA is designed to immediately stabilize the lung and reduce RACE while gradually reopening collapsed tissue over hours or days. At the core of SLA is time-controlled adaptive ventilation (TCAV), a method to adjust the parameters of the airway pressure release ventilation (APRV) modality. Since the acutely injured lung at any given airway pressure requires more time for alveolar recruitment and less time for alveolar collapse, SLA adjusts inspiratory and expiratory durations and inflation pressure levels. The TCAV method SLA reverses the open first and stabilize second OLA method by: (i) immediately stabilizing lung tissue using a very brief exhalation time (≤0.5 s), so that alveoli simply do not have sufficient time to collapse. The exhalation duration is personalized and adaptive to individual respiratory mechanical properties (i.e., elastic recoil); and (ii) gradually recruiting collapsed lung tissue using an inflate and brake ratchet combined with an extended inspiratory duration (4–6 s) method. Translational animal studies, clinical statistical analysis, and case reports support the use of TCAV as an efficacious lung protective strategy.