Airway Pressure Release Ventilation Research Articles

Mechanical ventilation management and airway pressure release ventilation practice in acute respiratory distress syndrome: A cross‐sectional survey of intensive care unit clinicians in mainland China

Mechanical ventilation management and airway pressure release ventilation practice in acute respiratory distress syndrome: A cross‐sectional survey of intensive care unit clinicians in mainland China

Early pathophysiology-driven airway pressure release ventilation versus low tidal volume ventilation strategy for patients with moderate-severe ARDS: study protocol for a randomized, multicenter, controlled trial

BackgroundConventional 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.MethodsThe 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 disseminationThe 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 registrationThe study was registered at Clinical Trials.gov (NCT03549910) on June 8, 2018.

Airway pressure release ventilation (APRV) versus pressure support ventilation (PSV)-A prospective intervention trial comparing haemodynamic parameters in intensive care patients.

Assisted mechanical ventilation may alter the pressure profile in the thorax compared to normal breathing, which can affect the blood flow to and from the heart. Studies suggest that in patients with severe lung disease, airway pressure release ventilation (APRV) may be haemodynamically beneficial compared to other ventilator settings. The primary aim of this study was to investigate if APRV affects cardiac index in intubated intensive care patients without severe lung disease when compared to pressure support ventilation (PSV). The secondary aim comprised potential changes in other haemodynamic and ventilatory parameters. Twenty patients were enrolled in the intensive care unit (ICU) at Sahlgrenska University Hospital. Eligible patients met the inclusion criteria; 18 years of age or above, intubated and mechanically ventilated, triggering and stable on PSV mode, with indwelling haemodynamic monitoring via a pulse-induced continuous cardiac output (PiCCO) catheter. The study protocol started with a 30-min interval on PSV mode, followed by a 30-min interval on APRV mode, and finally a 30-min interval back on PSV mode. At the end of each interval, PiCCO outputs, ventilator outputs, arterial and venous blood gas analyses, heart rate and central venous pressure were recorded and compared between modes. There was no significant difference in cardiac index (3.42 vs. 3.39 L/min/m2) between PSV and APRV, but a significant increase in central venous pressure (+1.0 mmHg, p = .027). Furthermore, we found a significant reduction in peak airway pressure (-3.16 cmH2O, p < .01) and an increase in mean airway pressure (+2.1 cmH2O, p < .01). No statistically significant change was found in oxygenation index (partial pressure of O2 [pO2]/fraction of inspired oxygen) nor in other secondary outcomes when comparing PSV and APRV. There was no significant association between global end-diastolic volume index and cardiac index (R2 = 0.0089) or central venous pressure (R2 = 0.278). All parameters returned to baseline after switching the ventilator mode back to PSV. We could not detect any changes in cardiac index in ICU patients without severe lung disease during APRV compared to PSV mode, despite lower peak airwaypressure and increasedmean airway pressure.

Inconsistent Methods Used to Set Airway Pressure Release Ventilation in Acute Respiratory Distress Syndrome: A Systematic Review and Meta-Regression Analysis.

Airway pressure release ventilation (APRV) is a protective mechanical ventilation mode for patients with acute respiratory distress syndrome (ARDS) that theoretically may reduce ventilator-induced lung injury (VILI) and ARDS-related mortality. However, there is no standard method to set and adjust the APRV mode shown to be optimal. Therefore, we performed a meta-regression analysis to evaluate how the four individual APRV settings impacted the outcome in these patients. Methods: Studies investigating the use of the APRV mode for ARDS patients were searched from electronic databases. We tested individual settings, including (1) high airway pressure (PHigh); (2) low airway pressure (PLow); (3) time at high airway pressure (THigh); and (4) time at low pressure (TLow) for association with PaO2/FiO2 ratio and ICU length of stay. Results: There was no significant difference in PaO2/FiO2 ratio between the groups in any of the four settings (PHigh difference -12.0 [95% CI -100.4, 86.4]; PLow difference 54.3 [95% CI -52.6, 161.1]; TLow difference -27.19 [95% CI -127.0, 72.6]; THigh difference -51.4 [95% CI -170.3, 67.5]). There was high heterogeneity across all parameters (PhHgh I2 = 99.46%, PLow I2 = 99.16%, TLow I2 = 99.31%, THigh I2 = 99.29%). Conclusions: None of the four individual APRV settings independently were associated with differences in outcome. A holistic approach, analyzing all settings in combination, may improve APRV efficacy since it is known that small differences in ventilator settings can significantly alter mortality. Future clinical trials should set and adjust APRV based on the best current scientific evidence available.

Successful application of airway pressure release ventilation in a child with severe acute respiratory distress syndrome induced by trauma: a case report

BackgroundTrauma 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 presentationA 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.ConclusionAirway 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.

Awareness and practice of airway pressure release ventilation mode in acute respiratory distress syndrome patients among nurses in Saudi Arabia

BackgroundThis study aimed to assess the knowledge and current practice of using the airway pressure release ventilation (APRV) mode with acute respiratory distress syndrome (ARDS) patients and identify barriers to not using this mode of ventilation among nurses who work in critical areas in Saudi Arabia.MethodsBetween December 2022 and April 2023, a cross-sectional online survey was disseminated to nurses working in critical care areas in Saudi Arabia. The characteristics of the respondents were analyzed using descriptive statistics. Percentages and frequencies were used to report categorical variables.ResultsOverall, 1,002 nurses responded to the online survey, of whom 592 (59.1%) were female. Only 248 (24.7%) nurses had ever used APRV mode, whereas only 229 (22.8%) received training on APRV mode. Moreover, 602 (60.0%) nurses did not know whether APRV was utilized in their hospital. Additionally, 658 (65.6%) nurses did not know whether APRV mode was managed using a standard protocol. Prone positioning was the highest recommended intervention by 444 (43.8%) when a conventional MV failed to improve oxygenation in patients with ARDS. 323 (32.2%) respondents stated that the P-high should be set equal to the plateau pressure on a conventional ventilator, while 400 (39.9%) said that the P-low should match PEEP from a conventional ventilator. Almost half of the respondents (446, 44.5%) stated that the T-high should be set between 4 and 6 s, while 415 (41.4%) said that the T-low should be set at 0.4 to 0.8 s. Over half of the nurses (540, 53.9%) thought that the maximum allowed tidal volume during the release phase should be 4–6 ml/kg. Moreover, 475 (47.4%) believed that the maximum allowed P-high setting should be 35 cm H2O. One-third of the responders (329, 32.8%) stated that when weaning patients with ARDS while in APRV mode, the P-high should be reduced gradually to reach a target of 10 cm H2O. However, 444 (44.3%) thought that the T-high should be gradually increased to reach a target of 10 s. Half of the responders (556, 55.5%) felt that the criteria to switch the patient to continuous positive airway pressure (CPAP) were for the patient to have an FiO2 ≤ 0.4, P-high ≤ 10 cm H2O, and T-high ≥ 10 s. Lack of training was the most common barrier to not using APRV by 615 (61.4%).ConclusionThe majority of nurses who work in critical care units have not received sufficient training in APRV mode. A significant discrepancy was observed regarding the clinical application and management of APRV parameters. Inadequate training was the most frequently reported barrier to the use of APRV in patients with ARDS.

Efficacy of Airway Pressure Release Ventilation in treating acute respiratory distress syndrome

Efficacy of Airway Pressure Release Ventilation in treating acute respiratory distress syndrome

The Use of Extracorporeal Membrane Oxygenation (ECMO) and Protective Mechanical Ventilation in the Treatment of Acute Respiratory Failure

Acute respiratory failure (ARF) affects 2 million people in the United States each year. The ARF's hallmark is a heterogeneous injury, with normal tissue intermingled with a large volume of low compliance and collapsed tissue. Mechanical ventilation is necessary to oxygenate and ventilate those patients but if set inappropriately can cause ventilator-induced lung injury (VILI). To avoid VILI, extracorporeal membrane oxygenation (ECMO) can replace the pulmonary function of gas exchange . The optimal method of mechanical ventilation for the patient on ECMO is unknown. Rest the Lung Approach (RLA) buys time for the lung to heal in the collapsed state. Open Lung Approach (OLA) attempts to open the entire lung very quickly. ARDS-related mortality has not been further reduced using the RLA and even it increases with OLA. Thus, the Mechanical Breath Profile (MBP) component of time would play a critical role in both lung opening and collapses. The Time-Controlled Adaptive Ventilation (TCAV) method of setting and adjusting the Airway Pressure Release Ventilation (APRV) mode uses an extended time at inspiration to open viscoelastic lung tissue and a very brief expiratory time to prevent re-collapse during exhalation. The expiratory time is personalized and adaptive as it is set by changes in respiratory system compliance (CRS). The TCAV method is a novel Stabilize the Lung Approach (SLA). We postulate that the SLA TCAV method would be a highly lung-protective ventilation strategy that would protect from VILI and gradually reopen the lung allowing the patient to be liberated from ECMO.

An international RAND/UCLA expert panel to determine the optimal diagnosis and management of burn inhalation injury

BackgroundBurn inhalation injury (BII) is a major cause of burn-related mortality and morbidity. Despite published practice guidelines, no consensus exists for the best strategies regarding diagnosis and management of BII. A modified DELPHI study using the RAND/UCLA (University of California, Los Angeles) Appropriateness Method (RAM) systematically analysed the opinions of an expert panel. Expert opinion was combined with available evidence to determine what constitutes appropriate and inappropriate judgement in the diagnosis and management of BII.MethodsA 15-person multidisciplinary panel comprised anaesthetists, intensivists and plastic surgeons involved in the clinical management of major burn patients adopted a modified Delphi approach using the RAM method. They rated the appropriateness of statements describing diagnostic and management options for BII on a Likert scale. A modified final survey comprising 140 statements was completed, subdivided into history and physical examination (20), investigations (39), airway management (5), systemic toxicity (23), invasive mechanical ventilation (29) and pharmacotherapy (24). Median appropriateness ratings and the disagreement index (DI) were calculated to classify statements as appropriate, uncertain, or inappropriate.ResultsOf 140 statements, 74 were rated as appropriate, 40 as uncertain and 26 as inappropriate. Initial intubation with ≥ 8.0 mm endotracheal tubes, lung protective ventilatory strategies, initial bronchoscopic lavage, serial bronchoscopic lavage for severe BII, nebulised heparin and salbutamol administration for moderate-severe BII and N-acetylcysteine for moderate BII were rated appropriate. Non-protective ventilatory strategies, high-frequency oscillatory ventilation, high-frequency percussive ventilation, prophylactic systemic antibiotics and corticosteroids were rated inappropriate. Experts disagreed (DI ≥ 1) on six statements, classified uncertain: the use of flexible fiberoptic bronchoscopy to guide fluid requirements (DI = 1.52), intubation with endotracheal tubes of internal diameter < 8.0 mm (DI = 1.19), use of airway pressure release ventilation modality (DI = 1.19) and nebulised 5000IU heparin, N-acetylcysteine and salbutamol for mild BII (DI = 1.52, 1.70, 1.36, respectively).ConclusionsBurns experts mostly agreed on appropriate and inappropriate diagnostic and management criteria of BII as in published guidance. Uncertainty exists as to the optimal diagnosis and management of differing grades of severity of BII. Future research should investigate the accuracy of bronchoscopic grading of BII, the value of bronchial lavage in differing severity groups and the effectiveness of nebulised therapies in different severities of BII.Graphical

Knowledge and practice of using airway pressure release ventilation mode in ARDS patients: A survey of physicians

BackgroundLimited data is available on awareness and clinical management of the airway pressure release ventilation (APRV) mode of ventilation for acute respiratory distress syndrome (ARDS) patients among physicians who work at in adult critical areas. This study aimed to assess the knowledge and current practice of using APRV mode with ARDS patients and identify barriers to not using this mode of ventilation among physicians who work in adult critical areas in Saudi Arabia. MethodsBetween November 2022 and April 2023, a cross-sectional online survey was disseminated to physicians who work in adult critical areas in Saudi Arabia. The characteristics of the respondents were analyzed using descriptive statistics. Percentages and frequencies were used to report categorical variables. ResultsOverall, 498 physicians responded to the online survey. All responders (498, 100 %) reported that APRV is indicated in patients with ARDS, but 260 (52.2 %) did not know if there was an institutionally approved APRV protocol. Prone positioning was the highest recommended intervention by 164 (33.0 %) when a conventional MV failed to improve oxygenation in patients with ARDS. 136 (27.3 %) responders stated that the P-high should be set equal to the plateau pressure on a conventional ventilator while 198 (39.8 %) said that P-low should be 0 cmH2O. Almost half of (229, 46.0 %) responders stated that the T-high should be set between 4 and 6 s, while 286 (57.4 %) said that the T-low should be set at 0.4–0.8 s. The maximum allowed tidal volume during the release phase should be 4–6 ml/kg. Moreover, just over half (257, 51.6 %) believed that the maximum allowed P-high setting should be 35 cmH2O. One third of the responders (171, 34.3 %) stated that when weaning patients with ARDS while in APRV mode, the P-high should be reduced gradually to reach a target of 10 cmH2O. However, 284 (36.9 %) thought that the T-high should be gradually increased to reach a target of 10 s. Most responders (331, 66.5 %) felt that the criteria to switch the patient to CPAP would be to have an FiO2 ≤ 0.4, P-high ≤10 cm H2O, and T-high ≥10 s. Lack of training has been the most common barrier to not using APRV by 388 (77.9 %). ConclusionThere is a lack of consensus on the use of APRV mode, probably due to several barriers. While there were some agreements on the management of ventilation and oxygenation, there were variations in the selection of the initial setting of APRV. Education, training, and the presence of standardized protocols may help to provide better management.

Sustained vs. Intratidal Recruitment in the Injured Lung During Airway Pressure Release Ventilation: A Computational Modeling Perspective.

During mechanical ventilation, cyclic recruitment and derecruitment (R/D) of alveoli result in focal points of heterogeneous stress throughout the lung. In the acutely injured lung, the rates at which alveoli can be recruited or derecruited may also be altered, requiring longer times at higher pressure levels to be recruited during inspiration, but shorter times at lower pressure levels to minimize collapse during exhalation. In this study, we used a computational model to simulate the effects of airway pressure release ventilation (APRV) on acinar recruitment, with varying inspiratory pressure levels and durations of exhalation. The computational model consisted of a ventilator pressure source, a distensible breathing circuit, an endotracheal tube, and a porcine lung consisting of recruited and derecruited zones, as well as a transitional zone capable of intratidal R/D. Lung injury was simulated by modifying each acinus with an inflation-dependent surface tension. APRV was simulated for an inhalation duration (Thigh) of 4.0 seconds, inspiratory pressures (Phigh) of 28 and 40 cmH2O, and exhalation durations (Tlow) ranging from 0.2 to 1.5 seconds. Both sustained acinar recruitment and intratidal R/D within the subtree were consistently higher for Phigh of 40 cmH2O vs. 28 cmH2O, regardless of Tlow. Increasing Tlow was associated with decreasing sustained acinar recruitment, but increasing intratidal R/D, within the subtree. Increasing Tlow was associated with decreasing elastance of both the total respiratory system and transitional subtree of the model. Our computational model demonstrates the confounding effects of cyclic R/D, sustained recruitment, and parenchymal strain stiffening on estimates of total lung elastance during APRV. Increasing inspiratory pressures leads to not only more sustained recruitment of unstable acini but also more intratidal R/D. Our model indicates that higher inspiratory pressures should be used in conjunction with shorter exhalation times, to avoid increasing intratidal R/D.

Ratchet recruitment in the acute respiratory distress syndrome: lessons from the newborn cry.

Patients with acute respiratory distress syndrome (ARDS) have few treatment options other than supportive mechanical ventilation. The mortality associated with ARDS remains unacceptably high, and mechanical ventilation itself has the potential to increase mortality further by unintended ventilator-induced lung injury (VILI). Thus, there is motivation to improve management of ventilation in patients with ARDS. The immediate goal of mechanical ventilation in ARDS should be to prevent atelectrauma resulting from repetitive alveolar collapse and reopening. However, a long-term goal should be to re-open collapsed and edematous regions of the lung and reduce regions of high mechanical stress that lead to regional volutrauma. In this paper, we consider the proposed strategy used by the full-term newborn to open the fluid-filled lung during the initial breaths of life, by ratcheting tissues opened over a series of initial breaths with brief expirations. The newborn's cry after birth shares key similarities with the Airway Pressure Release Ventilation (APRV) modality, in which the expiratory duration is sufficiently short to minimize end-expiratory derecruitment. Using a simple computational model of the injured lung, we demonstrate that APRV can slowly open even the most recalcitrant alveoli with extended periods of high inspiratory pressure, while reducing alveolar re-collapse with brief expirations. These processes together comprise a ratchet mechanism by which the lung is progressively recruited, similar to the manner in which the newborn lung is aerated during a series of cries, albeit over longer time scales.

Airway Pressure Release Ventilation in COVID-19-Associated Acute Respiratory Distress Syndrome-A Multicenter Propensity Score-Matched Analysis.

Background: There are limited and partially contradictory data on the effects of airway pressure release ventilation (APRV) in COVID-19-associated acute respiratory distress syndrome (CARDS). Therefore, we analyzed the clinical outcome, complications, and longitudinal course of ventilation parameters and laboratory values in patients with CARDS, who were mechanically ventilated using APRV. Methods: Respective data from 4 intensive care units (ICUs) were collected and compared to a matched cohort of patients receiving conventional low tidal volume ventilation (LTV). Propensity score matching was performed based on age, sex, blood gas analysis, and APACHE II score at admission, as well as the implementation of prone positioning. Findings: Forty patients with CARDS, who were mechanically ventilated using APRV, and 40 patients receiving LTV were matched. No significant differences were detected for tidal volumes per predicted body weight, peak pressure values, and blood gas analyses on admission, 6 h post admission as well as on day 3 and day 7. Regarding ICU survival, no significant difference was identified between APRV patients (40%) and LTV patients (42%). Median duration of mechanical ventilation and duration of ICU treatment were comparable in both groups. Similar complication rates with respect to ventilator-associated pneumonia, septic shock, thromboembolic events, barotrauma, as well as the necessity for hemodialysis were detected for both groups. Clinical characteristics that were associated with increased mortality in a Cox proportional hazards regression analysis included age (hazard ratio [HR] 1.08, 95% confidence interval [CI] 1.04-1.1; P < .001), severe acute respiratory distress syndrome (HR 2.62, 95% CI 1.02-6.7; P = .046) and the occurrence of septic shock (HR 17.18, 95% CI 2.06-143.2; P = .009), but not the ventilation mode. Interpretation: Intensive care unit survival, duration of mechanical ventilation, and ICU treatment as well as ventilation-associated complication rates were equivalent using APRV compared to conventional LTV in patients with CARDS.

Evaluation of ventilatory ratio in airway pressure release ventilation (APRV) in patients with acute respiratory failure: Brief communication

Evaluation of ventilatory ratio in airway pressure release ventilation (APRV) in patients with acute respiratory failure: Brief communication

Effects of three spontaneous ventilation modes on respiratory drive and muscle effort in COVID-19 pneumonia patients

BackgroundHigh drive and high effort during spontaneous breathing can generate patient self-inflicted lung injury (P-SILI) due to uncontrolled high transpulmonary and transvascular pressures, with deterioration of respiratory failure. P-SILI has been demonstrated in experimental studies and supported in recent computational models. Different treatment strategies have been proposed according to the phenotype of elastance of the respiratory system (Ers) for patients with COVID-19. This study aimed to investigate the effect of three spontaneous ventilation modes on respiratory drive and muscle effort in clinical practice and their relationship with different phenotypes. This was achieved by obtaining the following respiratory signals: airway pressure (Paw), flow (V´) and volume (V) and calculating muscle pressure (Pmus).MethodsA physiologic observational study of a series of cases in a university medical-surgical ICU involving 11 mechanically ventilated patients with COVID-19 pneumonia at the initiation of spontaneous breathing was conducted. Three spontaneous ventilation modes were evaluated in each of the patients: pressure support ventilation (PSV), airway pressure release ventilation (APRV), and BiLevel positive airway pressure ventilation (BIPAP). Pmus was calculated through the equation of motion. For this purpose, we acquired the signals of Paw, V´ and V directly from the data transmission protocol of the ventilator (Dräger). The main physiological measurements were calculation of the respiratory drive (P0.1), muscle effort through the ΔPmus, pressure‒time product (PTP/min) and work of breathing of the patient in joules multiplied by respiratory frequency (WOBp, J/min).ResultsTen mechanically ventilated patients with COVID-19 pneumonia at the initiation of spontaneous breathing were evaluated. Our results showed similar high drive and muscle effort in each of the spontaneous ventilatory modes tested, without significant differences between them: median (IQR): P0.1 6.28 (4.92–7.44) cm H2O, ∆Pmus 13.48 (11.09–17.81) cm H2O, PTP 166.29 (124.02–253.33) cm H2O*sec/min, and WOBp 12.76 (7.46–18.04) J/min. High drive and effort were found in patients even with low Ers. There was a significant relationship between respiratory drive and WOBp and Ers, though the coefficient of variation widely varied.ConclusionsIn our study, none of the spontaneous ventilatory methods tested succeeded in reducing high respiratory drive or muscle effort, regardless of the Ers, with subsequent risk of P-SILI.

Safety of Fiberoptic Bronchoscopy in Airway Pressure Release Ventilation Mode in Critically Ill Patients: Are These Results Safe?

Safety of Fiberoptic Bronchoscopy in Airway Pressure Release Ventilation Mode in Critically Ill Patients: Are These Results Safe?

First Stabilize and then Gradually Recruit: A Paradigm Shift in Protective Mechanical Ventilation for Acute Lung Injury.

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.

Combined Effects of Prone Positioning and Airway Pressure Release Ventilation on Oxygenation in Patients with COVID-19 ARDS.

Coronavirus disease 2019 (COVID-19) can cause acute respiratory distress syndrome (ARDS). Invasive mechanical ventilation (IMV) support and prone positioning are essential treatments for severe COVID-19 ARDS. We aimed to determine the combined effect of prone position and airway pressure release ventilation (APRV) modes on oxygen improvement in mechanically-ventilated patients with COVID-19. This prospective observational study included 40 eligible patients (13 female, 27 male). Of 40 patients, 23 (57.5%) were ventilated with APRV and 17 (42.5%) were ventilated with controlled modes. A prone position was applied when the PaO2/FiO2 ratio <150 mmHg despite IMV in COVID-19 ARDS. The numbers of patients who completed the first, second, and third prone were 40, 25, and 15, respectively. Incident barotrauma events were diagnosed by both clinical findings and radiological images. After the second prone, the PaO2/FiO2 ratio of the APRV group was higher compared to the PaO2/FiO2 ratio of the control group [189 (150-237)] vs. 127 (100-146) mmHg, respectively, (P=0.025). Similarly, after the third prone, the PaO2/FiO2 ratio of the APRV group was higher compared to the PaO2/FiO2 ratio of the control group [194 (132-263)] vs. 83 (71-136) mmHg, respectively, (P=0.021). Barotrauma events were detected in 13.0% of the patients in the APRV group and 11.8% of the patients in the control group (P=1000). The 28-day mortality was not different in the APRV group than in the control group (73.9% vs. 70.6%, respectively, P=1000). Using the APRV mode during prone positioning improves oxygenation, especially in the second and third prone positions, without increasing the risk of barotrauma. However, no benefit on mortality was detected.

710 Assessing the Impact of Prone Positioning Among Adult Burn Patients with Acute Respiratory Distress Syndrome

Abstract Introduction Critically-ill burn patients are at high risk for extensive adverse systemic complications due to the severe inflammatory reaction following deep thermal injury. A common but dangerous pulmonary complication associated with deep burns is acute respiratory distress syndrome (ARDS), with incidence and mortality ranging up to 24% and 31%, respectively. Prone positioning (PP) as a means of improving mortality in patients with ARDS has become more widely utilized. However, PP is not well described in the burn population and remains controversial due to the risk of wound complications. We hypothesize that PP in burn patients with ARDS would improve mortality compared to non-prone (NP) patients without adverse outcomes. Methods Retrospective data were collected for all burn patients with ARDS from 2018-21. A total of 7 patients who underwent prone positioning (PP) were matched via TBSA, age, and gender 1:2 with 14 patients not proned (NP). Categorical variables were presented as count (percentage) and continuous variables presented as mean (SD). P values were two-sided and P&amp;lt; 0.05 significant. Results A total of 58 adult burn patients with ARDS were identified from the burn registry between the years of 2018-2021 and 7 of these were identified as having been treated with PP. Matching was completed to identify 14 NP burn patients with ARDS. Characteristics of these groups are shown in Table 1. The PP patients had significantly higher APACHE II scores, airway pressure release ventilation (APRV) usage, and tracheostomy placement. For the PP patients, mean days to ARDS diagnosis from injury was 4.7±2.6, mean days to PP from ARDS diagnosis was 4.1±6.0, and total days prone was 4.3±3.5. P/F ratios for both the PP and NP groups are shown in Figure 1. P/F ratios for the PP group were declining prior to PP and increased after PP. P/F ratios for the NP group gradually improved without PP. There was no difference in mortality between the two groups (PP=42.8%,NP=57.1%,p=0.6) despite the significantly increased APACHE II scores. No wound complications were noted in the PP group. Conclusions ARDS remains a significant cause of mortality in burn patients. The PP patients had similar mortality compared to the NP group despite a two-fold increased expected mortality estimated by the Apache II scores. None of the PP patients had wound complications due to PP. PP appears to be a safe and useful adjunct therapy for burn patients with severe ARDS. Applicability of Research to Practice ARDS is a significant cause of mortality in severe burn patients, this study evaluates PP as a treatment.

Effects of airway pressure release ventilation on lung physiology assessed by electrical impedance tomography in patients with early moderate-to-severe ARDS

ObjectiveThe 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).MethodsIn 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.ResultsTwelve 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 PaO2/FiO2 (r = 0.624, p = 0.001) and lower PaCO2 (r = -0.408, p = 0.048).ConclusionsAPRV optimizes the distribution of ventilation and perfusion, reducing lung heterogeneity, which potentially reduces the risk of ventilator-induced lung injury.