The time-controlled adaptive ventilation protocol: mechanistic approach to reducing ventilator-induced lung injury

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

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.

Airway pressure release ventilation for lung protection in acute respiratory distress syndrome: an alternative way to recruit the lungs

PURPOSE OF REVIEW

Airway pressure release ventilation (APRV) is a modality of ventilation in which high inspiratory continuous positive airway pressure (CPAP) alternates with brief releases. In this review, we will discuss the rationale for APRV as a lung protective strategy and then provide a practical introduction to initiating APRV using the time-controlled adaptive ventilation (TCAV) method.

RECENT FINDINGS

APRV using the TCAV method uses an extended inspiratory time and brief expiratory release to first stabilize and then gradually recruit collapsed lung (over hours/days), by progressively 'ratcheting' open a small volume of collapsed tissue with each breath. The brief expiratory release acts as a 'brake' preventing newly recruited units from re-collapsing, reversing the main drivers of ventilator-induced lung injury (VILI). The precise timing of each release is based on analysis of expiratory flow and is set to achieve termination of expiratory flow at 75% of the peak expiratory flow. Optimization of the release time reflects the changes in elastance and, therefore, is personalized (i.e. conforms to individual patient pathophysiology), and adaptive (i.e. responds to changes in elastance over time).

SUMMARY

APRV using the TCAV method is a paradigm shift in protective lung ventilation, which primarily aims to stabilize the lung and gradually reopen collapsed tissue to achieve lung homogeneity eliminating the main mechanistic drivers of VILI.

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

BACKGROUND

This 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.

METHODS

Between 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.

RESULTS

Overall, 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%).

CONCLUSION

The 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.

Future directions in ventilator-induced lung injury associated cognitive impairment: a new sight

Mechanical ventilation is a widely used short-term life support technique, but an accompanying adverse consequence can be pulmonary damage which is called ventilator-induced lung injury (VILI). Mechanical ventilation can potentially affect the central nervous system and lead to long-term cognitive impairment. In recent years, many studies revealed that VILI, as a common lung injury, may be involved in the central pathogenesis of cognitive impairment by inducing hypoxia, inflammation, and changes in neural pathways. In addition, VILI has received attention in affecting the treatment of cognitive impairment and provides new insights into individualized therapy. The combination of lung protective ventilation and drug therapy can overcome the inevitable problems of poor prognosis from a new perspective. In this review, we summarized VILI and non-VILI factors as risk factors for cognitive impairment and concluded the latest mechanisms. Moreover, we retrospectively explored the role of improving VILI in cognitive impairment treatment. This work contributes to a better understanding of the pathogenesis of VILI-induced cognitive impairment and may provide future direction for the treatment and prognosis of cognitive impairment.

Management of severe acute respiratory distress syndrome: a primer

This narrative review explores the physiology and evidence-based management of patients with severe acute respiratory distress syndrome (ARDS) and refractory hypoxemia, with a focus on mechanical ventilation, adjunctive therapies, and veno-venous extracorporeal membrane oxygenation (V-V ECMO). Severe ARDS cases increased dramatically worldwide during the Covid-19 pandemic and carry a high mortality. The mainstay of treatment to improve survival and ventilator-free days is proning, conservative fluid management, and lung protective ventilation. Ventilator settings should be individualized when possible to improve patient-ventilator synchrony and reduce ventilator-induced lung injury (VILI). Positive end-expiratory pressure can be individualized by titrating to best respiratory system compliance, or by using advanced methods, such as electrical impedance tomography or esophageal manometry. Adjustments to mitigate high driving pressure and mechanical power, two possible drivers of VILI, may be further beneficial. In patients with refractory hypoxemia, salvage modes of ventilation such as high frequency oscillatory ventilation and airway pressure release ventilation are additional options that may be appropriate in select patients. Adjunctive therapies also may be applied judiciously, such as recruitment maneuvers, inhaled pulmonary vasodilators, neuromuscular blockers, or glucocorticoids, and may improve oxygenation, but do not clearly reduce mortality. In select, refractory cases, the addition of V-V ECMO improves gas exchange and modestly improves survival by allowing for lung rest. In addition to VILI, patients with severe ARDS are at risk for complications including acute cor pulmonale, physical debility, and neurocognitive deficits. Even among the most severe cases, ARDS is a heterogeneous disease, and future studies are needed to identify ARDS subgroups to individualize therapies and advance care.

Mechanical ventilation in patients with acute respiratory distress syndrome: current status and future perspectives

INTRODUCTION

Although there has been extensive research on mechanical ventilation for acute respiratory distress syndrome (ARDS), treatment remains mainly supportive. Recent studies and new ventilatory modes have been proposed to manage patients with ARDS; however, the clinical impact of these strategies remains uncertain and not clearly supported by guidelines. The aim of this narrative review is to provide an overview and update on ventilatory management for patients with ARDS.

AREAS COVERED

This article reviews the literature regarding mechanical ventilation in ARDS. A comprehensive overview of the principal settings for the ventilator parameters involved is provided as well as a report on the differences between controlled and assisted ventilation. Additionally, new modes of assisted ventilation are presented and discussed. The evidence concerning rescue strategies, including recruitment maneuvers and extracorporeal membrane oxygenation support, is analyzed. PubMed, EBSCO, and the Cochrane Library were searched up until June 2023, for relevant literature.

EXPERT OPINION

Available evidence for mechanical ventilation in cases of ARDS suggests the use of a personalized mechanical ventilation strategy. Although promising, new modes of assisted mechanical ventilation are still under investigation and guidelines do not recommend rescue strategies as the standard of care. Further research on this topic is required.

Challenges in ARDS Definition, Management, and Identification of Effective Personalized Therapies

Over the last decade, the management of acute respiratory distress syndrome (ARDS) has made considerable progress both regarding supportive and pharmacologic therapies. Lung protective mechanical ventilation is the cornerstone of ARDS management. Current recommendations on mechanical ventilation in ARDS include the use of low tidal volume (VT) 4-6 mL/kg of predicted body weight, plateau pressure (PPLAT) < 30 cmH2O, and driving pressure (∆P) < 14 cmH2O. Moreover, positive end-expiratory pressure should be individualized. Recently, variables such as mechanical power and transpulmonary pressure seem promising for limiting ventilator-induced lung injury and optimizing ventilator settings. Rescue therapies such as recruitment maneuvers, vasodilators, prone positioning, extracorporeal membrane oxygenation, and extracorporeal carbon dioxide removal have been considered for patients with severe ARDS. Regarding pharmacotherapies, despite more than 50 years of research, no effective treatment has yet been found. However, the identification of ARDS sub-phenotypes has revealed that some pharmacologic therapies that have failed to provide benefits when considering all patients with ARDS can show beneficial effects when these patients were stratified into specific sub-populations; for example, those with hyperinflammation/hypoinflammation. The aim of this narrative review is to provide an overview on current advances in the management of ARDS from mechanical ventilation to pharmacological treatments, including personalized therapy.

Myths and Misconceptions of Airway Pressure Release Ventilation: Getting Past the Noise and on to the Signal

In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge and expose our ignorance. To quote Murray Gell-Mann (1969 Nobel Prize laureate in Physics): "Scientific orthodoxy kills truth". In mechanical ventilation, the goal is to provide the best approach to support patients with respiratory failure until the underlying disease resolves, while minimizing iatrogenic damage. This compromise characterizes the philosophy behind the concept of "lung protective" ventilation. Unfortunately, inadequacies of the current conceptual model-that focuses exclusively on a nominal value of low tidal volume and promotes shrinking of the "baby lung" - is reflected in the high mortality rate of patients with moderate and severe acute respiratory distress syndrome. These data call for exploration and investigation of competitive models evaluated thoroughly through a scientific process. Airway Pressure Release Ventilation (APRV) is one of the most studied yet controversial modes of mechanical ventilation that shows promise in experimental and clinical data. Over the last 3 decades APRV has evolved from a rescue strategy to a preemptive lung injury prevention approach with potential to stabilize the lung and restore alveolar homogeneity. However, several obstacles have so far impeded the evaluation of APRV's clinical efficacy in large, randomized trials. For instance, there is no universally accepted standardized method of setting APRV and thus, it is not established whether its effects on clinical outcomes are due to the ventilator mode per se or the method applied. In addition, one distinctive issue that hinders proper scientific evaluation of APRV is the ubiquitous presence of myths and misconceptions repeatedly presented in the literature. In this review we discuss some of these misleading notions and present data to advance scientific discourse around the uses and misuses of APRV in the current literature.

Airway Pressure Release Ventilation With Time-Controlled Adaptive Ventilation (TCAV™) in COVID-19: A Community Hospital's Experience

Santa Cabrini Ospedale, a community hospital in Montreal, Canada, used the airway pressure release ventilation following a time-controlled adaptive ventilation (APRV-TCAV™) approach for several patients in the first wave of the coronavirus disease 2019 (COVID-19) outbreak in the spring of 2021. Based on favorable patient responses, it became the primary mode of invasive mechanical ventilation—from initiation through extubation—during the second and third waves of COVID-19. In this article, we describe our success with APRV-TCAV™ over more conventional modes and protocols and look at three cases that aptly demonstrate our experience. We then outline several risks with our approach and the lessons learned from our experience. While we generally saw improvement in patients’ clinical course with APRV-TCAV™, there are inherent risks with this approach that others must prepare for if they attempt to implement it in their practice.

Effects of time-controlled adaptive ventilation on cardiorespiratory parameters and inflammatory response in experimental emphysema

The time-controlled adaptive ventilation (TCAV) method attenuates lung damage in acute respiratory distress syndrome. However, so far, no study has evaluated the impact of the TCAV method on ventilator-induced lung injury (VILI) and cardiac function in emphysema. We hypothesized that the use of the TCAV method to achieve an expiratory flow termination/expiratory peak flow (E_FT/E_PF) of 25% could reduce VILI and improve right ventricular function in elastase-induced lung emphysema in rats. Five weeks after the last intratracheal instillation of elastase, animals were anesthetized and mechanically ventilated for 1 h using TCAV adjusted to either E_FT/E_PF 25% or E_FT/E_PF 75%, the latter often applied in ARDS. Pressure-controlled ventilation (PCV) groups with positive end-expiratory pressure levels similar to positive end-release pressure in TCAV with E_FT/E_PF 25% and E_FT/E_PF 75% were also analyzed. Echocardiography and lung ultrasonography were monitored. Lung morphometry, alveolar heterogeneity, and biological markers related to inflammation (interleukin [IL]-6, CINC-1), alveolar pulmonary stretch (amphiregulin), lung matrix damage (metalloproteinase [MMP]-9) were assessed. E_FT/E_PF 25% reduced respiratory system peak pressure, mean linear intercept, B lines at lung ultrasonography, and increased pulmonary acceleration time/pulmonary ejection time ratio compared with E_FT/E_PF 75%. The volume fraction of mononuclear cells, neutrophils, and expression of IL-6, CINC-1, amphiregulin, and MMP-9 were lower with E_FT/E_PF 25% than with E_FT/E_PF 75%. In conclusion, TCAV with E_FT/E_PF 25%, compared with E_FT/E_PF 75%, led to less lung inflammation, hyperinflation, and pulmonary arterial hypertension, which may be a promising strategy for patients with emphysema.

Time-Controlled Adaptive Ventilation Versus Volume-Controlled Ventilation in Experimental Pneumonia

OBJECTIVES

We hypothesized that a time-controlled adaptive ventilation strategy would open and stabilize alveoli by controlling inspiratory and expiratory duration. Time-controlled adaptive ventilation was compared with volume-controlled ventilation at the same levels of mean airway pressure and positive end-release pressure (time-controlled adaptive ventilation)/positive end-expiratory pressure (volume-controlled ventilation) in a Pseudomonas aeruginosa-induced pneumonia model.

DESIGN

Animal study.

SETTING

Laboratory investigation.

SUBJECTS

Twenty-one Wistar rats.

INTERVENTIONS

Twenty-four hours after pneumonia induction, Wistar rats (n = 7) were ventilated with time-controlled adaptive ventilation (tidal volume = 8 mL/kg, airway pressure release ventilation for a Thigh = 0.75-0.85 s, release pressure (Plow) set at 0 cm H2O, and generating a positive end-release pressure = 1.6 cm H2O applied for Tlow = 0.11-0.14 s). The expiratory flow was terminated at 75% of the expiratory flow peak. An additional 14 animals were ventilated using volume-controlled ventilation, maintaining similar time-controlled adaptive ventilation levels of positive end-release pressure (positive end-expiratory pressure=1.6 cm H2O) and mean airway pressure = 10 cm H2O. Additional nonventilated animals (n = 7) were used for analysis of molecular biology markers.

MEASUREMENTS AND MAIN RESULTS

After 1 hour of mechanical ventilation, the heterogeneity score, the expression of pro-inflammatory biomarkers interleukin-6 and cytokine-induced neutrophil chemoattractant-1 in lung tissue were significantly lower in the time-controlled adaptive ventilation than volume-controlled ventilation with similar mean airway pressure groups (p = 0.008, p = 0.011, and p = 0.011, respectively). Epithelial cell integrity, measured by E-cadherin tissue expression, was higher in time-controlled adaptive ventilation than volume-controlled ventilation with similar mean airway pressure (p = 0.004). Time-controlled adaptive ventilation animals had bacteremia counts lower than volume-controlled ventilation with similar mean airway pressure animals, while time-controlled adaptive ventilation and volume-controlled ventilation with similar positive end-release pressure animals had similar colony-forming unit counts. In addition, lung edema and cytokine-induced neutrophil chemoattractant-1 gene expression were more reduced in time-controlled adaptive ventilation than volume-controlled ventilation with similar positive end-release pressure groups.

CONCLUSIONS

In the model of pneumonia used herein, at the same tidal volume and mean airway pressure, time-controlled adaptive ventilation, compared with volume-controlled ventilation, was associated with less lung damage and bacteremia and reduced gene expression of mediators associated with inflammation.

Time controlled adaptive ventilation™ as conservative treatment of destroyed lung: an alternative to lung transplantation

Background

Acute respiratory distress syndrome (ARDS) often requires controlled ventilation, yielding high mechanical power and possibly further injury. Veno-venous extracorporeal membrane oxygenation (VV-ECMO) can be used as a bridge to recovery, however, if this fails the end result is destroyed lung parenchyma. This condition is fatal and the only remaining alternative is lung transplantation. In the case study presented in this paper, lung transplantation was not an option given the critically ill state and the presence of HLA antibodies. Airway pressure release ventilation (APRV) may be valuable in ARDS, but APRV settings recommended in various patient and clinical studies are inconsistent. The Time Controlled Adaptive Ventilation (TCAV™) method is the most studied technique to set and adjust the APRV mode and uses an extended continuous positive airway pressure (CPAP) Phase in combination with a very brief Release Phase. In addition, the TCAV™ method settings are personalized and adaptive based on changes in lung pathophysiology. We used the TCAV™ method in a case of severe ARDS, which enabled us to open, stabilize and slowly heal the severely damaged lung parenchyma.

Case presentation

A 43-year-old woman presented with Staphylococcus Aureus necrotizing pneumonia. Progressive respiratory failure necessitated invasive mechanical ventilation and VV-ECMO. Mechanical ventilation (MV) was ultimately discontinued because lung protective settings resulted in trivial tidal volumes. She was referred to our academic transplant center for bilateral lung transplantation after the remaining infection had been cleared. We initiated the TCAV™ method in order to stabilize the lung parenchyma and to promote tissue recovery. This strategy was challenged by the presence of a large bronchopleural fistula, however, APRV enabled weaning from VV-ECMO and mechanical ventilation. After two months, following nearly complete surgical closure of the remaining bronchopleural fistulas, the patient was readmitted to ICU where she had early postoperative complications. Since other ventilation modes resulted in significant atelectasis and hypercapnia, APRV was restarted. The patient was then again weaned from MV.

Conclusions

The TCAV™ method can be useful to wean challenging patients with severe ARDS and might contribute to lung recovery. In this particular case, a lung transplantation was circumvented.

Atelectrauma Versus Volutrauma: A Tale of Two Time-Constants

OBJECTIVES

Elucidate how the degree of ventilator-induced lung injury due to atelectrauma that is produced in the injured lung during mechanical ventilation is determined by both the timing and magnitude of the airway pressure profile.

DESIGN

A computational model of the injured lung provides a platform for exploring how mechanical ventilation parameters potentially modulate atelectrauma and volutrauma. This model incorporates the time dependence of lung recruitment and derecruitment, and the time-constant of lung emptying during expiration as determined by overall compliance and resistance of the respiratory system.

SETTING

Computational model.

SUBJECTS

Simulated scenarios representing patients with both normal and acutely injured lungs.

MEASUREMENTS AND MAIN RESULTS

Protective low-tidal volume ventilation (Low-Vt) of the simulated injured lung avoided atelectrauma through the elevation of positive end-expiratory pressure while maintaining fixed tidal volume and driving pressure. In contrast, airway pressure release ventilation avoided atelectrauma by incorporating a very brief expiratory duration () that both prevents enough time for derecruitment and limits the minimum alveolar pressure prior to inspiration. Model simulations demonstrated that has an effective threshold value below which airway pressure release ventilation is safe from atelectrauma while maintaining a tidal volume and driving pressure comparable with those of Low-Vt. This threshold is strongly influenced by the time-constant of lung-emptying.

CONCLUSIONS

Low-Vt and airway pressure release ventilation represent markedly different strategies for the avoidance of ventilator-induced lung injury, primarily involving the manipulation of positive end-expiratory pressure and , respectively. can be based on exhalation flow values, which may provide a patient-specific approach to protective ventilation.

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

Acute respiratory distress syndrome (ARDS) causes a heterogeneous lung injury and remains a serious medical problem, with one of the only treatments being supportive care in the form of mechanical ventilation. It is very difficult, however, to mechanically ventilate the heterogeneously damaged lung without causing secondary ventilator-induced lung injury (VILI). The acutely injured lung becomes time and pressure dependent, meaning that it takes more time and pressure to open the lung, and it recollapses more quickly and at higher pressure. Current protective ventilation strategies, ARDSnet low tidal volume (LVt) and the open lung approach (OLA), have been unsuccessful at further reducing ARDS mortality. We postulate that this is because the LVt strategy is constrained to ventilating a lung with a heterogeneous mix of normal and focalized injured tissue, and the OLA, although designed to fully open and stabilize the lung, is often unsuccessful at doing so. In this review we analyzed the pathophysiology of ARDS that renders the lung susceptible to VILI. We also analyzed the alterations in alveolar and alveolar duct mechanics that occur in the acutely injured lung and discussed how these alterations are a key mechanism driving VILI. Our analysis suggests that the time component of each mechanical breath, at both inspiration and expiration, is critical to normalize alveolar mechanics and protect the lung from VILI. Animal studies and a meta-analysis have suggested that the time-controlled adaptive ventilation (TCAV) method, using the airway pressure release ventilation mode, eliminates the constraints of ventilating a lung with heterogeneous injury, since it is highly effective at opening and stabilizing the time- and pressure-dependent lung. In animal studies it has been shown that by “casting open” the acutely injured lung with TCAV we can (1) reestablish normal expiratory lung volume as assessed by direct observation of subpleural alveoli; (2) return normal parenchymal microanatomical structural support, known as alveolar interdependence and parenchymal tethering, as assessed by morphometric analysis of lung histology; (3) facilitate regeneration of normal surfactant function measured as increases in surfactant proteins A and B; and (4) significantly increase lung compliance, which reduces the pathologic impact of driving pressure and mechanical power at any given tidal volume.

Risk factors for acute respiratory distress syndrome in severe burns: prospective cohort study

INTRODUCTION

Age and inhalation injury are important risk factors for acute respiratory distress syndrome (ARDS) in the burned patient; however, the impact of interventions such as mechanical ventilation, fluid balance (FB), and packed red blood cell transfusion remains unclear. The purpose of this study was to determine the incidence of moderate and severe ARDS and its risk factors among burn-related demographic variables and clinical interventions in mechanically ventilated burn patients. Risk factors for death within 28 days were also evaluated.

METHOD

A prospective longitudinal study was carried out over a period of 30 months between July 2015 and December 2017. Patients older than 18 years, with a burn injury and under mechanical ventilation were included. The outcomes of interest were diagnosis of ARDS up to seven days after admission and death within 28 days. The proportional Cox regression risk model was used to obtain the hazard ratio for each independent variable.

RESULTS

The cases of 61 patients were analyzed. Thirty-seven (60.66%) of the patients developed ARDS. The groups of patients with or without ARDS did not present differences regarding age, sex, burned body surface, or prognostic scores. Factors independently related to the occurrence of ARDS were age (hazard ratio [HR] = 1.04; 95% confidence interval [CI] 1.02-1.06; P < 0.001), inhalation injury (HR = 2.50; 95% CI 1.25-5.02; P = 0.01), and static compliance (HR = 0.97; 95% CI 0.94-0.99; P = 0.03). Tidal volume, driving pressure, acute renal injury, and FB between days 1 and 7 were similar in both groups. Accumulated FBs of 48, 72, 96, and 168 hours were also similar. Mortality at 28 days was 40.98% (25 patients). ARDS (HR = 3.63, 95% CI 1.36 to 9.68; P = 0.01) and burned body surface area (HR = 1.03, 95% CI 1.02 to 1.05; P < 0.001) were associated with death in 28 days.

CONCLUSION

ARDS was a frequent complication and a risk factor for death in patients under mechanical ventilation, with large burned areas. Age and inhalation injury were independent factors for ARDS. Current tidal volume, driving pressure, red blood cell transfusion, acute renal injury, and FB were not predictors of ARDS.

A comprehensive review of the use and understanding of airway pressure release ventilation

Introduction: Airway pressure release ventilation (APRV) is a mode of ventilation typically utilized as a rescue or alternative mode for patients with acute respiratory distress syndrome (ARDS) and hypoxemia that is refractory to conventional mechanical ventilation. APRV's indication and efficacy continue to remain unclear given lack of consensus amongst practitioners, inconsistent methodology for its use, and scarcity of convincing evidence.Areas covered: This review discusses the history of APRV, how APRV works, rationales for its use, and its theoretical advantages and disadvantages. This is followed by a review of current available literature examining APRV's use in the intensive care unit, with further focus on its use in the pediatric intensive care unit.Expert opinion: APRV is a ventilation mode with theoretical risks and benefits. Appropriate study of APRV's clinical efficacy is difficult given a heterogeneous patient population and widely variable use of APRV between centers. Despite a paucity of definitive evidence in support of either mode, it is possible that the use of APRV will begin to outpace the use of high-frequency oscillatory ventilation (HFOV) for the management of refractory hypoxemia as more attention is paid to benefits of spontaneous breathing and minimizing sedation. Furthermore, APRV's role during ECMO deserves further investigation.