Should Airway Pressure Release Ventilation Be the Primary Mode in ARDS?

Abstract

Airway pressure release ventilation (APRV) was originally described as a mode to treat lunginjured patients with the goal to maintain a level of airway pressure that would not depress the cardiac function, deliver mechanical breaths without excessive airway pressure, and to allow unrestricted spontaneous ventilation. Indeed, based on its design, APRV has technological features that serve the goals of safety and comfort. Animal studies suggest that APRV leads to alveolar stability and recruitment which result in less lung injury. These features are sought in patients at risk for lung injury or with ARDS. APRV allows unrestricted spontaneous ventilation, which is welcome in the era of less sedation and increased patient mobility (the effects in terms of lung injury remain to be explored). However, we must highlight that the performance of APRV is dependent on the operator-selected settings and the ventilator's performance. The clinician must select the appropriate settings in order to make effective the imputed benefits. This is a challenge when the ventilator's performance is not uniform, and the outcomes depend on high precision settings (very short expiratory time), where small variations can lead to undesired outcomes (de-recruitment or large tidal volumes leading to lung injury). Finally, we do not have evidence that APRV (as originally described) improves relevant clinical outcomes of patients with ARDS. For APRV to become the primary mode of ventilation for ARDS, it will require development of sound protocols and technological enhancements to ensure its performance and safety. For now, APRV does have a greater potential for adversely affecting patient outcome than improving it; unless definitive data are forthcoming demonstrating outcome benefits from the use of APRV in ARDS, there is no reason to consider this approach to ventilatory support. Key words: Airway pressure release ventilation, biphasic positive-pressure breathing, lung injury, work of breathing, auto PEEP [Respir Care 2016;61(6):761-773.

Airway Pressure Release Ventilation as a Rescue Therapy in Pediatric Acute Respiratory Distress Syndrome

“…A large part of the spontaneous respiration occurs in the longer inspirium duration. Although spontaneous respiration has a positive effect on the protection of diaphragm functions, there is insufficient information about the effect on lung dynamics and VILI formation of spontaneous breathing occurring in the long P high duration during APRV [16]. In the current study, the mean number of mandatory breaths during APRV was determined as 12.8 ± 1.0.…”

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

“…The combination of recent experimental and clinical evidence demonstrates that TCAV not only does this, but also minimises alveolar heterogeneity and microstrain, conducting airway microstrain, and potentially recruits the chest wall in extrapulmonary ARDS. Although there are limitations to the clinical studies of TCAV with ZHOU et al's [20] prospective review not being blinded and ANDREWS et al's [8] retrospective review being exclusive to trauma patients, where trauma patients carry a specific phenotype of ARDS [101], and randomised controlled trials are needed to test the efficacy of the TCAV protocol further [13], this review of experimental evidence demonstrates that TCAV may be effective in preventing VILI and ARDS by a pleiotropy of mechanisms.…”

“…It is important to note that APRV, as with all modes, can be set in a multitude of ways and thus we must analyse the protocol using APRV in order to compare efficacy in published studies. In order to clarify the confusion in nomenclature [13], one well-accepted protocol of setting APRV was recently defined as time-controlled adaptive ventilation (TCAV) [14], and refers to the protocol first described by HABASHI [15], with an extended time at the plateau pressure, creating a continuous positive airway pressure (CPAP) phase, and a brief release in CPAP, creating a release phase. The release phase augments carbon dioxide removal and the resultant slope of the expiratory flow-time curve from the passive pressure release provides continuous feedback of changes in respiratory system elastance [15][16][17][18].…”

Current and evolving standards of care for patients with ARDS

“…In the early phase of ARDS, augmented spontaneous breathing may induce patient-ventilator dyssynchrony and high tidal volumes which could promote lung injury. [48] Airway pressure release ventilation (APRV) is a time-cycled mode in which airway pressure alternates between high and low pressure settings, but also allows spontaneous breathing [49]. Although a single center RCT recently showed improved physiological and clinical outcomes [50], a pediatric ARDS trial was stopped early because of increased mortality in the APRV arm [51], and a recent meta-analysis 14 studies showed improvements in oxygenation with APRV but no difference in ICU stay and mortality between groups [52].…”