Early application of airway pressure release ventilation may reduce the duration of mechanical venti
Zhou et al. “Early application of airway pressure release ventilation may reduce the duration of mechanical ventilation in acute respiratory distress syndrome.”
Since the ARDSnet trial, low tidal volume (LTV) strategies have been the gold standard for mechanical ventilation in patients with acute respiratory distress syndrome (ARDS). This trial randomly assigned patients meeting the Berlin definition of ARDS to LTV vs airway pressure release ventilation (APRV). APRV, a ventilator mode more often utilized in surgical ICUs, is based on the principle of optimizing lung recruitment. The study’s authors aimed to evaluate whether early initiation of APRV would allow improve mechanics, oxygenation and reduce the duration of mechanical ventilation in patients with ARDs.
Some more background on APRV:
Airway pressure release ventilation centers around the idea of maximizing recruitable alveolar units. As an overview, the ventilator delivers a breath at a specific pressure (P high), for a particular time (T high) In this study, P high was established based off of the last plateau pressure. The patient can initiate spontaneous breaths over that P high for the fixed amount of time (T high) at which point the pressure is rapidly released to a set P low. T low is generally determined by flow with the goal of maintaining alveolar recruitment.
138 patients at West China Hospital
Intubated <48 hours
Diagnosed with ARDS as defined by Berlin criteria
Randomized to APRV (71) or LTV (67)
APRV set up: P high at last plateau pressure or 30 cm H2O (whichever was lower), P low 5 cm H2O, T low set by peak expiratory flow- release phase terminated when flow approached 50% of peak expiratory flow, cycle frequency 10-14/minute
LTV by ARDSnet protocol
The APRV group had as statistically significant increase in ventilator-free days (19 vs 2, P<0.001) as well as a statistically significant decrease in ICU LOS. ICU mortality was also decreased in the APRV group (19.7% vs 34.3% in LTV).
Take Home Points:
This study has some limitations including small sample size and a non-blinded protocol, however, overall, its results are globally very positive. While providers in the emergency department may be less familiar with this mode of ventilation, pressure-controlled modes of ventilation including APRV represent an additional alternative in the patients presenting with profound hypoxemic respiratory failure in the setting of ARDS and are worth considering in that subset of patients who prove difficult to oxygenate with more conventional modes of ventilation. This study was not conducted in an emergency department, however, it seems reasonable to extrapolate “early initiation” to include the ED setting, when caring for patients presenting with a condition with such high associated morbidity and mortality. We are fortunate to practice in an environment at a major academic center where other adjuncts to improve oxygenation in the intubated patient including flo-lan, INO and ECMO are readily available, however, for those ED providers in a more resource-limited setting, familiarity with this mode of ventilation as either an initial or escalated mode of ventilation in the management of the patient with ARDS seems a very reasonable practice.