Critical Care and Shock

Effect of Airway Pressure Release Ventilation (APRV) with Pressure Support (PS) on Indices of Oxygenation and Ventilation in Patients with Severe ARDS: A Cohort Study

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Background: Airway pressure release ventilation (APRV) is an alternative approach to the “open-lung” ventilation strategy and has recently emerged as an alternative ventilatory strategy in patients with severe ARDS.

Aims: Our objective was to assess the effect of APRV+low level pressure support (PS) on indices of oxygenation and ventilation in patients with severe ARDS.

Methods: During the study period we recorded oxygenation and ventilation data (for up to 96 hours) as well as the use of sedative and vasopressor agents in patients in our MICU with severe ARDS (PaO2/FiO2<150) who we switched to APRV+PS from low tidal volume assist-controlled (AC) ventilation. Vd/Vt was measured by volumetric capnography. Patients were followed until hospital discharge or death.

Results: Twenty-two patients with severe ARDS secondary to sepsis were studied. The patients were on AC for 4±3.5 days prior to conversion to APRV. The PaO2/FiO2 increased (134±48 to 210±87 mmHg; p=0.03) while the Vd/Vt fell significantly (66±10 to 54±10%; p=0.01) by 24 hours. These changes were maintained throughout the study period. The total daily dose of sedative and vasopressor agents decreased by 46% and 55% respectively by 24 hours. While these patients were critically ill with a high anticipated mortality, 12 (54%) survived to hospital discharge.

Conclusions: APRV+PS improves oxygenation and V/Q mismatching in patients with severe ARDS allowing a decrease in the use of sedative agents. While the survival benefit of APRV could not be assessed in this study, APRV should be considered in the ventilatory strategy of patients with severe ARDS.