PURPOSE: Airway pressure release ventilation (APRV) is a pressure-limited, time-cycled mode of mechanical ventilation developed for patients with acute respiratory distress syndrome (ARDS) and diseases associated with low lung compliance. In these patients conventional mechanical ventilation produces dangerously high peak and plateau pressures and insufficient mean airway pressures for adequate alveolar recruitment. APRV can also support oxygenation and ventilation in patients with other causes of respiratory failure. Limited research exists regarding the clinical practice of using APRV. This paper describes the clinical experience of using APRV at a single institution in predominantly medical ICU patients.
METHODS: A retrospective analysis was performed on patients who were ventilated using APRV between July 2001 and July 2004. Complete data were available on 60 of 76 patients. Data were obtained immediately prior to and 8-24 hours after the ventilator was changed from a conventional mode to APRV.
RESULTS: Among 60 total patients, 36 patients had acute lung injury or ARDS, while 24 had other diagnoses. Mean APACHE II scores were 25.3 and 23.3 in patients with and without ARDS, respectively. Refractory hypoxemia and/or high airway pressures were the most common reasons for using APRV. APRV resulted in significant improvements in PO2/FIO2 ratios (p<0.001) and FIO2 requirements (p<0.001)(see table). PCO2 levels decreased (p<0.001) despite similar minute ventilation values. APRV also lowered peak airway pressures (PAP)(p=0.002) while raising mean airway pressures (MAP)(p<0.001). APRV was well tolerated in 53 of 60 patients. A history of obstructive lung disease (n=11) did not predict whether APRV would be tolerated. Barotrauma occurred in 3 patients.
CONCLUSION: APRV improves oxygenation in patients with and without ARDS. APRV can also improve alveolar ventilation, probably by decreasing dead space ventilation. APRV provides higher MAP while limiting PAP. APRV is generally well tolerated.
CLINICAL IMPLICATIONS: APRV can be used to improve oxygenation in patients with refractory hypoxemia and high FIO2 requirements. Large randomized controlled trials are needed to determine whether APRV can improve mortality in patients with ARDS.
DISCLOSURE: Jason Graff, None.