Treatment of critically ill patients with acute hypercarbic respiratory failure by average volume-assured pressure support mode.

OBJECTIVES: Average volume-assured pressure support (AVAPS), a dual mode, delivers a set tidal volume (TV) per kg by adjusting the pressure between upper and lower inspiratory positive airway pressures (IPAP). Thus, ventilation is presumed to be happened effectively by sending a guaranteed TV. This study was aimed to evaluate the effectiveness of AVAPS mode in critically ill patients with acute hypercarbic respiratory failure (HRF) and compare the results with bilevel positive airway pressure-spontaneous/timed (BPAP-S/T) mode.

METHODS: Sixty patients were assigned to BPAP-S/T (n = 29) and AVAPS modes (n = 31). Maximum IPAP was started at 20 cmH2 O and minimum IPAP was set at 5 cmH2 O higher than expiratory positive airway pressure (EPAP) in AVAPS mode. IPAP was started at 15 cmH2 O in BPAP-S/T mode. IPAP levels were titrated up to 30 cmH2 O during noninvasive mechanic ventilation (NIMV) with a targeted TV of 6-8 mL/kg. Patients were followed for 5 days.

RESULTS: No differences were found in pH, paCO2 , HCO3 , TV and EPAP between the two groups when compared separately by days. Maximum IPAP levels were significantly high in AVAPS mode in all times (P < 0.001). The length of stay (LOS) in intensive care unit (ICU) (P = 0.994) and hospital (P = 0.509), hours of NIMV use per day (P = 0.101) and NIMV success rate (P = 0.931) were identical between the two groups. ICU (P = 0.931), hospital (P = 0.800), 6-month (P = 0.919) and 1-year (P = 0.645) mortality rates were also not different between the both groups.

CONCLUSIONS: AVAPS mode had similar efficiency with BPAP-S/T mode regarding the NIMV treatment success in critically ill patients with acute HRF.