P209 Spontaneous/timed (S/T) versus average volume assured pressure support (AVAPS) non-invasive ventilation (NIV) in acute hypercapnic respiratory failure

Abstract

Introduction Standard practice in the treatment of decompensated hypercapnic respiratory failure following medical management is to initiate NIV. Typically, prescribed inspiratory and expiratory pressures are delivered using spontaneous/timed mode of NIV. Newer devices offer a volume targeted pressure regulated means of delivering NIV so called AVAPS (Average Volume Assured Pressure Support) mode. There has been little data to date of the effectiveness of AVAPS in an acute setting. Aim To compare the outcomes for patients given either S/T or AVAPS mode of NIV, specifically; the amount of time spent in hospital, blood gas normalisation and time spent on NIV Method Retrospective analysis of patient notes for admissions between December 2015 to September 2017 of all patients with decompensated respiratory failure from any cause requiring NIV. Patients with completed NIV usage charts and documented NIV settings, baseline ABG and at least 1 ABG within the first 24 hours of starting NIV were included in the study. Results 45 AVAPS (male 49%, age 70±14 years) and 28 S/T (male 43%, age 70±17 years) care episodes were eligible for inclusion within the study. The S/T group consisted of 19 (68%) obstructive and 5 (18%) restrictive cases of lung disease and 4 (14%) mixed/other cases. In the AVAPS group there were 30 (67%) obstructive and 6 (13%) restrictive cases of lung disease and 9 (20%) mixed/other cases. Only the time spent on NIV in the first 24 hours was significantly different between the 2 groups, with a shorter time spent on NIV in the AVAPS group (p=0.049). ABG parameters did not differ between the 2 groups (table 1). Acidosis resolved within 1–4 hours in 28.89% of the AVAPS group compared to 10.71% in the S/T group (p=0.068). Conclusion Our data demonstrates that AVAPS mode results in a shorter period of time on NIV in the first 24 hours, which may be due to a speedier resolution of acidosis. There were no differences in outcomes in other physiological parameters. AVAPS was thus non-inferior to S/T mode in outcomes. These data suggest AVAPS can safely be used as an alternative to S/T mode.