Average volume assured pressure support ventilation (AVAPS) mode in management of acute hypercapnic respiratory failure

Background: Although AVAPS mode has been studied in chronic respiratory failure, studies evaluating its efficacy in acute hypercapnic respiratory failure (AHRF) are limited. Objective: To investigate the benefits of ST/AVAPS mode in delivering NIV for patients with AHRF compared to the conventional ST/BiPAP mode. Patients and methods: Patients were randomized to receive NIV using either BiPAP-ST mode (group I) or BiPAP ST/AVAPS (group II). Glasgow coma scale (GCS), respiratory rate (RR), heart rate, arterial blood pressure, arterial blood gas (ABG) and Exhaled tidal volume (VT) were recorded before initiation of NIV and at 1, 12, 48 and 72 hrs following therapy. Results: After randomization, 30 Patients were enrolled into group I and 30 patients in group II. At 1 hr, significant improvement was observed in PaO2 in both groups I and II. At 12 hour, group II showed significant improvement in GCS, RR and PH with a sustained improvement in PaO2 and SaO2 in group II. At 48 hours, it showed significant improvement in PaCO2 with maintained improvement in the other parameters. Meanwhile, in group I, only RR showed a significant improvement at 12 hrs (p=0.006) with further significant improvement in other clinical and gasometrical parameters at 48 hrs. Furthermore, the duration spent on NIV was significantly less in group II than in group I. Conclusion: Both ST/BiPAP and AVAPS modes are effective in management of patients with AHRF. However, AVAPS modes showed more rapid and steady improvement of clinical parameters and less duration on NIV.