AVAPS Versus BiPAP in Acute Hypercapnic Respiratory Failure: A Systematic Review and Meta-Analysis

Noninvasive ventilation (NIV) is increasingly used in acute and chronic hypercapnic respiratory failure (HRF), with BiPAP traditionally considered the standard mode. Average volume assured pressure support (AVAPS) adjusts inspiratory pressure to maintain target tidal volume, potentially improving CO₂ clearance. Its comparative clinical effectiveness remains uncertain. We conducted a systematic review and meta-analysis per PRISMA 2020 guidelines (PROSPERO ID: CD1031775), searching MEDLINE, EMBASE, Cochrane CENTRAL, Scopus, Web of Science, and gray literature through March 2025. Eligible studies were RCTs or comparative cohort studies in adults (≥18 years) with acute HRF or equivalent emergency indications, directly comparing AVAPS and BiPAP. Primary outcomes were endotracheal intubation and short-term mortality; secondary outcomes included arterial blood gases (pH, pO₂, pCO₂) and hospital length of stay (LOS). Random-effects meta-analysis (Hartung-Knapp) and one-way ANOVA of arm-level means were applied, with evidence graded using GRADE. Eleven studies met inclusion criteria (n = 280 for intubation, n = 300 for mortality). AVAPS significantly reduced intubation risk compared with BiPAP (RR 0.43, 95% CI 0.23-0.79; p = 0.027; I² = 0%), corresponding to a 57% relative and 4.7% absolute risk reduction (NNT ≈ 21). No significant difference in short-term mortality was observed (RR 0.87, 95% CI 0.38-2.00; p = 0.62; I² = 31.8%), though exploratory NNT favored AVAPS (47). Physiological outcomes and LOS were similar between groups (all p > 0.63). In adults with acute HRF, AVAPS lowers intubation rates compared with BiPAP, without clear short-term survival benefit. Physiological outcomes and LOS appear equivalent. AVAPS may be preferred for selected patients, though larger, high-quality RCTs are needed to confirm the mortality effects.