AVAPS-NIV Treatment in Hypercapnic Respiratory Failure with Insufficient Response to Fixed-Level PS-NIV.

Introduction: Noninvasive ventilation (NIV) for acute hypercapnic respiratory failure (AHRF) is an established treatment modality. Current evidence does not conclude any superiority between fixed pressure support (PS) and aver-age volume-assured pressure support (AVAPS) modes. However, given the ability of rapid PaCO2 decline in AVAPS mode, we hypothesized that COPD patients with AHRF who did not show the desired reduction in PaCO2 with fixed-level PS-NIV might benefit from the AVAPS mode.Materials and Methods: Patients admitted to the non-ICU pulmonary ward with acute exacerbation of COPD (AECOPD) and AHRF were included con-secutively in this observational study. Patients with hypercapnic respiratory failure due to obesity-hypoventilation, neurological diseases, or chest wall deformities were excluded. All patients started NIV treatment with fixed pres-sure support (PS) and patients who did not reach clinical and laboratory stability under PS-NIV treatment were switched to the average volume -as-sured pressure support (AVAPS) mode of NIV.Results: Thirty-five COPD patients with hypercapnic respiratory failure were included. Under PS-NIV treatment, 14 (40%) patients showed a 17.9 (-0.0-29.2) percent change in terms of PaCO2 , meaning no improvement or worsening. Therefore, these patients were treated with AVAPS mode. Arterial PaCO2 and pH levels significantly improved after AVAPS-NIV administration. AVAPS-NIV treatment created a significantly better PaCO2 change rate than using PS-NIV (-11.4 (-22.0 --0.5)vs 8.2 (-5.3-19.5), p= 0.02]. Independent predictors of AVAPS mode requirement were higher Charlson Comorbidity Index (OR= 1.74 (95% CI= 1.02-2.97)] and higher PaCO2 upon admission (OR= 1.18 (95% CI= 1.03-1.35)]. Thirteen (92.8%) patients reaching signif-icant clinical stability with AVAPS-NIV were able to return to fixed-level PS-NIV and maintain acceptable PaCO2 levels.Conclusion: Our study demonstrated that patients can benefit from AVAPS-NIV despite insufficient response to fixed-level PS-NIV.