Background: Despite recent encouraging results, the use of noninvasive ventilation (NIV) in the management of acute exacerbations in chronic obstructive pulmonary disease (COPD), complicated by acute respiratory failure (ARF), is not always successful. Failure of NIV may require an immediate intubation after a few hours (usually 1-3) of ventilation ('early failure') or may result in clinical deterioration (one or more days later) after an initial improvement of blood gas tension and general conditions ('late failure').
Materials and methods: We enrolled 122 patients affected by COPD complicated by ARF, and treated with NIV. The schedule of NIV provided sessions of 2-6 h twice daily.
Results: Ninety-nine (81%) patients showed a progressive improvement of the clinical parameters and were discharged. Among the remaining 23 patients, 13 had an early failure and 10 had a late failure. In the 'success' group and 'late failure' groups we found after an increase of pH 2 h of NIV (from 7.31 +/- 0.05 to 7.38 +/- 0.04 P < 0.001 and from 7.29 +/- 0.03 to 7.36 +/- 0.02 P < 0.001, respectively) and a decrease of PaCO2 (from 80.93 +/- 9.79 to 66.48 +/- 5.95 P < 0.001 and from 85.96 +/- 10.77 to 76.41 +/- 11.02 P < 0.001, respectively). After 2 h of NIV in the 'late failure' group there were no significant changes in terms of pH (from 7.20 +/- 0.10 to 7.28 +/- 0.06) nor PaCO2 (from 92.86 +/- 35.49 to 93.68 +/- 23.68). The 'early failure' group had different characteristics and, owing to more severe conditions, the value of pH, of Glasgow Coma Score, and Apache II Score were the best predictors of the failure; while, among the complications on admission, metabolic alterations were the only independently significant predictor.
Conclusions: Our study confirms that NIV may be useful to avoid intubation in approximately 80% of patients with COPD complicated by moderate-severe hypercapnic respiratory failure.