Exercise Endurance before and after Long-Term Noninvasive Ventilation in Patients with Chronic Respiratory Failure

Background: Noninvasive mechanical ventilation (NIV) is known to reduce hypoventilation and improves respiratory and peripheral muscle endurance in patients with chronic respiratory failure (CRF) due to thoracic restriction. Objectives: To compare the effect of short-term NIV on endurance in patients with CRF due to thoracorestriction and chronic obstructive pulmonary disease (COPD) and to evaluate differences in spiroergometric data during exercise testing. Methods: Thirty-five patients with CRF due to COPD and 24 patients with CRF due to thoracorestriction entered the trial. Constant work rate exercise testing at 75% of the maximal workload, pulmonary function and arterial blood gas testing were performed before and after 3 months of NIV. Measurements were compared between and within groups. Results: The non-COPD group increased their exercise time significantly from 4.7 ± 1.81 to 6.59 ± 3.15 min (p = 0.0032). There was no change in the COPD group (4.57 ± 2.19 min before and 5.39 ± 3.09 min after NIV, p = 0.09). CO 2 levels at rest fell in both groups (COPD 52.30 ± 7.77 to 46.06 ± 4.61 mm Hg and non-COPD 47.82 ± 5.19 to 43.79 ± 4.15 mm Hg). While COPD patients increased their minute ventilation (13.47 ± 2.73 to 14.88 ± 2.67 l/min), non-COPD patients decreased their oxygen uptake from 6.27 ± 1.61 to 5.54 ± 1.35 ml/kg. Conclusions: NIV improved endurance only in the non-COPD group. This and the reduction in CO 2 are achieved by lowering energetic requirements. COPD patients though decreased their resting CO 2 by increased minute ventilation.