BACKGROUND: Exercise intolerance limits chronic restrictive respiratory failure (CRF) patients from participating in daily activities. The specific modalities that could improve exercise tolerance in these patients remain to be established. OBJECTIVE: To investigate exercise endurance and associated physiological responses with non-invasive ventilation (NIV) during exercise in restrictive CRF patients. METHODS: Eighteen patients (63 +/- 11 years, total lung capacity (TLC) = 59 +/- 16% of predicted value) performed maximal exercise in spontaneous breathing conditions (MWLE) and during two constant workload exercise (CWLE) tests at 75% Pmax, with or without NIV in random order. "NIV Responders" were defined by an increase in CWLE duration of more than 50% when using NIV. RESULTS: For the whole group, CWLE duration when using NIV increased from 5.6 +/- 4.6 to 9.6 +/- 8.1 min. Increase in CWLE duration correlated with reduction in heart rate and oxygen desaturation, and dyspnea relief during exercise. NIV responders (n = 9) showed more severe lung restriction (TLC: 2.6 +/- 0.7 versus 3.5 +/- 1.1L; forced vital capacity: 1.0 +/- 0.16 versus 1.46 +/- 0.38 L). At the end of MWLE, responders had a lower Vt (0.60 +/- 0.09 versus 0.89 +/- 0.34 L), a higher dead-space ratio (0.51 +/- 0.06 versus 0.38 +/- 0.12) and lower oxygen pulse (4.5 +/- 1.2 versus 7.4 +/- 3.9 ml/beat). CONCLUSION: In severely restrictive patients, NIV during exercise significantly improved exercise duration and tolerance and increased alveolar ventilation. TRIAL REGISTRATION: The enrollment of the patients started before July 1, 2005.

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