Weekly Cuirass Ventilation Improves Blood Gases and Inspiratory Muscle Strength in Patients with Chronic Air-Flow Limitation and Hypercarbia

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Abstract
We studied the effects of an 8-h, once-a-week schedule of cuirass ventilation (CV) in 5 patients with advanced chronic air-flow limitation and chronic hypercarbia (PaCO2, 58.6 .+-. 10.1 mm Hg; mean .+-. SD). Repeated measurements of arterial blood gases, maximal inspiratory mouth pressure (Pimax), 12-min walking distance, and respiratory cycle were performed during a 1-mouth run-in period. Quality of life and transdiaphragmatic pressure were measured once. All patients completed the planned 4-month study. Four of them were ventilated for longer periods because CV could not be discontinued at the end of the study. PaCO2 showed a significant fall starting during the first month; PaO2 significantly increased from the second month, whereas Pimax significantly rose from the third month on. Maximal trnsdiaphragmatic pressure increased in the 2 patients with abnormal baseline values. The fall in PaCO2 was associated with an increase in tidal volume because of a longer inspiratory time. Significant improvements in quality of life and in the 12-min walking distance were observed. We conclude that weekly CV improves blood gases, inspiratory muscle strength, and clinical conditions of patients with chronic air-flow limitation and chronic hypercarbia, probably because of correction of chronic inspiratory muscle fatigue.