[Short-term effects of respiration with external negative ventilation --shield-type respirator-- on the pulmonary...

With the objective to test the effect of intermittent and short term rest in respiratory muscles in patients with COPD and maintained hypercapnia we have studied 34 patients in a stable condition: 23 were part of the study group (Group I) and 11 were the control group (Group II). After a complete functional basal study, patients in Group I were treated with intermittent rest of their respiratory muscles, through a negative pressure external respirator--shield type--during three consecutive days. We got, in this study group, a significative improvement in the maximum inspiratory pressure measured at residual volume (PI max RV), which went from 66.6 +/- 15.9 to 71.2 +/- 15.2 (p < 0.005), as well as a lowering, also significative, of partial pressure of CO2 in arterial blood (PaCO2) and in expired air (EFCO2), which went from 55.2 +/- 7.2 to 52.3 +/- 3 (p < 0.0002) and 3.3 +/- 0.5 to 3.1 +/- 0.5 (p < 0.01), respectively. Maximum inspiratory pressure measured to functional residual capacity (PI max FRC) experienced an increase in the limit of statistical signification. Rest of the parameters did not significantly change. These results back the hypothesis that in stabilized COPD with CO2 retention, a chronic fatigue of respiratory muscles could exist, and that intermittent rest of these muscles could mean an hypercapnia diminution, due to the improvement in the function of respiratory muscles.