EFFECTS OF POSITIVE EXPIRATORY PRESSURE BREATHING DURING EXERCISE IN PATIENTS WITH COPD

The effect of breathing with a positive expiratory pressure of 5 cm H2 O was investigated in eight patients with COPD (mean [SD] FEV(1) = 54 [13] percent predicted). Specific work of breathing (Wsp) and myoelect rical activity of the following respiratory muscles were measured at r est: scalene muscle, parasternal muscle, and abdominal muscles. Minute ventilation (VE), end-tidal CO2 (FETCO(2)), physiologic dead space ve ntilation (VD/VT), oxygen uptake (VO2), and carbon dioxide output (VCO 2) were measured at rest and during an incremental bicycle exercise te st. Dyspnea sensation during exercise was quantified using the CR10 Bo rg-scale. All measurements were performed with and without positive ex piratory pressure (PEP). During PEP breathing at rest mean (SEM) Wsp i ncreased from 0.54 (0.13) J/L to 1.08 (0.10) J/L. The SEM VE decreased from 12.4 (1.0) L/min to 10.5 (1.1) L/min, and SEM VD/VT decreased fr om 0.39 (0.03) to 0.34 (0.03). There was a tendency for an increased p hasic respiratory muscle activity during PEP breathing of all three mu scles as compared with undisturbed breathing, but the changes were not statistically significant. During the exercise test with PEP, VE, VD/ VT, VO2, and VCO2 were significantly lower, and FETCO(2) was significa ntly higher as compared with the values obtained during the exercise t est with undisturbed breathing. Dyspnea sensation during the exercise test with PEP, however, was higher than during the test with undisturb ed breathing. The PEP breathing at rest may be useful in patients with COPD as it increases the efficiency of ventilation by reducing dead s pace ventilation. This beneficial effect also occurs during exercise, but here it is accompanied by increased dyspnea sensation.