Effects of added resistance to breathing during exercise in obstructive lung disease

Forty-nine men performed progressive submaximal treadmill exercise to determine the cardiopulmonary and subjective response to added resistance to breathing. Twenty subjects (controls), FEV1/FVC% = 79.2 +/- 1.4 (mean +/- SEM), were compared with 19 mildly obstructed men (OB1), FEV1/FVC% = 66.9 +/- 0.5, and 10 with moderate obstruction (OB2), FEV1/FVC% = 53.7 +/- 1.9. Separate exercise trials were performed with no added resistance (NAR), R1 = 3.5 cm H2O/L/s inspiratory and 1.5 cm H2O/L/s expiratory resistance, and R2 = 5 cm HKO/L/s inspiratory and 1.5 cm H2O/L/s expiratory resistance. Analysis of cardiopulmonary parameters was made at an oxygen consumption rate of VO2 = 1.5 L/min for all 3 obstruction groups at all 3 resistances. With NAR, all 3 groups had similar respiratory rate (RR), tidal volume (VT), minute ventilation (VE), end-tidal PCO2 (PETCO2), respiratory exchange ratio (R), heart rate (HR), and mouth pressure swing (Poral). With both R1 and R2 compared with NAR, control and OB1 subjects (at VO2 = 1.5 L/min) had reduced RR, VE, and R, and increased VT and Poral (p less than 0.01 for all). Changes with added resistance for OB2 subjects were in the same directions, but were significant only for VE and with R1 for RR. Heart rate did not change; PETCO2 increased in control subjects and with R2 in OB1 subjects. Separate analysis showed that except for the smaller increase in PETCO2 in OB2 subjects, none of the changes with added resistance in the OB1 or OB2 groups were different from changes in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)