Pulmonary haemodynamic response to two-stage exercise in patients with chronic bronchitis

The pressure/flow relationship in the pulmonary circulation has been studied in 43 patients with chronic bronchitis, at rest (R) and during exercise at two levels: 30 or 40 W (E1), and 60 or 80 W (E2), without interruption. For the entire group, pulmonary vascular resistance was 142 +/- 70 dyn X s X cm-5 at rest, 131 +/- 55 at the first exercise level and 118 +/- 60 at the second level. Individual changes were variable, however; a "linearity index" was computed as delta(PPA-PW)/delta Q from the first to the second exercise level divided by the same value from rest to the first exercise level. This index was below 0.75 in 27 patients (i.e. the pressure/flow slope was lower for the second exercise level and the pressure/flow curve was concave to the flow axis), it was above 1.25 in nine patients (i.e. the slope increased with exercise and the pressure/flow curve was convex to the flow axis), and the pressure/flow relationship was close to rectilinear in seven patients. Functional disturbances were mild in these subjects, and in the majority of them pulmonary vascular resistance did not increase with exercise.