Pulmonary blood volume in chronic lung disease: changes with legs raised and during exercise

Pulmonary blood volume (PBV) was measured by double injection (pulmonary artery trunk and wedged pulmonary artery) in 43 patients with chronic lung disease, at rest supine, with the legs raised, and during light exercise. At rest, PBV was reduced slightly in group 1 (eight with silicosis), but notably in groups 2 (16 bronchitis patients) and 3 (19 patients! with pulmonary vascular restriction). With the legs raised, PBV increased by 14 percent in group 1, 7 per cent in group 2, and 5 percent in group 3. From rest to exercise, the pressure increase was much greater in groups 2 and 3 than in group 1. The slope of the pressure-volume curve, delta V/delta P, was lower in groups 2 and 3, which could mean that lung vessel distensibility was reduced in these groups, or that, despite its low value, PBV was near its maximum capacity already at rest.