Characteristics of adjustment of lung diffusing capacity to work

The response of lung diffusing capacity for CO (DLCO) to the onset of exercise or a change in work load was studied in four healthy males. Single-breath DLCO was measured during the transients 1) from rest to 40% of maximum O2 uptake (VO2 max); 2) from rest to 80% VO2 max; and 3) from steady-state exercise at 40 to 80% VO2 max. Protocols 1 and 2 consisted of 8.5 min of exercise while 3 consisted of 10.5 min of exercise at 40% VO2 max followed by 8.5 min at 80% VO2 max. DLCO was measured at 10, 20, 30, 60, 90, 240, and 510 s after onset of change in load. Half times of the responses (1, 39: 2, 43; 3, 56 s) were not statistically different. The percentage of the total response completed at each time interval indicated that 3 was significantly (P less than 0.05) slower than 1 and 2 at 10 and 20 s. The rapid response of DLCO at the onset of exercise may reflect a neural component in pulmonary vascular control during exercise.