Oxygenation in patients with chronic airflow obstruction after cessation of exercise

Although oxygenation has been widely investigated in patients with chronic airflow obstruction both at rest and during exercise, very little is known about their oxygenation in the postexercise recovery period. Recently, it has been shown that PaO2 may in fact be higher during the initial 20 to 120 seconds recovery phase, compared to rest and peak exercise levels. Since it is not established to what extent this improvement persists, we investigated the changes in oxygenation during this phase in patients with CAO. We measured arterial blood gas values, expired gases and ventilation at rest, peak exercise and during the first seven minutes of recovery in 18 male patients with moderate-severe CAO. Mean rest PaO2 (77 mm Hg) and peak exercise PaO2 (76 mm Hg) did not change significantly. Compared to peak exercise, PaO2 was significantly higher during recovery at one minute (93 mm Hg, p = 0.005) and at four minutes (91 mm Hg, p = 0.005), but not at seven minutes (86 mm Hg, p = 0.155) after exercise. All of the recovery PaO2 levels were significantly higher than resting PaO2. These results indicate that during the postexercise recovery period, oxygenation is better than at peak exercise or at rest. Regression analysis of the data predicts that oxygenation may return to resting levels 8 to 9 minutes after cessation of exercise.