Effect of oxygen on postoperative cardiovascular response to exercise

Objective: To evaluate the effect of supplemental oxygen on postoperative c ardiovascular response to submaximal exercise. Design: Randomised, controlled study. Setting: University hospital, Denmark. Subjects: 16 patients having major a bdominal operations. Interventions: A submaximal exercise test (heart rate up to 120 min(-1)) do ne twice on the third day after operation. Patients were given either 100% oxygen (4 L min(-1)) or air (21% oxygen, 4 L min(-1)) 30 minutes before and during the test in randomised order. During the tests they were monitored with a Holter tape recorder and a pulse oximeter. Main outcome measures: Heart rate during exercise. Results: At similar workloads there were significantly lower heart rates (m edian decrease 3 min(-1)) during exercise tests with oxygen compared with a ir (p < 0.05). Holter monitoring showed signs of myocardial ischaemia in 6 patients in relation to exercise testing, 4 of them related to both tests, 2 of them only when breathing air. Signs of myocardial ischaemia disappeare d when the exercise ended. Conclusion: During the late postoperative period supplementary oxygen reduc ed heart rate in response to exercise to the same degree as observed previo usly in non-surgical patients and surgical patients not taking exercise. Th ese findings do not suggest that decreased peripheral tissue oxygenation is responsible for the impaired cardiovascular response to exercise in postop erative patients.