CARDIAC OUTPUT AND PULMONARY VASCULAR PRESSURE GRADIENT DURING 60 MIN's HIGH INTENSITY EXERCISE IN NORMOXIA:

1066 Prolonged exercise at high intensities requires low transpulmonary pressure gradient (Ppam-Paod) and low pulmonary vascular resistance at high cardiac output. Therefore, we examined pulmonary circulation in trained athletes. Methods: 17 healthy, male subjects performed 60 min of cycling approx. 86% of ˙Vo2max (25±4 yrs, 77.1±6.5 kg, ˙Vo2max 4.1±0.6 1·min-1). Cardiac output (˙Qc) was measured by acetylene rebreathing. Pulmonary artery pressure (Ppam) and pulmonary occlusion pressure (Paod) and Ppam-Paod were measured by a Swan-Ganz-catheter and systemic arterial pressure in a. radialis (Psam) at rest, 8, 40, and 55 min during exercise, and 25 min after the test. Pulmonary and systemic vascular resistance (PVR, SVR) were calculated according to Gorlin. Results: During the test, mean power was 232±37 W, and mean ˙Qc was 22.1 1·min-1. Ppam-Paod increased from 8.3±3 to 19±3mmHg (8′, p<0.001) and decreased during the test to 15±6mmHg (55′, p<0.05). However, in 5 subjects Ppam-Paod increased from 18.4 (8′) to 21.2 mmHg (40′) as well as PVR. ˙Qc was constantly lower during the test (p<0.05) as well as stroke volume (131 vs. 106 ml at 40′, p<0.05). Interestingly, Psam as well as SVR were higher (p<0.05) in these subjects. However, the power achieved was not different. Conclusion: In 5 of 17 healthy subjects, increased transpulmonary pressure gradient was observed during constantly high intensive exercise. The lower stroke volume in these subjects may contribute to lower pulmonary and systemic blood flow as well as higher sympathetic drive to higher pulmonary and systemic vascular resistance.