[Cardiovascular response to exercise at high altitude in workers chronically exposed to intermittent hypobaric hypoxia].

The isotonic work performance was assessed in 34 workers aged 35 +/- 5.8 years old that had working shifts of four days at 4500 m over the sea level and resting periods of other four days at the sea level during at least two years. Subjects were assessed in one occasion at the sea level, and at the first and fourth day of the working shift at 4500 m over the sea level. Resting arterial oxygen saturation in these three periods was 97 +/- 1.1, 88 +/- 18 and 91 +/- 1.1% respectively (p < 0.01), and markedly decreased during maximal and submaximal exercise at 4500 m over the sea level. Exercise duration in the three periods was 931 +/- 210, 775 +/- 105 and 778 +/- 105 seg respectively (p < 0.001). Heart rate in the resting period was at least 10% higher and maximal and submaximal rates were lower at high altitude. No differences in blood pressure or packed red cell volume were observed. Exercise duration correlated inversely with age (r = -0.49 p = 0.03) and directly with maximal heart rate (r = 0.44 p = 0.009) at the sea level. No correlation between aerobic capacity and other measured parameters was observed. These results show no differences in the cardiovascular response to exercise between the first and fourth day of stay at high altitude in workers chronically exposed to intermittent hypobaric hypoxia.