[Exercise limitation in patients with chronic obstructive pulmonary disease at the altitude of Bogota (2640 m). Breathing pattern and arterial gases at rest and peak exercise].

OBJECTIVE

To describe the response to exercise of normal subjects and patients with chronic obstructive pulmonary disease (COPD) in Bogota, Colombia (altitude: 2640 m; atmospheric pressure: 560 mm Hg) and compare it with data published on COPD patients at sea level. Healthy people increase their minute ventilation to attenuate hypoxemia (PaCO2: 30 mm Hg; PaO2: 63 mm Hg).

MATERIAL AND METHOD

A descriptive study was carried out on healthy subjects and COPD patients. Exercise limitation was determined by an incremental test on a cycle ergometer.

RESULTS

The study enrolled 16 healthy subjects and 25 COPD patients (forced expiratory volume in 1 second: 43.3% [SD 13%]). Minute ventilation at rest was greater in COPD patients compared with healthy subjects, it was not adequately sustained during exercise, and there was a reduction in peak oxygen uptake (53.0% [15%]). At peak exercise, inspiratory capacity decreased (-0.62 [0.34] L), the ratio of minute ventilation to maximal voluntary ventilation increased, and severe hypoxemia occurred (PaO2: 49.9 [9.9] mm Hg). There was significant correlation between hypoxemia and the percentage of predicted peak oxygen uptake (r=0.60), leg fatigue (r=-0.62), percentage of predicted peak inspiratory capacity (r=0.61), and the percentage of predicted peak tidal volume (r=0.49). Minute ventilation at rest was shown to be higher, there was a greater reduction in the inspiratory capacity during exercise, and hypoxemia was more severe at rest and during exercise for patients with COPD in Bogota, compared with those at sea level.

CONCLUSIONS

Patients with COPD living in Bogota were shown to have lower tolerance to exercise evidenced by ventilatory limitation and severe hypoxemia. Increased minute ventilation at rest, greater reduction in inspiratory capacity, and severity of hypoxemia during exercise were the main differences between COPD in Bogota and at sea level.