Physiological changes related to rapid altitude shifts in La Paz, Bolivia

Abstract

Due to the bowl shaped topography of La Paz, Bolivia, the residents of the city are constantly changing altitude from 3100 meters, in a common residential area to 4100 m at El Alto, an upper industrial city and airport area. In order to access cardio­respiratory alterations occurring with rapid altitude changes, 15 soldiers [average age = 19 years, Weight = 59.07 Kg., Heigh = 165 cm], residents of El Alto (4000 m), were examined in a mobil unit equipped with a computerized cardio-ventilatory apparatus. Following calibration of the ventilatory apparatus, and after 15 minutes of rest, over the next 6 hours, subjects were connected via mouthpiece to a one way flow valve for 15 minutes. Expired gas was collected in Douglas bags. The electrocardiogram was monitored with 3 standard chest leads. Finger oximetry was recorded. Blood was drawn for arterial gases analysis. These were analyzed at 3600m with a Radiometer Blood Gas MK2 pH. The same procedure was repeated the next day on descent to the forest of Aranjuez (3100 m). Saturation rose from 87.8 ± 2.83% to 91.47 ± 1.40% (p< .001). Heart rate changed from 72.5 ± 10.2 to 68.3 ± 7.9 (p< .05) beats per minute. Alveolar ventilation (BTPS) diminished from 7,117 ± 1,232 ml to 6,197 ±  844 ml (p < .05). Oxygen consumption greatly increased from 172 ±  30 to 300 ± 42 ml/min (p < .001). Carbon dioxide production did not change significantly 266 ± 43.23 to 245 ± 32 ml/min. The respiratory Quotient diminished from 1.5 to 0.8 Arterial partial oxygen tension (PaO₂) increased from 54 ± 2.79 to 64 ± 6.33 mmHg (p< .001). PaCO₂ changed from 33 ± 2.2 to 34 ± 1.57 (p < .05). The pH decreased from 7.434 ± 0.026 to 7.381 ± 0.335 (p< .001). This research demonstrates that when patients are analyzed in a cardio­-pulmonary laboratory after they descend or ascend to it, the change in altitude must be considered in interpretation of results. Rapid altitude shifts in La Paz, force residents to constantly adapt, producing respiaratory acidosis on descent within the city.