EFFECTS OF HIGH-ALTITUDE PERIODIC BREATHING ON ARTERIAL OXYHAEMOGLOBIN SATURATION AND HEART RATE

We aimed to investigate the effect of periodic breathing (PB) at high altitude on arterial oxygen saturation (SaO2) and heart rate (HR). Nine élite climbers, males, age 24-52 underwent overnight cardio-respiratory monitoring (Lifeshirt System Vyasis) at sea level and at Everest North Base Camp (5180m), during the 1st (BC1) and the 10th (BC2) night. Between the two measurements all subjects climbed up to 7000m and spent at least 2 nights at 6100m with no use of oxygen and no symptoms of AMS. Their breathing pattern, SaO2 and HR were analysed. At sea level no respiratory disturbances were observed. PB was commonplace in all subjects at HA. PB cycle duration significantly increased (p<0.0001) from BC1 (21.7±1.9 s) to BC2 (26.7±2.1 s). From the BC1 to the BC2 mean SaO2 increased significantly during wakefulness (77%±3 vs 82%± 3;p<0.001). The mean higher SaO2 levels with PB of all subjects were 75.3±3.6% at BC1 and 82.4±2.9% at BC2 (p<0.0008). The mean lower SaO2 levels with PB of all subjects were 68.2±4.0% at BC1 and 74.5±4.3% at BC2 (p<0.01). HR fluctuates with ventilation, with an increase whenever ventilation is resumed or increased after a respiratory pause or hypoventilation. HR reached a peak before the end of the ventilatory phase and then decreased suddenly in most cases. The mean higher HR during PB was 72.4±8.8 at BC1 and 63.3±6.0 at BC2 (p<0.0002) and the mean lower HR was 53.6±7.5 at BC1 and 43.6±7.3 at BC2 (p