Respiratory events and periodic breathing in cyclists sleeping at 2,650-m simulated altitude

Abstract

Moi Chow. Respiratory events and periodic breathing in cyclists sleeping at 2,650-m simulated altitude. J Appl Physiol 92: 2114-2118, 2002; 10.1152/japplphysiol.00737. 2001.-We examined the initial effect of sleeping at a simulated moderate altitude of 2,650 m on the frequency of apneas and hypopneas, as well as on the heart rate and blood oxygen saturation from pulse oximetry (Sp O 2 ) during rapid eye movement (REM) and non-rapid eye movement (NREM) sleep of 17 trained cyclists. Pulse oximetry revealed that sleeping at simulated altitude significantly increased heart rate (3 Ϯ 1 beats/min; means Ϯ SE) and decreased Sp O 2 (Ϫ6 Ϯ 1%) compared with baseline data collected near sea level. In response to simulated altitude, 15 of the 17 subjects increased the combined frequency of apneas plus hypopneas from baseline levels. On exposure to simulated altitude, the increase in apnea was significant from baseline for both sleep states (2.0 Ϯ 1.3 events/h for REM, 9.9 Ϯ 6.2 events/h for NREM), but the difference between the two states was not significantly different. Hypopnea frequency was significantly elevated from baseline to simulated altitude exposure in both sleep states, and under hypoxic conditions it was greater in REM than in NREM sleep (7.9 Ϯ 1.8 vs. 4.2 Ϯ 1.3 events/h, respectively). Periodic breathing episodes during sleep were identified in four subjects, making this the first study to show periodic breathing in healthy adults at a level of hypoxia equivalent to 2,650-m altitude. These results indicate that simulated moderate hypoxia of a level typically chosen by coaches and elite athletes for simulated altitude programs can cause substantial respiratory events during sleep. pulse oximetry; apnea; hypopnea RECENT STUDIES ON THE USE of altitude by athletes suggest that the best effect on subsequent physical performances may be gained by sleeping in a moderately hypoxic condition (equivalent to altitudes of ϳ2,200-3,000 m) while training close to sea level (21,22). The response to this "live high, train low" approach varies widely between individuals, with some athletes showing substantial performance gains and others showing no effect or even a negative outcome (7). Athletes spend a substantial amount of time asleep while exposed to the live high, train low stimulus (3), and the respiratory events during their sleep time increase as altitude increases (28). However, substantial differences appear to exist between individuals in both the magnitude of this effect and the altitude of onset (2,8, 39). Although sleep disturbance has been shown to decrease subsequent physical work capacity and increase the self-perception of fatigue (1), no studies have monitored the sleep physiology of athletes undergoing a live high, train low program.Hyperventilation is among the first physiological adjustments to an acute increase in altitude in an attempt to compensate for the reduced PO 2 (10, 30). Episodes of hyperventilation may be separated by intervals of hypopnea or apnea. When respiratory events are cyclic and conta...

Prevalence of central sleep apnea during continous positive airway pressure (CPAP) titration in subjects with obstructive sleep apnea syndrome at an altitude of 2640 m

“…It is known that at significant altitudes, chronic hypocapnia, and hypoxemia generate certain instabilities of the respiratory system during sleep. This can increase the presence of central apnea and periodic breathing [9], and it has been proposed to be a risk factor for central apnea with positive pressure [10]. The aims of the present study were to establish CompSA prevalence in people with OSA who have been long-term residents in Bogota, Colombia, and to establish which variables in the baseline polysomnogram (PSG) or in the comorbidities are related to its appearance.…”

Prevalence of pulmonary hypertension and its association with respiratory disturbances in obese patients living at moderately high altitude

“…The exposure to a moderate altitude such as that of Mexico City increases apnea/hypopnea index and heart rate, and decreases blood oxygen saturation. 29 Our data allow us to conclude that at a moderate altitude, alveolar hypoventilation, which implicates the presence of abnormal chest wall mechanics and/or impaired ventilatory control, is the main risk factor for the severity of PH. Obesity by itself also plays a role for PH severity, but restrictive lung disease did not account for PH.…”

The Effects of Altitude Associated Central Apnea on the Diagnosis and Treatment of Obstructive Sleep Apnea: Comparative Data from Three Different Altitude Locations in the Mountain West

“…In the Mountain West, several studies done at altitude indicate that an increase in central apneas (episodes ≥ 10 sec without airfl ow and no evidence of respiratory effort) occurs even among healthy individuals. [1][2][3][4] Overall apnea-hypopnea index (AHI) is higher for individuals with obstructive sleep apnea (OSA), and obstructive events convert to predominately central events at altitude. 5 This degree of respiratory disturbance is corrected in part by moving affected individuals from altitude to sea level.…”