Strength and cycle time of high-altitude ventilatory patterns in unacclimatized humans

Abstract

Respiration was monitored with magnetometers in 12 healthy supine young adults at sea level and in an altitude chamber at simulated high altitudes of 8,000, 9,000, 11,000, and 14,000 ft. Periodic breathing that was strong enough to include apnea at the time of minimum ventilation was seen in all subjects at high altitude. Cycle time of periodic breathing ranged from 12 to 34 s. On average across the population the incidence of periodic breathing increased with altitude. Cycle time of the periodic pattern increased as strength of the pattern increased. After normalizing to a standard pattern strength, cycle time decreased as altitude increased. The study included two series of experiments, the second occurring 3 wk after the first and involving seven of the same subjects. The standard cycle time at 14,000 ft for each subject in the second series was the same as in the first series to within, on the average, 6%. Each subject studied at 11,000 ft in both series reproduced his cycle time to within, on the average, 9%. The variation of standard cycle time for a given subject is less than the variation across the population, indicating characteristic cycle times for some individuals (one-way analysis of variance, P less than 0.025).

Periodic breathing at high altitude and ventilatory responses to O2 and CO2.

“…is lower than those reported previously in a hypoxic chamber (WAGGENER et al, 1984) and at altitudes higher than 5,300 m (LAHIRI et al, 1983;SUTTON et al, 1979;WEST et al, 1986) but is similar to that in the studies of WELL et al(1978) and HACKETT et al (1987). Figure 2 shows the relationship between ventilatory chemosensitivities and PB index.…”

“…In this case, circulation time should have been prolonged. On the other hand, WAGGENER et al (1984) and VoGEL and HARRIS (1967) found increased cardiac output in the hypoxic chamber or at high altitude. In these cases, circulation time should have been shortened.…”

“…Some (BERSSENBRUGE et al, 1983;LAHIRI et al, 1983;WHITE et al, 1987;GLEESON et al, 1988) insist that high peripheral chemosensitivity is an important determinant for PB at high altitude; others (PowLEs et al, 1978;WEST et al, 1986) conclude that there is no positive relationship between them. Some (CHERNIACK and LONGOBARDO,1973;KHoo et al, 1982;PRYOR,1951) propose a hypothesis that circulation delay is one of the important factors for PB, but others (WAGGENER et al, 1984;WEST et al, 1986) show that circulation time at high altitude is shorter than that at sea level. Furthermore, there seems no agreement whether PB comonly found in sojourners to high altitudes is just a physiologically adaptive phenomenon to hypoxia (HOUSTON, 1984) (if so, it may be advantageous) or a pathological response to hypoxia in lowland climbers (HACKETT et al, 1987) (if so, it should be reduced).…”

Acute mountain sickness is related to nocturnal hypoxemia but not to hypoventilation

“…Transient reductions in breathing amplitude to v50% baseline over 5-10 s were also scored as apnoeas/hypopnoeas if they occurred as part of a periodic breathing pattern with waxing and waning of ventilation with periods of hyperventilation alternating with central apnoeas/ hypopnoeas over at least three successive cycles ( fig. 1) [24,25]. Central apnoeas/hypopnoeas were identified by absence of rib cage-abdominal asynchrony [14].…”

Continuous electronic data capture of physiology, behavior and experience in real life: towards ecological momentary assessment of emotion

“…Increased during respiratory muscle fatigue or dysfunction Apnea and hypopnea detection Diagnostic components of sleep apnea/hypopnea syndrome and periodic breathing. Hypopnea defined as !50% baseline Vt for O10 s. Apnea defined as !25% baseline Vt for O10 s Apnea and hypopnea classification Phase relation between chest and abdomen classifies apnea/hypopnea events into central, mixed, and obstructive (1808) types Magnitude of periodic Vt oscillations Magnitude of oscillations of periodic breathing and Cheyne-Stokes respiration cycles associated with apnea or hypopnea (Waggener et al, 1984) Cycle time of periodic Vt oscillations Cycle length of periodic breathing and Cheyne-Stokes respiration. Longer cycle time points to a basis in chronic heart failure, shorter times to idiopathic central sleep apnea syndrome (Waggener et al, 1984) Forced expiratory volume in 1 s (FEV 1.0 ) Requires a voluntary breathing maneuver.…”