title: Effects of hypoxia on the circadian patterns in men.
abstract: We tested the hypothesis that acute hypoxia may alter the circadian pattern of body temperature in adult humans. Six healthy subjects were studied in normoxia, hypoxia (approximately 13% inspired O(2)), and again normoxia, each session lasting >24 h and spaced a few days apart, with a constant routine protocol of sustained wakefulness and minimal activity. Some parameters (e.g., tympanic and abdominal temperatures, heart rate) were recorded continuously; others (e.g., oxygen consumption and pulmonary ventilation) were monitored for approximately 10 min every 2 h. The amplitudes of the circadian oscillation of tympanic, abdominal, and calf skin temperatures were reduced in hypoxia, averaging, respectively, 61%, 80% and 50% of the normoxic amplitude. Oxygen consumption and pulmonary ventilation, which presented a circadian pattern in normoxia, had no longer significant oscillations during hypoxia, whereas the opposite was the case for heart rate and diastolic pressure. Therefore, acute hypoxia can disturb the normal circadian patterns and, specifically, depress those of body temperature. These effects, qualitatively similar to those observed in chronically hypoxic animals and humans, could contribute to sleep disturbances at high altitude.
authors.affiliation: Human Physiology Laboratory, and Underwater and Hyperbaric Medicine Postgraduate Medical School, G. D'Annunzio University, School of Medicine, Chieti, Italy.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Bosco
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ionadi
authors.forename: Saverio
authors.initials: S
authors.lastname: Panico
authors.forename: Fabio
authors.initials: F
authors.lastname: Faralli
authors.forename: Riccardo
authors.initials: R
authors.lastname: Gagliardi
authors.forename: Piergiorgio
authors.initials: P
authors.lastname: Data
authors.forename: Jacopo P
authors.initials: JP
authors.lastname: Mortola
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D001831:Body Temperature / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D012016:Reference Values; D015656:Respiratory Mechanics / Q000502:physiology