Exercise breathing pattern during chronic altitude exposure.
Breathing pattern in response to maximal exercise was examined in four subjects during a 7-day acclimatisation to a simulated altitude of 4247 m (barometric pressure, PB = 59.5 kPa). Graded exercise tests to exhaustion were performed during normoxia (day 0), and on days 2 and 7 of hypoxia, respectively. Ventilation was significantly augmented in the hypoxic environment, as were both the mean inspiratory flow (VT/TI) and inspiratory duty cycle (TI/TTOT) components of it. VI/TI was increased due to a significant increase in tidal volume (VT) and a corresponding decrease in inspiratory time duration (TI). Throughout a range of exercise ventilation, TI/TTOT was increased due to an apparently greater decrease in expiratory time duration (TE) with respect to TI. In all cases, the relation between VT and TI displayed a typical range 2 behaviour, with evidence of a range 3 occurring at very high ventilatory rates. There was essentially no difference observed in the VT-TI relation during exercise between the normoxic and hypoxic conditions. No significant changes were observed in the breathing pattern in response to exercise within the exposure period (from day 2 to day 7), although there was a discernible tendency to a higher stage 3 plateau by day 7 of altitude exposure.
Mekjavic
I B
IB
School of Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada.
Moric
C
C
Goldberg
S V
SV
Morrison
J B
JB
Walsh
M L
ML
Banister
E W
EW
Schoene
R B
RB
D000064:Acclimatization / Q000502:physiology; D000328:Adult; D000531:Altitude; D001945:Breathing Exercises; D015444:Exercise / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D012119:Respiration / Q000502:physiology*; D013997:Time Factors