Intermittent hypoxia increases ventilation and Sa_O2 during hypoxic exercise and hypoxic chemosensitivity

Abstract

The purpose of this study was 1) to test the hypothesis that ventilation and arterial oxygen saturation (Sa(O2)) during acute hypoxia may increase during intermittent hypoxia and remain elevated for a week without hypoxic exposure and 2) to clarify whether the changes in ventilation and Sa(O2) during hypoxic exercise are correlated with the change in hypoxic chemosensitivity. Six subjects were exposed to a simulated altitude of 4,500 m altitude for 7 days (1 h/day). Oxygen uptake (VO2), expired minute ventilation (VE), and Sa(O2) were measured during maximal and submaximal exercise at 432 Torr before (Pre), after intermittent hypoxia (Post), and again after a week at sea level (De). Hypoxic ventilatory response (HVR) was also determined. At both Post and De, significant increases from Pre were found in HVR at rest and in ventilatory equivalent for O2 (VE/VO2) and Sa(O2) during submaximal exercise. There were significant correlations among the changes in HVR at rest and in VE/VO2 and Sa(O2) during hypoxic exercise during intermittent hypoxia. We conclude that 1 wk of daily exposure to 1 h of hypoxia significantly improved oxygenation in exercise during subsequent acute hypoxic exposures up to 1 wk after the conditioning, presumably caused by the enhanced hypoxic ventilatory chemosensitivity.

Cerebral hypoperfusion during hypoxic exercise following two different hypoxic exposures: independence from changes in dynamic autoregulation and reactivity

“…Elevations in ventilatory chemosensitivity to hypoxia following hypoxic exposure are consistent with previous reports (8, 11, 20, 26 -28, 42). The lack of influence of this elevation in ventilatory chemosensitivity during normoxic exercise has been reported (9,21). Consistent with our findings, Katayama et al (22) has shown that increasing ventilatory chemosensitivity following exposure to IH was related to an improved Sa O 2 during hypoxic exercise.…”

“…mosensitivity is only one of multiple signals that integrate to increase ventilation (45); however, following exposure to IH, an enhanced chemosensitivity activation was evident during hypoxic exercise (21). Although cerebral perfusion was not monitored in that study (21), it seems reasonable to speculate that an enhanced ventilatory chemosensitivity to hypoxic exercise would result in subsequent hypocapnia and reductions in cerebral perfusion.…”

“…Although cerebral perfusion was not monitored in that study (21), it seems reasonable to speculate that an enhanced ventilatory chemosensitivity to hypoxic exercise would result in subsequent hypocapnia and reductions in cerebral perfusion. Consistent with this notion, cerebral oxygenation has been reported to fall during submaximal exercise at high altitude (15).…”

Effects of Intermittent Altitude Exposures on Acclimatization of 4,300 M

“…However, this adaptation was accomplished in fewer hours, and thus could be considered a more efficient method of acclimatizing people to altitude. Our results support most of the previous research measuring resting ventilation before and after intermittent exposures to various altitudes (49,51,72,88,92), but differ from a recently published study (80). However, that study (80) only exposed volunteers to altitude for 2 h-d" 1 , and a longer exposure time may be needed to induce the beneficial ventilatory changes we observed.…”

Fitness and therapeutic potential of intermittent hypoxia training: a matter of dose

“…These investigations also show that the break in training for one or two days do not significantly affect the outcome of the IHT course. These conclusions were also expressed by Katayama et al [56,57], Koehle et al [58] and others. Later on, Katayama et al [59] conducted a study using the hypoxic tent, which was supported by 12.3% O 2 , one and 3 hours during the week.…”