In normoxia sensation of breathing effort (Be) during incremental exercise increases linearly with esophageal pressure swings (dPes) (Kayser et al. JAP, 1997) while that of leg effort (Le) increases exponentially with power output. Little is known about the sensation of Be and Le and their correlates in hypobaric hypoxia although increased sensation mediated by the carotid may be expected (Ward & Whipp, J Physiol 1989). Fourteen healthy subjects (age 41[14], mean[SD] yr, height 176[3]cm, weight 75[9]kg) did an incremental (30 watt/3min) cyclergometer test until volitional exertion (Wmax), while heart rate (Hr), ventilation (Ve), respiratory rate (Rr) , saturation (Sat), and esophageal pressure (Pes) were monitored. At each power output the subjects indicated their Be and Le on a modified Borg scale (1-10). Experiments were done at sea level and after acclimatization to 4560m. At altitude Wmax was 15[8]% lower; Hr was higher, Ve was higher, Rr was higher and Sat was lower at all power outputs. Both exponential Le and Be vs. power relationships were shifted upward in hypoxia, but for Be more so than for Le. The slope of the linear relationship between dPes and Be was steeper in hypoxia. The increased respiratory muscle effort (increased dPes) only partially correlated to the increased Be, the remainder being explained by the progressive drop in Sat from 86[4] at rest to 74[7]. It follows that in conditions of natural hypobaric hypoxia the ‘dyspneogenic‘ effect from the stimulation of the carotid bodies amplifies breathing effort sensation beyond that related to the respiratory muscle effort only. Whether such a mechanism also plays a role in the increase in Le remains an open question.
Correlates of respiratory and leg effort sensation in normoxia and hypobaric hypoxia
POMIDORI, Luca;COGO, Annaluisa;
2008
Abstract
In normoxia sensation of breathing effort (Be) during incremental exercise increases linearly with esophageal pressure swings (dPes) (Kayser et al. JAP, 1997) while that of leg effort (Le) increases exponentially with power output. Little is known about the sensation of Be and Le and their correlates in hypobaric hypoxia although increased sensation mediated by the carotid may be expected (Ward & Whipp, J Physiol 1989). Fourteen healthy subjects (age 41[14], mean[SD] yr, height 176[3]cm, weight 75[9]kg) did an incremental (30 watt/3min) cyclergometer test until volitional exertion (Wmax), while heart rate (Hr), ventilation (Ve), respiratory rate (Rr) , saturation (Sat), and esophageal pressure (Pes) were monitored. At each power output the subjects indicated their Be and Le on a modified Borg scale (1-10). Experiments were done at sea level and after acclimatization to 4560m. At altitude Wmax was 15[8]% lower; Hr was higher, Ve was higher, Rr was higher and Sat was lower at all power outputs. Both exponential Le and Be vs. power relationships were shifted upward in hypoxia, but for Be more so than for Le. The slope of the linear relationship between dPes and Be was steeper in hypoxia. The increased respiratory muscle effort (increased dPes) only partially correlated to the increased Be, the remainder being explained by the progressive drop in Sat from 86[4] at rest to 74[7]. It follows that in conditions of natural hypobaric hypoxia the ‘dyspneogenic‘ effect from the stimulation of the carotid bodies amplifies breathing effort sensation beyond that related to the respiratory muscle effort only. Whether such a mechanism also plays a role in the increase in Le remains an open question.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
