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Carotid chemoreceptors and respiratory adaptations to dead space loading during incremental exercise
N C Syabbalo1, T Zintel, R Watts
1Division of Respiratory Medicine, Royal University Hospital, Saskatoon, Saskatchewan, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|September 1, 1993
Summary
Adding dead space (VD) during exercise increases breathing depth and slows frequency. This response is not mediated by carotid chemoreceptors (CC), as confirmed by experiments using hyperoxia to silence the CC.
Area of Science:
- Exercise Physiology
- Respiratory Control
- Cardiovascular Physiology
Background:
- Dead space (VD) loading during exercise typically increases tidal volume and decreases respiratory frequency.
- The role of carotid chemoreceptors (CC) in this breathing pattern response remains unclear.
Purpose of the Study:
- To investigate the involvement of carotid chemoreceptors (CC) in the breathing pattern response to added dead space (VD) during maximal incremental exercise.
Main Methods:
- Nine healthy subjects performed bicycle ergometer tests under four conditions: air with VD (AVD), air control (AC), 100% O2 with VD (O2VD), and 100% O2 control (O2C).
- Hyperoxia (100% O2) was used to silence the CC.
- Breathing pattern was analyzed at a matched ventilation level (75% of maximal ventilation).
Main Results:
- Breathing pattern was significantly deeper and slower in both AVD and O2VD conditions compared to AC and O2C conditions.
- The increase in tidal volume with VD loading was not significantly different whether CC were active or silenced.
- No significant difference in breathing pattern was observed between AC and O2C conditions.
Conclusions:
- The altered breathing pattern observed during dead space (VD) loading in exercise is not mediated by the carotid chemoreceptors (CC).
- These findings suggest other neural or humoral mechanisms are responsible for the observed changes in breathing pattern.