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Hering-Breüer reflexes in high-altitude infants
J P Mortola1, T Trippenbach, R Rezzonico
1Department of Physiology, McGill University, Montreal, Quebec, Canada.
Clinical Science (London, England : 1979)
|March 1, 1995
Summary
High-altitude infants show altered breathing patterns due to hypoxia, with stronger inspiratory reflexes and weaker expiratory reflexes mediated by vagal nerves.
Area of Science:
- Physiology
- Neonatal Research
- Altitude Medicine
Background:
- Pulmonary ventilation is similar in high-altitude and low-altitude newborns.
- Breathing patterns differ, being deeper and slower at high altitude.
Purpose of the Study:
- Investigate the role of vagal reflexes in high-altitude infant breathing pattern differences.
- Quantify the strength of Hering-Breüer inspiratory inhibitory and expiratory facilitatory reflexes.
Main Methods:
- Measured breathing patterns in high-altitude (3600-4050m) and low-altitude (400m) infants.
- Assessed inspiratory inhibitory reflex using inspiratory time during occluded breaths (Tloccl).
- Assessed expiratory facilitatory reflex using expiratory duration during occluded breaths (TEoccl).
Main Results:
- Inspiratory time during occlusion (Tloccl) was significantly longer at high altitude (14% increase).
- Expiratory duration during occlusion (TEoccl) was significantly shorter at high altitude (79-87% of low-altitude values).
Conclusions:
- High-altitude hypoxia increases vagal input to the inspiratory off-switch.
- Hypoxia reduces tonic vagal expiratory facilitation in high-altitude infants.
- Vagal reflex alterations likely contribute to modified breathing patterns in high-altitude newborns.