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Reflex changes in tracheal smooth muscle tone during high-frequency oscillation
G C Man1, K K Teo, C T Kappagoda
1Department of Medicine, University of Alberta, Edmonton, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 1, 1990
Summary
High-frequency oscillatory ventilation (HFOV) reduces tracheal smooth muscle tension and upper airway resistance in dogs. This effect is mediated by a vagal nerve mechanism, suggesting HFOV
Area of Science:
- Physiology
- Respiratory Mechanics
Background:
- Tracheal smooth muscle tension and upper airway resistance are critical factors in respiratory mechanics.
- Conventional intermittent positive pressure ventilation (IPPV) may influence these parameters.
- High-frequency oscillatory ventilation (HFOV) is an alternative ventilation mode with potential effects on airway tone.
Purpose of the Study:
- To investigate the impact of HFOV on tracheal smooth muscle tension.
- To determine the effect of HFOV on upper airway resistance.
- To elucidate the underlying mechanism, specifically the role of vagal nerve pathways.
Main Methods:
- Anesthetized dogs were ventilated using HFOV and IPPV (with and without positive end-expiratory pressure, PEEP).
- Tracheal smooth muscle tension was measured above the tracheostomy.
- Upper airway airflow resistance (Ruaw) was assessed.
- Vagotomy was performed by cooling the vagi to 8°C to interrupt afferent traffic.
Main Results:
- Tracheal smooth muscle tension was significantly lower during HFOV compared to IPPV and IPPV with PEEP.
- Upper airway resistance (Ruaw) was significantly reduced during HFOV compared to IPPV and IPPV with PEEP.
- The difference in muscle tension between ventilation modes disappeared when vagal afferent traffic was interrupted.
Conclusions:
- HFOV induces relaxation of tracheal smooth muscle.
- HFOV leads to a reduction in upper airway resistance.
- These effects are mediated through a vagally dependent mechanism.