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Respiratory reflexes evoked by tracheal distension
Summary
Intrathoracic trachea distension significantly prolonged expiratory duration in dogs, while extrathoracic trachea distension had less effect. These findings suggest potential extravagal influences on respiratory control.
Area of Science:
- Respiratory Physiology
- Tracheal Reflexes
Background:
- The respiratory system relies on intricate neural feedback mechanisms.
- Tracheal receptors play a role in regulating breathing patterns.
Purpose of the Study:
- To investigate the effects of intrathoracic (ITT) and extrathoracic trachea (ETT) distension on respiratory timing.
- To explore the role of vagal and potentially extravagal pathways in mediating these responses.
Main Methods:
- Anesthetized and ventilated dogs underwent controlled distension of ITT and ETT segments.
- Respiratory timing parameters, including expiratory duration (TE), inspiratory time (TI), and peak phrenic amplitude (PPA), were measured.
- Experiments were repeated after vagotomy to assess the role of vagal nerves.
Main Results:
- ITT distension significantly prolonged TE in 12/13 dogs, whereas ETT distension prolonged TE in only 5/13 dogs.
- Inhibition of inspiration (shortened TI, reduced PPA) occurred in some experiments, but effects on TI and PPA were generally not significant.
- After vagotomy, ITT distension shortened TE in 8/13 dogs, and ETT distension was mostly ineffective.
Conclusions:
- Tracheal distension, particularly ITT, influences expiratory duration.
- The observed effects, especially post-vagotomy, suggest the involvement of extravagal afferent pathways in modulating respiratory reflexes.