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Pulmonary afferent activity during high-frequency ventilation at constant mean lung volume
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 1, 1986
Summary
High-frequency ventilation (HFV) increases slowly adapting pulmonary stretch receptor (PSR) activity, which prolongs expiration. Rapidly adapting pulmonary stretch receptors (RARs) showed increased activity only at low lung volumes during HFV.
Area of Science:
- Respiratory Physiology
- Neuroscience
- Pulmonary Mechanoreception
Background:
- High-frequency ventilation (HFV) is known to prolong expiration, but the underlying neural mechanisms involving pulmonary afferents are not fully understood.
- Pulmonary stretch receptors (PSRs) and rapidly adapting receptors (RARs) are key sensory components of the respiratory system.
- Previous studies have not detailed the specific responses of these receptors during HFV under controlled lung volumes.
Purpose of the Study:
- To investigate the discharge patterns of slowly adapting pulmonary stretch receptors (PSRs) and rapidly adapting pulmonary stretch receptors (RARs) during high-frequency ventilation (HFV).
- To determine if changes in PSR and RAR activity during HFV can explain the reflex prolongation of expiration.
- To compare receptor activity during HFV with that during normal-frequency ventilation pauses at constant lung volumes.
Main Methods:
- Recorded electrophysiological responses from 21 PSRs and 8 RARs in anesthetized, open-chest dogs.
- Applied high-frequency ventilation (HFV) at 15 Hz while maintaining constant mean end-expiratory lung volume and end-tidal PCO2.
- Compared receptor discharge during HFV to the end-expiratory pause during normal-frequency ventilation.
Main Results:
- Average PSR discharge significantly increased during HFV compared to normal ventilation, though not all PSRs showed this increase.
- RARs were largely inactive during HFV and normal ventilation at or above functional residual capacity.
- At low lung volumes, RAR discharge increased markedly during HFV.
Conclusions:
- Increased PSR discharge during HFV, even without increased lung volume, is sufficient to mediate the expiratory prolongation reflex.
- HFV alters pulmonary afferent activity, with PSRs playing a crucial role in the observed expiratory effects.
- RARs contribute to the response primarily at reduced lung volumes during HFV.