Lung reflexes in anaesthetized rabbits with elastase-induced emphysema

Area of Science:

• Pulmonary Physiology
• Respiratory Medicine
• Pathology

Background:

• Elastase-induced emphysema is a model for studying chronic obstructive pulmonary disease (COPD).
• Vagal pulmonary reflexes play a crucial role in respiratory control and are potentially affected by lung diseases.

Purpose of the Study:

• To investigate the impact of elastase-induced emphysema on vagal pulmonary reflexes in rabbits.
• To assess the excitability of pulmonary stretch receptors and lung receptors with non-myelinated vagal afferents in emphysematous lungs.

Main Methods:

• Emphysema was induced in rabbits using intratracheal porcine pancreatic elastase.
• Histological, pathological, and lung mechanics assessments confirmed emphysema.
• The Hering-Breuer inflation reflex (HBIR) and ventilatory responses to phenyldiguanide were measured under anesthesia.

Main Results:

• Emphysema significantly increased the strength of the Hering-Breuer inflation reflex (HBIR) at inflation volumes exceeding tidal volume (VT).
• The slope of the HBIR versus inflation volume curve was significantly steeper in the emphysema group.
• The early ventilatory response to phenyldiguanide, indicating non-myelinated vagal afferent excitability, was not significantly different between groups.
• Emphysematous rabbits exhibited decreased VT and increased inspiratory time (TI).

Conclusions:

• Elastase-induced emphysema enhances pulmonary stretch receptor excitability, as evidenced by an augmented HBIR.
• Receptors with non-myelinated vagal afferents appear unaffected in this emphysema model.
• Emphysema alters breathing patterns, characterized by reduced tidal volume and prolonged inspiratory time.