Pressure outside the extrapulmonary airway in dogs

Area of Science:

• Physiology
• Respiratory Mechanics
• Pulmonary Medicine

Background:

• Understanding extrapulmonary airway pressure is crucial for respiratory mechanics.
• Positive pressure ventilation can alter airway pressure dynamics.
• Previous studies have not fully characterized transmural pressures in extrapulmonary airways.

Purpose of the Study:

• To measure static and dynamic transmural pressures of extrapulmonary airways.
• To investigate pressure changes in the mediastinum and neck during lung inflation.
• To assess the influence of surrounding tissues on airway pressure.

Main Methods:

• Anesthetized dogs were suspended in a standing position.
• Thin, fluid-filled catheters were used to measure pressures.
• Pressures were recorded within and on the anterior surface of airways in the mediastinum and neck during positive pressure lung inflation and forced deflation.

Main Results:

• The change from mediastinal to cervical static extra-airway pressures (Pea) was gradual, occurring through the thoracic outlet and neck.
• Static Pea in the mediastinum was more positive than pleural pressure during lung inflation.
• During forced deflation, dynamic mediastinal Pea remained close to pleural pressures, suggesting a small effect of tissue restitution forces.

Conclusions:

• Extrapulmonary airway pressure changes are not abrupt but gradual.
• Tissue forces generated by airway narrowing have a minor effect on reducing anterior airway surface pressure.
• These findings contribute to a better understanding of respiratory mechanics during positive pressure ventilation.