Blood flow distribution to upper airway muscles

Area of Science:

• Physiology
• Respiratory System
• Muscle Blood Flow

Background:

• Understanding blood flow to respiratory muscles is crucial for respiratory physiology.
• Previous studies have focused on diaphragm blood flow, with less known about upper airway muscle perfusion.

Purpose of the Study:

• To quantify and compare blood flow to various upper airway muscles, diaphragm, and parasternals during spontaneous breathing and inspiratory resistance loading.
• To determine the relative contribution of blood flow to different respiratory muscles under varying respiratory loads.

Main Methods:

• Radiolabeled microspheres (15-microns) were used to measure regional blood flow in anesthetized, tracheotomized dogs.
• Blood flow was measured in upper airway muscles (alae nasi, laryngeal, tongue, cervical strap, hyoid), diaphragm (DI), and parasternals (PS).
• Measurements were taken during spontaneous breathing and against inspiratory resistance (-28 cmH2O).

Main Results:

• Posterior cricoarytenoid (PCA) muscle blood flow (24.0 ml/min/100g) was greater than diaphragm (DI) (18.0 ml/min/100g) and similar to parasternals (PS) (21.4 ml/min/100g).
• Blood flow to alae nasi (AN), tongue, laryngeal adductors, cervical strap, and cricothyroid muscles was significantly lower (8.0 ml/min/100g) than DI and PCA.
• Inspiratory resistance loading increased blood flow to AN (7.5x), PCA (3.4x), DI (3.2x), and PS (1.9x).

Conclusions:

• At rest, the main glottic dilator (PCA) receives blood flow comparable to main inspiratory muscles (DI).
• In response to inspiratory load, PCA and AN exhibit significant increases in blood flow, potentially exceeding that of the diaphragm.
• These findings highlight the critical role of upper airway muscles in respiratory loading and their vascular adjustments.