The Effects of Hyper- and Hypocapnia on Phonatory Laryngeal Airway Resistance in Women

Abstract

Purpose The larynx has a dual role in the regulation of gas flow into and out of the lungs while also establishing resistance required for vocal fold vibration. This study assessed reciprocal relations between phonatory functions—specifically, phonatory laryngeal airway resistance (R law )—and respiratory homeostasis during states of ventilatory gas perturbations. Method Twenty-four healthy women performed phonatory tasks while exposed to induced hypercapnia (high CO 2 ), hypocapnia (low CO 2 ), and normal breathing (eupnea). Effects of gas perturbations on R law were investigated as were the reciprocal effects of R law modulations on respiratory homeostasis. Results R law remained stable despite manipulations of inspired gas concentrations. In contrast, end-tidal CO 2 levels increased significantly during all phonatory tasks. Thus, for the conditions tested, R law did not adjust to accommodate ventilatory needs as predicted. Rather, stable R law was spontaneously accomplished at the cost of those needs. Conclusions Findings provide support for a theory of regulation wherein R law may be a control parameter in phonation. Results also provide insight into the influence of phonation on respiration. The work sets the foundation for future studies on laryngeal function during phonation in individuals with lower airway disease and other patient populations.