Deglutitive subglottic air pressure and respiratory system recoil.

The purpose of this experiment was to confirm the presence of positive subglottic air pressure during swallowing, known as deglutitive subglottic air pressure (DPsub), in a group of healthy individuals. We also sought to determine if respiratory system recoil is responsible for generating the pressure. Ten healthy volunteers underwent direct DPsub measurement via percutaneous puncture of the cricothyroid membrane. Simultaneous DPsub and nasal airflow volumes were recorded while participants swallowed calibrated boluses over a wide range of lung volumes. Body plethysmography was used to determine functional residual capacity and residual volume. A custom respiratory recoil measurement system was used to measure recoil pressures. Regression analysis of lung volume on DPsub and lung volume on recoil pressure yielded strong linear relationships (P < 0.0001, R (2) = 0.71 and P < 0.0001, R (2) = 0.69, respectively). A mixed-model analysis of the effect of method (direct puncture or recoil) on pressure showed that there was no effect (F = 0.63; P = 0.43). By confirming the presence of DPsub in healthy adults and showing that respiratory system recoil is the most likely mechanism that generates DPsub, treatment of persons with dysphagia has even greater potential to be expanded to include consideration of factors that affect respiratory control and recoil forces.