Mechanical properties of the passive pharynx in Vietnamese pot-bellied pigs. I. Statics

Tuck, Stephanie A., and John E. Remmers. Mechanical properties of the passive pharynx in Vietnamese potbellied pigs. I. Statics. J Appl Physiol 92: 2229–2235, 2002. First published October 19, 2001; 10.1152/japplphysiol. 00761.2001.—The static mechanical properties of the passive pharynx were investigated in Vietnamese pot-bellied pigs by using an isolated upper airway preparation. During general anesthesia and neuromuscular blockade, cross-sectional area (A) of the pharynx was measured while airway pressure (Paw) was held at various pressures in the absence of airflow. The static A-Paw relationship was measured during application of 0, 1, and 2 cm of caudal tracheal displacement. Relative to humans, closing pressures (Pclose) of the pig pharynx were very low ( 15 to 35 cmH2O). Tracheal displacement significantly decreased compliance of the hypopharynx (from 0.074 0.02 cm/cmH2O with no displacement to 0.052 0.01 cm/cmH2O with 2 cm of displacement) and decreased Pclose of the oropharynx (from 18.2 9.9 cmH2O to 24.1 10.5 and 28.7 12.3 cmH2O with 1 and 2 cm of displacement, respectively). Tracheal displacement did not affect A of the pharyngeal segments. In conclusion, tracheal displacement decreased collapsibility of the passive pharynx. The pharynx of the pot-bellied pig is structurally more resistant to collapse than the human pharynx.