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J Appl Physiol (February 8, 2002). doi:10.1152/japplphysiol.00762.2001
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Articles in PresS, published online ahead of print February 8, 2002
J Appl Physiol, 10.1152/jap.00762.2001
Submitted on July 23, 2001
Accepted on February 4, 2002

Mechanical Properties of The Passive Pharynx in Vietnamese Pot-Bellied Pigs: II Dynamics

Stephanie A Tuck1* and John E Remmers1

1 Medicine, University of Calgary, Calgary, Alberta, Canada

* To whom correspondence should be addressed. E-mail: stephanie.tuck{at}mcgill.ca.

We described the dynamic mechanical properties of the passive pharynx in Vietnamese pot-bellied pigs and the effects of caudal tracheal displacement. During general anaesthesia and neuromuscular blockade, airflow through the upper airway (V) and pharyngeal cross-sectional area (A) were measured during ramp decreases in pressure downstream from the pharynx (PDOWN). Measurements were made with 0, 1 and 2 cm of caudal tracheal displacement. Airflow limitation and/or negative pressure dependence (NPD) were observed in all animals. Tracheal displacement (2 cm) increased peak airflow (VMAX) by 205.1±105.1% (p<0.05) relative to VMAX with no displacement and increased the magnitude of NPD, expressed as % decrease in V from VMAX, from 22.9±27.4% to 56.6±37.5% (p<0.05). Initial decreases in PDOWN narrowed all levels of the pharynx, but once VMAX was reached, further decreases in PDOWN narrowed the hypopharynx but not the nasopharynx and oropharynx. We conclude that the hypopharynx is the flow-limiting site in the pig pharynx. Tracheal displacement improved airflow dynamics as VMAX increased, but also resulted in pronounced NPD.




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