Document Detail

Increases in middle ear pressure resulting from counter-diffusion of oxygen and carbon dioxide into the middle ear of monkeys.
MedLine Citation:
PMID:  9349867     Owner:  NLM     Status:  MEDLINE    
The mechanism of middle ear (ME) pressure regulation is incompletely understood. Previously, Hergels and Magnuson reported an unexpected increase in ME pressure for human subjects who partially evacuated their relative positive ME pressures by swallowing. They suggested that a novel, but unknown mechanism for the generation of gas was responsible for the pressure increase. In this experiment, the MEs of rhesus monkeys were inflated with N2 via the eustachian tube and post inflation ME pressures were recorded for up to three hours. Eleven of 20 experiments showed an initial increase in ME pressure caused by the inflation followed by stable pressures for the remainder of the followup period. In 9 of the experiments, a rapid and temporally discrete decrease in ME pressure was observed during the course of followup. Following the observed pressure decrease which was interpreted as a transient eustachian tube opening, ME pressures showed a progressive increase characterized by a kinetic pattern similar to that of the human experiment. To understand the mechanism responsible for this effect, the monkey experiment was simulated using a mathematical model of ME pressure regulation. Free parameters of the model were taken from experimental data for monkeys. The model accurately predicted the time course of pressure change documented in the monkey experiments. The effect is driven by a decrease in the preexisting ME partial pressures of CO2, O2 and H2O consequent to tubal openings at relative positive pressures, with the subsequent counter diffusion of those gases from blood to ME causing the observed increase in total ME pressure. The results reported by Hergels and Magnuson can also be explained by this mechanism.
W J Doyle
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Acta oto-laryngologica     Volume:  117     ISSN:  0001-6489     ISO Abbreviation:  Acta Otolaryngol.     Publication Date:  1997 Sep 
Date Detail:
Created Date:  1997-12-16     Completed Date:  1997-12-16     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0370354     Medline TA:  Acta Otolaryngol     Country:  NORWAY    
Other Details:
Languages:  eng     Pagination:  708-13     Citation Subset:  IM    
Department of Otolaryngology, Children's Hospital of Pittsburgh, USA.
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MeSH Terms
Carbon Dioxide / blood,  physiology*
Ear, Middle / blood supply,  physiology*
Macaca mulatta
Models, Biological
Oxygen / blood,  physiology*
Grant Support
Reg. No./Substance:
124-38-9/Carbon Dioxide; 7782-44-7/Oxygen

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