Abstracts

Conclusions: It is suggested that oxygen consumption by bacteria could be a cause of the negative middle ear pressure in earswith otitis media. Objective: To determine whether oxygen consumption and production of carbon dioxide by bacteria could be a cause of negative pressure in ears with otitis media. Methods: Hermetically-sealed tubes (2ml of volume) containing 1 ml of culture media with Streptococcus pneumoniae leaving 1ml of airspace were connected to a micro-pressure sensor, and were maintained at 37 degree centigrade in a water bath. Chronological changes of air pressure in the tube were monitored for 15 hours (bacterial group), and were compared with those in the tubes containing culture media only (controls). Also, partial pressures of oxygen and carbon dioxide in the culture media ofthose bottles were measured. Results: The pressure of the bacterial group were significantly lower than that of controls (bacterial group; -94.692mmH2O, control group; 4.611.1mmH2O, 2 way-ANOVA, P<0.001). The partial pressures of oxygen were lower (bacterial group; -86.022.1mmHg, control group; -34.67.93mmHg, 2 way-ANOVA, P<0.0001) and those of carbon dioxide were significantly higher in the bacterial group than in the control group (bacterial group; 11.83.8mmHg, control group; -0.230.41mmHg, 2 way-ANOVA, P<0.0001).