The effect of respiratory mode on human middle ear pressure.

The purpose of this study was to examine the effect of respiratory mode on the human middle ear pressure. The partial pressure of carbon dioxide in the venous blood (PvCO2) and the middle ear pressure were increased by hypoventilation, and decreased by hyperventilation. The partial pressure of oxygen in the venous blood showed little change. It was considered that CO2 diffused into the middle ear cleft according to the partial pressure gradient when the PvCO2 was elevated by hypoventilation, resulting in increase of the middle ear pressure, whereas CO2 diffused into the blood from the middle ear cleft when the PvCO2 was reduced by hyperventilation, resulting in decrease of the middle ear pressure. These findings suggest that bidirectional gas exchange via the middle ear mucosa functions actively in the human middle ear and plays an essential role in the regulation of the middle ear pressure.