PO2 levels in middle ear effusions and middle ear mucosa.

We measured PO2 values in mucoid and serous middle ear effusions (M-MEE, S-MEE) and in the middle ear mucosa of patients with otitis media with effusion (OME) and compared these values with those obtained from patients with middle ear barotrauma (MEBT). The mean and S.D. values of PO2 in M-MEE, S-MEE and MEBT effusions were 28.9 +/- 11.3, 31.5 +/- 9.5 and 37.0 +/- 15.4 mmHg, respectively; the mean and S.D. values in mucosa were 27.1 +/- 11.9, 27.0 +/- 13.2 and 32.5 +/- 1.0 mmHg, respectively. In health, PO2 values in middle ear mucosa are regulated by its blood supply, oxygen solubility in blood and the blood-to-cavity partial pressure gradient of the gas. When the Eustachian tube (ET) function is severely impaired, PO2 values in the middle ear air cavity depend on the mucosal condition, though some studies have shown a lack of relationship between ET function and PO2 values. Our results show that PO2 values in MEBT are consistently higher than in OME, suggesting that the attributable factor could be a better ET function in MEBT.