We studied the middle ear (ME) pressure in 13 atelectatic ears to evaluate the effect of politzerization or ME inflation by a catheter using both room air and a gas mixture. The gas contained 12% O2, 6% CO2 and 82% N2. Tympanometry was performed before and after the treatment. The elevated ME pressure induced by the treatments, whether with room air or the gas mixture, declined rapidly within the first 30 min. However, at 35 and 45 min after the treatment with room air, the mean decrease in pressure was significantly greater than with the gas mixture, which might be due to slow oxygen absorption through the ME mucosa.