Quantitative analysis of gas losses and gains in the middle ear

Quantitative analysis of the amount of gas entering and leaving the middle ear (ME) was performed in patients with central perforation or with ventilating tubes. Patients were divided into a 'balanced pressure group' (BP) where pressure remained close to atmospheric throughout the measuring period and an 'unbalanced pressure group' (UBP) where pressure decreased continuously throughout measurements. The rate of gas gain was 41.0 +/- 19.9 microl/h (mean +/- SD, n = 17) in the BP group, significantly higher than in the UBP group (21.4 +/- 9.6 microl/h, n = 8). The rate of gas loss was 34.8 +/- 17.7 and 36.1 +/- 15.9 microl/h in the BP and UBP groups, respectively. Deglutition frequency was 27 +/- 13.4 deglutition/h in the BP group, significantly higher than the deglutition frequency of the UBP group (16 +/- 8.9 deglutition/h). It seems that the amount of gas entering the ME per deglutition is rather stable and does not change significantly with ME pressure level. Negative ME pressure may result from decreased gas gain rate due to increased intervals between deglutitions and loss of interdependence between the rate of gas entering and leaving the ME.