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 ventila ting tubes. Patients were divided into a 'balanced pressure group' (BP) whe re pressure remained close to atmospheric throughout the measuring period a nd an 'unbalanced pressure group' (UBP) where pressure decreased continuous ly throughout measurements. The rate of gas gain was 41.0 +/- 19.9 mu l/h ( mean +/- SD, n = 17) in the BP group, significantly higher than in the UBP group (21.4 +/- 9.6 mu l/h, n = 8). The rate of gas loss was 34.8 +/- 17.7 and 36.1 +/- 15.9 mu l/h in the BP and UBP groups, respectively. Deglutitio n frequency was 27 +/- 13.4 deglutition/h in the BP group, significantly hi gher than the deglutition frequency of the UBP group (16 +/- 8.9 deglutitio n/h). It seems that the amount of gas entering the ME per deglutition is ra ther stable and does not change significantly with ME pressure level. Negat ive ME pressure may result from decreased gas gain rate due to increased in tervals between deglutitions and loss of interdependence between the rate o f gas entering and leaving the ME. (C) 1998 Elsevier Science B.V. All right s reserved.