Ninety-one normal infants were followed longitudinally for varying periods from November 1975 to April 1977 to assess the correlation between tympanometry and pneumatic otoscopy and to study the pathogenesis of acute and chronic otitis media early in life. Type A (normal) tympanograms correlated with normal otoscopic findings in 92% of instances. Type B tympanograms, indicating reduced drum compliance with a relatively flat pressure curve, were associated with abnormal otoscopic findings in 93% of cases. The A8 (reduced compliance, normal pressure) and C (normal compliance, negative pressure) tympanograms were less consistent predictors of otoscopic findings. The correlation of tympanometric and otoscopic findings were similar in infants above and below 7 months of age. Tympanometry provided some insight into the natural history of otitis in 71 infants followed 12 to 17 months. Infants who failed to develop otitis had type B curves in only one of 240 determinations (0.4%). This pattern did not appear in those who developed acute otitis media (AOM) until the month preceding the first attack; nine of 29 tests (31%) made under these circumstances were type B. When a type B curve appeared in an asymptomatic study infant who had not previously had otitis, AOM developed within a month in nine of ten instances. At the time of diagnosis of first AOM, 87% of tympanograms were type B with the remainder type A8 or C. Sixty-three percent of tympanograms obtained from 25 infants during the six months following first AOM were type B, indicating that abnormal middle ear function was often prolonged. Fifteen of these 25 developed recurrent otitis during follow-up.
Coupled Effects of Stress, Moisture Content and Gas Pressure on the Permeability Evolution of Coal Samples: A Case Study of the Coking Coal Resourced from Tunlan Coalmine
