PubMed · 6918905
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L R Thomson. Understanding tympanometry.. https://pubmed.ncbi.nlm.nih.gov/6918905/
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Early detection and treatment of hearing loss can prevent a lifetime of difficulties. Severe sensorineural hearing loss is present in approximately one in 1,000 newborns. Many newborns have mild to moderate hearing loss, either conductive or sensorineural, that interferes with normal functioning. The family physician is in an excellent position to identify hearing impairment at an early stage. During well-child visits, simple checklists and screening tests can be completed to aid in detection of a hearing loss. The Joint Committee on Infant Hearing and the National Institutes of Health Consensus Statement recommend screening all infants for hearing loss, preferably during the newborn period. Children at high risk for hearing loss should be referred for auditory function tests, such as behavioral observation audiometry, auditory brain stem response, otoacoustic emissions testing, visual reinforcement audiometry and conditioned play audiometry. The advantages and limitations of each test should be understood by the family physician. An infant is never too young to be treated for hearing loss. The earlier intervention begins, the greater the chance a child will develop to maximum potential.
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OBJECTIVE: To estimate the rate of exchange of selected gases across the middle ear (ME) mucosa and define the exchange limitations. DESIGN: At separate sessions, the ME was inflated via the eustachian tube with a bolus of pure nitrogen, carbon dioxide, oxygen, or nitrous oxide, and ME pressures were recorded by tympanometry at selected intervals for up to 4 hours. The slope of the function relating pressure change to pressure was calculated by least squares regression and used as an estimate of the rate constant for exchange of that gas (experiment 1). Because of the slow rate of nitrogen exchange, a second experiment was performed in which the tensor veli palatini muscle was unilaterally paralyzed. The ME was inflated with nitrogen, and the slope of the rate-pressure function for measurements at 24-hour intervals was used to estimate the rate constant. SUBJECTS: Ten juvenile cynomolgus monkeys, six for experiment 1 and four for experiment 2. RESULTS: The relative, average rate constants for carbon dioxide, nitrous oxide, oxygen, and nitrogen were 1, 10.7, 18.6, and greater than 700, respectively. Comparisons of these rates with those predicted by theory show that oxygen and carbon dioxide exchange is diffusion limited, and nitrous oxide and nitrogen is perfusion limited. CONCLUSIONS: The perfusion limitation for nitrogen suggests that its exchange rate is notably increased by inflammation from increased mucosal blood flow. Targeting inflammation for therapy of persistent ME effusions may decrease the rate of nitrogen exchange and reestablish normal ME pressure regulation.