Procedures and ETF testing Measurements
Eustachian tube function (ETF) was measured in each ear using a modified pressure-equilibration test. An earplug containing two probes was introduced into the ear canal. One probe was connected to a constant flow pump at a speed of 25ml/min, the other probe was coupled to a high-resolution manometer and data of MEP was obtained from a computer which showed the MEP-time curve. The ME was inflated and positive pressure was applied. When the ET spontaneously opened, the pump was manually stopped and air was discharged through the ET until the latter closed passively. The pressure at which the ET opened passively was the opening pressure(Po) and the pressure at which it closed passively was the closing pressure(Pc). We restricted the upper limit of positive pressure to 700 daPa because some patients felt uncomfortable when the pressure exceeded the above level. If the ET remained closed when the pressure reached the upper limit, we defined it as negative passive opening function. The active opening function test was then carried out (Fig. 1),7 the ME was first inflated to +200 daPa following which the patient was instructed to swallow at least ten times. The residual pressure(Pr) remaining in the ME after swallowing was recorded. The number of swallows and number of times the ET opened (judged by the appearance of the swallow waveform) were also noted down. Each time the ET opened, the MEP change was recorded as ΔP and the duration of ET opening was recorded as Δt (Fig. 2). Next, similar testing was carried out at a MEP of -200 daPa. To improve accuracy and misjudgment of ET opening, ET opening was only defined when ΔP>3daPa and Δt<1.5s.8 Patients were classified into four types according to the test results: 1. with both active and passive ET opening function; 2. with only passive opening function; 3. with only active opening function; 4. without active or passive opening function.