吸纯氧和高度提升对低压舱耳气压功能检查的复合影响

目的 比较低压舱内4000m吸空气和6900m吸纯氧对耳气压功能的影响.方法11名男性健康志愿者采用自身对照方法,均参加空气组(4000m暴露呼吸空气)和纯氧组(6900m暴露呼吸纯氧)两组试验,两次试验间隔2周以上.志愿者在地面高度分别吸空气或纯氧1h,然后在低压舱内以20m/s的速度上升至目标高度停留5min,再以20m/s的速度下降至地面高度.记录两组志愿者试验前后不同时间点主观症状、鼓膜充血程度、声导抗和纯音听阈等指标的变化,并对声导抗指标和听阈变化进行统计学分析.结果检查过程中空气组和纯氧组分别有4人(4耳)和7人(7耳)主诉发生耳痛,且纯氧组发生压痛的高度较高.出舱即刻两组分别有3人(3耳)和5人(5耳)鼓膜Ⅲ度充血,试验后纯氧组有4人(6耳)充血程度随时间延长而加重,出舱3h及24h两组鼓膜充血程度差异有统计学意义.出舱即刻两组分别有11人(15耳)和11人(14耳)为正常的A型鼓室图.纯氧组出舱即刻静态声顺值的增加量明显高于空气组(P<0.05),出舱3h和24h中耳压的减少量明显高于空气组(P<0.05).两组试验均可致咽鼓管功能下降.出舱3h和24h时纯氧组个别频率纯音听阈的增加量明显高于空气组(P<0.05).结论吸入纯氧并增加高度可提高低压舱耳气压功能检查的筛选度,且对24h内的鼓膜充血程度、声导抗和纯音听阈有较大影响.

Compound effects of inhaling pure oxygen and lifting height on ear baric function in a hypobaric chamber

Objective To compare the ear baric function between 4000m altitude chamber test with inhaling air and 6900m altitude chamber test with inhaling pure oxygen.Methods Eleven healthy male volunteers attended two tests as two groups by self-comparison. As the air group the volunteers inhaled air at 4000m, while as the pure oxygen group they inhaled pure oxygen at 6900m altitude, and the time interval between the two tests was more than two weeks. During the test, the volunteers breathed air or pure oxygen at random for 1h, and then were exposed at a speed of 20m/s to the target altitude for 5min. Hereafter they were sent back to the ground at the same speed. The changes of subjective symptoms, degree of tympanic congestion, acoustic immitance index and pure-tone auditory threshold were recorded before and after the test. The acoustic impedance index and pure-tone threshold were statistically analyzed.ResultsFour volunteers (4 ears) in air group and 7 volunteers (7 ears) in pure oxygen group reported ear pain in altitude chamber exposures, respectively. The pain-triggering altitude was higher in the pure oxygen group. Immediately after tests, there were 3 (3 ears) and 5 volunteers (5 ears) with Ⅲ degree congestion of the tympanic membrane in the two groups respectively. Four volunteers (6 ears) developed gradually aggravated hemorrhages after altitude exposure. And the tympanic membrane congestion difference between groups was statistically significant at 3 and 24h after tests (P<0.01). The type A tympanogram appeared in 11 (15 ears) and 11 (14 ears) volunteers respectively immediately after tests. The increase of static compliance value was significantly greater in pure oxygen group than in air group immediately after tests (P<0.05), the decrease of middle ear pressure was more significant in pure oxygen group than in air group at 3 and 24h after tests (P<0.05). Both the two altitude exposure tests resulted in eustachian tube dysfunction. At 3 and 24h after the tests, the increase of individual frequency pure-tone threshold was significantly higher in pure oxygen group than in air group (P<0.05).Conclusion Breathing pure oxygen and lifting height could increase the screening degree of ear baric function test in hypobaric chamber, and have greater influence on degree of tympanic congestion, acoustic immittance and pure-tone auditory threshold in 24 hours.