Ostfeld E J, Silberberg A
Department of Polymer Research, Weizmann Institute of Science, Rehovot, Israel.
Laryngoscope. 1991 Mar;101(3):297-304. doi: 10.1288/00005537-199103000-00014.
The gas contents of the physiological middle ear periodically cycle through two phases in steady state. During phase I, the eustachian tube is shut and the middle ear gas space is effectively closed. Gas is absorbed or produced at the mucosal surface, and the total pressure changes correspondingly. During phase II, which is of very short duration, the eustachian tube opens, a bolus of gas passes between the middle ear and the nasopharynx, and the total pressure in the middle ear rapidly adjusts to that in the nasopharynx. Since nasopharyngeal pressure fluctuates in time, so does the pressure in the middle ear. The effect of these pressure changes is to produce a level of ventilation in the middle ear, which depends on a combination of three parameters: the volume of the middle ear, multiplied by the mean amplitude of pressure variations in the nasopharynx, divided by the mean elapsed time between successive eustachian tube openings. Assuming steady-state conditions, the composition of middle ear gas can be computed and is predicted to range from PN2 = 621, PO2 = 46, PCO2 = 46, PH2O = 47 mm Hg in the case when nasopharynx fluctuations are small, to a match with nasopharyngeal gas composition, when the fluctuations are large.
在稳态下，生理中耳的气体含量会周期性地循环经历两个阶段。在第一阶段，咽鼓管关闭，中耳气腔有效封闭。气体在黏膜表面被吸收或产生，总压力相应变化。在持续时间非常短的第二阶段，咽鼓管打开，一团气体在中耳和鼻咽之间通过，中耳的总压力迅速调整至鼻咽的压力。由于鼻咽压力随时间波动，中耳压力也会如此。这些压力变化的作用是在中耳产生一定程度的通气，其取决于三个参数的组合：中耳的容积乘以鼻咽压力变化的平均幅度，再除以连续两次咽鼓管开放之间的平均经过时间。假设处于稳态条件，中耳气体的成分可以计算得出，预计范围从鼻咽波动较小时的PN2 = 621、PO2 = 46、PCO2 = 46、PH2O = 47毫米汞柱，到波动较大时与鼻咽气体成分匹配的情况。
