Sadé J
Ear Research Laboratory, Sackler School of Medicine, Tel-Aviv, Israel.
Acta Otolaryngol. 1997 Mar;117(2):289-92. doi: 10.3109/00016489709117789.
Retraction of the elastic pars flaccida (PF) is the first reaction to a middle ear (ME) negative pressure in adults. Such retraction reduces middle ear volume, thereby elevating the ambiant pressure. PF retraction acts therefore as a buffering mechanism which counteracts ME negative pressure. Measurements of the volume of the retracted PF were performed by filling the retracted PF space with a liquid. Measurements of 15 PF retraction pockets stages I showed them to have a volume of 1-3 m3 (average 2 mm3) and 23 retraction pockets stage II presented a volume of 4-8 m3 (average 5-8 mm3). It was calculated that retraction of the PF stage I and II may counteract 1-80 mm H2O of negative ME pressure-depending on the degree of retraction and the extent of mastoid pneumatization. The range of PF retraction suggests that normal pressure in the ME fluctuates, up to 8 mm H2O in average pneumatic ears (10 cm2) extending eventually to 80 mm2 in ears with sclerotic mastoids. Other mechanisms which may also serve the ME as pressure buffers by reducing its volume-once a negative pressure sets in-are retraction of the pars tensa, swelling of the mucosa or flooding the ME cavity with an exudate.
弹性松弛部（PF）的内陷是成人中耳（ME）负压的首要反应。这种内陷会减小中耳容积，从而升高周围压力。因此，PF内陷起到一种缓冲机制的作用，可抵消中耳负压。通过用液体填充内陷的PF空间来测量内陷PF的容积。对15个I期PF内陷袋的测量显示其容积为1 - 3立方毫米（平均2立方毫米），23个II期内陷袋的容积为4 - 8立方毫米（平均5 - 8立方毫米）。据计算，I期和II期PF的内陷可抵消1 - 80毫米水柱的中耳负压，这取决于内陷程度和乳突气化程度。PF内陷的范围表明，中耳的正常压力会波动，在平均含气中耳（10平方厘米）中可达8毫米水柱，最终在乳突硬化的耳朵中可扩展至80毫米水柱。一旦出现负压，其他可能通过减小中耳容积来作为压力缓冲的机制包括紧张部内陷、黏膜肿胀或中耳腔被渗出液充满。
