Division of Pediatric Otolaryngology, Children's Hospital of Pittsburgh of UPMC, Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15224, USA.
Laryngoscope. 2011 Feb;121(2):404-8. doi: 10.1002/lary.21275. Epub 2011 Jan 13.
OBJECTIVES/HYPOTHESIS: Determine the role of mastoid volume in middle ear pressure (MEP) regulation. The hypothesis was that inert gas exchange between blood and middle ear (ME) is slower for larger mastoid volumes.
Prospective.
For 21 enrolled subjects, the bilateral surface areas and volumes of the mastoid and tympanum were measured from computed tomography scans in 20 subjects with a wide range of mastoid volumes. Then, 19 subjects were reclined in a chair, fitted with a non-rebreathing mask and breathed room air for 20 minutes (acclimation), a gas composition of 25% N(2)O, 20% O(2), balance N(2) for 30 minutes (experiment), and room air for 30 minutes (recovery). Bilateral MEPs were recorded by tympanometry every 2 minutes. The slopes of the MEP-time functions during N(2)O breathing were calculated to the first observation of eustachian tube opening and divided by the estimated blood-ME N(2)O gradient to yield a N(2)O time constant. Sufficient data were available for 16 right and 11 left MEs to calculate the time constant.
MEP did not change during the baseline period, but within 10 minutes of breathing the N(2)O mixture showed a progressive increase. The right-left correlation for the time constant was 0.87 (n = 10 ears, P = .001). Regression of the time constants on ME volume showed an inverse relationship (n = 23 ears, r = -41, P = .05). A better data fit was the curvilinear relationship predicted by a mathematical model of the mastoid acting as a ME ear gas reserve.
These results support the tested hypothesis that the mastoid could serve as ME gas reserve.
目的/假设：确定乳突体积在中耳压力（MEP）调节中的作用。假设是，对于较大的乳突体积，血液和中耳（ME）之间的惰性气体交换较慢。
前瞻性。
在 20 名具有广泛乳突体积的受试者的计算机断层扫描中，测量了 21 名受试者的双侧乳突和鼓膜的表面积和体积。然后，19 名受试者斜靠在椅子上，戴上非重复呼吸面罩，呼吸 20 分钟（适应期），然后呼吸 30 分钟的 25%N（2）O、20%O（2）、平衡 N（2）（实验期），最后呼吸 30 分钟的室内空气（恢复期）。通过鼓室压测量法每隔 2 分钟记录双侧 MEP。计算 N（2）O 呼吸期间 MEP-时间函数的斜率，直到观察到咽鼓管开放的第一次观察，并将其除以估计的血液-ME N（2）O 梯度，以获得 N（2）O 时间常数。有足够的数据可用于计算 16 个右侧和 11 个左侧 ME 的时间常数。
MEP 在基线期间没有变化，但在呼吸 N（2）O 混合物的 10 分钟内显示出逐渐增加。时间常数的左右相关性为 0.87（n = 10 只耳朵，P =.001）。时间常数与 ME 体积的回归显示出反比关系（n = 23 只耳朵，r = -41，P =.05）。更好的数据拟合是由乳突作为 ME 耳气体储备的数学模型预测的曲线关系。
这些结果支持了经过测试的假设，即乳突可以作为 ME 气体储备。
