栗鼠鼓膜的气体扩散：反复穿孔的影响

Gas diffusion across the tympanic membrane in chinchillas: effect of repeated perforations.

作者信息

Felding Ulrik N, Banks Juliane M, Doyle William J

机构信息

Department of Pediatric Otolaryngology, Children's Hospital of Pittsburgh, Pittsburgh, PA, USA.

出版信息

Auris Nasus Larynx. 2004 Dec;31(4):353-9. doi: 10.1016/j.anl.2004.07.006.

DOI:10.1016/j.anl.2004.07.006

PMID:15571907

Abstract

OBJECTIVE

Earlier studies documented a slow diffusion of gas across the tympanic membrane (TM) in humans and animals. However, structural changes caused by repeated TM perforations could affect gas diffusion rates. This possibility was evaluated using a chinchilla model.

METHODS

In six chinchillas, the right TM was perforated four times at 2-week intervals; the left TM served as a control. Approximately 12 weeks after the fourth perforation and when the right TMs had healed, a probe was introduced into the external canal and sealed to the environment. For 120 min, pressure in the probe was continuously monitored and probe gas was sampled at 10 min intervals and analyzed for composition by online mass spectrometry. Percent compositions for CO(2) and O(2) were calculated and these data were recast as partial-pressure versus time functions. The information contained in those functions was used to estimate time-constants for transTM O(2) and CO(2) diffusion.

RESULTS

In all experiments, CO(2) percent composition in the probe increased as a curvilinear function of time while that for O(2) decreased linearly. For all animals and both gases, the rate of change in probe partial-pressure was greater for the right TM. Average values of the right and left time-constants were (6.7 +/- 2.4) x 10(-3) and (4.2 +/- 2.2) x 10(-3)min(-1)TM(-1) for CO(2), and (2.3 +/- 0.8) x 10(-3) and (1.5 +/- 0.5) x 10(-3)min(-1)TM(-1) for O(2). Between side differences in these time-constants were statistically significant (P < 0.05, 2-tailed, paired, Student's t-test). The average right/left, transTM time-constant ratio was 1.66 +/- 0.43 for CO(2) and 1.61 +/- 43 for O(2); both were significantly different from a value of 1.0 (P < 0.05, 2-tailed Student's t-test).

CONCLUSION

These results document an increased rate of diffusive gas exchange across TMs that had been repeatedly perforated. This effect may be caused by structural thinning secondary to scar formation and could have implications for middle ear pressure regulation in ears with a history of repeated myringotomies and/or tympanostomy tube insertions.

摘要

目的

早期研究记录了气体在人类和动物鼓膜（TM）上的缓慢扩散。然而，反复鼓膜穿孔引起的结构变化可能会影响气体扩散速率。本研究使用龙猫模型评估了这种可能性。

方法

选取6只龙猫，右侧鼓膜每隔2周穿孔4次；左侧鼓膜作为对照。在第4次穿孔后约12周且右侧鼓膜愈合时，将一根探针插入外耳道并密封与外界环境隔绝。持续监测探针内压力120分钟，每隔10分钟采集探针内气体样本，并通过在线质谱分析其成分。计算二氧化碳（CO₂）和氧气（O₂）的百分比组成，并将这些数据重新整理为分压与时间的函数关系。利用这些函数中的信息来估算经鼓膜的氧气和二氧化碳扩散的时间常数。

结果

在所有实验中，探针内二氧化碳的百分比组成随时间呈曲线函数增加，而氧气的百分比组成呈线性下降。对于所有动物和两种气体，右侧鼓膜的探针分压变化率均更大。右侧和左侧二氧化碳时间常数的平均值分别为（6.7±2.4）×10⁻³和（4.2±2.2）×10⁻³分钟⁻¹鼓膜⁻¹，氧气时间常数的平均值分别为（2.3±0.8）×10⁻³和（1.5±0.5）×10⁻³分钟⁻¹鼓膜⁻¹。这些时间常数的两侧差异具有统计学意义（P<0.05，双侧，配对，学生t检验）。二氧化碳的平均右侧/左侧经鼓膜时间常数比值为1.66±0.43，氧气为1.61±0.43；两者均与1.0有显著差异（P<0.05，双侧学生t检验）。