Mover-Lev H, Levy D, Luntz M, Harell M, Ar A, Sadé J
Department of Bioengineering, Sackler School of Medicine, Tel Aviv University, Israel.
Ann Otol Rhinol Laryngol. 1997 Apr;106(4):314-9. doi: 10.1177/000348949710600410.
The middle ear (ME) steady state gas composition resembles that of mixed venous blood. We changed arterial and venous blood gases by artificially ventilating anesthetized guinea pigs and measured simultaneous ME gas changes during spontaneous breathing, hyperventilation, and hypoventilation. During hyperventilation, PaCO2 and PvCO2 (a = arterial, v = venous) decreased from 46.0 and 53.0 mm Hg to 17.9 and 37.5 mm Hg, respectively, while PaO2 and PvO2 (85.6 and 38.2 mm Hg) did not change. This was accompanied by an ME PCO2 decrease from 70.4 to 58.8 mm Hg and a PO2 decrease from 36.8 to 25.4 mm Hg. During hypoventilation, PaCO2 and PvCO2 increased to 56.8 and 66.4 mm Hg, while PvO2 decreased to 21.8 mm Hg. The ME PCO2 increased simultaneously to 88.8 mm Hg and the ME PO2 decreased to 25.4 mm Hg. The ME PO2 decrease during hyperventilation may be explained by a 33% decrease in ME mucosa perfusion, calculated from the ME ventilation-perfusion ratio. This study shows that ME gas composition follows fluctuations of blood gas levels and thus may affect total ME pressure.
中耳（ME）的稳态气体成分与混合静脉血相似。我们通过人工通气麻醉的豚鼠来改变动脉血和静脉血的气体成分，并在自发呼吸、过度通气和通气不足期间测量中耳气体的同步变化。过度通气期间，动脉血二氧化碳分压（PaCO2）和静脉血二氧化碳分压（PvCO2）（a = 动脉，v = 静脉）分别从46.0和53.0 mmHg降至17.9和37.5 mmHg，而动脉血氧分压（PaO2）和静脉血氧分压（PvO2）（85.6和38.2 mmHg）未发生变化。与此同时，中耳二氧化碳分压从70.4 mmHg降至58.8 mmHg，氧分压从36.8 mmHg降至25.4 mmHg。通气不足期间，PaCO2和PvCO2分别升至56.8和66.4 mmHg，而PvO2降至21.8 mmHg。中耳二氧化碳分压同时升至88.8 mmHg，中耳氧分压降至25.4 mmHg。过度通气期间中耳氧分压的降低可能是由于根据中耳通气-灌注比计算得出的中耳黏膜灌注减少了33%。本研究表明，中耳气体成分随血气水平的波动而变化，因此可能影响中耳总压力。
