Shams H, Powell F L, Hempleman S C
Department of Medicine, University of California, San Diego, La Jolla.
Respir Physiol. 1990 May-Jun;80(2-3):163-70. doi: 10.1016/0034-5687(90)90080-i.
We measured ventilation (V1) and arterial blood gases in awake Pekin ducks exposed to normoxia at sea level, normobaric hypoxia achieved by lowering FIO2 at normal barometric pressure (NORMO), and hypobaric hypoxia achieved with a low pressure chamber and 21% O2 (HYPO). Average normoxic values were: V1 = 0.46 L . (kg.min)-1, PaO2 = 99.7 Torr, PaCO2 = 30.1 Torr. At PIO2 = 90 Torr, NORMO and HYPO measurements were not significantly different (P greater than 0.05). At PO2 = 46 Torr, NORMO V1 was less than HYPO V1 but blood gases were not significantly different: VI = 1.00 vs 1.45 L . (kg.min)-1; PaO2 = 31.3 vs 33.0 Torr; PaCO2 = 11.5 vs 10.6 Torr. Although both tidal volume (VT) and respiratory frequency (fR) were greater in HYPO, similar blood gases with NORMO and HYPO suggest similar parabronchial ventilation. The results suggest increased physiologic dead space, caused by reduced efficacy of aerodynamic valving, with reduced gas density in hypobaria.
我们在清醒的北京鸭中测量了通气量（V1）和动脉血气，这些鸭子分别暴露于海平面常氧环境、通过在正常气压下降低吸入氧分数（FIO2）实现的常压低氧环境（NORMO）以及使用低压舱和21%氧气实现的低压低氧环境（HYPO）。常氧环境下的平均测量值为：V1 = 0.46 L·(kg·min)-1，动脉血氧分压（PaO2）= 99.7 Torr，动脉血二氧化碳分压（PaCO2）= 30.1 Torr。在吸入氧分压（PIO2）= 90 Torr时，NORMO组和HYPO组的测量结果无显著差异（P大于0.05）。在氧分压（PO2）= 46 Torr时，NORMO组的V1低于HYPO组，但血气无显著差异：V1分别为1.00和1.45 L·(kg·min)-1；PaO2分别为31.3和33.0 Torr；PaCO2分别为11.5和10.6 Torr。尽管HYPO组的潮气量（VT）和呼吸频率（fR）均更高，但NORMO组和HYPO组相似的血气结果表明支气管旁通气相似。结果表明，在低压环境中，由于气体密度降低导致气动瓣膜效率降低，生理无效腔增加。
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