Rodriguez M N, Art T, Rollin F, Desmecht D, Amory H, Linden A, Lekeux P
Laboratory for Functional Investigation, Faculty of Veterinary Medicine, University of Liege, Brussels, Belgium.
Zentralbl Veterinarmed A. 1990 May;37(4):241-6. doi: 10.1111/j.1439-0442.1990.tb00900.x.
The mechanics of breathing was investigated in six healthy calves breathing either air or a mixture of 79% helium and 21% oxygen (He-O2). Intrapleural pressure (Ppl) was measured with an esophageal balloon catheter and transpulmonary pressure was obtained by subtracting the mouth pressure (Pm) from Ppl. Respiratory airflow (V) was measured using a Fleisch pneumotachograph N degrees 3 and tidal volume (Vt) was electronically derived by integrating V with respect to time. Respiratory airflow, Vt, Ppl and Pm were simultaneously recorded while the calves breathed first air (1 min), secondly He-O2 (1 min) and finally air again (1 min). The pulmonary function values were calculated on the tracings and the He-O2 values were compared to the corresponding "air" values. The ventilatory response to resistance unloading was characterized by a significant increase in minute volume exclusively due to an increase in respiratory frequency, while Vt remained unchanged. A decrease of 32% in the total pulmonary resistance (RL) and 16% in the work per litre of ventilation (Wrm/l) were observed when calves breathed He-O2. The effect of the He-O2 on RL and on Wrm/l suggests that, in the bovine species, airflow turbulances in the upper part of the respiratory tract play a significant role in the total airways resistance.
对六头健康小牛进行了呼吸力学研究，这些小牛呼吸的气体为空气或79%氦气和21%氧气的混合气体（氦氧混合气）。使用食管气囊导管测量胸膜腔内压（Ppl），通过从Ppl中减去口腔压力（Pm）来获得跨肺压。使用3号弗莱施呼吸流速计测量呼吸气流（V），并通过对V关于时间进行积分以电子方式得出潮气量（Vt）。在小牛先呼吸空气（1分钟）、接着呼吸氦氧混合气（1分钟）、最后再呼吸空气（1分钟）的过程中，同时记录呼吸气流、Vt、Ppl和Pm。根据记录计算肺功能值，并将氦氧混合气状态下的值与相应的“空气”状态下的值进行比较。对阻力卸载的通气反应表现为分钟通气量显著增加，这完全是由于呼吸频率增加所致，而Vt保持不变。当小牛呼吸氦氧混合气时，观察到总肺阻力（RL）降低了32%，每升通气功（Wrm/l）降低了16%。氦氧混合气对RL和Wrm/l的影响表明，在牛这一物种中，呼吸道上部的气流湍流在总气道阻力中起重要作用。
