Magnussen H, Willmer H, Scheid P
Respir Physiol. 1976 Feb;26(1):129-46. doi: 10.1016/0034-5687(76)90057-8.
Air sac gas exchange was studied in ducks by measuring the rates of inert gas uptake and of O2 and CO2 equilibration in caudal thoracic air sac whose ventilation was prevented by surgival sealing of the ostia. The data were analyzed on a model incorporating three possible routes by which air sac gas could be exchanged with the surrounding tissue: (1) into the blood perfusing the air sac walls; (2) into the adjoining air sac via tissue membranes; (3) into the bronchial system of the lung via diffusion through lung tissue bordering upon the caudal thoracic air sac. Exchange rates of gases via the two latter paths were found to be small as compared with the first route. From application of model parameters to O2 and CO2 exchange in air sacs under physiological conditions the following conclusions were drawn: (1) the caudal thoracic air sac makes the major contribution to total gas exchange between air sacs and blood; (2) this exchange can account for less than 5% of total respiratory gas exchange; (3) the exchange is too small to account for the O2 and CO2 partial pressures in caudal thoracic air sacs of ducks. Other mechanisms like gas exchange in neopulmonic parabronchi, which conduct air to the caudal air sacs during inspiration or re-inspiration of dead space appear to play a more significant role in the deviation of O2 and CO2 partial pressures in the caudal air sacs from those in inspired air.
通过测量尾段胸气囊中惰性气体摄取率以及氧气和二氧化碳平衡率，对鸭的气囊气体交换进行了研究。该尾段胸气囊的通气通过手术封闭开口来阻止。数据在一个模型上进行分析，该模型包含气囊气体与周围组织进行交换的三种可能途径：（1）进入灌注气囊壁的血液；（2）通过组织膜进入相邻的气囊；（3）通过与尾段胸气囊相邻的肺组织扩散进入肺的支气管系统。与第一种途径相比，发现通过后两种途径的气体交换速率较小。根据将模型参数应用于生理条件下气囊中的氧气和二氧化碳交换，得出以下结论：（1）尾段胸气囊对气囊与血液之间的总气体交换起主要作用；（2）这种交换占总呼吸气体交换的比例不到5%；（3）这种交换太小，无法解释鸭尾段胸气囊中的氧气和二氧化碳分压。其他机制，如新肺副支气管中的气体交换，在吸气或死腔再吸气期间将空气输送到尾气囊，似乎在尾气囊中氧气和二氧化碳分压与吸入空气中的分压偏差中起更重要的作用。
