Ohale L O, Ghoshal N G
Am J Vet Res. 1982 Apr;43(4):633-8.
Ten Rambouillet ewes (2 groups of 5 each) were surgically implanted with a reversible tracheal bypass cannula constructed so that the sheep could breathe normally through the nostrils when the flow-through insert was in place or through the tracheal opening when the bypass insert was adjusted. In 1 group, an electroretinogram recorded an increased amplitude and decreased duration of the b wave during bypassed breathing. When the ewes were allowed to breathe simultaneously through the tracheal opening and nostrils, the b-wave amplitude was decreased, compared with the amplitude during normal nasal breathing alone. Several recordings for individual breathing phases were consistent for each animal. In the 2nd group, arterial blood gas analysis showed no differences in the partial pressures (PCO2 and PO2) during both breathing phases. Seemingly, functional elimination of the upper respiratory cooling of venous blood influences the heat exchange in the ophthalmic plexus and cavernous sinus, resulting in relatively warmer blood reaching the eye.
十只兰布耶母羊（每组5只，共两组）通过手术植入了一个可逆的气管旁路插管，该插管的构造使得绵羊在通气插入物就位时能够通过鼻孔正常呼吸，或者在旁路插入物调整后通过气管开口呼吸。在一组中，视网膜电图记录显示，在旁路呼吸期间，b波的振幅增加，持续时间缩短。当母羊被允许同时通过气管开口和鼻孔呼吸时，与仅通过正常鼻腔呼吸时的振幅相比，b波振幅降低。每只动物的几个个体呼吸阶段的记录都是一致的。在第二组中，动脉血气分析显示两个呼吸阶段的分压（PCO2和PO2）没有差异。显然，上呼吸道对静脉血冷却功能的消除会影响眼丛和海绵窦中的热交换，导致相对较热的血液到达眼睛。
