Physiological Role of Intracardiac Shunting in Chelonians

海龟表现出间歇性的排泄模式， 通气周期中穿插着各种呼吸暂停， 持续时间 与这种解释模式相关的是循环的 肺和全身血流的变化。 解剖结构导致 这些血流的变化可能与 从右到左（R-L;肺旁路）和从左到右（L-R; 肺再循环）心内分流。 这些 心血管变化可影响肺气体交换， 影响CO2和O2的运输。 的功能意义 心内分流的可能性仍然是推测性的 这 这项研究将确定心内 海龟在间歇性通风时的分流。 具体 该研究将确定：1）肺动脉和肺动脉之间的流量比， 和全身回路（即R-L和L-R分流） 和呼吸暂停和2）胆碱能和肾上腺素能阻滞的影响 心内分流的方向和大小， 这些影响与呼吸模式、肺气体 交换和血气运输。 研究将在 在25 ℃条件下对拟龟进行活体实验。 所有目标 将在长期装备的自由潜水中完成， 自发换气的动物 的连续测量 肺和体循环血流量，通气，气体交换，肺 气体和血液气体将被制造。 将对结果进行分析 在当前几种假设的背景下， 心内分流的呼吸“益处”。 的假设 提出的不一定是新颖的，然而，实验 本提案中概述的将首次具体 检查这种独特类型的功能意义 心血管调节

Turtles exhibit intermittent ventilatory patterns in which brief periods of ventilation are interspersed with apneas of variable duration. Associated with this ventilatory pattern are cyclic changes in pulmonary and systemic blood flow. Due to the anatomy of the heart, these changes in blood flow may be associated with both right-to-left (R-L; pulmonary bypass) and left-to-right (L-R; pulmonary recirculation) intracardiac shunting. These cardiovascular changes can influence pulmonary gas exchange, affecting both CO2 and O2 transport. The functional significance of intracardiac shunting has remained primarily speculative. This study will determine the physiological role of intracardiac shunting during intermittent ventilation in turtles. Specifically the study will determine; 1) the flow ratios between the pulmonary and systemic circuits (i.e. R-L and L-R shunts) during ventilation and apnea and 2) the effects of cholinergic and adrenergic blockade on the direction and magnitude of intracardiac shunt and correlate these effects with changes in ventilatory patterns, pulmonary gas exchanged and blood gas transport. Studies will be conducted in the turtle, Pseudemys scripta, in vivo at 25oC. All objectives will be accomplished in chronically instrumented, freely diving, spontaneously ventilating animals. Continuous measurements of pulmonary and systemic blood flows, ventilation, gas exchange, lung gases and blood gases will be made. The results will be analyzed within the context of several current hypotheses addressing the respiratory "benefits" of intracardiac shunting. The hypotheses presented are not necessarily novel, however, the experiments outlined in this proposal will for the first time specifically examine the functional significance of this distinctive type of cardiovascular regulation.