Interaction of Ventilation and Perfusion with Diffusion in Cutaneous Gas Exchange

这项拟议的研究将继续进行脊椎动物皮肤气体交换的持续分析，以及可能对其进行调节的方法。一个关键的问题涉及血液流动变化在调节皮肤气体交换方面的有效性；这个问题的解决需要在微循环水平上精确区分大量流向皮肤的血液变化的表现方式。皮肤微循环的变化，(2)管状红细胞压积，(3)毛细血管重新聚集，(4)重新聚集的毛细血管的间距，和/或(5)在1-4中的空间和时间的异质性。这五个变量将首先在隔离的灌流皮肤制剂中测量摄氧量时被量化；这项准备将提供关于这五个变量的实验变化如何与皮肤气体交换的大小相关的信息。一项补充性研究将在体内表征这五个变量，以确定它们在完整动物中的实际变化。另一个关键问题涉及皮肤在水中的扩散边界层的阻力：它们的阻力是很大、可以忽略不计，还是介于两者之间？第二个系列的实验将直接检验氧气扩散边界层可能在多大程度上限制与不同流动状态的动物的皮肤气体交换。在实验准备中，皮肤和氧气扩散边界层的绝对和相对阻力将被量化。这些问题很重要，因为尽管皮肤是脊椎动物的主要气体交换之一，但我们对皮肤气体交换的了解还太粗略，无法对脊椎动物的气体交换有一个全面和全面的了解。

The proposed research will continue an ongoing analysis of cutaneous gas exchange in vertebrates and the means by which it may be regulated. One critical question concerns how effective changes in blood flow can be in regulating cutaneous gas exchange; resolution of this question requires a precise distinction among the ways in which changes in bulk blood flow to the skin might be manifested at the microcirculatory level. Variation in cutaneous microcirculation, (2) tube hematocrit, (3), capillary recruitment, (4) the spacing of recruited capillaries, and/or (5) spatial and temporal heterogeneity in 1- 4. These five variables will first be quantified while oxygen uptake is measured in an isolated perfused skin preparation; this preparation will yield information on how experimental variation in these five variables is related to the magnitude of cutaneous gas exchange. A complementary study will characterize the five variables in vivo to determine how they actually vary in an intact animal. Another critical question concerns the resistance of diffusion boundary layers about skin in water: Is their resistance large, negligible, or somewhere in between? A second series of experiments will directly examine the extent to which oxygen diffusion boundary layers may limit cutaneous gas exchange with animals of different flow regimes. In an experimental preparation, the absolute and relative resistances of the skin and the oxygen diffusion boundary layer will be quantified. These issues are important ones because, although skin is one of the primary gas exchangers of vertebrates, our knowledge of cutaneous gas exchange is as yet too sketchy to achieve a general and comprehensive understanding of vertebrate gas exchange.