McNab Brian K
Department of Zoology, University of Florida, Gainesville, FL 32611, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2006 Nov;145(3):287-94. doi: 10.1016/j.cbpa.2006.02.024. Epub 2006 Feb 28.
A relationship exists among the calculated rate of metabolism of an animal enclosed in a chamber, chamber volume and air flow rate. A "critical" flow rate, defined as the minimal flow rate that produces a complete mixture of chamber gases, characterizes each chamber/animal combination. At flow rates below the critical flow rate, calculated rates of metabolism decrease with flow rate and approach zero as flow rate approaches zero. These calculated rates are unreliable estimates of rate of metabolism. At flow rates greater than the critical flow rate, calculated rates of metabolism are independent of flow rate because a reciprocal relationship exists between flow rate and the differential in oxygen content found between the air entering and exiting the chamber; they represent an accurate estimate of the animal's rate of metabolism under the conditions to which the animal is exposed. The critical flow rate increases with chamber volume, the animal's rate of metabolism and with any factor that increases rate of metabolism, including body mass, activity and in endotherms ambient temperatures below thermoneutrality, although chamber volume is its single most important determinant. Some evasions of the critical flow rate are discussed.
封闭在一个腔室内的动物的计算代谢率、腔室体积和气流速率之间存在一种关系。“临界”流速被定义为产生腔室气体完全混合的最小流速，它表征了每个腔室/动物组合的特征。在低于临界流速的情况下，计算出的代谢率随流速降低，并在流速接近零时趋近于零。这些计算出的速率是不可靠的代谢率估计值。在高于临界流速的情况下，计算出的代谢率与流速无关，因为流速与进入和离开腔室的空气中发现的氧含量差异之间存在反比关系；它们代表了动物在其所处条件下代谢率的准确估计值。临界流速随腔室体积、动物的代谢率以及任何增加代谢率的因素而增加，这些因素包括体重、活动以及在恒温动物中低于热中性的环境温度，尽管腔室体积是其最重要的单一决定因素。文中还讨论了一些对临界流速的规避情况。
