Ivy Catherine M, Scott Graham R
Department of Biology, McMaster University, Hamilton, ON, Canada.
Department of Biology, McMaster University, Hamilton, ON, Canada.
Respir Physiol Neurobiol. 2017 Jan;235:95-103. doi: 10.1016/j.resp.2016.10.012. Epub 2016 Oct 29.
We examined ventilatory acclimatization to hypoxia (VAH) in CD1 mice, and contrasted results obtained using the barometric method on unrestrained mice with pneumotachography and pulse oximetry on restrained mice. Responses to progressive step reductions in O fraction (21%-8%) were assessed in mice acclimated to normoxia and hypobaric hypoxia (barometric pressure of 60kPa for 6-8 weeks). Hypoxia acclimation increased the hypoxic ventilatory response (primarily by increasing breathing frequency rather than tidal volume), arterial O saturation (Sa) and heart rate in deep hypoxia, hypoxic chemosensitivity (ventilatory O/CO equivalents versus Sa), and respiratory water loss, and it blunted the hypoxic depression of metabolism and body temperature. Although some effects of hypoxia acclimation were qualitatively similar between methods, the effects were often greater in magnitude when assessed using pneumotachography. Furthermore, whereas hypoxia acclimation reduced ventilatory O equivalent and increased pulmonary O extraction in barometric experiments, it had the opposite effects in pneumotachography experiments. Our findings highlight the importance of considering the impact of how breathing is measured on the apparent responses to hypoxia.
我们研究了CD1小鼠对低氧的通气适应（VAH），并对比了对自由活动小鼠采用气压法以及对束缚小鼠采用呼吸流速描记法和脉搏血氧测定法所获得的结果。在适应常氧和低压低氧（气压60kPa，持续6 - 8周）的小鼠中，评估其对氧分压逐步阶梯式降低（从21%降至8%）的反应。低氧适应增加了低氧通气反应（主要通过增加呼吸频率而非潮气量）、动脉血氧饱和度（Sa）以及深度低氧时的心率、低氧化学敏感性（通气氧/二氧化碳当量与Sa的关系）和呼吸失水量，并且减弱了低氧对代谢和体温的抑制作用。虽然两种方法所得的低氧适应的某些效应在性质上相似，但采用呼吸流速描记法评估时，效应的程度往往更大。此外，在气压实验中，低氧适应降低了通气氧当量并增加了肺氧摄取，而在呼吸流速描记法实验中则产生相反的效应。我们的研究结果凸显了考虑呼吸测量方式对低氧表观反应影响的重要性。
