Fernando S S, Saunders K B
Department of Medicine, St. George's Hospital Medical School, London, UK.
Respir Physiol. 1995 Feb;99(2):205-14. doi: 10.1016/0034-5687(94)00089-i.
We used single inspiratory capacity breaths of 5, 6 or 8% CO2 in air to obtain ventilatory responses in normal subjects, with ensemble averaging of repeated runs to define stimulus and response (Protocol 1). We also compared the effect of an inspiratory capacity (IC) breath of 8% CO2 with that of two tidal volumes (TV) at the same concentration (Protocol 2). The ventilatory response was defined first as the ratio of peak changes in ventilation and end-tidal PCO2, and secondly by the ratio of their integrals. We obtained group mean values of 0.21 L min-1 mmHg-1 for the peak method and 0.80 L min-1 mmHg-1 for integrals (Protocol 1). There was no significant difference between IC and TV response values (Protocol 2) either by the peak method (0.17 vs 0.19 L min-1 mmHg-1) or by integrals (0.47 vs 0.53 L min-1 mmHg-1). A significant decrease in ventilation was seen in the second tidal volume 8% CO2 breath, even though the stimulus was unperceived by four out of five subjects. CO2 responses can be obtained from these techniques, but the necessary analysis is too cumbersome for general use. Taking a deep breath had no detectable separate effect, but CO2 in the airway may depress ventilation even at concentrations which the subject cannot detect.
我们采用在空气中含5%、6%或8%二氧化碳的单次吸气容量呼吸，来获取正常受试者的通气反应，并对重复测试结果进行总体平均以确定刺激因素和反应（方案1）。我们还比较了8%二氧化碳的吸气容量（IC）呼吸与相同浓度下两个潮气量（TV）呼吸的效果（方案2）。通气反应首先定义为通气量峰值变化与呼气末二氧化碳分压的比值，其次定义为它们积分的比值。通过峰值法，我们得到的组均值为0.21 L·min⁻¹·mmHg⁻¹，通过积分法得到的组均值为0.80 L·min⁻¹·mmHg⁻¹（方案1）。无论是通过峰值法（0.17对0.19 L·min⁻¹·mmHg⁻¹）还是积分法（0.47对0.53 L·min⁻¹·mmHg⁻¹），IC和TV反应值之间均无显著差异（方案2）。在第二次8%二氧化碳潮气量呼吸时，尽管五名受试者中有四名未察觉到刺激，但通气量仍出现了显著下降。可以从这些技术中获得二氧化碳反应，但所需的分析过于繁琐，不适合普遍使用。进行深呼吸未发现有可检测到的单独影响，但气道中的二氧化碳即使在受试者无法察觉的浓度下也可能抑制通气。
