低于麻醉浓度的异氟烷最低肺泡浓度对低氧通气反应两项测试的影响。

Temp J A, Henson L C, Ward D S

Department of Anesthesiology, University of Rochester School of Medicine, New York 14642.

Anesthesiology. 1994 Apr;80(4):739-50. doi: 10.1097/00000542-199404000-00005.

BACKGROUND

These experiments were designed to study the effect of 0.1 minimum alveolar concentration isoflurane on the hypoxic ventilatory response as measured by two common methods of hypoxic testing: when normocapnic hypoxia was induced abruptly and when it was induced gradually. We hypothesized that any disparity in results would be due to an isoflurane effect that was manifested differently in the two tests.

METHODS

After 20 min for uptake and equilibration of 0.1 minimum alveolar concentration end-tidal isoflurane or carrier gas in hyperoxia, isocapnic hypoxia was induced either abruptly over 60-80 s ("step" test) or gradually over 10 min ("ramp" test), followed by 20 min of isocapnic hypoxia at 45 mmHg end-tidal oxygen. Control of the hypoxic and isocapnic stimuli was accomplished accurately by a computer-controlled dynamic end-tidal forcing system. Eight subjects performed each test in the presence and absence of isoflurane.

RESULTS

For both step tests and ramp tests, 0.1 minimum alveolar concentration isoflurane had no effect on minute ventilation during the defined periods of hypoxia. With isoflurane, delta VE45, the acute change in ventilation from hyperoxia to hypoxia, was 97 +/- 20% (mean +/- SEM) of the control response for step tests and 100 +/- 25% of the control response for ramp tests. The step tests produced significantly larger acute hypoxic responses than did the ramp tests, but by the end of 20 min of hypoxia, ventilation was similar for both tests.

CONCLUSIONS

Neither method of hypoxic testing demonstrated the level of isoflurane effect reported by others. A comparison of the two methods of hypoxic testing suggests that ramp tests, as commonly performed, do not allow adequate time for full expression of the acute hypoxic ventilatory response. Step tests also better separated the opposing hypoxic effects of carotid body stimulation and central ventilatory depression.

背景

这些实验旨在研究0.1最低肺泡浓度异氟烷对低氧通气反应的影响，该影响通过两种常见的低氧测试方法来衡量：即突然诱导正常碳酸血症性低氧和逐渐诱导正常碳酸血症性低氧时的情况。我们假设，结果的任何差异都将归因于异氟烷效应，该效应在两种测试中表现不同。

方法

在高氧环境中，待0.1最低肺泡浓度的呼气末异氟烷或载气摄取并平衡20分钟后，通过在60 - 80秒内突然诱导（“阶梯”测试）或在10分钟内逐渐诱导（“斜坡”测试）产生等碳酸血症性低氧，随后在呼气末氧分压为45 mmHg的情况下进行20分钟的等碳酸血症性低氧。通过计算机控制的动态呼气末强制系统精确控制低氧和等碳酸血症刺激。8名受试者在有和没有异氟烷的情况下分别进行每种测试。

结果

对于阶梯测试和斜坡测试，在规定的低氧期内，0.1最低肺泡浓度的异氟烷对分钟通气量均无影响。使用异氟烷时，从高氧到低氧时通气的急性变化ΔVE45，在阶梯测试中为对照反应的97±20%（平均值±标准误），在斜坡测试中为对照反应的100±25%。阶梯测试产生的急性低氧反应明显大于斜坡测试，但在低氧20分钟结束时，两种测试的通气情况相似。