Katsuya H, Sakanashi Y
Division of Emergency Medicine, Kumamoto University Hospital, Kumamoto University School of Medicine, Japan.
J Clin Monit. 1989 Apr;5(2):82-6. doi: 10.1007/BF01617878.
We postulated that the fractional inspired oxygen concentration (FIO2) required to achieve a certain value of arterial oxygen saturation (SaO2) can be used as an indicator of pulmonary gas exchange impairment in patients during mechanical ventilation. We tested this hypothesis in 20 patients. By reducing FIO2 in increments of 10 vol% of capacity while monitoring SaO2 with pulse oximetry, we could determine FI98, FI97, FI96, and FI95; that is, the FIO2 that yields 98, 97, 96, and 95% SaO2, respectively. On the basis of our data, we chose FI98 as the most appropriate index, as an SaO2 of 97% or below could not be achieved even with a low FIO2 in some of the patients. To test the significance of the newly proposed index, we compared FI98 with the alveolar-arterial oxygen tension difference, P(A - a)O2, and with the respiratory index, which are routinely used elsewhere. The correlation between FI98 and P(A - a)O2 was excellent: P(A - a)O2 = 490.5 * FI98 + 117.2 with a correlation coefficient of 0.906 (P less than 0.01). FI98 also correlated significantly with the respiratory index: respiratory index = 4.354 * FI98 - 0.776 (r = 0.889, P less than 0.01). We conclude that FI98 may be used as a simple index for the rough estimation of pulmonary gas exchange impairment without the need for invasive procedures. However, further studies are needed to confirm the validity of our method in hemodynamically unstable patients or when other brands of pulse oximeters are used.
我们推测，在机械通气过程中，达到一定动脉血氧饱和度（SaO2）值所需的吸入氧分数（FIO2）可作为患者肺气体交换受损的指标。我们在20名患者中验证了这一假设。通过以容量的10%为增量逐步降低FIO2，同时用脉搏血氧仪监测SaO2，我们可以确定FI98、FI97、FI96和FI95；即分别产生98%、97%、96%和95% SaO2的FIO2。根据我们的数据，我们选择FI98作为最合适的指标，因为在一些患者中，即使使用低FIO2也无法达到97%或更低的SaO2。为了检验新提出指标的意义，我们将FI98与常规在其他地方使用的肺泡-动脉氧分压差P(A - a)O2以及呼吸指数进行了比较。FI98与P(A - a)O2之间的相关性极佳：P(A - a)O2 = 490.5 * FI98 + 117.2，相关系数为0.906（P小于0.01）。FI98与呼吸指数也显著相关：呼吸指数 = 4.354 * FI98 - 0.776（r = 0.889，P小于0.01）。我们得出结论，FI98可作为一种简单指标，用于粗略估计肺气体交换受损情况，而无需进行侵入性操作。然而，需要进一步研究以证实我们的方法在血流动力学不稳定患者或使用其他品牌脉搏血氧仪时的有效性。
