Thomsen Lars P, Weinreich Ulla M, Karbing Dan S, Wagner Peter D, Rees Stephen E
Respiratory and Critical Care Group, Department of Health Science and Technology, Center for Model-based Medical Decision Support, Aalborg University, Fredrik Bajers Vej 7E, 9220, Aalborg, Denmark,
J Clin Monit Comput. 2014 Dec;28(6):547-58. doi: 10.1007/s10877-014-9622-2. Epub 2014 Oct 2.
Bedside estimation of pulmonary gas exchange efficiency may be possible from step changes in FIO2 and subsequent measurement of arterial oxygenation at steady state conditions. However, a steady state may not be achieved quickly after a change in FIO2, especially in patients with lung disease such as COPD, rendering this approach cumbersome. This paper investigates whether breath by breath measurement of respiratory gas and arterial oxygen levels as FIO2 is changed can be used as a much more rapid alternative to collecting data from steady state conditions for measuring pulmonary gas exchange efficiency. Fourteen patients with COPD were studied using 4-5 step changes in FIO2 in the range of 0.15-0.35. Values of expired respiratory gas and arterial oxygenation were used to calculate and compare the parameters of a mathematical model of pulmonary gas exchange in two cases: from data at steady state; and from breath by breath data prior to achievement of a steady state. For each patient, the breath by breath data were corrected for the delay in arterial oxygen saturation changes following each change in FIO2. Calculated model parameters were shown to be similar for the two data sets, with Bland-Altman bias and limits of agreement of -0.4 and -3.0 to 2.2 % for calculation of pulmonary shunt and 0.17 and -0.47 to 0.81 kPa for alveolar to end-capillary PO2, a measure of oxygen abnormality due to shunting plus regions of low [Formula: see text] A/[Formula: see text] ratio. This study shows that steady state oxygen levels may not be necessary when estimating pulmonary gas exchange using changes in FIO2. As such this technique may be applicable in patients with lung disease such as COPD.
在吸入氧分数（FIO₂）发生阶跃变化并随后在稳态条件下测量动脉氧合的情况下，有可能在床边评估肺气体交换效率。然而，FIO₂改变后可能无法迅速达到稳态，尤其是在患有慢性阻塞性肺疾病（COPD）等肺部疾病的患者中，这使得这种方法很麻烦。本文研究了在改变FIO₂时逐次呼吸测量呼吸气体和动脉氧水平是否可以作为一种更快的替代方法，以取代从稳态条件收集数据来测量肺气体交换效率。对14名COPD患者进行了研究，FIO₂在0.15 - 0.35范围内进行了4 - 5次阶跃变化。在两种情况下，使用呼出的呼吸气体值和动脉氧合来计算和比较肺气体交换数学模型的参数：从稳态数据；以及在达到稳态之前的逐次呼吸数据。对于每位患者，对逐次呼吸数据进行了校正，以考虑每次FIO₂变化后动脉血氧饱和度变化的延迟。结果表明，两个数据集的计算模型参数相似，计算肺分流时的布兰德 - 奥特曼偏差和一致性界限分别为 - 0.4和 - 3.0至2.2%，肺泡至终末毛细血管氧分压（PO₂）的偏差和一致性界限分别为0.17和 - 0.47至0.81kPa，肺泡至终末毛细血管氧分压是由于分流加[公式：见正文]A/[公式：见正文]比值低的区域导致的氧异常的一种度量。这项研究表明，在使用FIO₂变化估计肺气体交换时，可能不需要稳态氧水平。因此，这种技术可能适用于患有COPD等肺部疾病的患者。
