Vikne Harald, Kjeserud Jon Arild, Westgaard Willy, Baalsrud Westlie Ruben, Kåsin Jan Ivar, Medbø Jon Ingulf, Gjøvaag Terje, Holmedahl Nils Henrik
Norwegian Institute of Aviation Medicine, Norwegian Armed Forces Joint Medical Services, Oslo, Norway.
Department of Interdisciplinary Health Sciences, Institute of Health and Society, University of Oslo, Oslo, Norway.
PLoS One. 2025 Jun 23;20(6):e0326674. doi: 10.1371/journal.pone.0326674. eCollection 2025.
Commercial pulse oximeters may not be well calibrated for oxygen saturations below 70%, conditions that may be met in high altitude aviation and mountaineering. We therefore examined the bias and variability of heart rate (HR) and blood oxygen saturation (SpO2) of four different pulse oximeters (PO) at arterial blood oxygen saturation (SaO2) between 55 and 100%.
Seventeen healthy participants (age 33 ± 11 (mean ± standard deviation (SD)) yr) were exposed to controlled desaturation at rest by stepwise reduction of the oxygen fraction in the breathing air between 20.9 and 8%. Parallel measurements of HR (n = 383) and blood oxygen saturation (n = 304) from four pulse oximeters (RAD-97, PM100N, M7500 and Nell1-SR) and from reference instruments (by hemoximetry and electrocardiography (ECG)) were taken during the exposure. The validity was assessed in intervals of 55-70%, 70-85% and 85-100% SaO2 using the Bland-Altman method (bias and 95% limits of agreement (LoA)) and the root mean square error for variability. The demarcation criteria for agreement between methods were ±6 percentage points O2Hb saturation and ±6 bpm HR.
At the 85-100% SaO2 interval, all POs but the Nell1-SR were in agreement with the reference for O2 saturation. Only M7500 agreed with the reference for the 70-85% interval and none of the POs were in agreement with the reference for the 55-70% interval. The pulse oximeters and ECG were not in agreement for HR at neither the 55-70% nor the 85-100% interval but agreed at the 70-85% interval except the RAD-97. All pulse oximeters increased the bias or the variability for SpO2 significantly by reductions in oxygen saturation, while no systematic differences were found for HR.
The study shows that medically approved pulse oximeters are not in agreement with reference measurements of neither blood oxygen saturation nor HR at SaO2 levels below 70%, and their readings should therefore be interpreted cautiously during severe desaturation.
商业脉搏血氧仪对于低于70%的血氧饱和度可能校准不佳，而在高空飞行和登山等情况下可能会出现这种情况。因此，我们研究了四种不同脉搏血氧仪（PO）在动脉血氧饱和度（SaO2）为55%至100%时心率（HR）和血氧饱和度（SpO2）的偏差和变异性。
17名健康参与者（年龄33±11（平均±标准差（SD））岁）在静息状态下通过逐步降低呼吸空气中的氧分数，使其在20.9%至8%之间进行控制性去饱和。在去饱和过程中，同时测量了来自四种脉搏血氧仪（RAD-97、PM100N、M7500和Nell1-SR）以及参考仪器（通过血液氧含量测定法和心电图（ECG））的HR（n = 383）和血氧饱和度（n = 304）。使用Bland-Altman方法（偏差和95%一致性界限（LoA））以及变异性的均方根误差，在SaO2为55 - 70%、70 - 85%和85 - 100%的区间内评估有效性。方法间一致性的分界标准为氧合血红蛋白饱和度±6个百分点和HR±6次/分钟。
在SaO2为85 - 100%的区间内，除Nell1-SR外的所有PO在血氧饱和度方面与参考值一致。只有M7500在70 - 85%的区间内与参考值一致，而在55 - 70%的区间内没有PO与参考值一致。在55 - 70%和85 - 100%的区间内，脉搏血氧仪和ECG在心率方面均不一致，但在70 - 85%的区间内除RAD-97外均一致。所有脉搏血氧仪随着血氧饱和度的降低，SpO2的偏差或变异性均显著增加，而在HR方面未发现系统差异。
该研究表明，医学上认可的脉搏血氧仪在SaO2水平低于70%时，在血氧饱和度和心率的参考测量方面均不一致，因此在严重去饱和期间对其读数应谨慎解读。
