Barker S J, Hyatt J, Shah N K, Kao Y J
University of California, Irvine Medical Center, Department of Anesthesiology, Orange 92613-1491.
Anesthesiology. 1993 Aug;79(2):248-54. doi: 10.1097/00000542-199308000-00009.
Previous studies have shown that pulse oximeters whose sensors are positioned improperly may yield erroneously low saturation (SpO2) values on normoxemic subjects. The behavior of oximeters with malpositioned sensors during hypoxemia has not been studied. The current study is aimed at determining the behavior of several different pulse oximeters over a wide range of arterial oxygen saturation (SaO2).
In each of 12 healthy volunteers, a radial artery cannula was inserted, and eight different pulse oximeters, five of which had malpositioned sensors, were applied. Subjects breathed controlled mixtures of nitrogen and oxygen to slowly vary their SaO2 from 100% to 70%. Arterial blood samples were analyzed and pulse oximeter data were recorded at five stable SaO2 values for each subject.
The oximeters with malpositioned sensors vary greatly in their behavior, depending on both the actual SaO2 and the manufacturer and model. One oximeter underestimated saturation at all SaO2 values, while three others underestimated at high SaO2 and overestimated at low SaO2. Linear regression analysis shows a decrease in the slope of SpO2 versus SaO2 in most cases, indicating a loss of sensitivity to SaO2 changes. Between-subject variation in response curves was significant.
The calibration curves of the pulse oximeters studied were changed greatly by sensor malpositioning. At low SaO2 values, these changes could cause the oximeter to indicate that a patient was only mildly hypoxemic when, in fact, hypoxemia was profound. It is recommended that sensor position be checked frequently and that inaccessible sensor locations be avoided whenever possible.
先前的研究表明，传感器位置不当的脉搏血氧仪可能会在血氧正常的受试者身上得出错误的低饱和度（SpO2）值。低氧血症期间传感器位置不当的血氧仪的行为尚未得到研究。当前的研究旨在确定几种不同的脉搏血氧仪在广泛的动脉血氧饱和度（SaO2）范围内的行为。
在12名健康志愿者中，每人均插入一根桡动脉插管，并应用了8种不同的脉搏血氧仪，其中5种的传感器位置不当。受试者呼吸氮气和氧气的受控混合物，以使他们的SaO2从100%缓慢变化至70%。对每个受试者在5个稳定的SaO2值时进行动脉血样本分析并记录脉搏血氧仪数据。
传感器位置不当的血氧仪行为差异很大，这取决于实际的SaO2以及制造商和型号。一种血氧仪在所有SaO2值下均低估饱和度，而其他三种在高SaO2时低估，在低SaO2时高估。线性回归分析表明，在大多数情况下，SpO2与SaO2的斜率下降，表明对SaO2变化的敏感性丧失。受试者之间反应曲线的差异很大。
所研究的脉搏血氧仪的校准曲线因传感器位置不当而发生了很大变化。在低SaO2值时，这些变化可能导致血氧仪显示患者仅为轻度低氧血症，而实际上低氧血症很严重。建议经常检查传感器位置，并尽可能避免传感器位置不易触及的情况。
