Anstey C
Department of Intensive Care, Nambour General Hospital, Queensland, Australia.
Anaesth Intensive Care. 2000 Feb;28(1):31-6. doi: 10.1177/0310057X0002800105.
The in vivo P50 (P50iv) provides a useful index of haemoglobin-oxygen affinity and is calculated according to software algorithms incorporated into commercial blood gas analysers. These algorithms are known to be inaccurate at high haemoglobin saturation (SpO2 > 97%) although just how inaccurate has not been documented. This study examines the arterial blood gas profiles of patients admitted to a busy secondary referral Intensive Care Unit and stratifies them according to haemoglobin saturation in order to quantify the accuracy and potential clinical utility of the Siggaard-Andersen algorithm (SAA) for assessing P50iv in blood with SpO2 > 90%. Sicker patients, as identified by plasma pH < 7.35 or [lactate] > 2.0 mmol/l, were substratified and the SAA assessed as before. In both groups, the results show not only that the SAA is completely unreliable above 97% saturation, a fact acknowledged by Siggaard-Andersen in 1984, but it is also inaccurate in the range 92% < or = SpO2 < or = 97%, thus rendering P50iv calculations suspect in 90% of the patients in each of the study groups.
体内P50（P50iv）可作为血红蛋白与氧亲和力的有效指标，通过商用血气分析仪内置的软件算法进行计算。已知这些算法在高血红蛋白饱和度（SpO2>97%）时不准确，不过具体有多不准确尚无文献记载。本研究对一家繁忙的二级转诊重症监护病房收治的患者的动脉血气分析数据进行了检查，并根据血红蛋白饱和度进行分层，以量化西格gaard - 安德森算法（SAA）在评估SpO2>90%血液中P50iv时的准确性和潜在临床实用性。对于通过血浆pH<7.35或[乳酸] > 2.0 mmol/l确定的病情较重的患者，进行亚分层并如前所述评估SAA。在两组中，结果均显示，不仅SAA在饱和度高于97%时完全不可靠（西格gaard - 安德森在1984年就已承认这一事实），而且在92%≤SpO2≤97%范围内也不准确，因此在每个研究组中90%的患者中，P50iv的计算结果都值得怀疑。
