监护仪上的血氧饱和度(SpO2),即脉搏血氧仪测量的外周动脉血氧饱和度,是危重病人最常用的监测指标之一,它可以反映组织氧合状态,是持续无创评估氧合状态的标准做法,常被视为「第五生命体征」。 但是临床上是否经常遇到如下问题? 1. 血氧 100%,但患者自觉呼吸困难,是患者紧张还是真有问题? 2. 血氧 99%,但患者昏迷、呼吸浅慢,甚至类似下颌式呼吸,继续用药观察还是考虑机械通气? 3. 多少为相对正常值:95%?90%?85%? 一、 什么是最佳血氧饱和度 二、 异常数值分析 一氧化碳中毒及慢性重度吸烟者 一氧化碳中毒及慢性重度吸烟者体内会存在高浓度的碳氧血红蛋白,其脉搏血氧仪的读数会偏高,这可能会掩盖危及生命的动脉血氧饱和度下降。 血糖控制不佳的糖尿病患者 在血糖控制不佳的 2 型糖尿病患者中,当糖化血红蛋白 A1c 水平超过 7% 时,会导致脉搏血氧仪的测定值高于实际值。这可能与血红蛋白与氧的亲和力增加有关。 灌注不足 血流动力学不稳定时,或者肢体抬高、血管收缩及周围血管病导致肢体灌注不良时,脉搏血氧仪读数可能偏低。当收缩压低于 80 mmHg 时,标准脉搏血氧仪的准确性急剧下降。 重度贫血 低血红蛋白浓度,尤其 HGB 低于 5 g/dL 时,可能会导致读数偏低。 静脉淤血 三尖瓣关闭不全或心肌病等会引起静脉淤血,而血氧仪会将检测到的氧合不足的搏动性的静脉血当作动脉血的一部分,这可能会导致 SpO2 读数偏低。 运动或噪声伪影 较差的信噪比会导致信号伪影和血氧仪读数偏低。最常见的原因是以下情况引起的运动:寒战、癫痫发作、传感器受压。波形通常不稳定且形状异常。新型脉搏血氧仪似乎受运动伪影的影响较小。 低体温 由于周围血管收缩和寒战,低体温可能会干扰脉搏血氧测定。这可能造成对急性低氧血症的识别延迟,尤其是使用手指探头时。低体温患者应使用耳朵或前额探头进行监测,从而降低延迟识别急性氧饱和度下降的可能性。采取保暖措施应该会解决这一问题。 三、 总结 文章开头的那几个问题,你觉得可能是哪些原因? 欢迎评论区留言~ 参考文献 1.Jubran A. Pulse oximetry. Intensive Care Med 2004; 30:2017. 2.Neff TA. Routine oximetry. A fifth vital sign? Chest 1988; 94:227. 3.Chan ED, Chan MM, Chan MM. Pulse oximetry: understanding its basic principles facilitates appreciation of its limitations. Respir Med 2013; 107:789. 4.Grace RF. Pulse oximetry. Gold standard or false sense of security? Med J Aust 1994; 160:638. 5.Hanning CD, Alexander-Williams JM. Pulse oximetry: a practical review. BMJ 1995; 311:367. 6.Ralston AC, Webb RK, Runciman WB. Potential errors in pulse oximetry. III: Effects of interferences, dyes, dyshaemoglobins and other pigments. Anaesthesia 1991; 46:291. 7.Mendelson Y. Pulse oximetry: theory and applications for noninvasive monitoring. Clin Chem 1992; 38:1601. 8.Ross PA, Newth CJ, Khemani RG. Accuracy of pulse oximetry in children. Pediatrics 2014; 133:22. 9.Stoneham MD. Uses and limitations of pulse oximetry. Br J Hosp Med 1995; 54:35. Jubran A. Pulse oximetry. Crit Care 2015; 19:272. 10. Ayas N, Bergstrom LR, Schwab TR, Narr BJ. Unrecognized severe postoperative hypercapnia: a case of apneic oxygenation. Mayo Clin Proc 1998; 73:51. 11.Van de Louw A, Cracco C, Cerf C, et al. Accuracy of pulse oximetry in the intensive care unit. Intensive Care Med 2001; 27:1606. 12.Wouters PF, Gehring H, Meyfroidt G, et al. Accuracy of pulse oximeters: the European multi-center trial. Anesth Analg 2002; 94:S13. 13.Webb RK, Ralston AC, Runciman WB. Potential errors in pulse oximetry. II. Effects of changes in saturation and signal quality. Anaesthesia 1991; 46:207. 14.Jubran A, Tobin MJ. Reliability of pulse oximetry in titrating supplemental oxygen therapy in ventilator-dependent patients. Chest 1990; 97:1420. 15. Perkins GD, McAuley DF, Giles S, et al. Do changes in pulse oximeter oxygen saturation predict equivalent changes in arterial oxygen saturation? Crit Care 2003; 7:R67. 16.American Thoracic Society, American College of Chest Physicians. ATS/ACCP Statement on cardiopulmonary exercise testing. Am J Respir Crit Care Med 2003; 167:211. 17.Guan Z, Baker K, Sandberg WS. Misalignment of disposable pulse oximeter probes results in false saturation readings that influence anesthetic management. Anesth Analg 2009; 109:1530. 18.Moyle JT. Uses and abuses of pulse oximetry. Arch Dis Child 1996; 74:77. 19.Mardirossian G, Schneider RE. Limitations of pulse oximetry. Anesth Prog 1992; 39:194. 20.Ortega R, Hansen CJ, Elterman K, Woo A. Videos in clinical medicine. Pulse oximetry. N Engl J Med 2011; 364:e33. 21.Barker SJ. 'Motion-resistant' pulse oximetry: a comparison of new and old models. Anesth Analg 2002; 95:967. 22.Gehring H, Hornberger C, Matz H, et al. The effects of motion artifact and low perfusion on the performance of a new generation of pulse oximeters in volunteers undergoing hypoxemia. Respir Care 2002; 47:48. 23. Talke P, Stapelfeldt C. Effect of peripheral vasoconstriction on pulse oximetry. J Clin Monit Comput 2006; 20:305. 24.Hinkelbein J, Genzwuerker HV, Fiedler F. Detection of a systolic pressure threshold for reliable readings in pulse oximetry. Resuscitation 2005; 64:315. 25.Broome IJ, Mills GH, Spiers P, Reilly CS. An evaluation of the effect of vasodilatation on oxygen saturations measured by pulse oximetry and venous blood gas analysis. Anaesthesia 1993; 48:415. 26.Wilson BJ, Cowan HJ, Lord JA, et al. The accuracy of pulse oximetry in emergency department patients with severe sepsis and septic shock: a retrospective cohort study. BMC Emerg Med 2010; 10:9. 27.MacLeod DB, Cortinez LI, Keifer JC, et al. The desaturation response time of finger pulse oximeters during mild hypothermia. Anaesthesia 2005; 60:65. |
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