Assessing oxygenation in the transport environment

Abstract

The physical signs of hypoxemia often are not seen until profound hypoxemia occurs; therefore a variety of devices commonly are used to assess patient oxygenation. Despite the high reliance on oxygen monitoring equipment when caring for the critically ill, medical personnel often fail to appreciate the advantages and limitations of these devices. In fact, profound hypoxemia can exist in the absence of reliable physical signs. Arterial blood gas measurements, the traditional gold standard for assessing a patient's oxygen and acid base status in the hospital setting, only recently have been simplified for transport use. But their inability to perform real-time continuous measurements limits their acceptance into the transport environment. Although used to assess neonatal hypoxemia, the real value of transcutaneous oxygen monitoring may be in avoiding retinal damage as a result of excessive tissue oxygenation. Finally, despite the simplicity, reliability, and popularity of pulse oximeters, few EMS medical personnel really understand how perfusion states, motion, hemoglobinopathies, intravenous dyes, nail polish, and skin color may lead to interpretation errors. This article discusses the limitations of the physical examination, arterial blood gas measurements, transcutaneous monitoring, and pulse oximetry in determining a patient's oxygenation status.