Emergency Procedures Exam 1 Practice

Pulse oximetry estimates arterial oxygen saturation by sending red and infrared light through a finger and measuring how much is absorbed by hemoglobin. It assumes only two main forms: oxyhemoglobin and deoxyhemoglobin. When other forms are present, readings can be misleading. Smoking introduces carbon monoxide, which binds to hemoglobin to form carboxyhemoglobin. COHb absorbs light in a way that resembles oxyhemoglobin at the wavelengths the device uses, so the pulse oximeter can’t distinguish it from O2-bound hemoglobin. As a result, the reading can appear normal or high even though the actual oxygen delivery is compromised. This makes pulse oximetry readings falsely reassuring in smokers with carbon monoxide exposure. Other groups can have accuracy issues for different reasons, but the smoking-related pitfall specifically involves carboxyhemoglobin causing an overestimate of oxygen saturation.