Final answer:
Pulse oximetry can be unreliable due to factors like poor blood perfusion or carbon monoxide presence. Arterial blood gas analysis is needed to get a complete picture of oxygenation status.
Step-by-step explanation:
While pulse oximetry is a useful tool for monitoring oxygen levels, it can sometimes be unreliable due to various factors. One reason is that the device relies on the absorption of light by hemoglobin in the blood to measure oxygen saturation. Conditions such as poor blood perfusion or the presence of certain substances like carbon monoxide can affect the accuracy of the readings. Another lab test that can provide a more complete picture of oxygenation status is arterial blood gas (ABG) analysis. This test measures the partial pressure of oxygen (pO2) directly from the arterial blood, providing a more accurate assessment of oxygen levels in the body.