Which abnormality can pulse oximetry not accurately detect?

Pulse oximetry is a non-invasive method used to measure the oxygen saturation level in the blood. It works by using light absorption characteristics of oxygenated and deoxygenated hemoglobin. While it is effective for detecting hypoxaemic conditions—where there is a deficiency of oxygen in the tissues—its limitations arise with certain abnormalities.

Pulse oximetry is particularly poor at detecting carboxyhaemoglobinaemia, a condition where carbon monoxide binds to hemoglobin, thus preventing proper oxygen binding. In carboxyhaemoglobinaemia, pulse oximetry can falsely indicate a normal oxygen saturation level, as it cannot differentiate between oxyhemoglobin and carboxyhemoglobin due to their similar light absorption characteristics.

Arrhythmias, which are irregular heartbeats, and conductive disturbances, which relate to problems in the heart’s electrical conduction system, do not influence the pulse oximeter's ability to measure oxygen saturation directly. Pulse oximetry measures the oxygen saturation in the blood regardless of how the heart is beating. Hence, while pulse oximetry can be an essential tool in assessing oxygen levels, it is ineffective for providing accurate data in cases of carboxyhaemoglobinaemia and cannot give reliable information about the rhythm or