Which device can determine the percentage of oxygen bound to hemoglobin?

The device that accurately determines the percentage of oxygen bound to hemoglobin is the pulse oximeter. This non-invasive tool measures the absorption of specific wavelengths of light as they pass through the skin, typically at a fingertip or earlobe. Because hemoglobin changes its light absorption characteristics depending on whether it is oxygenated or deoxygenated, the pulse oximeter can calculate the ratio of oxygenated hemoglobin (HbO2) to total hemoglobin (Hb), thereby providing a percentage value of oxygen saturation (SpO2). This information is crucial in clinical settings for assessing a patient's respiratory function and overall oxygenation status.

Other devices mentioned play different roles: the sphygmomanometer measures blood pressure, the capnometer measures the concentration of carbon dioxide in exhaled breath, and the electrocardiogram assesses the heart's electrical activity. None of these can provide direct information about oxygen saturation in the blood. Thus, the pulse oximeter is the correct device for determining the percentage of oxygen bound to hemoglobin.