Which assessment test measures the level of oxygen in the blood?

Pulse oximetry is a non-invasive assessment that specifically measures the level of oxygen saturation in the blood. It utilizes light absorption properties of hemoglobin to determine how much oxygen is bound to red blood cells, providing an immediate reading of the patient's oxygen saturation levels. This method is widely used in clinical settings due to its ease of use, speed, and ability to continuously monitor a patient's oxygen levels without the need for blood sampling.

Arterial blood gas analysis, while also a test used to assess oxygen levels, provides more comprehensive information including oxygen partial pressure, carbon dioxide levels, and blood pH, requiring a blood draw as opposed to a non-invasive measurement. Pulmonary function tests evaluate lung function and capacity but do not directly measure blood oxygen levels. A chest X-ray is an imaging tool that can help visualize the structures within the chest but does not provide specific data regarding oxygen levels in the blood.