An oximeter is a medical device used to measure the oxygen saturation level in a person's blood. It typically clips onto a fingertip or earlobe and uses light sensors to determine how much oxygen is being carried by red blood cells. This information is crucial for assessing respiratory function and overall health. Oximeters are commonly used in hospitals, clinics, and even at home for patients with conditions like asthma or COPD. They provide quick and non-invasive readings, helping healthcare providers monitor patients' oxygen levels and make informed decisions about treatment.