A pulse oximeter is a small, non-invasive device used to measure the oxygen saturation level in a person's blood. It typically clips onto a fingertip and uses light sensors to determine how much oxygen is being carried by red blood cells. This information is crucial for monitoring respiratory conditions and ensuring that the body is receiving enough oxygen. The device is commonly used in hospitals, clinics, and even at home for patients with conditions like asthma, COPD, or during surgery. A normal oxygen saturation level ranges from 95% to 100%. Readings below this range may indicate a need for medical attention.