An oximeter measures your oxygen levels. Usually, children are not afraid of this one. All you have to do is put your finger in the clip, and it does not hurt a bit because the clip is padded on the inside. Once you put your finger in, the oximeter does its job! Usually, people with severe heart and lung problems keep an oximeter at home because their oxygen levels can drop at anytime. They have to frequently measure their oxygen levels. If your oxygen levels happens to be low and you're not a heart or lung patient, then you may experience a light head, fainting, or disorientation.