Finger-tip pulse oximeter measures blood oxygen level (% oxygen saturation of hemoglobin). Also give pulse rate reading. Waveform display will allow user to see if oxygen measurement may not be possible, or may not be accurate (for example with cold hands or low blood pressure). Colour OLED display. Powered by 2 AAA batteries (included). Highly recommended for cancer patients who are undergoing treatment, especially when the lungs are affected. FDA-certified. To be used under the guidance of a medical or naturopathic doctor. Remove nail polish for accurate reading.