Unlike standard pulse oximeters that only measure pulse rate and blood oxygen saturation, this advanced unit tracks three additional indicators of heart and lung function. Using the same technology employed by hospitals, it monitors respiration rate (RRp) by measuring breaths per minute as well as hydration and breathing effort via changes in one’s Pleth Variability Index (PVi). Changes in blood circulation is displayed via Perfusion Index (Pi), which measures the strength of blood flow to the clipped-on finger. Its LED panel simultaneously displays all five metrics in easy-to-read numbers. Pairs with a free app to store results. Requires two AAA batteries.