For centuries, doctors have turned to a variety of vital signs to quickly assess the well-being of patients. A visit to the ER these days might result in as many as five measurements being taken, each offering unique clues as to what’s going inside the complex human body. Recently, though, a new number has popped up that may turn out to be the single most useful piece of information available to understand someone’s underlying health condition.
Heart rate variability (HRV) offers insights into recovery from illness, injury or exercise, can track levels of physical and emotional stress, and even act as a predictor of cardiac failure. Advances in technology, including image sensors, now make HRV measurement accessible to anyone with a chest strap or smartphone.
Among the more common measures, heart and respiratory rate are the simplest to take — you just need a watch with a second hand to count. More specialized equipment is needed for body temperature, blood-oxygen level and blood pressure, but they’re also quite straightforward. The history of blood-pressure measurement dates back 300 years, when Reverend Stephen Hales stuck tubes into a horse to see how high the column of blood would climb. Today, you merely need an arm cuff attached to some electronics.
