38. Measuring Blood Flow
When a patient is getting ready for a serious procedure like dialysis, bypass surgery, or a coronary angiogram, doctors must test how well blood flows through their arteries. This is commonly done using the Allen Test. With the Allen Test, the doctor will press two spots on the wrist to stop blood flow for a few seconds. After the pressure is released, they then monitor to see how long it takes to return color to the area.
A study found that a free smartphone app called Instant Heart Rate is more accurate at analyzing blood flow than the Allen Test. Using a smartphone’s camera lens and light, the app tracks the light reflection from a person’s finger. It also examines changes in color or brightness that indicate changes in pulse.