Perfusion index refers to the ratio of pulsatile blood flow to non-pulsatile static blood flow in the monitored parts, such as fingers, toes and earlobes. The perfusion index indicates the pulse intensity of the monitoring site.
The greater the pulsatile blood flow, the more pulsatile components and the greater the PI value. Therefore, the measurement site (skin, nails, bones, etc. ) and the patient's own blood perfusion (arterial blood flow) will affect the PI value. Therefore, whether the PI value is normal or not is a relative concept, relative to the absolute value of the tested patient in a healthy state.
Extended data:
The more valuable and informative aspect of pi lies in its trend. Just like blood pressure and heart rate, although everyone's blood pressure and heart rate are within the normal range, they are also different. When they change sharply, they may still be within the normal range, but individuals themselves will feel uncomfortable.
The characteristics of each individual will make everyone's PI different. For example, people with cold hands and feet have relatively low PI on their hands, and people with long hand movements have relatively high PI on their hands.
Different diseases of each individual will lead to different changes in PI. For example, the PI of shock patients will decrease before shock and increase after spinal anesthesia, and the PI of patients with congenital heart disease is obviously different before and after catheterization.
Baidu Encyclopedia -pi (Blood Perfusion Index)