How do automatic blood pressure cuffs/machines know when to stop inflating the cuff for each individual person?
In: Engineering
Basically, vibrations from blood pumping through the arteries are detected by the device, which let it know how far to inflate and when to deflate.
“The new models use “fuzzy logic” to decide how much the cuff should be inflated to reach a pressure about 20 mm Hg above systolic pressure for any individual. When the cuff is fully inflated to this pressure, no blood flow occurs through the artery. As the cuff is deflated below the systolic pressure, the reducing pressure exerted on the artery allows blood to flow through it and sets up a detectable vibration in the arterial wall. When the cuff pressure falls below the patient’s diastolic pressure, blood flows smoothly through the artery in the usual pulses, without any vibration being set up in the wall. Vibrations occur at any point where the cuff pressure is sufficiently high that the blood has to push the arterial wall open in order to flow through the artery.
The vibrations are transferred from the arterial wall, through the air inside the cuff, into a transducer in the monitor that converts the measurements into electrical signals.”
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1121444/
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