A Wearable Watch to Monitor Blood Pressure?
It seems like it ought to be easy—a wearable watch-like device that continuously monitors blood pressure. But it’s not easy, unless the wearer sits still, as when taking a BP measurement with an arm-cuff device. There have been BP watches with inflatable wrist cuffs—e.g. from Omron Healthcare (Lake Forest, IL)—but a wrist wearable monitor that works continuously while a person goes through normal activities and gives accurate readings remains elusive. However, researchers at the National Institute of Standards and Technology, collaborating with clinicians at Tufts University School of Medicine, are working on a mechanical model, made of silicon, metal and sensors that simulates a human wrist. With that—called “the Crushinator”—they are proceeding toward an accurate watch-like prototype. MORE
Image Credit: NIST
David W Gerdt
The article is interesting and there are many uses for continuous blood pressure, whatever continuous means. Ambulatory BP cuffs that power up every hour for 24 hours are continuous. A beat by beat blood pressure monitor is different because then you can measure blood pressure variability like heart rate variability is measured. Then you can measure baroreceptor sensitivity or orthostatic hypotension and many other parameters. The wrist watch BP monitor is a miniaturization of Omron’s current wrist monitor that works fairly well, personally, on two AA battery cells. Omron is marketing this and all their other BP monitors as personal health monitors; they are not for prescriptive use. A Charlottesville company, CareTaker Medical, is selling an FDA approved continuous noninvasive blood pressure (CNIBP) monitor that measures every heartbeat’s pressures and it is approved for prescriptive use. CTM’s product, CareTaker, obtains the arterial pulse wave form from a comfortable, lightly pressurized cuff that fits around the finger. The wave form is not any different than what could be obtained with an invasive catheter pressure monitor. So, the question is, why do you need an artificial wrist to get the signature of the pulse when there are already other good ways to get it and there really isn’t anything else to measure? After working on the wrist for many years, we found the finger to be a much better place because there is much less body noise, especially at low frequencies where lie the heart rate (1HZ) and respiration (.2 Hz). Optical systems to detect these very low frequencies have been and are plagued by shot noise which compromises their low frequency detection limits but excel at higher frequencies.