Editors' ChoiceCardiovascular Disease

Monitoring blood pressure with your bathroom scale

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Science Translational Medicine  17 Jun 2015:
Vol. 7, Issue 292, pp. 292ec101
DOI: 10.1126/scitranslmed.aac7156

Arterial blood pressure is a vital sign that is measured every time we see a nurse or visit the doctor. They listen for the characteristic sequence of sounds from the brachial artery as the pressure in a fully inflated arm cuff is slowly lowered, a method described in 1905 by the Russian surgeon Nikolai Korotkoff. By relating the sounds to the underlying physiology, Korotkoff discovered a way to determine the systolic and diastolic arterial pressures noninvasively. Since then, not much has changed in how we measure arterial blood pressure noninvasively—despite a hypertension epidemic and a clear need to track blood pressure closely, regularly, and ideally unobtrusively in a sizeable patient population.

Kim and co-workers have now taken a new look at this challenge with a new approach that relies on ballistocardiography. A method first described over a century ago, ballistocardiography registers tiny, imperceptible (by humans) motions of the body resulting from the body’s reaction force to each cardiac ejection of blood into the aorta. These motions can be picked up easily and continuously—for example, with accelerometers on the body, by standing on a sensitive bathroom scale, or by clever analysis of video recordings of the head. The authors demonstrate that the ballistocardiogram can determine the pulse transit time, or the time it takes the arterial pulse wave to travel from the heart (or a central thoracic location) to a peripheral artery. This time interval correlates with arterial blood pressure and therefore can be used to track blood pressure noninvasively. In human subjects, the ballistocardiography–derived pulse transit time showed best agreement with diastolic blood pressure and had the strongest correlation (0.7) with systolic blood pressure. The approach and initial results by Kim et al. open the door to obtaining blood pressure readings every time we step on a bathroom scale or look into a mirror. One caveat of the method is the need for calibration, so Dr. Korotkoff’s legacy will therefore continue for a while.

C.-S. Kim et al., Ballistocardiography as proximal timing reference for pulse transit time measurements: Potential for cuffless blood pressure monitoring. IEEE Trans. Biomed. Eng. 10.1109/TBME.2015.2440291 (2015). [Abstract]

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