December 27, 2024
How Did Blood Pressure Monitoring Devices Evolve? A Timeline of Change
Over the course of nearly 300 years, blood pressure measurement technology has evolved significantly, from invasive tubes inserted into blood vessels, to mercury manometers, pulse-obscuring sphygmomanometers, inflatable cuffs, and now even wearable monitoring watches. Accessibility and ease of use have seen remarkable progress, especially when considering the gradual pace of earlier technological advancements.
Blood Pressure was first measured in 1733 by inserting a brass pipe connected to a glass tube into a horse’s let artery. In 1828 a mercury manometer for the measurement of arterial pressure was described in a doctoral dissertation. In 1881 the first sphygmomanometer was invented, measuring the pressure required to completely obscure the pulse in a restricted artery. In 1896 the first inflatable cuff was introduced, and in 1905, Dr. Korotkoff discovered the difference between systolic blood pressure and diastolic blood pressure, corresponding to the appearance and disappearance of sounds within an artery as pressure is applied and released.
Still today, trained medical professionals use a manual sphygmomanometer with a stethoscope, listening for the Korotkoff sound while manually inflating and deflating a cuff. Omron Healthcare began to develop a blood pressure monitor in 1973. In 1984 A&D introduced the UA-500 Series, the first oscillometric models for consumer use. And finally in 1991 Omron introduced the world's first automated blood pressure monitor that changed blood pressure monitoring forever, making it possible for people without medical training to take blood pressure readings at home.
The first iPhone came out in 2007, and Android 1.0 was released in 2008, ushering in a new mobile era for humanity, with smartphones replacing a host of products like cameras, television sets, calendars, dictionaries, maps, and more. We have discussed measuring body temperature with a smartphone in an earlier blog post, and it only seems natural that people want their smartphones to be making blood pressure measurements too.
In 2013 the International Medical Device Regulators Forum or IMDRF formed the Software as a Medical Device Working Group. Chaired by FDA, it created the key definitions, the framework for risk categorization, the quality management system, and the clinical evaluation for Software as a Medical Device.
A Scientific American article published in 2014 and titled “Blood Pressure Apps May Be Dangerously Wrong” looks into the challenges of creating a regulatory framework for the new “software as a medical device” category. Regulators like the FDA have had to find the delicate balance between encouraging innovation and protecting users from ineffective, inaccurate, and unsafe products.
“Consumers have a strong tendency to download and favorably rate apps that are advertised to measure blood pressure and heart rate, despite a lack of validation for these apps.” - reads a Journal of the American Society of Hypertension article published in 2015.
A validation study published in 2016 found that one of the top 50 best-selling iPhone apps, with over 148 000 units sold, provided highly inaccurate blood pressure estimates. The app would falsely reassure approximately 77.5% of its hypertensive users that their blood pressure is within a safe range.
FDA’s current Software as a Medical Device web page was published in 2018 and its Artificial Intelligence (AI) and Machine Learning (ML)-Based Software as a Medical Device Action Plan - in 2021. According to a MedTech Intelligence article, FDA clearances for SaMD have been on a strong growth trajectory, nearly doubling in both 2020 and 2023. In 2024, as more and more medical apps incorporate AI and ML, a corresponding dedicated FDA page was created.
With this FDA framework in place, the future of apps and devices for health monitoring at home looks promising. New technologies, sensors & wearables, AI & ML-based tools will continue to transform digital health.
