Cuffless BP monitoring – not for the faint of heart

smart watch and phone

Over the past decade, a plethora of PR [1, 2, 3], media reports [4, 5, 6], and peer-reviewed papers [7, 8, 9] has led to enthusiasm, confusion, and disappointment regarding the alluring prospects of cuffless blood pressure (BP) monitoring in wearables. The enthusiasm has been largely sustained by the widespread health benefits of, and the attractive commercial applications for, a seamless hypertension management solution that is virtually invisible – part of what people are already wearing, such as smartwatches, earbuds, smart rings, and apparel.

Such a solution would provide almost effortless measurements of BP taken throughout the day, enabling the seamless diagnosis and management of hypertension, free from the burdens associated with properly porting and donning a BP cuff. However, this excitement has been stifled by well-publicised industry setbacks [10, 11, 12], potentially misleading medical claims [13], and moderately unfavourable peer-reviewed articles authored by experts in the field [14, 15, 16], intimating that existing solutions are missing the mark.

Despite the increasing public health crisis [17, 18], widely championed support by leaders in cardiorespiratory health [19, 20, 21], a multi-billion dollar market for FDA-approved routine BP monitoring solutions [22, 23], and hundreds of millions of R&D dollars directed towards cuffless BP monitoring [24], there are no over-the-counter FDA-approved cuffless BP monitoring solutions to date that have been proven to successfully address the use case of seamless hypertension management. With the enormous amount of investment in this one specific goal, why do we still not have a commercial solution in our hands (or on our wrists) today? 

Performance standards, technological advances, and risks

For some R&D efforts, the answer is simple – FDA clearance has simply not been achievable, due to the inability to pass critical performance standards. This has been the case for popular reports documenting the deficiencies of leading smartwatch consumer brands [10, 25]. Yet, in many cases, the answer is much more complex. 

There is no single reason why an FDA-cleared OTC cuffless blood pressure measurement solution is unavailable in the marketplace today. In fact, there are many disparate challenges that, acting together, have pushed out the realisation of seamless hypertension management further into the future. While the progress towards FDA-cleared cuffless BP monitoring may feel lengthy, significant technological advances, regulatory modernisation, and clinical use case validation are rapidly advancing and aligning.  

Key challenges confronting OTC cuffless BP monitoring: 

1) Scientific risks

Scientific risk is perhaps the most uncomfortable challenge of them all, as it can only be addressed by definitive experimental proof. At the heart of scientific risks is that cuffless BP monitoring solutions intrinsically do not directly measure blood pressure, but measure proxies (indirect measurements) for BP. To date, all classical approaches to engineering indirect BP measurements with the accuracy of direct measurements have failed. The good news is that new machine learning approaches have provided a “reason to believe” that is getting stronger with each passing year [26, 27].

2) Engineering risks

A good way to mitigate engineering risks is to begin the product development phase with a clear product vision, having a well-defined and precise user experience and target audience in mind. Medical products that try to achieve too much for too many use cases ultimately achieve neither. Starting with a well-defined product vision at the outset, engineering teams can do what they do best – build the right product within the right timeline. Marketable consumer use cases require an affordable, portable, easy-to-use product that isn’t rough around the edges. 

3) Use case risks

Use case risks can be among the most challenging to predict, but their importance cannot be overemphasised. As any experienced product team will affirm, a viable product requires more than a functionally working solution; rather, all of the critical product goals must be met for a given use case. Indeed, the development of a high-adherence solution encouraging numerous BP measurements each month is perhaps the most cited justification for the sizeable R&D investments in cuffless BP monitoring. But if the product is too complex, uncomfortable, or inconvenient to use, adherence will be poor, regardless of whether the solution is cuffless and calibration-free. 

The bottom line is that a revolutionary new technology that does not enable a compelling new use case or that does not significantly enhance an existing one will not generate a revolutionary product. 

4) Regulatory risks

The regulatory process for a new technology takes significant time and investment. It is important to be aware that even if a cuffless BP monitor meets accuracy requirements within the desired engineering specs, and even if it engages end-users for high adherence, the FDA’s blessing is still not guaranteed. Even with a high level of preparation, it has reportedly taken Valencell approximately nine months from the point of its first supplemental FDA submission to receive acceptance for its proposed 510(k) validation plan. Moreover, even with a validation plan accepted by the FDA, there are many more months of work to be completed before the company can submit a formal 510(k). 

5) Commercial risks

From the outset, it is important to make sure the proposed medical solution can meet a significant market need. What problem would be solved by such a solution that couldn’t be solved with existing technology today? Would solving that problem justify the required level of investment? From the beginning of product development, such a product concept should be vetted for commercial viability. If commercial viability isn’t clear, the R&D investment should be adjusted accordingly.

Many players in the field of cuffless BP monitoring have focused their resources towards developing passive wearable solutions to enable seamless measurements of numerous BP readings throughout the day, in the background, without users having to take time out of their day for a BP spot-check. However, the medical community has not yet converged on a compelling, definitive public health value for such a device to be continuously worn, especially considering the risk of data overload for physicians (28, 29).

6) Medical acceptance risks

A key challenge for those developing new medical solutions is that, while the largest growth opportunities often reside within the medical community, the lowest-risk go-to-market approach frequently does not. The medical community, by its nature, can be extremely resistant to change – and especially to disruptive technology. It may make better sense to reach out to end users first to help shape product development and demonstrate the value proposition in preparation for a future growth opportunity within the medical community.  

The promise of seamless hypertension management via cuffless BP monitoring, while extremely alluring for both the marketplace and for public health at large, is also extremely challenging to achieve. This R&D endeavor is not for the faint of heart (pun intended). At the time of this article, to the best of the author’s knowledge, there is still not a single cuffless BP monitoring solution cleared by the FDA for OTC use, despite the collective hundreds of millions in R&D spending, from companies large and small, directed towards this goal. 

The risks are wide and deep but not unsurmountable, with a well-engineered solution having a clear intended use for a specific, medically impactful, and commercially viable use case. By overcoming these challenges, hypertension management will change more in the next five years than it has in the past 100.   

About the author

Dr Steven LeBoeufDr Steven LeBeouf is president and co-founder, Valencell, Inc. Inventor of more than 100 granted patents in the field of wearable biomedical sensing, before founding Valencell in 2006, Dr. LeBoeuf pioneered innovations in solid-state materials, multiwavelength optoelectronic devices, high-power electronics, nanostructured materials and devices, and biochemical sensor systems, while serving as a senior scientist and biosensor project lead for General Electric. He holds a Ph.D. in Electrical Engineering from North Carolina State University, and a BSc degree in Electrical Engineering and Mathematics from Louisiana Tech University.