When validating a new medical device, it is critical to compare performance against trusted reference methods. Because the Aktiia bracelet and app need to measure accurately all day no matter how you are sitting, standing, or lying down, one of our challenges has been to conduct validation trials with reference methods that could perform in these conditions as well.
Today, blood pressure can be measured several ways:
There are of course accurate invasive measurements like arterial lines, which we have used for a prior clinical trial. However, it’s not realistic to have subjects walking around with an invasive device connected to them as they go about their daily life.
There are also oscillometric cuffs, like the ones you can get at the pharmacy. But their large error tolerances can create problems when used as a reference device in a trial.
Another method is auscultation, which is how physicians and nurses measure with a cuff and stethoscope when you go in for an office visit. Because this requires a trained operator, clinical trials frequently use two operators to make sure they agree.
Another noteworthy method is volume clamp, which involves continuous beat-to-beat monitoring of arterial pressure, often at the finger. This has been used in research labs for continuous, non-invasive measurement in different body positions.
Auscultation is seen as the most widely accepted non-invasive reference method in clinical investigations, and is what we used in our latest clinical trial. But there are very few publications assessing the behavior of auscultation for body positions other than sitting and relaxed. This begs the question – can we blindly trust the auscultation data to validate our own device in other body positions?
In our clinical trial we added a second reference device to each patient – volume clamp at the finger. This allowed us to gather comparison data on the performance of auscultation in other body positions. Across 75 subjects, we found that auscultation did not detect the consistent changes in DBP when subjects stood up or lay down, as volume clamp did. This result was scientifically surprising, and we felt was worth sharing with peers.
We’re proud to say that our results have just been published as a letter to the editor in Blood Pressure Monitoring Journal, and have been accepted to be presented at American Heart Association “Hypertension 2020 Scientific Session”. We expect that by sharing these findings we’ll contribute to the knowledge of clinicians and researchers around the use and limitations of auscultation. At Aktiia, we are committed to continuing to publish our results and contributing to the scientific and medical communities and literature.
On another note, thank you to everyone who answered our survey from last month on which newsletter topics you were most interested in. The top topics of interest were product updates (72%), research/clinical trials (63%), regulatory progress (43%), hypertension information (33%), and company updates (29%). Thank you for your input!