They enlisted 85 volunteers, more than half with a diagnosis of hypertension and nearly all on medications for the condition.Researchers checked blood pressure twice with the app, following the instructions provided by the developer, and then compared the average result from those two readings to a separate measurement from a traditional blood pressure cuff.
Healthy people have a systolic blood pressure, the measurement when the heart beats, of less than 120 mmHg, and diastolic pressure, when the heart rests, of less than 80 mmHg. Blood pressure above 140 mmHg systolic or 90 mmHg diastolic are considered hypertension.
The average differences between the app results and the traditional cuff were 12.4 mmHg for systolic blood pressure and 10.1 mmHg for diastolic blood pressure.Generally, the app overestimated low blood pressure and underestimated hypertension.
It’s hard to imagine any mobile app to measure blood pressure without a hardware component that does the job of a cuff, said Dr. Beverly Green, a researcher at Group Health Research Institute in Seattle who wasn’t involved in the study.
“I am not an engineer, but from what I understand, you need a cuff (the thing that wraps around your arm and is pumped up) preferably on the upper arm, to get an accurate BP,” Green said by email.
“The cuff compresses the arteries and measures the amount of pressure the heart needs to get blood out to the arteries and the pressure of the arteries when the heart is relaxed,” Green added.