Design and evaluation of a low-cost sphygmomanometer to monitor women with pre-eclampsia in low-resource settings

Abstract

We developed and pilot tested a sphygmomanometer designed to monitor pregnant women in low-resource settings. Blood pressure was assessed in 138 subjects, including healthy adults (n=85), pregnant women (n=42), and women at-risk for pre-eclampsia (n=11) using the novel sphygmomanometer, manual auscultation, and the GE Dinamap Procare 400. Accuracy of the device was evaluated by comparing measurements of the test device and the Dinamap in healthy volunteers and pregnant women in Texas and in women at risk for pre-eclampsia in Malawi. Measurements from the test device in pregnant and healthy volunteer populations differed from those collected using the auscultatory method by 0.2 mmHg (95% CI: -18.8 to 19.2, systolic) and -2.8 mmHg (95% CI: -21.0 to 15.4, diastolic). In women at risk for pre-eclampsia, measurements with the test device differed from those of the Dinamap on average by 2.9 mmHg (95% CI: -29.3 to 35.1, systolic) and -5.4 mmHg (95% CI: -45.8 to 34.9, diastolic). Compared against the auscultatory method, measurements with the Dinamap differed on average by 0.0 mmHg (95% CI: -31.8 to 31.9, systolic) and -3.7 mmHg (95% CI: -28.6 to 21.3, diastolic). Accuracy was reduced when patients were moving or not seated during measurement. When testing the device against British Hypertension Society standards, the device achieved a grade of A/A in pregnant persons. This sphygmomanometer has the potential to provide low-resource hospitals with an affordable, accurate option for regular blood pressure monitoring. However, algorithm improvements are needed to reduce sensitivity to subject motion and posture.