Noninvasive Determination of Blood Pressure by Heart Sound Analysis Compared With Intra-Arterial Monitoring in Critically Ill Children—A Pilot Study of a Novel Approach

Objectives: To develop a novel device to predict systolic and diastolic blood pressure based on measured heart sound signals and evaluate its accuracy in comparison to intra-arterial blood pressure readings. Study Design: Prospective, observational pilot study. Setting: PICU. Patients: Critically ill children (0–18 yr) undergoing continuous blood pressure monitoring via radial artery intra-arterial catheters were enrolled in the study after informed consent. The study included medical, cardiac, and surgical PICU patients. Interventions: Along with intra-arterial blood pressure, patient’s heart sounds were recorded simultaneously by a highly sensitive sensor taped to the chest. Additional hardware included a data acquisition unit and laptop computer. Subsequently, advanced signal processing technologies were used to minimize random interfering signals and extract and separate S1 and S2 signals. A computerized model was then developed using artificial neural network systems to estimate blood pressure from the extracted heart sound analysis. Measurements and Main Outcomes: We found a statistically significant correlation for systolic (r = 0.964; R² = 0.928) and diastolic (r = 0.935; R² = 0.868) blood pressure readings (n = 491) estimated by the novel heart-sound signal–based method and those recorded by intra-arterial catheters. The mean difference of the individually paired determinations of the blood pressure between the heart-sound–based method and intra-arterial catheters was 0.6 ± 7 mm Hg for systolic blood pressure and –0.06 ± 5 mm Hg for diastolic blood pressure, which was within the recommended range of 5 ± 8 mm Hg for any new blood pressure devices. Conclusions: Our findings provide proof of concept that the heart-sound signal-based method can provide accurate, noninvasive blood pressure monitoring.