High-fidelity measurement of pulse arrival time in critically ill children using standard bedside monitoring equipment

<i>Objective</i>. Pulse arrival time (PAT) is known to be correlated with blood pressure. Although PAT can be measured using electrocardiography (ECG), photoplethysmography (PPG), and other signals commonly available in clinical settings, recent literature has noted that devices recording these waveforms are often subject to many hardware-specific factors related to digital filtering, clock synchronization, temporal resolution, and latency. These factors can introduce relative timing errors between the ECG and PPG signals, resulting in a situation where traditional approaches for PAT measurement will not work as intended.<i>Approach</i>. In this work, we propose a methodology that accounts for these confounding factors and generates precise measurements of PAT using standard bedside monitoring equipment. This technique involves using heart rate variability to match heartbeats across waveforms and experimentally profiling the timing systems of bedside medical devices to correct various timing-related artifacts. To improve the precision of the resulting PAT measurements, we model temporal uncertainties stemming from the finite temporal resolution of the waveform samples.<i>Main results</i>. We apply this approach to a dataset comprising approximately 1.6 million hours of continuous ECG and PPG data from over 10 000 unique patients in a pediatric intensive care unit. After demonstrating that the observed timing artifacts are consistent across the entire dataset, we show that accounting for them results in more reasonable distributions of PAT measurements across age groups.<i>Significance</i>. It is our hope that this work will spur discussion around the standardization of PAT measurement using routinely collected signals in a clinical environment.