To combat the unmet need of early detection and monitoring of postpartum hemorrhage (PPH), the leading cause of maternal death, a wearable short-wave infrared (SWIR) photoplethysmography (PPG) sensor was developed for real-time detection and monitoring of hemodilution, a compensatory response to PPH. The device uses wavelengths at 900 and 1300nm, ideal for monitoring hemoglobin and water contributions in blood, respectively. These wavelengths minimally absorb melanin, which has been shown to bias PPG results in pulse oximetry. High signal-to-noise PPG signals have been acquired from both the 900nm and 1300nm channels in human volunteers. Further, the hemodilution sensing capabilities were tested by flowing sheep blood through a pulsatile flow phantom. The ratio of the peak amplitudes of the PPG waveforms from both LEDs showed a linear correlation, demonstrating feasibility to detect hemodilution and provide a low-cost, fully wireless, continuous monitoring tool for early diagnosis and monitoring of PPH.
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