(363) Continuous Transabdominal Fetal Pulse Oximetry (TFO) in Pregnant Ewe Models under Induced Fetal Hypoxia

Thursday, February 9, 2023

10:30 AM – 12:00 PM

Objective: Fetal heart rate monitoring is a poor predictor of fetal hypoxia for its high false-positive rate. Using a novel TFO, this study aims to demonstrate feasibility of continuous, non-invasive assessment of fetal arterial blood oxygen saturation (fSpO₂) in hypoxic in-utero lamb models.

Study Design: Fetal hypoxia was induced in 5 gravid term ewes via inflatable balloon catheter in the infrarenal aorta (Fig 1). Fetal carotid arterial lines were used for arterial blood gases (ABG/fSaO₂). The right fetal forelimb was left exposed for conventional pulse oximetry, and TFO device was placed on the ewe’s abdomen. The balloon was inflated stepwise to decrease the ewe’s distal mean arterial pressure (dMAP) in 5mmHg increments. Each dMAP step was maintained for 10 min, and fSaO₂ was recorded at 2.5, 5, and 10 min. The balloon was fully deflated after two consecutive readings of fSaO₂ < 15%. Maximum of three rounds were performed. A subset of photoplethysmography (PPG) signals collected by the TFO and concurrently collected fSaO₂ values were used to calibrate the TFO machine learning (ML)-based algorithm for determining fSpO₂ from PPG signals. The TFO was calibrated under six scenarios. In each scenario, PPG data collected from four ewes and a specific fractional PPG data in the 5^thewe, designated as target sheep (TS), was used for calibration. The calibration setup at 0% TS PPG data was repeated five times where in each calibration event, the TS PPG data was increased to 20%, 40%, 50%, 60%, and 80% consecutively. Each sheep was used as the TS once for this process (Fig 2).

Results: In Fig 2, the TS fSpO₂ correlated with concurrent fSaO₂ values shown in each subplot scenario shows better correlations when more data was used for calibration. When at least 50% of the TS PPG data contributed to the calibration, fSpO₂ was found to be highly correlative with fSaO₂ (r > 0.61 and p< 0.001).

Conclusion: The study confirmed feasibility of continuous transabdominal fetal pulse oximetry, and highlighted the need for collection of additional datasets to improve accuracy of estimating fSpO₂ from PPG with the ML-based algorithm.

Primary & Presenting Author(s)

Weitai Qian, MS
UC Davis College of Engineering
Davis, California, United States

Coauthor(s)

Kourosh Vali, BS
Graduate Student, Electrical & Computer Engineering
University of California Davis
Davis, California, United States
Begum Kasap, MS (she/her/hers)
PhD Candidate
Electrical & Computer Engineering, University of California Davis
Davis, California, United States
CP
Christopher D. Pivetti, MS
Staff Research Associate III, Department of Surgery
University of California Davis Health
Sacramento, California, United States
Christina M. Theodorou, MD
University of California at Davis Medical Center
Sacramento, California, United States
EK
Edwin S. Kulubya, MD
University of California at Davis Medical Center
Sacramento, California, United States
KY
Kaeli J. Yamashiro, DO
Resident, Department of Surgery
University of California Davis Health
Sacramento, California, United States
AW
Aijun Wang, PhD
University of California Davis
Sacramento, California, United States
HH
Herman L. Hedriana, MD
Chief of Obstetrics
University of California Davis
Sacramento, California, United States
DF
Diana Lee Farmer, MD
Professor & Chair, Department of Surgery
University of California Davis Health
Sacramento, California, United States
SG
Soheil Ghiasi, PhD
Associate Professor, Electrical & Computer Engineering
University of California Davis
Davis, California, United States