Using pulse oximetry waveforms to detect coarctation of the aorta

Fig. 1. Example of neonatal pulse oximetry screening algorithm. Reprinted from the public domain at the CDC’s Congenital Heart Defects Information for Healthcare Providers (https://www.cdc.gov/ncbddd/heartdefects/hcp.html) [18]. Note that an indeterminate zone merits repeated screening in order to attempt to minimize false positives

Fig. 2. Schematic of aortic arch with and without coarctation. a Shows normal fetal circulation with a patent ductus arteriosus (PDA) connecting the pulmonary artery to the aorta. b Shows normal constriction of the PDA in post-natal circulation. c Shows the most common location for aortic coarctation. Note the head, neck and upper extremity vessels branch off the aorta proximal to the most common location to have coarctation of the aorta. The arteries that perfuse the legs are located more distal from the coarctation. Thus, waveform analysis is able to identify pulse oximetry signal characteristics both proximal and distal to site of coarctation

Fig. 3. Preoperative differences in maximum rates of rise and fall. The Y-axis represents a normalized slope (waveform amplitude divided by time) where a greater difference means there was a noticeable difference when comparing upper vs lower extremity waveforms. There was no significant difference in rate of rise between groups (p value 0.54), but there was a significant difference of rate of fall between the control and the coarctation group (p value 0.004)

Fig. 4. Postoperative differences in maximum rates of rise and fall. The Y-axis represents a normalized slope (waveform amplitude divided by time). There was no significant difference between groups in rate of rise (p value 0.61) or fall (p value 0.93) following surgical repair of coarctation of the aorta

Fig. 5. Utility for the proposed pulse oximetry screening algorithm. Here we show the receiver operating characteristic curve for the linear discriminant analysis classifier used in classifying subjects as having a COA or not. The area under the curve is 0.78. The suggested operating conditions are indicated by the red circle, with a suggested operating point at a sensitivity of 0.61 and a specificity of 0.94

Fig. 6. Schematic of waveform analysis. Here we demonstrate a pulse oximetry waveform with superimposed electrocardiogram (ECG). Rate of rise and fall are determined by specific points for each waveform cycle. The maximum (rate of rise or fall) is calculated over a rolling 40-ms window between the points at the trough and peak. The average (rate of rise or fall) is calculated between points located at the 20th and 80th percent of the waveform amplitude. Phase delay and peak delay are the time intervals between the peak R wave of ECG to the trough or peak of the pulse oximetry waveform as indicated