Detection of patent ductus arteriosus using photoplethysmography
Methods and systems are described for detecting the likelihood of patent ductus arteriosus (PDA) in an infant using electrocardiogram and photoplethysmographic pulse signals obtained from the upper body and foot of the infant.
1. A system for detecting patent ductus arteriosus (PDA) in an infant comprising a photoplethysmograph having one or more channels, one or more computing devices comprising one or more processors, a memory unit, a display device, and a computer-readable storage medium including computer-readable code that is read by the one or more processors to perform a method comprising the steps of:
a) obtaining or receiving electrocardiogram (ECG) signals from the infant;
b) obtaining or receiving photoplethysmographic (PPG) signals from a site on the upper body (UB) of the infant, and optionally from a foot (F) of the infant;
c) determining, for each PPG pulse a PPG pulse amplitude (AM), the AM defined as an amplitude between the end-diastolic maximum and the consecutive systolic decrease minimum for the UB PPG pulses;
d) determining the mean of one or more of the following parameters for a plurality of the PPG pulses:
(i) a relative pulse amplitude (rAM) by dividing the AM by the systolic decrease minimum to obtain a rAM for the upper body (rAM-UB) PPG pulses;
(ii) a pulse transit time (PTT-UB) between an R wave of the ECG and an onset of systolic decrease for the corresponding UB PPG pulse;
(iii) a ratio PTT-UB/rAM-UB between the pulse transit time (PTT-UB) and the relative pulse amplitude for the UB (rAM-UB) PPG pulse; and
(iv) a ratio rAM-UB/PTT-UB between the relative pulse amplitude for the UB (rAM-UB) PPG pulse and the pulse transit time (PTT-UB); and
e) detecting patent ductus arteriosus (PDA) in the infant when one or more of:
the relative pulse amplitude for the UB (rAM-UB) is elevated above normal,
the ratio PTT-UB/rAM-UB is decreased below normal, or
the ratio rAM-UB/PTT-UB is elevated above normal,
wherein the term “normal” refers to values of parameters obtained from infants with a closed ductus arteriosus.
2. The system of claim 1 , wherein the steps further comprise one or more of selecting a section of PPG pulses without movement noise for analysis, low-pass filtering PPG signals to reduce high frequency noise, and smoothing PPG signals using a moving average filter.
3. The system of claim 1 , wherein the photoplethysmograph has an infrared light source.
4. The system of claim 1 , wherein in step d) a parameter from 10-20 pulses is averaged to obtain a mean.
5. The system of claim 1 , wherein UB PPG signals are obtained or received from the right hand of the infant.
6. The system of claim 1 , wherein UB PPG signals are obtained or received from the forehead or an earlobe of the infant.
7. The system of claim 1 , wherein a closed ductus arteriosus is detected when the rAM-UB value is 1.5% or less.
8. The system of claim 1 , wherein a patent ductus arteriosus (PDA) is detected when the rAM-UB value is above 2%.
9. The system of claim 1 , wherein a patent ductus arteriosus (PDA) is detected when the rAM-UB value is above a predetermined value in a range of 1.7% to 2.6%.
10. The system of claim 1 , wherein a closed ductus arteriosus is detected when the PTT-UB/rAM-UB ratio is 50 ms/% or more.
11. The system of claim 1 , wherein a patent ductus arteriosus (PDA) is detected when the PTT-UB/rAM-UB value is below 30 ms/%.
12. The system of claim 1 , wherein a patent ductus arteriosus (PDA) is detected when the PTT-UB/rAM-UB value is below a predetermined value in a range of 25 ms/% to 35 ms/%.
13. The system of claim 1 , wherein a closed ductus arteriosus is detected when the rAM-UB/PTT-UB ratio is 24%/s or less.
14. The system of claim 1 , wherein a patent ductus arteriosus (PDA) is detected when the rAM-UB/PTT-UB value is above 30%/s.
15. The system of claim 1 , wherein a patent ductus arteriosus (PDA) is detected when the rAM-UB/PTT-UB value is above a predetermined value in a range of 30%/s to 35%/s.
16. The system of claim 1 , further comprising obtaining or receiving echocardiographic measurements from the infant and using one or more of the following parameters in combination with rAM-UB or in place of rAM-UB: ratio left atrium diameter/aorta diameter, left pulmonary artery peak end diastolic velocity, and left ventricle shortening fraction.