Investigation of photoplethysmographs from the anterior fontanelle of neonates.

Photoplethysmography (PPG) signals have been investigated at a new anatomical site, the anterior fontanelle (ANTF), on the hypothesis that blood supply at this location is preferentially preserved during cases of poor peripheral circulation which might cause the commercial pulse oximeters to fail to estimate accurately arterial blood oxygen saturation (SpO2). Two custom built reflectance PPG sensors have been developed, one for placement on the fontanelle and one on the periphery (foot). A PPG processing system and software were also developed to process the raw PPG signals and to estimate SpO2. A pilot study on sixteen babies, (9 male, 7 female) with a median age of 15.5 d (interquartile range = 46.8 d) and a median weight of 3.15 kg (SD = 0.93 kg), on a neonatal intensive care unit (NICU) has been carried out. PPG signals from the ANTF were of good quality and high signal-to-noise ratio. The amplitudes of the ANTF PPGs were found to be sensitive to changes in amplitude when amplitudes were observed at the reference PPG site. Bland-Altman analysis of the gold standard blood gas analysis reveals that all three sensors are inaccurate at SaO2 < 85-90 %, but the ANTF sensor shows better mean difference than the commercial device.

Development of an optoelectronic sensor for the investigation of photoplethysmographic signals from the anterior fontanel of the newborn.

There is a need for more reliable, non-invasive and alternative measurement sites for the monitoring of arterial blood oxygen saturation in critically ill newborns at times of peripheral compromise. The anterior fontanelle, a unique anatomical feature of the newborn, has been presented as an alternative site for the estimation of oxygen saturation. A multi-wavelength non-invasive optoelectronic sensor has been designed and developed for the investigation of photoplethysmographic (PPG) signals and blood oxygen saturation values from the fontanelle. In vivo thermal tests of the optical sensor show that under normal operating conditions the heating at the skin surface was negligible (<0.1 °C). Good quality PPGs with large amplitudes and high signal to noise ratio were recorded at all three (red, infrared and green) wavelengths prior to clinical measurements.