Novel integrated wearable sensors for multi-parameter monitoring in critically ill newborns
For preterm infants and severely ill newborns undergoing intensive or intermediate care, it is crucial to monitor their vital signs, in particular their cardio-respiratory system: the heart rate and respiration are monitored by ECG (electrocardiogram), the arterial oxygen saturation (SpO2) by pulse oximetry of the upper (pre-ductal measurements), and of the lower (post-ductal measurements) body to assess for patent ductus arteriosus, especially in case of right-to-left shunt due to persistent pulmonary hypertension, but also to detect cyanotic congenital heart defects, and moreover the oxygenation (StO2) of the fragile brain by NIRS (near-infrared spectroscopy).
State-of-the-art probes for SpO2 are usually attached around the hand/wrist and foot, two locations allowing transmission PPG (photoplethysmography), but also prone to motion artefacts due to the tendency of babies to move arms and legs. This results in inaccurate measurements and many false alarms. In particular the high oxygen saturation values (SpO2 > 95%) are not measured accurately enough to prevent the risk of hyperoxaemia, which in preterm infants may affect the normal growth of blood vessels in the retina (capillary proliferation with development of retinopathy of prematurity) with the danger of visual impairment or blindness. Moreover, and even more important is the growing evidence for short- and long-lasting deleterious effects of hyperoxaemia with its production of hyper-reactive oxygen species (free radicals) acting as an oxidative stress on cells and organs in the newborn infant with physiologically reduced anti-oxidative defence mechanisms. Although the brain is the most fragile organ, the tiny infants, which interferes with daily care.
The aims of this project are to build a novel integrated system, which is able to monitor the SpO2 more robustly and accurately, uses up less body surface of the newborn infant, monitors brain oxygenation, and fuses the data intelligently to achieve a higher sensitivity, specificity and reliability. To prevent motion artefacts, the novel SpO2 sensors will be positioned on the trunk, which can hardly be moved by neonates. Since transmittance PPG is not feasible over this body part, we will employ reflection PPG, which results in raw signals with possible bias and lower signal-to-noise ratio. To alleviate the problem redundancy will be added by means of multi-channel probes and intelligent signal integration with the ECG R-peak signal. Oxygenation of the brain will be closely monitored by a NIRS sensor on the head. In contrast to standard monitoring, the data from the different sources will be intelligently fused and integrated. The hardware integration as multi-parameter probes will lead to smaller probes using up less space on the body and reducing the number of connected cables.
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