Preterm infants are at high risk of brain injury, mainly due to low blood flow and oxygenation in the brain. With this project we aim to assess the impact of various physiological and environmental factors on brain oxygenation level in the very preterm infants undergoing intensive care. The various factors to be investigated include blood pressure fluctuations, cardiac output, apnoeas, oxygen desaturations, ventilation changes and blood sampling procedures. We will use Near Infrared Spectroscopy to measure cerebral oxygenation non-invasively by the cotside of preterm infants, and correlate the changes with the various factors being investigated. The project will provide important knowledge on the effects of common physiological events, and interventional therapies on brain oxygen levels in these very small infants. The information may provide the basis on which brain protection strategies can then devised. Large amount of data has been collected on infants studied whilst receiving care in the Neonatal Intensive Care Unit at Monash Medical Centre (MMC). Cerebral oxygenation is measured at the cotside using Near Infrared Spectroscopy (NIRS) and expressed as tissue oxygenation index (TOI, %). The TOI is derived by commercially available NIRS (NIRO 200, Hamamatsu Photonics K.K., Japan). The application of NIRS in newborn infants has been described in our previous study. The NIRS produces near-infrared light which can penetrate biological tissues. Light is delivered to the baby by an optode secured to the head by an elasticised bandage over the temporoparietal region; a second receiving optode is positioned 4 cm away. Analogue signals of cardiorespiratory parameters, including arterial blood pressure, ECG, thoracic impedance, transcutaneous partial pressure of carbon dioxide, beat-to-beat arterial oxygen saturation (SaO2) recorded from right upper limb, were collected continuously and simultaneously with TOI measurements. Data was digitalised at 400Hz (PowerLab 16SP, ADInstruments, NSW, Australia) and averaged at 1Hz. The infants are studied weekly, for 2-3 hours at each study. During the study, the infant spends half of the time sleeping prone (on the belly) and half of the time sleeping supine (on the back). Effects of physiological changes and clinical events will be correlated with changes in TOI in the preterm infants. We are currently analysing the effects of apnoeas and periodic breathing on the brain oxygenation in these preterm infants, and how these change during different sleeping positions. References: Shepherd, K.L., Yiallourou, S.R., Odoi, A., Brew, N., Yeomans, E., Willis, S., Horne, R.S.C., and Wong, F.Y. (2019). Effects of Prone Sleeping on Cerebral Oxygenation in Preterm Infants. J Pediatr 204, 103-110 e101. Shepherd, K.L., Yiallourou, S.R., Horne, R.S.C., and Wong, F.Y. (2018). Prone sleeping position in infancy: Implications for cardiovascular and cerebrovascular function. Sleep Med Rev 39, 174-186. Shepherd, K.L., Yiallourou, S.R., Odoi, A., Yeomans, E., Willis, S., Horne, R.S.C., and Wong, F.Y. (2020). When does prone sleeping improve cardiorespiratory status in preterm infants in the NICU? Sleep 43.
Preterm brain, brain oxygenation, infant sleep, periodic breathing, apnoea, paediatric
Joint PhD/Exchange Program