Apnoea of prematurity and changes in cerebral oxygenation and cerebral blood volume

The aim of this study was to analyse the behaviour of cerebral oxygenation and cerebral blood volume (CBV) in preterm infants during apnoea by means of near-infrared spectroscopy (NIRS). The sum of oxygenated and deoxygenated haemoglobin, the total cerebral haemoglobin (Hbtot) corresponds to CBV, whereas the difference of oxygenated minus deoxygenated haemoglobin (HbD) represents a value for cerebral oxygenation. During 2 hours of daytime sleep, 72 polygraphic tracings (including NIRS) were done in 58 premature infants. The main criteria for study entry were clinically evident episodes of apnoeas and prematurity. According to their length, apnoeas were divided into two groups: apnoeas of 5-14 seconds (Group 1) and apnoeas > or = 15 seconds (Group 2). Periodic breathing was excluded from analysis. A total number of 1345 apnoeas in Group 1 and 74 apnoeas in Group 2 were recorded, 647 (46%) fulfilled criteria for further analysis. We observed different patterns of CBV behaviour, but the majority, namely 94% in Group 1 and 87% in Group 2, showed a decrease of CBV during apnoea. There was always a cerebral deoxygenation (decrease in HbD) in association with apnoeas, which was significantly increased in apnoeas of longer duration.