The relationship between patterns of intermittent hypoxia and retinopathy of prematurity in preterm infants

BACKGROUND: We have previously shown an increased incidence of intermittent hypoxemia (IH) events in preterm infants with severe retinopathy of prematurity (ROP). Animal models suggest that patterns of IH events may play a role in ROP severity as well. We hypothesize that specific IH event patterns are associated with ROP in preterm infants. METHODS: Variability in IH event duration, severity, and the time interval between IH events (<= 80%, >= 10 s, and <= 3 min) along with the frequency spectrum of the oxygen saturation (SpO(2)) waveform were assessed. RESULTS: Severe ROP was associated with (i) an increased mean and SD of the duration of IH event (P < 0.005), (ii) more variability (histogram entropy) of the time interval between IH events (P<0.005), (iii) a higher IH nadir (P<0.05), (iv) a time interval between IH events of 1-20 min (P<0.05), and (v) increased spectral power in the range of 0.002-0.008 Hz (P<0.05), corresponding to SpO(2) waveform oscillations of 2-8 min in duration. Spectral differences were detected as early as 14 d of life. CONCLUSION: Severe ROP was associated with more variable, longer, and less severe IH events. Identification of specific spectral components in the SpO(2) waveform may assist in early identification of infants at risk for severe ROP.