Intermittent hypoxia and respiratory patterns during sleep of preterm infants aged 3 to 18 months residing at high altitude.

Study Objectives: The aim of this study was to determine the impact of apneas on oxygen saturation and the presence of intermittent hypoxia, during sleep of preterm infants (PTIs) born at high altitudes and compare with full-term infants (FTIs) at the same altitude.

Methods: PTIs and FTIs from 3 to 18 months were included. They were divided into three age groups: 3-4 months (Group 1); 6-7 months (Group 2), and 10-18 months (Group 3). Polysomnography parameters and oxygenation indices were evaluated. Intermittent hypoxia was defined as brief, repetitive cycles of decreased oxygen saturation. Kruskal-Wallis test for multiple comparisons, t-test or Mann-Whitney U-test were used.

Results: 127 PTI and 175 FTI were included. Total apnea-hypopnea index (AHI) was higher in PTI that FTI in all age groups (Group 1: 33.5/h vs. 12.8/h, p = 0.042; Group 2: 27.0/h vs. 7.4/h, p < 0.001; and Group 3: 11.6/h vs. 3.1/h, p < 0.001). In Group 3, central-AHI (8.0/h vs. 2.3/h, p < 0.001) and obstructive-AHI (1.8/h vs. 0.6/h, p < 0.008) were higher in PTI than FTI. T90 (7.0% vs. 0.5, p < 0.001), oxygen desaturation index (39.8/h vs. 11.3, p < 0.001) were higher in PTI than FTI, nadir SpO2 (70.0% vs. 80.0, p<0.001) was lower in PTI.

Conclusion: At high altitude, compared to FTI, PTI have a higher rate of respiratory events, greater desaturation, and a delayed resolution of these conditions, suggesting the persistence of intermittent hypoxia during the first 18 months of life. This indicates the need for follow-up of these infants for timely diagnosis and treatment of respiratory disturbances during sleep.