A cohort study reporting normal oximetry values in healthy infants under 4 months of age using Masimo technology

Objective: To determine sleeping saturation indices in healthy infants using a modern pulse oximeter with motion artefact extraction technology.

Design: Prospective cohort.

Setting: Home.

Subjects: Healthy term infants.

Intervention: Nocturnal pulse oximetry at home at 1 month of age (Recording 1) and repeated at age 3-4 months (Recording 2). Parents documented sleep times. Visi-Download software (Stowood Scientific) analysed data with artefact and wake periods removed.

Main outcome measures: Saturations (SAT50), desaturation index >4% (DI4) and >3% (DI3) from baseline/hour, delta index 12 s (DI12s), minimum saturations (SATmin), percentage time with saturations below 90% and 92%.

Results: Forty-five babies were studied at 1 month and 38 babies at 3-4 months. Mean (CI) SAT50, DI4, DI3, DI12s and SATmin (CI) were 97.05 (96.59 to 97.52), 16.16 (13.72 to 18.59), 25.41 (22.00 to 28.82), 0.96 (0.88 to 1.04) and 80.4% (78.8% to 82.0%) at 1 month, respectively, and 97.65 (97.19 to 98.12), 8.12 (6.46 to 9.77), 13.92 (11.38 to 16.47), 0.72 (0.65 to 0.78) and 84.7% (83.3% to 86.1%) at 3-4 months. Median (CI) percentage times with saturations below 90% and 92% were 0.39 (0.26 to 0.55) and 0.82 (0.60 to 1.23), respectively, at 1 month and 0.11 (0.06 to 0.20) and 0.25 (0.17 to 0.44) at 3-4 months. For paired samples (n=32) DI4 (P=0.006), DI3 (P=0.03), DI12s (P=0.001), percentage time with saturations below 90% (P=0.001) and 92% (P=0.000) all fell significantly and SATmin (P=0.004) rose between the two recordings.

Conclusion: Desaturation indices are substantially higher in young infants than older children where a DI4 over 4 is considered abnormal. These decrease by 3-4 months of age but still remain elevated compared with older children.