Reference values of diaphragmatic dimensions in healthy children aged 0-8 years

Abstract Purpose Diaphragmatic thickness (Tdi) and diaphragm thickening fraction (dTF) are widely used parameters in ultrasound studies of the diaphragm in mechanically ventilated children, but normal values for healthy children are scarce. We determined reference values of Tdi and dTF using ultrasound in healthy children aged 0–8 years old, and assessed their reproducibility. Method In a prospective, observational cohort, Tdi and dTF were measured on ultrasound images across four age groups compromising at least 30 children per group: group 1 (0–6 months); group 2 (7 months-1 year); group 3 (2–4 years); group 4 (5–8 years). Results Ultrasound images of 137 healthy children were included. Mean Tdi at inspiration was 2.07 (SD 0.39), 2.09 (SD 0.38), 1.73 (SD 0.33) and 1.70 (SD 0.30) mm for group 1, 2, 3 and 4 respectively. Mean Tdi at expiration was 1.63 (SD 0.33), 1.67 (SD 0.27), 1.40 (SD 0.23) and 1.40 (SD 0.24) mm for group 1, 2, 3 and 4 respectively. Mean Tdi at inspiration and mean Tdi at expiration for groups 1 and 2 were significantly greater than those for groups 3 and 4 (p < 0.001 respectively). Median dTF was 27.1% (SD 12.5), 24.7% (SD 8.6), 24.1% (SD 10.4) and 21.2% (SD 6.8) for group 1, 2, 3 and 4 respectively. The intraclass correlation coefficients for intra-rater and inter-rater reliability were 0.995 (95% CI 0.983–0.999) and 0.989 (95% CI 0.983–0.995), respectively. Conclusion Ultrasound measurements of Tdi and dTF were highly reproducible in healthy children aged 0–8 years. ClinicalTrials.gov identifier (NCT number): NCT04589910