Novel capnographic inhomogeneity indices in preterm infants and infants with cystic fibrosis

Abstract

<b>Introduction:</b> Volumetric capnography (VCap) is an easy test to assess lung function in diverse respiratory diseases. Novel capnographic inhomogeneity indices (CII) performed better than classical VCap indices in children with cystic fibrosis (CF), but their performance has never been explored in other disease groups, nor in infants. <b>Aim:</b> We assessed discriminative ability, variability, and comparability of CIIs and classical VCap indices in infants with CF, preterm and term-born infants. <b>Methods:</b> We analyzed 235 tidal breathing files of 27 CF, 54 preterm (PT) and 97 term-born (TB) infants (mean±SD post conceptional age 44.9±1.9 weeks). Primary outcomes were CII1 and CII2, slope III (SIII), and the capnographic index (KPIv). <b>Results:</b> CIIs were highest in CF followed by TB and PT infants (CII1 21.7±7.2% in CF, 19.8±5.5% in TB, 17.9±4.3% in PT infants; CII2 29.4±9.9% in CF, 25.5±7.3% in TB, 22.9±6.4% in PT infants). SIII was similar in all groups (SIII 55.9±17.0%/L in CF, 55.6±23.8%/L in PT and 49.3±16.0%/L in TB infants). KPIv was similar in CF and TB infants, but lower in PT infants (KPIv 20.8±10.5% in CF, 20.6±11.1% in TB infants, 16.8±8.1% in PT infants). Within-test variability was lowest in CIIs (Coefficient of Variation CII1 22.8±12.2%, CII2 21.7±8.6% vs SIII 30.2±10.8%, KPIv 35.5±10.3%). CIIs correlated with SIII and KPIv (R² CIIs-SIII=0.3-0.7, R² CIIs-KPIv = 0.9). <b>Conclusion:</b> Differences in CIIs between CF, PT, and TB infants suggest that CIIs have the potential to detect different underlying pathological processes in infants. CIIs correlated with classical VCap indices but showed lower variability and may thus be a promising alternative.