Respiratory reactance at 6 weeks predicts lower respiratory tract illness in early life in a South African birth cohort

Abstract

The use of the forced oscillation technique (FOT) to assess within-breath respiratory mechanics has lead to new insights into airway obstruction (Czovek et al., Thorax, 2016), flow limitation and lung inhomogeneity (Lorx et al., ERJ2017) in adults and older children. Aim: To test within-breath respiratory mechanics in a South African birth cohort (Drakenstein study) for predicting lower respiratory tract illness (LRTI) during the first 6 months of life. Methods: The within-breath changes of respiratory resistance (R) and reactance (X) were measured at 16 Hz with a modified FOT during natural sleep in healthy infants at 6-10 weeks. The mean total R and X values, and the changes between end-expiration and end-inspiration (ΔR and ΔX) were calculated. LRTI surveillance was performed and any episode was confirmed by study staff. Results: Acceptable assessments of respiratory mechanics were available in 666 infants (50.1% male, median[IQR] gestational age: 39[37;40] w, length z-score: -0.76[-1.67;0.11]) of which 113 infants had 177 LRTI episodes in the first 6 months of life. From the impedance variables, ΔX and ΔR were significantly different between the two groups (p Conclusion: This study is the first to show that within-breath measures of respiratory mechanics in infants may predict susceptibility to LRTI. The altered ΔX in healthy infants suggests that lung inhomogeneity may be a predisposing factor for lung disease in early life. Wellcome Trust;Gates Foundation;HRF