Intra-breath measures of respiratory mechanics in healthy African infants detect risk of respiratory illness in early life

Abstract

Lower respiratory tract illness (LRTI) is a leading cause of mortality and morbidity in children. Sensitive and noninvasive infant lung function techniques are needed to measure risk for and impact of LRTI on lung health. The objective of this study was to investigate whether lung function derived from the intra-breath forced oscillation technique (FOT) was able to identify healthy infants at risk of LRTI in the first year of life.Lung function was measured with the novel intra-breath FOT, in 6-week-old infants in a South African birth cohort (Drakenstein Child Health Study). LRTI during the first year was confirmed by study staff. The association between baseline lung function and LRTI was assessed with logistic regression and odds ratios determined using optimal cut-off values.Of the 627 healthy infants with successful lung function testing, 161 (24%) had 238 LRTI episodes subsequently during the first year. Volume dependence of respiratory resistance (ΔR) and reactance (ΔX) was associated with LRTI. The predictive value was stronger if LRTI was recurrent (n=50 (31%): OR 2.5, ΔX), required hospitalisation (n=38 (16%): OR 5.4, ΔR) or was associated with wheeze (n=87 (37%): OR 3.9, ΔX).Intra-breath FOT can identify healthy infants at risk of developing LRTI, wheezing or severe illness in the first year of life.

Applications of oscillometry in clinical research and practice

“…26,100 On the other hand, the changes in resistance appears to be more useful than reactance for children. 101,102 Obviously both parameters are based on the same impedance measurement; hence, it would not be surprising if they do covariate; nonetheless R 5-20 and A X appear to reflect different properties of the airways. 19 In order to interpret impedance measurements, we need to be able to correlate the parameters with tangible and quantifiable properties of the respiratory system.…”

Effect of nasal airway nonlinearities on oscillometric resistance measurements in infants

“…In vivo measurements. Oscillometric measurements of the respiratory system impedance (Z rs) were performed in healthy term newborns with a custom-made wave tube setup in a setting similar to that described previously (7,9). The study protocol was approved by the Institutional Clinical Ethics Committee of the University of Szeged (91/2011).…”

“…Although some discrepancy in previous estimates of the contribution of R n to R rs may be attributed to differences in methodology and population, measurement and interpretation of R n are profoundly complicated by the anatomic irregularity and complex flow rheology of the nasal passages. The nonlinear pressure (P)-flow (V=) relationship in the upper airways contributes to the dynamic changes in R rs , which have been well documented with intrabreath oscillometry in adults (2,19,21), children (1), and infants (7). Measurement of R rs at points of zero V= [namely at end expiration (R eE ) and end inspiration (R eI )] minimizes the nonlinear contribution of the nasal pathways and the consequent bias in the estimation of R of the lower respiratory tract.…”

Oscillometry of the respiratory system: a translational opportunity not to be missed

“…The hope is that, similar to preclinical oscillometry, a mathematical model able to fit the impedance data from conscious and spontaneously breathing subjects will become available. In the meantime, various approaches are being evaluated and include, for example, an intrabreath analysis of resistance and reactance or similar approaches which suggest that the changes of resistance over the tidal breathing cycle could be used to identify abnormalities ( 106 , 107 ). Similarly, it has been shown that changes in reactance over the breathing cycle in COPD is positive end-expiratory pressure dependent and could be used to assess the severity of the disease as a sign of flow limitation during tidal breathing ( 108 , 109 ).…”