Normative reference equations of airway dynamics assessed by whole‐body plethysmography during spontaneous breathing evaluated in infants, children, and adults

Effective specific airway resistance (sR(eff)), its reciprocal the effective specific airway conductance (sG(eff)) are computed as ratios between the integral of the resistive aerodynamic work of breathing (sWOB) and the integral of the tidal flow/volume loop, the reciprocal, respectively. Unfortunately, reference equations to obtain normative values for sR(eff), sG(eff), and sWOB are not yet available. To assess reference equations for sWOB, sR(eff), and sG(eff) during tidal breathing at resting level in healthy infants, children, and adults by a multidimensional model. Retrospectively exported data were collected from databases of five Swiss lung function centers, in which plethysmography (Jaeger Würzburg, Germany) was performed for the assessment of airway dynamics, static lung volumes, and forced breathing flow‐volume loops, in a collective of 28 healthy infants, 47 children, and 273 adults. From this cohort, reference equations were computed based on anthropometric measures, lung volumes, indices of the breathing pattern, and timing of breathing. By multi‐linear modeling reference equations of sR(eff), sG(eff), and sWOB could be defined taking as independent parameters apart from anthropometric parameters, also parameters given by the ratio between the tidal volume and functional residual capacity (FRC(pleth)/V (T)), and the ratio between V (T) and inspiratory time (V (T)/T (I)). An alternative statistical approach to define reference equations of airway dynamics reveals that apart from the subject's anthropometric measurements, parameters of the magnitude of static lung volumes, the breathing pattern, and the timing of breathing are co‐variants of reference equations of airway dynamics over a large age range.