Non-invasive measurements of respiratory system mechanical properties by the forced oscillation technique in spontaneously breathing, mixed-breed, normal term lambs from birth to 5 months of age

To provide a non-invasive approach for monitoring lung function in spontaneously breathing lambs from birth to 5 months of life by the forced oscillation technique (FOT). This report describes the experimental set-up, data processing, and identification of normal predicted values of resistance (Rrs) and reactance (Xrs) of the respiratory system, along with normal bronchodilator response for bronchial reversibility testing. Approach. Rrs and Xrs at 5, 11, and 19 Hz were measured monthly for 5 months in 20 normal term lambs that breathed spontaneously. In seven lambs, repeated measurements also were made within the first month of life (3, 7, 14, and 21 days of life). We determined repeatability and reproducibility of the measurements and characterized the relationship between lung mechanics and age, sex, and body dimensions, using regression analysis, and measured changes in lung mechanics in response to inhaled bronchodilator. Main results. Measurements provided repeatable and reproducible data. Rrs decreased, whereas Xrs increased, with growth from birth through the first 2 months of life, after which no statistically significant differences were detected. We identified normal values equations for Rrs and Xrs and each of the measured anthropometric variables. Respiratory system mechanics were not affected by bronchodilator. Significance. FOT provides reliable non-invasive measurement of respiratory system mechanics in spontaneously breathing term lambs from birth through the first 5 months of life. The methods and normal reference values defined in this study will allow testing the pathophysiological consequences of preterm birth and prolonged respiratory support on respiratory system mechanics. .