Application of a three-dimensional kinematic model for prediction of tidal volume in newborns: a pilot study

Background: Chest movement quantification and noninvasive monitoring have been useful in evaluation of newborn (NB) lung function. Different methods have already been tested, however, there is little progress regarding the agreement of these new tools in neonatal practice. Aim: To evaluate the agreement between the tidal volume (Vt) estimated by the three-dimensional analysis of the thoracoabdominal movement in the Matlab® software and the Vt predicted by the body weight of term newborns (NBs). Methods: This is a cross-sectional, quantitative and analytical study with NBs filmed for 2 minutes in a dorsal position and maximal exposure of the thoracoabdominal region. Vt (in ml) was estimated from the three-dimensional analysis of thoracoabdominal movement in the Matlab® software and compared to the predicted Vt per kilogram of weight for each NB (5 ml/kg), on a Bland-Altman plot. Results: Thirteen NBs (gestational age: 39.1 ± 0.8 weeks), with a mean weight and length of 3175.4 ± 493.8g and 49 ± 2.8cm, respectively, were included in the study. Vt estimated by the kinematic analysis was 16.3 ± 4.2 ml and 15.9 ± 2.5 ml according to the calculation for the predicted value for weight. The difference between the means of the studied values was 0.4 ml (bias), with p = 0.624 and confidence interval of -5.2 to 6.0 ml. Conclusions: The methods for Vt measuring are interchangeable in this sample of NBs, suggesting that the three-dimensional analysis of thoracoabdominal motion in Matlab® software can estimate the Vt of terms NBs, in a simple, fast and noninvasive way. Thus, the evaluation by Matlab® is promising and should be tested with methods that are gold standard for Vt evaluation.