Relationship of respiratory mechanics parameters acquired by forced oscillation technique (FOT) and morphological measurements in BALB/c mice

Purpose To assess the relationship between the mechanical properties of the respiratory system, characterized by the constant phase model (CPM) parameters R n , G, and H, and morphological measurements of 18-week-old male BALB/c mice ( n = 31): body mass, nose-to-anus-length (NAL), and ex vivo lung volume. Method A small animal ventilator (SAV), an animal model of lung inflammation (OVA), and a control group (Control) underwent two different protocols of respiratory mechanics assessment under basal conditions: bolus (B) and continuous infusion (CI), which distinguished the type of phosphate-buffered saline (PBS) injection used during the procedure. Thus, four groups were assessed: OVA-B (n = 6), Control-B (n = 7), OVA-CI ( n = 8), and Control-CI (n = 10). Results There were not any significant associations between ex vivo lung volume and the CPM parameters, in contrast to reported works when the volume of air trapped in the lungs is used instead of the whole organ volume. Significant negative correlations (p < 0.05) were found in the Control-CI group for the CPM parameters G and H with body mass (r= − 0.901 and r= − 0.759, respectively) and NAL (r= − 0.860 and r= − 0.861, respectively). In addition, differences in the η ( G/H ) parameter between the groups Control-CI and OVA-B (p = 0.020), and in the ex vivo lung volumes between Control-B and OVA-B (p = 0.031) were also observed. Conclusion The correlational analyses were deemed inconclusive in our overall study, despite some significant results, due to confounding results across the groups.