Total Lung Capacity Maneuver as a Tool Screen the Relative Lung Volume in Balb/c Mice

Assessment of the mechanical ventilation in rodents is widely performed using a mechanical ventilator for small animals (SAV). One of the main adjustable parameters in SAV is tidal volume, typically 10 mL/kg, which is configured in relation with the animal body weight. Traditionally, the preset TLC maneuver is used for alveolar recruitment; this study aims to explore the data from TLC to screen the relative lung volume in Balb/c mice, in order to analyze its relationship to the body weight of mice. The TLC maneuver allowed us to measure the relative delivered lung volume from PEEP (positive end-expiratory pressure) to 30 cm H\(_{2}\)O. In overall, one hundred twenty-four (124) 13–20 week-old Balb/c mice were used, animals were split into two groups using mean value of the body weight (24g) as a cutoff point. Group H (n =51) had animals with body weight higher than the mean value, while mice with lower body weight belonged to group L (n = 73). Significant positive correlation was found within animals in the group H (r = 0.6137); conversely, animals in group L did not present correlation for relative volume and body weight (\(r\approx 0\)). Additionally, an analysis of static compliance (Cstat) was conducted for each group using unpaired t-test (\(p<0.05\)). Therefore, it was possible to indicate that mice with lower body weight presented lower static compliance compared with those with greater body weight. Results suggest that tidal volume apparently depends on recruitment volume or compliance instead of the mice body weight.