Relationship between measurements of tidal volume and thoracic inflating volume by pressure plethysmography in mice

Abstract

To evaluate the accordance of tidal volume (TV) with thoracic inflating volume (TIV) measured by pressure whole-body or double-chamber plethysmography in mice. TV and TIV by double-chamber plethysmography were simultaneously measured in 6 mice with spontaneous respiratory frequencies 90 - 120/min; TV and TIV by whole-body plethysmography were measured in 8 paralyzed mice ventilated by fixed frequency. TIV value by double-chamber plethysmography was significantly higher than TV [(0.369 +/- 0.014) ml vs (0.356 +/- 0.012) ml, P < 0.01)] in 6 spontaneously breathing mice. TIV value by whole-body plethysmography was significantly lower than TV[(0.233 +/- 0.003) ml vs 0.3 ml, P < 0.001] in 8 paralyzed mice. The TV value assessed by TIV measurement can not be accurate, because of the humidifying and heating of inhaled air and negative thoracic pressure during the measurement.