High-resolution respiratory inductive plethysmography in rats: validation in anesthetized conditions

Respiratory monitoring is often required in experimental physiological and pharmacological studies in rodents. Currently, the mostly used techniques are direct measurement of airflow on intubated animals and whole body plethysmography.

Although the reliability of these methods has been broadly demonstrated, they also have several drawbacks such as invasiveness, high cost of use or confinement of the animals. Respiratory inductive plethysmography (RIP) is a non-invasive technique already used in medium-sized mammals that has not yet been evaluated in small rodents. The implementation of inductive plethysmography in rats represents an instrumental challenge because of the small inductances that are expected.

A rodent-specific RIP apparatus has been developed and compared to direct airflow measurement provided by a pneumotachograph (PNT) considered as the invasive gold standard for respiratory monitoring. The experiments were carried out on anesthetized rats artificially ventilated at different levels of tidal volumes (V _T) covering the whole physiological range.

Based on the Euclidian distance between signals, this study shows that after calibration, signals from RIP fit at 93% with PNT values. The Bland and Altman plot evidences differences between RIP and PNT lower than 20% and the values obtained are highly correlated (R  =  0.98, p  <  0.001).

This study demonstrates that it is possible to design RIP systems suitable for measurement of tidal volumes and airflow in anesthetized rats. Further studies will now be focused on the validation in extended physiological conditions.