Jacketed respiratory inductive plethysmography in rats: A translational non-invasive method for cardiorespiratory exercise monitoring

Abstract

Introduction

Respiratory inductive plethysmography (RIP) is one of the least restrictive methods for evaluating pulmonary ventilation. It has been used in humans since the 1980s as one of the clinical tests for functional exploration of the respiratory system under different conditions (sleep, rest or exercise) in healthy and in respiratory pathology patients. This method has been adapted and integrated into jacketed telemetry systems used in preclinical large animal research (safety pharmacology, fundamental or applied research, etc.). Thanks to the recent miniaturisation of jacketed telemetric systems, a new solution is available for assessing respiratory function combined with ECG in small mammals [1] (i.e. rats). As exercise was initially used to validate the measurement accuracy of dual-band respiratory inductance plethysmography in humans, it was of interest to qualify this solution in a similar way in rats. The aim is to assess the feasibility of a translational model using this technology to monitor physiological changes associated with exercise on a treadmill.

Methods

For this purpose, male Wistar rats (n = 10.8-9 weeks old) were exposed to an incremental treadmill exercise protocol with speed levels from 5 to 45 cm. s-1. Respiratory parameters (respiratory rate (RespR), minute ventilation (VM), Tidal volume (VT)) and peak inspiratory and expiratory flow (PIF, PEF, PENH) as well as cardiac (heart rate (HR)) and activity level (AL) were continuously monitored and analyzed over the last 30 seconds of each level.

Results

All animals were successfully fitted with the device and returned to their home cages. The control values measured after stabilization were for RespR 165 ± 8 brpm, HR 407 ± 9 bpm and AL 24 ± 4 mg. At least all animals ran successfully on the treadmill with the vest up to 35 cm/sec (n = 10), some reaching 45 cm/sec (n = 6). For the maximum plateau, exercise induced a significant physiological increase (Fig. 1) in respiratory parameters (RespR +74%, 116 ± 26 brpm, P < 0.01**//MV +334%, 1099 ± 197 mL. min-1, P < 0.01**//VT +197%, 4 ± 1 mL, P < 0.01**), as well as HR (+36%, 140 ± 13 bpm, P < 0.05*) and AL (+2358%, 504 ± 57 bpm, P < 0.05*). PIF and PEF showed a significant increase of 86 ± 9 ml. s-1 and 52 ± 11 mL. s- respectively. enhanced Pause (PENH) remained stable during exercise indicating no significant variation of airflow limitation.

Conclusion

In conclusion, this new telemetry jacket can be used to monitor the adaptation of respiratory parameters during a standard forced exercise protocol and in a non-invasive way in rats. It is convenient to use and well tolerated by the animal. This alternative method could be used to refine respiratory monitoring in exercise protocols and offers new perspectives for studying pathological and/or pharmacological phenotype alterations in various models.