Laboratory animals
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This report describes a simple, non-invasive electronic device that employs a compact accelerometer integrated circuit to transduce movements in the chest wall of an anaesthetized animal into an analogue signal that can be used to calculate the rate and relative depth of respiration. The device requires amplification by signal processing hardware/software which are common to most experimental laboratories. We assessed the sensitivity of the device by its ability to detect changes in respiratory patterns produced by modulating the depth of anaesthesia in isoflurane-anaesthetized Wistar rats. ⋯ Deepening the anaesthesia produced a gradual decrease in RR, a decrease in dominant spectral frequency of the electroencephalogram (EEG) but no change in the heart rate. There was a significant correlation between RR and the dominant spectral frequency of the EEG, indicating that one useful application of the monitor could be to identify anaesthetic stages. The results demonstrate that respiratory parameters can be recorded using a simply constructed, low-cost device and suggest an application in the monitoring of anaesthetic depth.
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Endotracheal intubation in mice is both a common and important technique. However, it is a difficult procedure because of the small orotracheal size and the success rate is variable. There have been many reports of refined techniques that facilitate intubation but only a few reports have proposed how to verify the proper placement of the endotracheal tube. ⋯ When the catheter was inserted correctly into the trachea, the water in the extension tube oscillated in synchrony with the movement of the mouse's thorax, indicating correct placement of the catheter. This method was simple, reliable and use materials that are routinely available. This method is helpful for experimental mouse models that require airway access.