A simple device for humidification of inspired gases during volatile anesthesia in rats

The typical setup for administering volatile anesthetics to laboratory rats does not provide for humidification of the inspired gases, although it is known that failing to provide humidification can lead to airway inflammation and impaired pulmonary function during prolonged experimental protocols. We developed a simple humidification system in which a nebulizer was inserted into the nonrebreathing circuit used with a standard isoflurane vaporizer. We show here that the nebulizer system resulted in anesthetic stability, as measured by withdrawal reflex latency. Although the isoflurane concentration in the delivered gases was reduced, the reduction was a consistent percentage of the vaporizer output throughout the anesthetic range, thereby permitting straightforward adjustment of the vaporizer output.