Instrumentation for small-animal capnometry

Monitoring of human vital signs - heart rate, respiratory rate, hemoglobin oxygen saturation and others - has become an indispensable part of the standard of care in a hospital setting. For example, vital sign monitoring during administration of general anesthesia is essential, given the role that the anesthesiologist plays in assuming physiologic control. In veterinary settings, however, vital sign monitoring under anesthesia is less common, and may consist simply of a visual assessment of respiratory rate. Vital sign monitoring is especially challenging in small animals, given the high metabolic rates and small volumes under consideration. In this paper, we present a unique nose-cone design and associated instrumentation which allows for measurement of respiratory parameters - e.g., anesthesia gas concentration, inspiratory and expiratory O₂, and inspiratory and expiratory CO₂ (capnometry). Such instrumentation facilitates a physiologic assessment of small animals undergoing general anesthesia, an increasingly important consideration as small animals play a greater role in in vivo biomedical studies. In addition, the techniques proposed herein are suitable for measurement on small respiratory volumes associated with neonatal monitoring.