Minimally invasive highly precise monitoring of respiratory rhythm in the mouse using an epithelial temperature probe

Background: Respiration is one of the essential rhythms of life. The precise measurement of respiratory behavior is of great importance in studies addressing olfactory sensory processing or the coordination of orofacial movements with respiration. An ideal method of measurement should reliably capture the distinct phases of respiration without interfering with behavior. New method: This new method involves chronic implantation of a thermistor probe in a previously undescribed hollow space located above the anterior portion of the nasal cavity without penetrating any soft epithelial tissues. Results: We demonstrate the reliability and precision of the method in head-fixed and freely moving mice by directly comparing recorded signals with simultaneous measurements of chest movements and plethysmographic measurements of respiration. Comparison with existing methods: Current methods have drawbacks in that they are either inaccurate or require invasive placement of temperature or pressure sensors into the sensitive nasal cavity, where they interfere with airflow and cause irritation and damage to the nasal epithelium. Furthermore, surgical placement within the posterior nasal cavity adjacent to the nasal epithelium requires extensive recovery time, which is not necessary with the described method. Conclusions: Here, we describe a new method for recording the rhythm of respiration in awake mice with high precision, without damaging or irritating the nasal epithelium. This method will be effective for measurement of respiration during experiments requiring free movement, as well as those involving imaging or electrophysiology.