Transcutaneous blood gas CO2 monitoring of induced ventilatory depression in mice.

We assessed a simple, noninvasive method of monitoring transcutaneous partial pressure of CO, (Ptcco(2)) in mice to determine whether it would provide an accurate and reproducible method to assess ventilatory depression in mice. To this, end, Ptcco(2) and Paco(2) (partial pressure of arterial CO2) measurements were performed on isoflurane-anesthetized male C57Bl/6 mice breathing differing percentages of CO2 or fentanyl, a known ventilatory depressive drug. All doses of fentanyl produced a sharp increase in Ptcco(2) values within 20 min with difference in Ptcco(2) values between saline and all fentanyl groups being statistically significant (P < 0.0001). A good correlation between Paco(2) and ptcco(2) values was established (r(2) = 0.91). A Bland-Altman analysis likewise found that Ptcco(2) measurements in the mice reliably and accurately reflected their Paco(2) values. Therefore, under controlled conditions, Ptcco(2) measurements were found to reliably reflect Paco(2) values in mice. Consequently, the ptcco(2) method can be used as a means to rapidly and quantitatively assess the ventilatory depressive properties of a wide spectrum of drugs, under varying conditions in numerous mouse models.