Method for noninvasive determination of arterial PCO2 in anesthetized rats

A method for the noninvasive determination of arterial PCO2 in mechanically ventilated rats is presented. In normotensive, rats under steady state conditions where a depth of anesthesia adequate to abolish spontaneous ventilatory effort was used, end-tidal CO2 and arterial PCO2 were highly correlated (r = 0.96; p less than 0.001). The regression equation for this relationship was: PaCO2 (mmHg) = 6.757 +/- 8.984 ETCO2(%). This method obviates the need for arterial cannulation and may be useful in neuropharmacological research in rats when knowledge of arterial CO2 alone is required.