Abstract
Objective—To evaluate the relationship between end-tidal partial pressure of CO2 (ETCO2) and PaCO2 in isoflurane-anesthetized harp seals.
Animals—Three 5-month-old 25- to 47-kg harp seals (Phoca groenlandica).
Procedures—PaCO2 was determined in serial arterial samples from isoflurane-anesthetized seals and compared with concomitant ETCO2 measured with a side-stream microstream capnograph. Twenty-four paired samples were subjected to linear regression analysis and the Bland-Altman method for assessment of clinical suitability of the 2 methods (ie, PaCO2 and ETCO2 determinations). The influence of ventilation rate per minute (VR) on the ETCO2 to PaCO2 difference (P[ET-a] CO2) was examined graphically.
Results—The correlation coefficient between the 2 measurements was 0.94. The level of agreement between ETCO2 and PaCO2 varied considerably. Values of ETCO2 obtained with a VR of < 5 underestimated PaCO2 to a greater degree (mean bias, −4.01 mm Hg) and had wider limits of agreement of −13.10 to 5.07 mm Hg (−4.01 mm Hg ± 1.96 SD), compared with a VR of ≥ 5 (mean bias, −2.24 mm Hg; limits of agreement, −7.79 to 3.30 mm Hg).
Conclusions and Clinical Relevance—These results indicate that a microstream sidestream capnograph provides a noninvasive, sufficiently accurate estimation of PaCO2 with intermittent positive ventilation at a VR ≥ 5 in anesthetized harp seals.
