Comparison of a sidestream capnograph and a mainstream capnograph in mechanically ventilated dogs.
OBJECTIVE
To compare the ability of a sidestream capnograph and a mainstream capnograph to measure end-tidal CO2 (ETCO2) and provide accurate estimates of PaCO2 in mechanically ventilated dogs.


METHODS
Randomized, double Latin square.


METHODS
6 healthy adult dogs.


METHODS
Anesthesia was induced and neuromuscular blockade achieved by IV administration of pancuronium bromide. Mechanical ventilation was used to induce conditions of standard ventilation, hyperventilation, and hypoventilation. While tidal volume was held constant, changes in minute volume ventilation and PaCO2 were made by changing the respiratory rate. Arterial blood gas analysis was performed and ETCO2 measurements were obtained by use of either a mainstream or a sidestream capnographic analyzer.


RESULTS
A linear regression model and bias analysis were used to compare PaCO2 and ETCO2 measurements; ETCO2 measurements obtained by both capnographs correlated well with PaCO2. Compared with PaCO2, mainstream ETCO2 values differed by 3.15 +/- 4.89 mm Hg (mean bias +/- SD), whereas the bias observed with the sidestream ETCO2 system was significantly higher (5.65 +/- 5.57 mm Hg). Regardless of the device used to measure ETCO2, bias increased as PaCO2 exceeded 60 mm Hg.


CONCLUSIONS
RelevancehAlthough the mainstream cas slightly more accurate, both methods of ETCO2 measurement correlated well with PaCO2 and reflected changes in the ventilatory status. However, ETCO2 values > 45 mm Hg may inaccurately reflect the severity of hypoventilation as PaCO2 may be underestimated during conditions of hypercapnia (PaCO2 > 60 mm Hg).
Teixeira Neto
Francisco J
FJ
Department of Veterinary Surgery and Anesthesiology, Faculdade de Medicina Veterinária e Zootecnia, Universidade Estadual Paulista, Botucatu, SP, 18618-000, Brazil.
Carregaro
Adriano B
AB
Mannarino
Rodrigo
R
Cruz
Mariângela L
ML
Luna
Stelio P L
SP
D000818:Animals; D019296:Capnography / Q000379:methods / Q000662:veterinary*; D002245:Carbon Dioxide / Q000097:blood*; D004283:Dog Diseases / Q000097:blood*; D004285:Dogs; D006985:Hyperventilation / Q000097:blood / Q000662:veterinary*; D007040:Hypoventilation / Q000097:blood / Q000662:veterinary*; D016014:Linear Models; D010313:Partial Pressure; D011897:Random Allocation; D012121:Respiration, Artificial / Q000662:veterinary*; D013990:Tidal Volume
D002245:Carbon Dioxide