MONITORING ADEQUACY OF VENTILATION BY CAPNOMETRY DURING THORACOTOMY IN DOGS

Objective-To determine whether end-tidal partial pressure of carbon di oxide (PETCO2) was a reliable estimate of Paco(2) in dogs undergoing t horacotomy. Design-Case series. Animals-18 dogs that underwent thoraco tomy. Procedure-Paco(2) and PETCO2 were measured shortly after inducti on of anesthesia, while dogs were breathing spontaneously; 5 minutes p rior to initial skin incision, while dogs were receiving intermittent positive-pressure ventilation (IPPV); 5, 30, and 60 minutes after the thoracic cavity was opened, while dogs were receiving IPPV; and after the thoracic cavity was closed and evacuated, when dogs were again bre athing spontaneously. For each period, arterial-end-tidal difference i n partial pressure of carbon dioxide (PaCO2-PETCO2) was compared with PaCO2-PETCO2 for the preceding period. Results-Significant changes in Paco(2)-PETCO2 from one period to the next were not detected except wh en values obtained 5 minutes after the thoracic cavity was opened were compared with values obtained 5 minutes before incision. The PaCO2-PE TCO2 was not constant for individual dogs. Clinical Implications-PETCO 2 was not a reliable indicator of adequacy of ventilation during thora cotomy in these dogs, because it differed greatly from Paco(2),and Pac o(2)-PETCO2 was not consistent.