Principles and Methods of Transcutaneous Carbon Dioxide Pressure ( TcPCO₂ ) Measurement for Continuous Free Flap Monitoring

Abstract

Transcutaneous carbon dioxide pressure ( TcPCO₂ ) was originally used for noninvasive measurement of the partial pressure of carbon dioxide ( PaCO₂ ) during arterial blood monitoring, and in various conditions, TcPCO₂ values were found to be more stable than transcutaneous oxygen pressure ( TcPO₂ ) values. In experiments involving animals, TcPCO₂ values were found to increase rapidly with each arterial and venous occlusion for abdominal pedicle flaps. In addition, at 37℃, TcPO₂ and TcPCO₂ were measured in healthy men. In these men, these variables were measurable at all skin surface sites ; moreover, the median values of TcPCO₂ ranged from 40 to 70mmHg. This study included the last 49 patients who underwent free flap surgery between January 2002 and June 2011. Of these patients, 2 had venous thrombosis. For those with compromised flaps, reanastomosis was immediately performed after identifying a TcPCO₂ value of >90mmHg. Our experimental and clinical results indicat that, at 37℃, TcPCO₂ values are more stable than TcPO₂ values ; moreover, TcPCO₂ can be used as a predictable method for monitoring vascular skin complications. Continuous monitoring of TcPCO₂ at 37℃ can provide objective information and alert doctors and nurses to the need for checking the free flaps.