Inappropriate cuff filling is responsible for various complications related to the use of an endotracheal tube (ETT). In this study, we evaluated an objective, noninvasive method for continuous assessment of leak around the ETT cuff by monitoring carbon dioxide pressure (P(CO2) in the upper airway. P(CO2) levels were measured by capnography simultaneously between the ETT cuff and the vocal cords, at the oropharynx, and in the nares of the nose. Cuff filling was regulated by an electronic controller to achieve the minimal pressure needed to prevent CO2 leak. Feasibility of the method was assessed in a human simulator and in a porcine model. Clinical function was evaluated in 60 patients undergoing surgery, comparing the method to the standard anesthesiologist evaluation. Linear correlations were observed between the ETT cuff pressure and P(CO2) level in the human simulator (R2 = 0.954, P < 0.0001) and in the porcine model (R2 > 0.98, P < 0.0001). Iodine leak around the ETT cuff, in the porcine model, occurred only when P(CO2) levels were >2 mm Hg. In the surgery patients, the mean ETT cuff pressure determined clinically by the anesthesiologist was significantly higher than the optimal cuff pressure assessed by P(CO2) (25.2 +/- 3.6 versus 18.2 +/- 7.8 mm Hg, respectively; P < 0.001). According to these findings, optimal ETT cuff filling pressure can be identified by monitoring P(CO2) at the nares or the oropharynx.
Implications: A new, objective, noninvasive method for optimizing endotracheal tube cuff filling based on monitoring carbon dioxide levels in the upper airways can be used to identify the minimal cuff pressure necessary to eliminate leak and prevent aspiration.