Minimal inflation volume for combitube oro-pharyngeal balloon

Background: Excessive filling of the oro-pharyngeal balloon of the Combitube may predispose to injury of the pharyngeal mucosa. We studied the minimum inflation volume for the oro-pharyngeal balloon that provides an adequate airway seal during spontaneous ventilation. Methods: Fifty patients were studied: 25 patients 37F and 25 patients with 41 F Combitube. After Combitube insertion the oro-pharyngeal cuff was inflated with 85 and 100 ml of air respectively. Spontaneous ventilation was maintained. Five ml aliquots of air were sequentially withdrawn from the oro-pharyngeal balloon. Air leak and oro-pharyngeal balloon pressure were checked after each air removal. When an air leak was detected, 5-ml of air was reinflated into the balloon to provide an adequate seal. Results: After correction for H₂O diffusion into the balloon the median minimum inflation volume for an airway seal was 57 ml for both sizes of Combitube. Corresponding mean cuff pressures were 63 ± 17 cm H₂O for 37 F and 68 ± 14 cm H₂O for 41F Combitube. For both sizes of Combitube the balloon pressure exceeded 120 cm H₂O when the oro-pharyngeal balloons were filled with the volume of air recommended by the manufacturer. Conclusions: We conclude that cuff volumes substantially less than those recommended by the manufacturer will provide an effective seal by the oropharyngeal balloon of the Combitube during spontaneous ventilation. This may be of importance in avoiding pharyngeal trauma by the Combitube.