Laboratory Evaluation of 4 Brands of Endotracheal Tube Cuff Inflator

INTRODUCTION: Routine measurement of endotracheal tube (ETT) cuff pressure is a standard in respiratory care, and several devices are available for measuring ETT cuff pressure. Yet an informed choice in the buying process is hindered by the present paucity of unbiased, comparative data.

METHODS: Four brands of cuff inflator were tested: Posey Cufflator, DHD Cuff-Mate 2, Rüsch Endotest, and SIMS-Portex Cuff Pressure Indicator. Ten randomly selected 8.0-mm-inner-diameter ETTs were modified and tested in a trachea model. The cuffs were gradually inflated and deflated. After each sequential change in cuff volume, cuff pressure measurements were simultaneously recorded with the cuff inflator and with a calibration analyzer. These data were compared using limits-of-agreement analysis. Then, with each of the 10 ETTs, each cuff inflator was used to measure 3 known (ie, measured with the calibration analyzer) cuff pressures: 20, 40, and 60 cm H₂O. Cuff pressure measurements were averaged, by brand, and compared to the respective baseline cuff pressure. Finally, using the 10 ETTs and trachea model, the ETT cuffs were inflated, in 0.25-mL increments, using only a syringe and the calibration analyzer. The cuff pressure and cuff volume data from that procedure were plotted and the best-fit regression line was determined.

RESULTS: There were differences in bias and precision among the tested cuff inflators. The Cuff-Mate 2 had the smallest bias and best precision. None of the cuff inflator brands accurately measured cuff pressure. In each case the Cuff-Mate 2 measured cuff pressures closest to actual. The Cuff-Mate 2 contains about half the compressible volume of that in the Endotest and Cufflator and < 20% of that in the Cuff Pressure Indicator. Regarding the relationship between cuff pressure and intracuff volume, the best-fit linear regression equation was: cuff volume = 0.05 x CP – 0.39 (r² = 0.96).

CONCLUSIONS: The 4 cuff inflators tested differ in bias and precision and none of the devices accurately measure cuff pressure. Cuff inflator manufacturers should design an accurate yet reasonably priced device to inflate ETT cuffs, and ideally that device should allow cuff-pressure checks without decreasing cuff pressure. In the meanwhile clinicians may opt to use my proposed cuff-pressure measurement technique, which minimizes the loss of cuff pressure during cuff-pressure checks and provides more accurate cuff-pressure measurements.