Chest
High-volume, Low-pressure Cuffs: Are They Always Low Pressure?
Section snippets
METHODS
We studied the effects of airway pressure on the performance of current ETT cuff designs by using a laboratory model to simulate the extremes of clinically employed positive pressure mechanical ventilation, ie, under conditions of high cl with low PIP vs markedly reduced cl with high PIP.
Three ETT cuff designs, LO, MED and HI were evaluated using 7.0- and 8.0-mm ID ETTs (Fig 1). Resting cuff volumes (the performed just inflated volume) were measured using a calibrated syringe. A mechanical lung
RESULTS
Resting cuff volumes ranged from 5.2 ml for the 7.0-mm ID LO, to 20.6 mL for the 8.0-mm ID HI ETT cuff (Table 1). When cl was 100 ml/cm H2O, a PIP of approximately 15 cm H2O (11 mm Hg) was generated; reducing cl to 15 ml/cm H2O resulted in a PIP of approximately 80 cm H2O (60 mm Hg). After cuff inflation to the predetermined leak volumes we noticed that the airway pressure was transmitted to the cuff, causing intracuff pressure to rise and fall with inspiration and exhalation (Fig 3). The
DISCUSSION
This in vitro experiment utilized a plastic tracheal model specifically recommended by the American National Standards Institute for the testing of ETT cuffs designed for prolonged intubation.10 Plastic tracheal models avoid the problems of rapid deterioration of freshly excised tracheas and poor correlation between animal species.11 While our mechanical model allowed strict control of test conditions, the absolute pressures reported may not accurately reflect in vivoresults. Unlike the poorly
CONCLUSION
The confounding problem of excessive intracuff pressure, which damages the trachea but is necessary to provide a seal at high PIP, has not been resolved. We recently determined that 55 percent of a group of mechanically ventilated SICU patients required cuff inflation pressures in excess of 25 mm Hg despite the use of high-volume, low-pressure cuffs (unpublished data, E.A. Radson, T.E. Banner, M.J. Banner, et al). This observation and the report of Stauffer et al9 suggest that current cuff
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From the University of Florida College of Medicine, Gainesville.