Method
Twenty one brain injured patients with PEG Foley catheter were studied and divided into three groups by indwelling duration. The balloon of Foley catheter was inflated with 5 ml of normal saline. We calculated the deflating velocity of the balloon by estimating remained amount of normal saline and indwelling duration at the time of replacement.

Results
In 6 patients, the PEG Foley catheter was pulled out easily before aspiration of remained normal saline. In all of these cases, remained amount of normal saline was less than 2 ml. The deflating velocities of the balloons were 0.057⁑0.024 ml/day in cases with 3 to 4weeks of indwelling duration, 0.066⁑0.005 ml/day with 4 to 5 weeks, 0.067⁑0.012 ml/day with above 5weeks. The mean deflating velocity was 0.063⁑0.016 ml/day in human. The deflating velocity was slower than that of the previous study in vitro.

Conclusion
The mean days of deflation of the balloon of total PEG Foley catheter down to 2.5 ml were 42.1 days. We suggest that the PEG Foley catheter would be replaced within 42 days after exchange. (J Korean Acad Rehab Med 2003; 27: 485-488)