Pressure infusors: variability in delivered infusion pressure.
A pressure infusor was used to apply external pressures of 300, 250, 200, and 150 mm Hg to 500-ml plastic bags of saline. At constant applied pressure, 50-ml aliquots of saline were periodically withdrawn. The delivered pressures were less than the applied pressures, and the difference increased as the volume of saline within the bag decreased. This inherent pressure difference should be considered when the system is used with a continuous flush device.