Abstract: In an infusion system, a source of pressurized liquid infusate is connected to the upstream end of a small-bore flow restrictor and drives a flow of infusate therethrough; the downstream end of the flow restrictor is connected to the patient. The infusate at the upstream end is in communication with an annulus inflatable by infusate pressure of at least 200 to 500 Torr; the infusate at the downstream end is in communication with another annulus inflatable by infusate pressure of only 35 to 110 Torr, as occurs during infiltration. Inflation of an annulus provides a visible indication and can provide electrical contact for an alarm.

Abstract: An infusion system utilizing a pressurized source of infusate comprises a capillary tube flow restrictor having sufficient length and suitably large ratio of length to internal diameter to provide reliably repeatable fluid resistance and minimum damage to infusate. The internal diameter of the flow restrictor may be made to decrease with increasing temperature so that the flow rate of the infusate is substantially independent of temperature. The flow restrictor may include means for indicating pressures and flow of infusate.