Fluid-infusion instrument - has fluid chamber kept pressurised by preloading mechanism acting on plunger

摘要

The instrument infuses fluid into a patient, having a tubular housing contg. a sliding plunger. The latter forms a seal between air and fluid chambers, the fluid one being connected via a pipe to the patient's vein. A pre-loading mechanism fits between the plunger and one end of the housing, so as to form the fluid chamber into a source of fluid under pressure. A unit separate from the mechanism sets a relatively constant infusion flow-rate. The pre-loading mechanism is accommodated under pressure between the plunger and the end of the air chamber, or under tension between the plunger and the end of the fluid chamber. ADVANTAGE - Low cost and constant flow rate even over long periods.