Cassette for intravenous-line flow-control system

A method for controlling the flow of intravenous fluid from a source to a patient, the method comprising:

• providing a cassette having:
• a membrane-based valve comprising:
• a rigid housing and a compliant membrane, the housing and the membrane coupled, defining a valving chamber;
• and
• a control valve, the control valve located between the membrane-based valve and the patient;
• wherein a first passage enters the valving chamber at a first mouth provided by the rigid housing, such that flow of fluid via the first passage into the chamber may be prevented when the membrane is forced against the first mouth and wherein a second passage exits the valving chamber at a second mouth provided by the housing, wherein the membrane is large enough and compliant enough and the second mouth is positioned far enough away from the membrane, so that a charge of pressurized fluid is urged by the membrane and may be provided to the patient when both the membrane is forced against the first mouth and the control valve restricts fluid flow;
• providing a control unit for receiving the cassette, the control unit having urging means for urging the membrane against the first mouth and controlling means for controlling the control valve;
• placing the cassette into the control unit;
• causing the controlling means to restrict flow through the control valve;
• dispensing fluid through the first mouth into the valving chamber;
• and
• causing the urging means to seal the membrane against the first mouth.

A method of using a membrane-based valve to smooth the flow of intravenous fluid from a source to a patient, the method comprising:

• providing a cassette having, in fluid communication:
• a membrane-based valve;
• a control means, wherein the control means is located between the membrane-based valve and the patient;
• and
• a pressure-conduction means, wherein the pressure-conduction means is located between the membrane-based valve and the source,
• the membrane-based valve comprising:
• a rigid housing and a compliant membrane;
• the housing and the membrane coupled, defining a valving chamber;
• the fluid communication being a first passage entering the valving chamber at a first mouth provided by the housing such that flow of fluid via the first passage into the chamber may be prevented when the membrane is forced against the first mouth and being a second passage exiting the valving chamber at a second mouth provided by the housing, so that a supply of pressurized fluid may be provided via the second passage to the patient when both the membrane is forced against the first mouth and the control means restricts fluid flow to the patient;
• providing a control unit for receiving the cassette, the control unit having means for urging the membrane against the first mouth, means for controlling the control means, and pressure means for alternately activating fluid flow through the first passage from the pressure-conduction means and deactivating fluid flow through the first passage while filling the pressure-conduction means with fluid from the source;
• placing the cassette into the control unit;
• filling the pressure-conduction means with fluid from the source;
• dispensing fluid through the first mouth into the valving chamber and through the control means to the patient;
• causing the control means to restrict flow to the patient;
• causing the means for urging the membrane to seal the membrane against the first mouth,
• so that a supply of pressurized fluid continues to be provided to the patient;
• and
• refilling the pressure-conduction means.