System and method for measuring volume of liquid in a chamber

A system for measuring the volume of a liquid in a subject chamber, the system comprising:

• transfer means for causing a reference volume of liquid to flow into and out of the subject chamber;
• an isolatable volume of a control gas in communication with the subject chamber such that the total volume of the control gas and the liquid is held constant;
• pressure-measurement means for measuring pressure in the isolatable volume;
• and
• control means for (i) controlling the transfer means, (ii) receiving pressure data from the pressure sensor before and after the reference volume of liquid has flown to or from the subject chamber, and (iii) calculating the volume of liquid in the chamber based on the pressure data, the reference volume and the volume of gas in the subject chamber when the subject chamber is empty of liquid.

A system for mixing and delivering medical liquids to a patient, the system comprising:

• a solvent-supply port;
• a solute-supply port;
• an outlet;
• a measurement chamber;
• a mixing chamber;
• a valve system which controls flow among the solvent-supply port, the solute-supply port, the outlet, the measurement chamber and the mixing chamber;
• an isolatable volume of a control gas in communication with the mixing chamber such that the total volume of the control gas and the liquid in the mixing chamber may be held constant;
• a pressure sensor in communication with the isolatable volume;
• a pressure adjuster which urges fluid into or out of the mixing chamber;
• a delta-volume system which measures changes in volume of liquid in the measurement chamber;
• and
• a controller, which (i) controls the valve system and the pressure adjuster so as to cause a reference volume of liquid to flow between the mixing chamber and the measurement chamber, (ii) receives pressure data from the pressure sensor before and after the reference volume of liquid has flown between the mixing chamber and the measurement chamber, (iii) receives volume data from the delta-volume system, and (iv) calculates the volume of liquid in the mixing chamber based on (a) the pressure data, (b) the reference volume and (c) the volume of gas in the mixing-chamber when the mixing chamber is empty of liquid.

A method for measuring the volume of a liquid in a subject chamber, the method comprising:

• isolating a volume of a control gas in communication with the chamber such that the total volume of the control gas and the liquid is held constant;
• measuring the initial pressure of the control gas;
• exchanging a reference volume of liquid between the subject chamber and a second chamber, after measuring the initial pressure of the control gas and while the volume of control gas remains otherwise isolated;
• measuring the final pressure of the control gas, after the second volume of liquid has been removed from the chamber and while the volume of control gas remains otherwise isolated;
• and
• calculating the volume of liquid in the chamber based on (a) the initial pressure, (b) the final pressure, (c) the reference volume and (d) the volume of gas in the subject chamber when the subject chamber is empty of liquid.

A method for measuring the volume of a liquid in a chamber, the method comprising:

• isolating a volume of a control gas in communication with the chamber such that the total volume of the control gas and the liquid is held constant;
• measuring the initial pressure of the control gas;
• removing at least a portion of the liquid from the chamber, after measuring the initial pressure of the control gas and while the volume of control gas remains otherwise isolated, the portion having a second volume;
• measuring the final pressure of the control gas, after the second volume of liquid has been removed from the chamber and while the volume of control gas remains otherwise isolated;
• and
• calculating the volume of liquid in the chamber based on (a) the initial pressure, (b) the final pressure, (c) the second volume and (d) the volume of gas in the chamber when the chamber is empty of liquid.

A method for measuring the volume of a liquid in a chamber, the method comprising:

• isolating a volume of a control gas in communication with the chamber such that the total volume of the control gas and the liquid is held constant;
• measuring the initial pressure of the control gas;
• adding a second volume of liquid to the chamber, after measuring the initial pressure of the control gas and while the volume of control gas remains otherwise isolated;
• measuring the final pressure of the control gas, after the second volume of liquid has been added to the chamber and while the volume of control gas remains otherwise isolated;
• and
• calculating the volume of liquid in the chamber based on (a) the initial pressure, (b) the final pressure, (c) the second volume and (d) the volume of gas in the chamber when the chamber is empty of liquid.