Cassette for tonometric calibration

• US 5,997,818 A
• Filed: 02/27/1997
• Issued: 12/07/1999
• Est. Priority Date: 02/27/1997
• Status: Expired due to Term

• Current Assignee: Terumo Cardiovascular Systems Corporation (Terumo Corporation)
• Original Assignee: 3M Company
• Inventors: Franta, David J., Hacker, Thomas G.
• Primary Examiner(s): Pyon, Harold Y.
• Application Number:
  US08/806,368
• Time in Patent Office: 1,013 Days
• Field of Search: 422/68.1, 422/83, 422/86, 422/101, 422/102, 422/104, 436/68, 436/64, 436/172, 210/321.1, 210/321.2, 210/321.3, 210/232, 210/445
• US Class Current: 422/68.1
• CPC Class Codes: A61B 5/14557 specially adapted to extracorporeal circuits
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10

Abstract

A cassette for tonometric calibration especially useful for systems that measure one or more blood parameters includes a cassette having an elongated fluid chamber. In one embodiment of the invention, the fluid chamber includes an expansion region that reduces the likelihood of bubble coalescence of the calibration gas. In another embodiment, inner wall sections of the chamber are provided with a hydrophilic surface. Optionally, a fitting is non-releasably coupled to a casing of the cassette and is movable between a first position for closing a calibration gas outlet port and a second position for venting the calibration gas outlet port. In another embodiment, the cassette includes an elongated sparging tube that extends in a direction generally parallel to the longitudinal axis of the chamber.

Claims

1. A cassette for tonometric calibration comprising:

a casing having a chamber for receiving a quantity of calibration liquid, said chamber having a longitudinal axis extending in an upright direction, said chamber including a lower portion having a gas inlet port for connection to a source of calibration gas, an upper portion having a gas outlet port and a middle portion located between said lower portion and said upper portion;

a gas filter assembly connected to said gas inlet port below said chamber for retaining liquid in said chamber for pretending liquid from leaking from solid chamber and for filtering calibration gas entering said chamber through said gas inlet port, wherein the calibration gas mixes with the calibration liquid in said lower section and said middle portion of said chamber; and

at least one sensor connected to said casing adjacent said middle portion of said chamber for sensing the partial pressure of gas in said chamber,

said chamber including an expansion region located between said middle portion and said upper portion, said expansion region having an area larger than the area of said middle portion in reference planes perpendicular to said longitudinal axis for facilitating the rupture of gas bubbles passing through the liquid, and wherein said middle portion includes wall sections having a hydrophilic surface for facilitating the passage of gas bubbles past said wall sections.

2. The cassette of claim 1 including a fitting coupled to said gas outlet port, said fitting being non-releasably connected to said casing, said fitting being movable between a first position for closing said gas outlet port and a second position for venting said gas outlet port.

3. The cassette of claim 1 wherein said middle portion has a hydrophilic surface.

4. The cassette of claim 3 wherein said hydrophilic surface comprises a coating of heparin.

5. The cassette of claim 1 including an elongated sparger tube connected to said gas inlet port.

6. The cassette of claim 5 wherein said sparger tube comprises polyetheresterketone.

7. The cassette of claim 5 wherein said sparger tube has a longitudinal axis that is collinear with said longitudinal axis of said chamber.