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Demand-responsive gas blending system for medical ventilator

  • US 4,702,240 A
  • Filed: 07/22/1986
  • Issued: 10/27/1987
  • Est. Priority Date: 07/22/1986
  • Status: Expired due to Term
First Claim
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1. A gas blending system for blending two gases in response to a sub-ambient demand applied by a ventilator or the like, said gas blending system comprising:

  • positive displacement gas pump means for periodically creating said sub-ambient demand;

    demand valve means, having an outlet, and an inlet adapted to be coupled to a pressure-regulated supply of a first gas, for providing a flow of said first gas from said inlet to said outlet, in proportion to the demand experienced by said outlet; and

    a blending valve, having a first inlet coupled to the outlet of said demand valve means, a second inlet coupled to a substantially ambient-pressure supply of a second breathable gas, and a blended gas outlet adapted to be fluidly coupled to said gas pump means, wherein said blending valve includes proportioning means for selectively adjusting the relative flow capacities of said first and second inlets;

    whereby, when said inlet of said demand valve means is coupled to a pressure-regulated supply of a first gas, and said blended gas outlet is coupled to said gas pump means, the total blended gas flow through said blended gas outlet is proportional to the total demand applied to said blended gas outlet by said gas pump means, and whereby the percentage of said first gas in said total blended gas flow is proportional to the ratio of the demand applied to said first blending valve inlet to the total demand applied to said blended gas outlet.

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