Insufflator

Claim 1

In an insufflator for introducing limited quantities of carbon dioxide into the human body for operational purposes, particularly for laparoscopy of the type including an inlet for connection to a source of carbon dioxide under pressure, an adapter connection for medical instruments, particularly, laparascopes and hysteroscopes, insertable in the human body, and pressure regulator means connected in series to the inlet and followed by a gas flow monitoring device, and through which, in series, the carbon dioxide is directed from the gas supply to the adapter connection, the improvement comprising, in combination, said pressure regulator means being constituted by two pressure regulators connected in series between said inlet and said flow-monitoring device and constantly adjusted to respective fixed gas supply pressures; said monitoring device comprising an expansion container having end and side walls with an inlet port located centrally of one end wall and an outlet port located centrally of the other end wall, the expansion container having a large cross-sectional area perpendicular to the flow direction therethrough, and having a peripheral zone spaced laterally from said inlet and outlet ports in which the gas flow velocity approaches a zero rate; sensing elements, providing currents corresponding to a measured variable of the gas flow, provided in said expansion container and including first sensing element located immediately in the area of said inlet port, and subjected to the gas flow, and a second sensing element located in said peripheral zone close to the side wall of said container at the maximum possible lateral spacing from said first element; a flow-directing cylindrical screen surrounding said first sensing element and shielding said second sensing element from the gas flow through said inlet port to said outlet port; a precision aperture, permanently adjusted to the maximum rate of flow, connected in series following said outlet port; an adjustable precision needle valve following said precision aperture; a pressure gauge connected to said adapter connection to indicate the back pressure at said adapter connection; a measuring bridge including said first and second sensing elements and having an input and an output; a source of electrical potential connected to the input of said measuring bridge; a measuring amplifier having an input connected to the bridge output and deriving the quotient of the respective currents of said first and second sensing elements, and having an output; an indicator, of the rate of gas flow per unit of time, connected to the amplifier output; the rate of flow being adjustable by said precision needle valve in accordance with the reading of said indicator; an integrator connected to the output of said amplifier; and a second indicator, for indicating the total gas flow, connected to said integrator, whereby the reading of said second indicator permits the drawing of a quantitative conclusion as to the size of the gas bubble in the human body.