Volume-limited ventilator with compliance compensator

Claim 2

In combination with a volume-limited ventilator for delivering a measured volume of gas into a delivery system adapted to be connected to the respiratory system of a patient; a compensator for maintaining the volume of gas delivered to the patient substantially constant regardless of changes in delivery pressure and the compliance of the delivery system, comprising: means defining first and second variable volume chambers having first and second operators, respectively, of different crosssectional areas and interconnected for common movement to vary the volumes of said chambers in inverse manner, said first chamber having the operator of smaller area; first means communicating between said first chamber and the delivery system to carry gas therebetween, whereby said first operator is responsive to the pressure in the system, and gas is delivered to the system upon decrease in the volume of said first chamber; a source of pressure substantially equal to said delivery pressure but separated from said delivery system; second means communicating between said source and said second chamber to transmit said substantially equal pressure to said second operator and means preventing movement of said operators in a direction supplying gas to said delivery system while the pressure in said delivery system is below a selected level.

Claim 3

The apparatus defined in claim 1 in which said ventilator comprises: a pair of chambers, one of which is connected to the delivery system and the other of which is connected to a cycling operating pressure to cyclically decrease the size of said delivery chamber; said first means connecting said first chamber of said compensator to the delivery chamber of the ventilator; and said second means connecting said second chamber of said compensator to the pressure cycling chamber of said ventilator.

Claim 4

The apparatus defined in claim 2 wherein said means for preventing movement of said operators includes: spring means biasing the operators of said compensator toward the end of their nondelivery stoke.

Claim 5

The apparatus defined in claim 3 in which said compensator operators are pistons slidable in cylinders, the space between said pistons being vented to the atmosphere; the chamber on the working face of said second piston being connected to the pressure cycling chamber of the ventilator; and the chamber on the operating face of said first piston of the compliance compensator being connected to the delivery chamber of the ventilator.

Claim 6

The apparatus defined in claim 4 in which said pistons are rigidly interconnected for common movement and the spring means biases said common moving pistons to the end of their nondelivery stroke, the constant of the spring and the areas of the pistons being selected to deliver a volume of gas into the delivery system substantially varying directly with the pressure in the delivery system to compensate for the compliance of the delivery system and deliver a substantially constant volume of air to the patient.

Claim 7

The apparatus defined in claim 5 in which the ventilator has a regulated stroke to deliver a constant gas volume from the ventilator, and in which the stroke of the compensator pistons varies in accordance with variation of the delivery pressure to increase the stroke of the compensator and the volume of gas delivered therefrom into the delivery system as the delivery pressure increases.

Claim 8

The appaRatus defined in claim 1 in which said first compensator chamber is connected to the respiratory gas supply of the ventilator to be filled therefrom as the compensator moves in its nondelivery stroke.

Claim 9

The apparatus defined in claim 1 in which: said ventilator comprises a cylinder having a piston therein defining a delivery chamber on one side thereof and an operating pressure chamber on the other side; means for cycling operating pressure into said pressure chamber to effect gas delivering strokes of said piston; means feeding respiratory gas into said delivery chamber in the nondelivery strokes of said piston;

Claim 10

The apparatus defined in claim 8 wherein said means for preventing movement of said operators includes spring means biasing the operators of said compensator toward the end of their nondelivery stroke; said compensator operators being interconnected pistons defining a delivery chamber by said first piston and an operating chamber by said second piston; and means venting the nonchamber sides of said compensator pistons to atmosphere.

Claim 11

In combination with a volume-limited ventilator for delivering ventilating gas to a patient, and including a delivery system, and means for cyclically introducing into said system a measured amount of said gas having a preselected volume when the pressure in said system is at a predetermined normal level, the improvement comprising: means defining a compensator chamber adapted to be filled with said gas; means communicating between said chamber and said delivery system to carry said gas between the chamber and the delivery system; means for forcing gas from said chamber into said delivery system through said communicating means, and including an operator movable in said chamber; and actuating means for said operator for sensing increases in the pressure in said system above said normal level and moving said operator in substantially direct relation to said pressure increases so as to maintain successive measure amounts of said gas substantially at said predetermined volume said actuating means including a means preventing movement of said operator in the direction for forcing gas from said chamber while the pressure in said system is below said normal level.

Claim 12

In combination with a volume-limited ventilator for delivering ventilating gas to a patient, and including a delivery system, and means for cyclically introducing into said system a measured amount of said gas having a preselected volume when the pressure in said system is at a predetermined normal level, the improvement comprising: means defining a compensator chamber adapted to be filled with said gas; means communicating between said chamber and said delivery system to carry said gas between the chamber and the delivery system; means for forcing gas from said chamber into said delivery system through said communicating means, and including an operator movable in said chamber; and actuating means for said operator for sensing increases in the pressure in said system above said normal level and moving said operator in substantially direct relation to said pressure increases so as to maintain successive measure amounts of said gas substantially at said predetermined volume said actuating means including a means preventing movement of said operator in the direction for forcing gas from said chamber while the pressure in said system is below said normal level.

Claim 13

The combination defined in claim 10 in which said introducing means include a delivery chamber, a pressure-actuated piston movable in said delivery chamber through a regulated stroke to force said measured amount of gas into said system, and a source for supplying gas to said delivery chamber in preparation for said stroke, said actuating means being responsive to an increase in the pressure required to move said piston to actuate said operator.

Claim 14

The combination defined in claim 11 in which said actuating means includes a sensing chamber having a sensing piston therein with a working face exposed to the pressure for moving the piston in said delivery chamber, said operator being a compensator piston having a working face in said compensator chamber of smaller area than the face of said sensing piston, said sensing and compensator pistons being connected for movement together so that increases in said moving pressure shift said compensator piston in a direction to force compensating gas into said delivery system.

Claim 15

The combination defined in claim 12 wherein said means for preventing movement of said operator includes a spring acting against said connected pistons and correlated with the area differential thereof to hold the pistons stationary while said moving pressure is below a preselected level, thereby to determine the pressure level above which the compensating action is produced.

Claim 16

The improvement defined in claim 10 in which: said ventilator includes a cylinder having a piston therein with a delivery chamber on one side thereof and an operating pressure chamber on the other side; means for cycling operating pressure into said pressure chamber to effect gas-deliveriNg strokes of said piston; means feeding respiratory gas into said delivery chamber in the nondelivery strokes of said piston; means regulating the stroke of said piston to limit the gas volume delivered from the ventilator; and a sensing chamber constituting part of said actuating means; means connecting said sensing chamber to said ventilator pressure chamber; and first and second pistons in said compensator and sensing chambers, respectively, interconnected for common movement, said first piston being smaller than said second piston whereby movement of said pistons in one direction in response to increases in said pressure chamber forces gas from said compensator chamber into said system.

Claim 17

The apparatus defined in claim 14 wherein said means for preventing movement of said operator includes: spring means biasing said first and second pistons in the other direction, toward the end of their nondelivery stroke; and means venting the nonchamber sides of said first and second pistons to atmosphere; said spring means holding said first and second pistons stationary while said operating pressure is below said predetermined level.

Claim 18

In combination with a volume-limited ventilator having a delivery piston movably disposed between drive and delivery chambers to pump gas from said delivery chamber in response to movement of said piston in one direction, means for supplying ventilating gas to said delivery chamber, a delivery system adapted for carrying gas from said delivery chamber to a patient, and means for supplying drive fluid under pressure cyclically to said drive chamber to reciprocate said piston through strokes of regulated length, thereby to pump said gas to said delivery system during successive strokes of the piston, the improvement comprising: means defining a pair of variable volume chambers having operators of different areas interconnected for common movement to vary the volumes of said chambers in inverse manner; means communicating between the chamber with the operator of smaller area and said delivery chamber so that the smaller operator is responsive to the pressure in the delivery system and delivers gas to said delivery chamber while decreasing the volume of the associated chamber; means communicating between the chamber with the operator of larger area and said drive chamber so that the larger operator is responsive to the pressure in the drive chamber, whereby said larger operator moves said smaller operator to deliver gas to said delivery system upon an increase in the pressure in said delivery system increasing the back pressure opposing movement of said piston, thereby to compensate for changes in volume of the gas delivered by said regulated strokes when the pressure in said delivery system changes; and means biasing said operators toward the end of their nondelivery stroke and thereby preventing movement of the operators while the pressure in said drive chamber is below a selected level.

Claim 19

In combination with a volume-limited ventilator having a delivery piston movably disposed between drive and delivery chambers to pump gas from said delivery chamber in response to movement of said piston in one direction, means for supplying ventilating gas to said delivery chamber, a delivery system adapted for carrying gas from said delivery chamber to a patient, and means for supplying drive fluid under pressure cyclically to said drive chamber to reciprocate said piston through strokes of regulated length, thereby to pump said gas to said delivery system during successive strokes of the piston, the improvement comprising: means defining a pair of variable volume chambers having operators of different areas interconnected for common movement to vary the volumes of said chambers in inverse manner; means communicating between the chamber with the operator of smaller area and said delivery chamber so that the smaller operator is responsive to the pressure in the delivery system and delivers gas to said delivery chamber while decreasing the volume of the associated chamber; means communicating between the chamber with the operator of larger area and said drive chamber so that the larger operator is responsive to the pressure in the drive chamber, whereby said larger operator moves said smaller operator to deliver gas to said delivery system upon an increase in the pressure in said delivery system increasing the back pressure opposing movement of said piston, thereby to compensate for changes in volume of the gas delivered by said regulated strokes when the pressure in said delivery system changes; and means biasing said operators toward the end of their nondelivery stroke and thereby preventing movement of the operators while the pressure in said drive chamber is below a selected level.

Claim 20

The improvement defined in claim 1 in which each of said operators is a piston slidable in a cylinder of comparable area, the space between said cylinders being vented to atmosphere.

Claim 21

The improvement defined in claim 17 in which said operator pistons are rigidly interconnected for common movement and said biasing means is a spring urging said operating pistons toward the end of their nondelivery stroke, the constant of the spring and the areas of the pistons being selected to deliver a volume of gas into the delivery system varying substantially directly with the pressure in the delivery system to compensate for the compliance of the delivery system and deliver a substantially constant volume of gas to the patient.

Claim 22

The improvement defined in claim 18 further including means for regulating the stroke of the delivery piston to deliver a constant gas volume from the delivery chamber, and for varying the stroke of the compensator pistons in accordance with variation of tHe delivery pressure to increase the stroke of the compensator pistons and the volume of gas delivered therefrom into the delivery system as the delivery pressure increases.