GB1248303A - Improvements in or relating to medical respirators - Google Patents

Abstract

1,248,303. Respirators. PYE Ltd. 2 Jan, 1970, No. 243/70. Heading A5T. A respirator comprises a switch 30 which controls flow of gas from a pressure source at port 43A via a pressure regulator into a variable first volume VIA during an expiration period, and controls flow from volume VIA for supply to a patient via a variable restriction 57A during at least part of an inspiration period, a gas container 50A being divided by a moveable member 54A into variable volumes VIA, V2A, respiratory gas pressure in the volume V2A being used to move member 54A to expel gas from volume VIA to the patient and the gas in volume V2A being subsequently transferred to volume VIA for supply to the patient. A pneumatic timing device 21 pressurises a pipe 25 and vents a pipe 26 during the exhalation period, set by control 28, and pressurises pipe 26 and vents pipe 25 during the inhalation period, set by control 27, to control switching valve 30 and a valve 40 in a face mask. During exhalation gas vents from the patient's lungs via the face mask and port 42 and gas flows into volume VIA from volume V2A, and from the pressure source via regulator 45A, which may be calibrated in terms of quantity of gas supplied during inhalation. During inhalation gas is supplied via regulator 45A to expand volume V2A by movement of member 54A to expel gas from volume VIA via valve 30 and variable restriction 57A, which may be calibrated in terms of inhalation period and is set to a value less than or equal to the period set by control 27, to the face mask either via valve 40 or directly via pipe 61. A mixture of gases may be supplied to the patient by providing apparatus as above, such as controls 45A, 57B, valve 32 and volumes V1B, V2B, for each gas. The volume V1 for each gas may have a maximum value dependent on the proportion of that gas in the mixture, which value may be varied by for example a screw such as 62 limiting the stroke of the moveable member. The moveable member may be acted on by a spring to assist movement in one direction and may comprise a free piston with equal or unequal area opposed faces, parallel diaphragms rigidly joined together at equal or unequal area rigid central parts having flexible rolling-diaphragm surrounds, or part of a bellows enclosed within a container, the internal volume of the bellows comprising volume V1 and the space between the bellows and container comprising volume V2.