Patent GB-1459680-A (GB)
Title: Respirator-
IPC: A61M16/00
Filed: 1974-04-25
Abstract: 1459680 Respiratory appliances TECNA CORP 25 April 1974 [26 April 1973 4 Oct 1973] 18129/74 Heading A5T A respirator comprises a displacement chamber 61 with a coil 75 deflecting the position of a piston 71 relative to a surface (62) and producing a signal proportional thereto to actuate a valve 57 to control the flow of gas from a supply to the chamber to move the piston 71 against the action of springs (72) away from the surface, the chamber 61 being in communication with a patient airway 154. Compressed air from compressor 12 or reservoir 26 is fed to accumulator 36 of similar construction to chamber 61. An oxygen valve 88 and an air valve 57 are respectively opened and closed to supply compressed oxygen from source 83 to chamber 61 for a selected portion of the travel of piston 71 and air for the remaining portion. A signal from a tidal volume control 196 determining the quantity of gas for a single breathing cycle is fed to an air volume detector 194 with the instantaneous piston 71 position signal representing the volume of chamber 61. A signal from an oxygen to air ratio control 209 is fed to an oxygen volume detector 207 with the piston position signal. A signal from a control 253 for choosing the minimum volume of chamber 61 required to trigger the apparatus is fed to a chamber empty detector 251 with the piston position signal, the detector output 'being sent to an inflation hold timer 257 which delays the onset of the inflation portion of the cycle. When the chamber 61 is at its maximum volume, detector 194 sends a signal to an AND gate (267) with a signal triggered by the selected ratio of exhalation time to inhalation time. The AND gate (267) sends a signal to an inhalation gate (273) with a signal from a respiration rate timer (274), the inhalation gate (273) causing an inhalation valve 106 to open and allow the air and oxygen to pass from chamber 61 to airway 154 and thence to a patient's mask. After a timer (289) times out, inflation of chamher 61 recommences and a valve 179 is energised to largely exhaust a balloon 159 in an exhalation valve 157 so that the patient can exhale. A continuous Train of cycles can be performed. A manual or timed signal connects a deep breathing increment control 203 instead of control 196 to detector 194 so that a larger volume can be inhaled. An integrator (396) ensures the exhalation time exceeds the previous inhalation time, lighting a lamp (418) if this is not so. If the patient reduces the pressure in airway 154 for a sufficient time, he can initiate inhalation. A drop in oxygen pressure adjacent source 83 causes the oxygen to be shut off by valve 57 and a lamp (514) to be lit. A low pressure in airway 154 at the instant of commencement of exhalation lights a lamp (343). Exceeding the desired maximum inhalation pressure ends inhalation and lights a lamp (443). A continuously running timer (474) is normally reset at the end of exhalation, if not reset it times out and lights a lamp (484). Abnormal pressure in airway 154 at the end of expiration lights a lamp (507). A mains failure lights a lamp (526) via an auxiliary supply. All alarm lamps remain lit after being triggered and also trigger a common audible alarm. In a second embodiment (Figs. 10-12B, not shown), a valve (93') opens to admit atmospheric air if the pressure in chamber (61') is too low. A nebuliser (120') is provided and optionally fed by a compressor (124'). The inspiratory flow rate can be varied during a breathing cycle e.g. to decrease the flow rate as inspiration progresses. When a maximum inspiration. pressure is execeeded, a valve (431') exhausts the chamber (61') to atmosphere.