GB1338226A - Lung ventilators - Google Patents

Abstract

1338226 Lung ventilators BRITISH OXYGEN CO Ltd 19 Jan 1971 [21 Jan 1970] 2938/70 Heading A5T A lung ventilator comprises a monitoring device which produces electrical signals corresponding to the integrated volume flow of gas to the patient during each inspiratory phase of his breathing, so that when the signals correspond to a desired integral volume flow, the monitoring device is stopped and the succeeding expiratory phase of the cycle started. A gas mixture is passed through a mixer 2 a pattern generator 4 and flow rate device 6. During the inspiratory phase a valve 8 is opened by a controller 10 allowing the gas to pass through a column sensor 12 which sends a signal to an integrator 14 which measures the integral volume of gas passing through the sensor and in turn sends a signal to a comparator 36 which compares this signal with a signal corresponding to a preset volume from a signal generator 38. When the two volumes equalise, a signal is sent to the controller 10 to cut off the inspiratory supply of gas by closing valve 8 and a simultaneous signal is sent to an auxiliary valve 34 which opens a valve 28 which allows the expiratory phase of the cycle to commence. When the patient exhales a build up of pressure in line 30 activates switch 39 which in turn actuates expiratory time switch- 40, and on completion of the expiratory time switch 40, and on completion of the expiratory time period, comparator 36 resets controller 10 to commence another inspiratory phase. A volume sensor 26 in the expiratory stream passes signals to an integrator 27, whose outlet signals are passed into a leak resistor when they reach equilibrium with the constant leaking signal, the balance position being indicated on a meter 42. Excessive deviation from this position, indicating a low breathing rate, or an excessive ventilation rate activates an alarm 44. Should the monitoring device fail a manual rebreathing bay 24 is used to ventilate the patient.