Patent GB-998472-A (GB)
Title: Improved apparatus for measuring blood pressure and pulse rate
Inventor: KOMPELIEN ARLON DALE
IPC: A61B5/0225
Filed: 1961-07-12
Abstract: 998,472. Measuring blood pressure. HONEYWELL Inc. July 12, 1961, No. 25248/61. Heading A5K. [Also in Division G1] Apparatus for measuring blood pressure, comprises a device, to grip a part of the body including a light source and a photo-sensitive cell, so arranged that the amount of light reaching the photo-cell from the source, varies according to the amount of blood in the gripped part of the body, and means for applying a progressively increasing pressure to the gripped part to oppose blood flow into it whereby the photo-cell gives a pulsing signal output due to variations in the light falling thereon, the A.C. component of which reaches a maximum amplitude when the pressure reaches the diastolic blood pressure and then falls to zero when the pressure increases to systolic blood pressure, and electrical circuits responsive to said component to store or record a first signal representative of the pressure when the said component has substantially a maximum amplitude and a second signal when said component has subsequently fallen substantially to zero. As shown, the A.C. component is divided into diastolic and systolic paths comprising amplifiers 55, 95 and relays 65, 96, the former also comprising a CR and diode network allowing only pulse trains of ascending amplitude to be applied to the input of the diastolic amplifier. The relays 65 and 96 contain switch contacts 66 and 97, activated by the pulsed output of the associated amplifier, which control the supply of voltage from transducer 34 to memory capacitors 70 and 102 and memory amplifiers 80 and 104, the pressure actuating the transducer being produced by a cam 33 and bellows 32 arrangement, forcing air trapped by valve 31, into an expandible chamber forming one of the gripping faces of the gripping device 10, Fig. 2 (not shown). In use, for example on an ear lobe, the pressure is gradually increased until the blood is just forced out of the lobe at minimum heart pumping pressure, giving a pulsating photo-cell output having an A.C. component increasing in amplitude to a maximum, at which time the increasing transducer voltage across the memory capacitor 70, periodically applied by relay contact 66, is read out by closing switch 85 to a recorder 100 giving the diastolic pressure. Pressure is now further increased, resulting in the reduction and final stoppage of the A.C. component the voltage across the memory capacitor 102 representing the systolic pressure, then being read out by closing switch 105. Valve 31 is now opened by means of a switch 41, reducing the pressure to zero. A pulse rate measuring circuit may be incorporated comprising a stepping relay 110, activated through diastolic relay contact 114, stepping up the output of a resistance divided 116 to a level proportional to the pulse rate. The measurement is taken at zero applied pressure prior to the blood pressure measurement with the CR, diode network shortcircuit by switch 60. Switches 40, 60, 59, 112, 136, 85, 105, 120 and cam 33 are controlled by a programmer 45, and switches 41, 75 and 101 are controlled by a time delay interval switch 131 activated by systolic relay contact 98.