Device for applying compressive pressure against a patient's limb

Abstract: A device for applying compressive pressures to a patient's limb having a sleeve (112) for placement on the patient's limb, with the sleeve having a plurality of chambers (114,116,118) arranged longitudinally along the sleeve including a monitored chamber (114), a device (120) responsive to a control signal for forming a fluid under pressure, a device (141) for generating said control signal, a device (141) for selecting a predetermined value of said control signal to be generated by the generating device to select a desired predetermined pressure to be formed by the forming device (120), a device (126,128,130,132,114a,114b,114c) for connecting the fluid from the forming device to the chambers (114,116,118) of the sleeves including the monitored chamber (114), a device (141) for comparing the pressure of the monitored chamber with the desired predetermined pressure of the selecting device, and a device (141) responsive to the comparing device (141) for modifying said control signal of the generating device (141) to control the forming device (120) to form the desired predetermined pressure.

Description: The present invention relates to a device for applying compressive pressures to a patient's limb. Blood flow in patient's extremities, particularly the legs, markedly decreases during extended terms of confinement. Such pooling or stasis is particularly acute in surgery and during recovery periods immediately thereafter. Blood flow compressive devices, such as shown in United States Patents 4,013,069 and 4,030,488, incorporated herein by reference, develop and facilitate the application of compressive pressures against a patient's limb and in so doing promote venous return. The device comprises a pair of sleeves which are wrapped about the patient's limbs, with a controller for supplying the pressurized fluid to the sleeves. Sleeve devices are disclosed in United States Patents 4,402,312 and 4,320,746, incorporated herein by reference. One use for the above mentioned devices is the prevention of deep venous thrombosis (DVT) which sometimes occurs in surgical patients when they are confined to bed. When a DVT occurs, the valves that are located within the veins of the leg can be damaged which in turn can cause stasis and high pressure in the veins of the lower leg. Patients who have this condition often have leg swelling (edema) and tissue breakdown (venous stasis ulcer) in the lower leg. US-A-4,370,975 discloses a device for applying compressive pressures to a patient's limb comprising a sleeve for placement on the patient's limb, the said sleeve having a plurality of chambers arranged along the sleeve including a monitored chamber, means for forming a fluid under pressure and means for connecting the fluid under pressure from the forming means to the chambers of the sleeve. In the past, the fluid supplied by the controller to the sleeves was controlled by a flow control valve, and it is desirable to provide an improved manner of controlling the pressure supplied to the sleeves. The present invention relates to an improved device for applying compressive pressures to a patient's limb. According to the present invention a device for applying compressive pressures to a patient's limb comprises means for forming a fluid under pressure; a sleeve for placement on the patient's limb, said sleeve having a plurality of chambers arranged longitudinally along the sleeve including a monitored chamber; means for connecting the fluid under pressure from the forming means to the chambers of the sleeve, including the monitored chamber and is characterised in that the means for forming a fluid under pressure are responsive to a control signal, and in that the device comprises: means for generating said control signal; means for selecting a predetermined value of said control signal to be generated by the generating means to select a desired predetermined pressure to be formed by the forming means; means for comparing the pressure of the monitored chamber with the desired predetermined pressure of the selecting means; and means responsive to the comparing means for modifying the said control signal generated by the generating means to control the forming means to form the desired predetermined pressure. A feature of the invention is that the pressure of the monitored chamber is compared by comparing means with the desired predetermined pressure of the selecting means. Another feature of the invention is the provision of means responsive to the comparing means for modifying the control signal of the generating means to control the forming means to form the predetermined pressure. Thus, a feature of the invention is that predetermined pressure is formed in a simplified manner merely by selection of push buttons. Another feature of the invention is that the predetermined pressure is formed by electrical signals. Yet another feature of the invention is that the predetermined pressure is formed with increased precision. The invention may be put into practice in various ways and one specific embodiment will be described by way of example to illustrate the invention with reference to the accompanying drawings in which: Figure 1 is a plan view of a controller for a compressive pressure device of the present invention; Figure 2 is a diagrammatic view of the device of the present invention; and Figures 3 to 5 are diagrammatic views of electrical signals utilized in the device of the invention. Referring now to Figure 2, there is shown a device generally designated 110 for applying compressive pressures to a patient's limb. The device 110 has a sleeve 112 for placement on the patient's limb having a plurality of inflatable chambers 114, 116, and 118 arranged longitudinally along the sleeve 112, including an ankle chamber 114 which will be referred to as the lower or remote chamber. Preferably it is chamber 114 which is monitored. The device 110 has a linear oscillator compressor 120 for forming a fluid, such as gas, under pressure. The compressor 120 is energized by an electrical cord 122 which may be connected to a suitable source of electrical energy by a plug 123, and which has a triac 124 electrically connected to the cord 122 for turning power on and off to the compressor 120. The output of the compressor 120 is connected by a conduit 126 to a plurality of solenoid valves 128, 130, and 132 which control distribution of the pressurized fluid from the compressor 120 to the sleeve chambers 114, 116, and 118 by associated conduits 114a, 114b, and 114c in a manner forming a compressive pressure gradient which decreases from the lower or remote chamber 114 to the upper or proximal chamber 118 of the sleeve 112. A conduit 134 is connected in fluid communication with the conduit 114a extending from the ankle chamber 114, and the conduit 134 is connected to a pressure transducer 136 which generates an electrical signal over an electrical lead 138 to a central processing system 141 (hereinafter "CPS") and to a suitable display 140 for indicating the pressure in the chamber 114. The CPS 141 is preset for a desired predetermined pressure, as will be described below, and the CPS 141 is electrically connected by an electrical lead 142 to the triac 124. The CPS 141 compares the selected desired predetermined pressure with the pressure measured by the transducer 136. The CPS 141 forms a sine wave signal, as shown in Figure 3, and rectifies the signal of Figure 3 into a plurality of electrical pulses, such as positive pulses, as shown in Figure 4. The CPS 141 normally generates a nominal number of pulses, such as 148, during a specified period of time. In response to the difference between the selected and measured pressures, the CPS 141 selects any number of the pulses of Figure 4 by inhibiting or filtering a calculated number of pulses to form the modified pulse pattern, as shown in Figure 5. The formed pulses are connected to the triac 124 over the lead 142 in order to control the fluid pressure formed by the compressor 120 by energizing and deenergizing the compressor 120 responsive to the formed number of pulses, the number of which may vary during different time periods, to obtain the desired predetermined pressure. Thus, the output of the compressor 120 is controlled by means of pulses through feedback pressure control for the compressor 120. A controller 144 with a suitable display is illustrated in Figure 1 which is utilized to control the device 110. The controller 144 has a cycle monitor portion 146, and a fault indicator display 148. The controller 144 has a pressure display 140, previously described in connection with Figure 2, which is used to show the set pressure, preferably the ankle pressure. An additional display 160 to the right of the cycle monitor 146 indicates whether or not the controller 144 has achieved the set pressure. The control membrane switches 152 and 154 are used for increasing and decreasing the set ankle pressure. To the left of the fault indicator 148 is hidden a membrane switch 156, which, when pressed, will cause the pressure display 140 to monitor ankle pressure for one complete cycle, e.g. of 72 seconds, after which the display 140 will revert to displaying the set pressure. During this monitoring phase, there should be no difference between the set pressure and the final compression pressure displayed. When the controller 144 is first turned on the following sequence of events will occur. The controller 144 will default to a set pressure of 45 mmHg and will show this on the display 140. The compressor 120 will come to full output during the inflation portion of the cycle in order to more quickly fill the sleeve 112. During this start up phase, the high pressure alarm 162 can be ignored, if necessary; however, as soon as the pressure at the end of the ankle compression exceeds some predetermined minimum value, the output of the compressor 120 will be reduced. The light emitting diode (hereinafter "LED") 160 indicating that the set pressure has not been achieved is lit. Within four cycles, the system reaches its set pressure. At that time, the running LED 164 will light, and the previous LED 160 will extinguish. If a pressure other than 45 mmHg is desired, pressing the upper pressure adjusting membrane switch 152 will increase the set pressure in 1 mmHg increments for each pressing of the switch. Holding the switch down for two seconds will result in the set pressure increasing at a rate of approximately 1 mmHg each half second for as long as the switch is held. Pressing the lower membrane switch 154 will decrease the set pressure in the same way. The set pressure range is 25 mmHg to 65 mmHg. When the set pressure is changed, the running LED 164 is extinguished and the adjusting LED is lit. The adjustment is completed within four cycles. The foregoing detailed description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.

Claims: A device for applying compressive pressures to a patient's limb comprising: means (120) for forming a fluid under pressure; a sleeve (112) for placement on the patient's limb, said sleeve having a plurality of chambers (114,116,118) arranged longitudinally along the sleeve including a monitored chamber (114); means (126,128,130,132,114a,114b,114c) for connecting the fluid under pressure from the forming means (120) to the chambers (114,116,118) of the sleeve, including the monitored chamber (114); characterized in that the means (120) for forming a fluid under pressure are responsive to a control signal, and in that the device comprises: means (141) for generating said control signal; means (141) for selecting a predetermined value of said control signal to be generated by the generating means (141) to select a desired predetermined pressure to be formed by the forming means (120); means (141) for comparing the pressure of the monitored chamber with the desired predetermined pressure of the selecting means; and means (141) responsive to the comparing means for modifying the said control signal generated by the generating means (141) to control the forming means (120) to form the desired predetermined pressure. A device as claimed in Claim 1 characterized in that the forming means (120) comprises a compressor. A device as claimed in Claim 1 or Claim 2 including means (122,123,124) for energizing the forming means (120), and in which the generating means (141) controls energization of the forming means (120). A device as claimed in Claim 1, 2 or 3 characterized in that the connecting means (126,128, 130,132) includes means for forming a compressive pressure gradient in the chambers (114,116,118) which decreases from a lower or remote portion to a proximal or upper portion of the sleeve. A device as claimed in Claim 4 characterized in that the monitored chamber comprises a lower or remote chamber of the sleeve. A device as claimed in any one of Claims 1 to 5 characterized in that the generating means (141) forms a predetermined sequence of pulses. A device as claimed in Claim 6 characterized in that the modifying means modifies the said predetermined sequence to a lesser number of pulses than the said predetermined sequence. A device as claimed in any one of Claims 1 to 7 characterized in that the generating means (141) comprises means for forming a signal comprising a sine wave, and means for rectifying the signal to form the sequence of pulses. A device as claimed in Claim 8 characterized in that the modifying means includes means for deleting pulses from the predetermined sequence.

Inventors: DYE JOHN F, DYE, JOHN F.
Applicants: KENDALL & CO, THE KENDALL COMPANY
Application year: 1990
Main classification: A61H23
IPC codes: A61H23, A61H1, A61H7