APPARATUS AND METHOD FOR CONTINUOUS PASSIVE MOTION OF THE LUMBAR REGION

Abstract: Apparatus for cycling the lower back of a person through a substantial range of lordosis. The apparatus includes a substantially static structure adjacent to the back of a person and a force applying apparatus (18) disposed between the static structure and the back of the person. The force applying apparatus includes a back engaging surface cyclically movable to increase and decrease the distance between the static structure and the back engaging surface so as to cycle the lower back through the range of lordosis. A transducer (54) has an output responsive to the force between the back engaging surface and the lower back and the output of the transducer is utilized by the force applying apparatus to control the force applied to the back. Timing circuitry (24) provides a force increasing period to increase the force applied to the back up to a preselected maximum and a force decreasing period to decrease the force on the back. A period of substantially constant force may be provided between the force increasing period and the force decreasing period.

Description: APPARATUS AND METHOD FOR CONTINUOUS PASSIVE MOTION OF THE LUMBAR REGION Background of the Invention This invention relates to method and apparatus for providing continuous passive motion to the body and more particularly to the lumbar region of the spine. U.S. Patent No. 4,981,131 issued to one of the inventors herein disclosed apparatus for cycling the lumbar region of the spine through a substantial range of lordosis for the purpose of relieving low back pain. The teachings of this patent are incorporated by reference herein. In this patent, an inflatable bladder in contact with the back is pressurized and depressurized to effect the substantial change in lordosis. There was no provision, however, to measure and control the force applied to the person's back throughout the inflate and deflate cycles. Therefore, the teachings in this patent could not readily accommodate variations in a person's spinal compliance, posture and position during the spinal mobilization. Nor did this patent teach adjustment of the location of the bladder to accommodate different individuals. Summary of the Invention The apparatus for cycling the lower back of a person through a substantial range of lordosis includes a substantially static structure adjacent to the back of a person and a force applying apparatus disposed between the static structure and the back. The force applying apparatus includes a back engaging surface cyclically movable to increase and decrease the distance between the static structure and the back engaging surface, thereby to cycle the lower back through the range of lordosis. A transducer is provided having an output responsive to the force between the back engaging surface and the lower back. The force applying apparatus is responsive to the output of the transducer to control the force applied to the back. In a preferred embodiment, the apparatus further includes programmable circuitry for controlling the force to be a preselected function of time. In this embodiment, the apparatus includes timing circuitry to provide a force increasing period to increase the force applied to the back to a preselected maximum and a force decreasing period to decrease the force on the back. A third, substantially constant force period may be provided between the force increasing period and the force decreasing period. In one embodiment, the force applying apparatus includes an inflatable and deflatable bladder and the transducer responds to pressure within the bladder. A pump supplies a fluid for inflating the bladder and a valve communicating with the bladder is provided for deflating the bladder. It is preferred that the location of the back engaging surface be adjustable in height so that the force engaging surface may be adapted to the lumbar region of a particular person. In yet other embodiments, the force applying apparatus includes a rack and pinion or a mechanical cam arrangement for cyclically increasing and decreasing the force on the person's back. In these mechanical embodiments, the force transducer is a load cell. The force feedback of the present invention allows a maximum force to be preselected by the user to accommodate for that particular user's spine compliance and other factors. Brief Description of the Drawing Fig. 1 is a cross-sectional view of an embodiment of the apparatus disclosed herein. Fig. 2 is a schematic illustration of layout of the components for the apparatus of the invention. Fig. 3 is a schematic illustration of the functional relationship among components of the apparatus of the invention. Fig. 4 is a graph of support pressure as a function of time. Fig. 5 is a logic diagram for the force feedback. Figs. 6 and 7 are diagrams of die main program loop and the interrupt process loop. Fig. 8 is a cross sectional view of a cam operated embodiment of the invention. Fig. 9 is a cross sectional view of a rack and pinion embodiment of the present invention. Figs. 10, 11 and 12 are perspective views of an embodiment of the invention permitting adjustment of the location of the inflatable bladder. Fig. 13 is a perspective view of an embodiment of the invention including multiple bladders. Fig. 14 is a cross-sectional view of the embodiment of Fig. 13. Fig. 15 is a perspective view of an embodiment of the invention permitting mechanical adjustment of the location of the inflatable bladder. Fig. 16 is cross-sectional view of the embodiment of Fig. 15. Fig. 17 is a cross-sectional view of an embodiment for supine use. Description of the Preferred Embodiment With reference first to Fig. 1 a person 10 is seated in a seat 12 having a bottom support 14 and a backrest portion 16. The seat 12 may typically be an automobile or other vehicle (aiφlane, boat) seat, or, for example, an office chair. Disposed between the person 10 and the backrest 16 in this embodiment is a continuous passive motion device 18. As will become clear below, the device 18 includes apparatus for cyclically moving the lumbar region 20 of the person 10 so as to cycle the lower back or lumbar region 20 through a substantial range of lordosis. As discussed in detail in applicant's prior U.S. Patent No. 4,981,131, research indicates that continuous passive motion of the lower back through a substantial range of lordotic movement ameliorates lower back pain. Such motion is not massage which relates merely to superficial tissues but constitutes motion of vertebrae with respect to one another. Because spinal compliance varies among individuals of a population, a force suitable for one individual may be insufficient or excessive for another person. The present invention recognizes these differences and provides preselected force versus time patterns to accommodate such variations in the general population. Fig. 2 is a schematic representation of the layout used in a commercial version embodying die present invention and available from Ergomedics, Inc. of Winooski, Vermont, assignee of the present application. In this embodiment, a pump 22, available from Appollo Enteφrises, Inc., Ontario, California, model 5000, is preferably a 12 volt alternating current (AC) pump similar to those used for aerating fish tanks. It is preferred mat the pump 22 be AC because AC pumps are less expensive than their direct current counteφarts. A control or processor circuit board 24 syndiesizes appropriate AC power which is supplied to the pump 22 through conductors 26. The processor board 24 operates on 12 volts DC supplied, for example, through the cigarette lighter in an automobile. The processor 24 converts the 12 volts DC to a four phase AC square wave for pump 22 operation. The four phase square wave switches from plus 12 volts for 6.92 msec, to 0 volts for 1.54 msec, to minus 12 volts for 6.66 msec, to 0 volts for 1.54 msec, back to plus 12 volts, etc. By this process is created a substantially 60 Hz wave form. Suitable pumps may be in the 10-150 Hz range. It is preferred that the flow rate be in me 4-6 liters per minute flow rate range with a minimum pressure of 150 millimeters of mercury. The pump 22 supplies air to a bladder 28 through a flexible tube 30. A valve 32 communicates with the tube 30 and when open allows air to flow out of the bladder 28. A suitable valve 32 is available under the designation part number B6673 from Bicron Electronics Company of Canaan, Connecticut. This valve is normally opened and closed when a voltage is applied. It includes a return spring for positive opening. The apparatus 18 includes a pressure transducer 34 which is in fluid communication with the bladder 28 through tubing 36. A preferred pressure transducer 34 is a silicon wafer providing a control voltage proportional to the pressure in the bladder 28. A suitable pressure transducer is available from Fujikura Ltd., Japan, type FPN-07PG. With reference now to Fig. 3, the apparatus 18 includes operator controls such as a timer 40, ON and OFF buttons 42 and 44 and a pressure control 46. A light emitting diode (LED) 48 may be provided to indicate when the unit is operating. An important aspect of this invention is the ability to control the force applied to the lumbar region to take into account variations in a user's spinal compliance and other factors such as variations in seating position. According to mis embodiment of the invention, upon torning on the unit, the pump 22 begins supplying air to the bladder 28 causing me pressure in the bladder 28 to rise. This pressure is continuously monitored by the pressure transducer 34. Because die pressure transducer 34 communicates with the bladder 28 dirough a line separate from that utilized by me pump 22, the pressure transducer 34 is isolated from me low level pressure fluctuations generated by die operation of the pump 22. The operator adjusts me desired pressure setting using the pressure control 46. The preselected pressure set by me user will be maintained wimin plus or minus 4 millimeters of mercury with respect to the nominal set point. This pressure hysteresis is illustrated in Fig. 4. Lines 50 and 52 bound die nominal preselected pressure which is adjustable to be in me range from 10 millimeters mercury to 140 millimeters of mercury. In order to assure appropriate performance, the pressure transducer 34 should have a sensitivity to pressure changes wi iin the bladder 28 of 2 millimeters of mercury. As shown in Fig. 4 the system cycles between two states, namely, an inflation period and a deflation period. A typical inflation profile is represented by die curve 54. During tiiis segment, pressure and hence force on the back increases to fall generally within the band defined by die lines 50 and 52. There may be some small amount of overshoot and undershoot depending on, for example, motion of me user. The time for inflation which is to the left of a line 56 and mat for deflation which is to me right of the line 56 may be adjusted by me user using the timer control 40. A typical profile is 60 seconds of inflation followed by 60 seconds of deflation. During the time-controlled inflation phase to the left of the line 56 in Fig. 4, the pump 22 fills the bladder to a pressure widiin the band around the preselected set point. The system will adjust me volume of air in me bladder in order to maintain a constant pressure in the bladder even if die user moves forward or backward in the seat. At the beginning of the cycle the pump 22 turns on to start filling the bladder 28 so as to increase the force to the back to provide die substantial change in the extent of lordosis. If, for example, the user were to move backward against the bladder during diis filling phase thereby increasing pressure above me pre-set pressure level, die valve 32 is opened to reduce the pressure until the pressure is within die preselected band. Similarly, if the user moves forward, away from me bladder 28, thereby reducing me pressure in me bladder below the pre-set pressure level, the pump 22 is activated to increase the pressure until the pressure is again widiin me preselected band. At me end of me inflation period, die pump 22 is turned off and die valve 32 is opened to die atmosphere allowing air to flow out of me bladder 28 allowing die spine to relax to its "neutral" condition. Fig. 5 is a block diagram illustrating the logic described above witii respect to Fig. 4. The logic illustrated in Fig. 5 is implemented by a main program loop shown in Fig. 6 and an interrupt process loop shown in Fig. 7. The components of a preferred embodiment of me BackCycler™ will now be described. When die ON button 42 is activated by me user the inflate cycle will begin. An optional sound transducer (not shown) will generate beeps at a frequency of approximately 600 Hz with a duration of 0.13 seconds and widi an interval between beeps of 0.083 seconds. If die ON button 42 is depressed while the unit is already on, the timer 40 will reset a cycle counter to the beginning of me inflate cycle. Depressing the OFF button 44 will turn off die unit and this may be signalled by a single beep having a duration of 0.13 seconds to alert me user mat the unit has been turned off. The preselected desired pressure in die bladder 28 is adjusted by me pressure control 46 which is an adjustable linear potentiometer in iis embodiment. The potentiometer in die pressure control 46 can be adjusted between 1 and 5, for a total resolution of 130 discrete points over me full scale. One on the scale represents 10 millimeters of mercury and 5 represents 140 millimeters of mercury on tins linear scale. The pressure control potentiometer 46 may be adjusted while me unit is operating. In this case, if the potentiometer is adjusted in the negative direction by any amount, the valve 32 will automatically open to decrease pressure thereby to decrease force on die back. Conversely, if die potentiometer is adjusted in me positive direction by any amount, the pump 22 will automatically increase pressure in me bladder 28, regardless of die cycle phase at which die unit is dien currently operating. The light emitting diode (LED) 48 is turned on when die unit itself is turned on. Once on, die LED indicator 48 remains on until me unit is turned off or is automatically turned off. The time cycle can be adjusted by the timer 40 between 10 seconds and an infinite period. When die timer 40 is set to the infinite inflation time period me force applying apparatus acts as a static support which actively controls the amount of force to me back. In this state, force will be controlled continuously as long as me device is turned on. The time cycle is defined as a complete inflate and deflate cycle and with me infinite setting the unit can be used as a static lumbar support. The processor board 24 is powered by a 12 volt DC source and while me unit is turned off the processor is continuously rarining in an idle mode. Maximum current draw in me idle mode is less than or equal to approximately 15 milliamps. At this level of draw, a typical car battery would last 1500 hours. The processor board 24 performs on-board diagnostic testing to assure appropriate performance. In a test mode, the following components are checked: processor, ram check, valve check, pump check, speaker check, zero calibration lookup table setup, 100 millimeter mercury calibration test, and a check to confirm that the full range of 0 to 140 millimeters of mercury can be read. The unit also includes voltage protection. In particular, a voltage above 18 volts will be clamped and will cause a fuse (not shown) to blow. If voltage should drop below 9.8 volts, the processor board 24 turns die pump 22 off to provide field effect transistor (FET) protection (not shown). The valve 32 and pressure transducer 34 will remain operative under diese conditions. If voltage drops below 4.6 volts on a 5 volt line to me processor board 24, men me processor is reset and held until the voltage goes above 4.6 volts. Once die voltage is greater man 4.6 volts, a delay of 0.2 seconds is observed before restarting the processor. Radio frequency (RF) noise suppression is provided on the FET during 60 Hz modulation of the pump 22. A capacitor (not shown) is provided to act as a 60 Hz noise suppression filter. An automatic shut off may be provided if a person is not sitting against me bladder 28 for a selectable period of time such as for 12 seconds. Widi reference now to Fig. 8 a mechanical continuous passive motion device 60 includes a motor 62 which drives a cam 64. The cam 64 moves a flexible panel 66 in and out to apply movement to the lumbar region of me spine. A load cell 68 measures the force between die flexible panel 66 and die back of a person (not shown). The cam 64 is driven by a belt 70 in contact widi the motor 62. Yet anomer mechanical embodiment of the invention is shown in Fig. 9. The apparatus 90 includes a motor 92 which drives a belt 94. The belt 94 turns a pinion 96 which engages a rack 98. By diis means, a movable surface 100 can be moved in and out to engage me lumbar region of me spine of a user (not shown). A load cell 102 responds to force on me surface 100. The mechanical devices illustrated in Figures 8 and 9 operate in substantially me same way as the pneumatic embodiment described above. As before, force increases for a period followed by a period of decreasing force so as to move the lumbar spine dirough substantial ranges of lordosis. Widi respect now to Figs. 10, 11 and 12, an embodiment is described which allows the location of d e force applying member to be adjusted to accommodate different individuals, or die particular preference of a given individual. In mese figures, a bracket 110 is adapted to receive a sleeve 112 which bears, in mis embodiment, an inflatable bladder unit 114. The bracket 110 includes an extension portion 116 which is wedged between a seat cushion 118 and a seat back 120 of a seat which may be found in, for example, an automobile. The upright portion of me bracket 110 is curved rearwardly so mat it engages a seat back 120 when the extending portion 116 is properly wedged between a seat cushion 118 and die seat back 120. The bracket 110 and sleeve 112 include cooperating adhering structures (not shown) such as hook and loop structures commonly known as Velcro ® so as to fix the location of die sleeve 112 with respect to me bracket 110 in the vertical direction as shown in mese figures. Wi i reference to Fig. 12, me location of me sleeve 112 may be adjusted by inserting die fingers between me bracket 110 and die sleeve 112 at its lower portion to release die hook and loop material after which the sleeve 112 is moved to a different vertical location whereupon die hook and loop structure is engaged yet again. In mis way, the location of die force applying section 114 may be adjusted as desired by a user. The bracket is fully removable from the sleeve 112 so diat the sleeve 112 may be placed on a substantially horizontal surface such as a bed or floor for use in a supine position as described below in conjunction widi Fig. 17. Yet anodier embodiment of the invention which provides a selectable location for the force applying member is shown in Figs. 13 and 14. This embodiment is particularly designed to be built into a seat such as me backrest portion 120 of an automobile. This embodiment includes a plurality of separate, spaced apart bladders 122, 124, 126, and 128. The user can select which one of die bladders to activate so as to adjust d e height of the force applying surface as desired. The operation of each of die spaced apart bladders is me same as the single bladder embodiment described in conjunction with me earlier figures in mis specification. Yet anomer embodiment of the invention is shown in Figs. 15 and 16. This design is also particularly suited to a built in application widiin me seat back 120 of a vehicle seat or other form of chair. A bladder 130 is fixed to a felxible material 132 which engages a rotatable shaft 134. The shaft 134 may be turned manually using a knob 136. As die knob 136 is rotated, die location of die bladder 130 moves up and down as shown by me arrows in Fig. 15 mereby to adjust die location of me bladder widi respect to a user. Fig. 17 illustrates die use of die present invention when the user is in a supine position. As shown in me figure, a person 10 is lying on his back on a substantially horizontal strucmre such as a bed 150. The force applying apparams 118 applies force in me lumbar region 20 of me individual 10. The force applying apparams 118 operates as described in conjunction with the odier figures in this specification. As widi die odier embodiments, die force applying apparams 118 moves the spine in the lumbar region 20 dirough a substantial range of lordotic movement while me person 10 is lying down. It is recognized diat modifications and variations of the present invention will be apparent to those skilled in the art and it is intended diat all such modifications and variations be included widiin die scope of die claims.

Claims: Claims 1. Apparams for cycling me lower back of a person through a substantial range of lordosis comprising: a substantially static strucmre adjacent to die back of a person; a force applying apparams disposed between die static strucmre and die back of die person, die force applying apparams including a back engaging surface cyclically movable to increase and decrease die distance between die static strucmre and die back engaging surface diereby to cycle the lower back through the range of lordosis; and a transducer having an output responsive to die force between die back engaging surface and die lower back, die force applying apparams responsive to the output of die transducer to control die force applied to the back and furdier inlcuding programmable circuitry for controlling me force to be a preselected function of time. 2. Apparams for cycling me lower back of a person through a substantial range of lordosis comprising: a substantially static strucmre adjacent to me back of a person; a force applying apparams disposed between die static strucmre and the back of me person, die force applying apparams including a back engaging surface cyclically movable to increase and decrease the distance between die static strucmre and die back engaging surface thereby to cycle me lower back through die range of lordosis; and a transducer having an output responsive to the force between die back engaging surface and die lower back, die force applying apparams responsive to the output of die transducer to control die force applied to the back and further including timing circuitry to provide a force increasing period to increase the force applied to die back to a preselected maximum value, and a force decreasing period to decrease the force on die back. 3. Apparams for cycling me lower back of a person dirough a substantial range of lordosis comprising: a substantially static strucmre adjacent to die back of a person; a force applying apparams disposed between die static strucmre and die back of die person, die force applying apparams including a back engaging surface cyclically movable to increase and decrease die distance between die static strucmre and die back engaging surface diereby to cycle me lower back through die range of lordosis; and a transducer having an output responsive to die force between die back engaging surface and die lower back, the force applying apparams responsive to the output of die transducer to control the force applied to die back and further adapted to provide a force increasing period to increase the force applied to die back to a preselected maximum value and to maintain me force value during operation of the apparams. 4. The apparams of claim 2 further including a substantially constant force period between me force increasing period and die force decreasing period. 5. Apparams for cycling the lower back of a person through a substantial range of lordosis comprising: a substantially static strucmre adjacent to die back of a person; a force applying apparams disposed between die static strucmre and die back of die person, die force applying apparams including a back engaging surface cyclically movable to increase and decrease die distance between die static strucmre and die back engaging surface diereby to cycle the lower back dirough die range of lordosis; and a transducer having an output responsive to the force between die back engaging surface and die lower back, die force applying apparams responsive to die output of the transducer to control me force applied to die back, die force applying apparams comprises an inflatable and deflatable bladder. 6. The apparams of claim 5 further including a pump for supplying a fluid for inflating die bladder and a valve communicating wim die bladder deflating die baldder. 7. Apparams for cycling me lower back of a person dirough a substantial range of lordosis comprising: a substantially static strucmre adjacent to die back of a person; a force applying apparatus disposed between die static strucmre and die back of die person, die force applying apparams including a back engaging surface cyclically movable to increase and decrease die distance between die static strucmre and die back engaging surface thereby to cycle die lower back dirough die range of lordosis; and a transducer having an output responsive to the force between die back engaging surface and die lower back, the force applying apparams responsive to die output of die transducer to control die force applied to die back wherein the location of die back engaging surface is adjustable in height. 8. The apparams of claim 5 wherein the transducer comprises a silicon wafer adapted to provide a voltage signal proportioned to pressure. 9. The apparams of claim 4 including a fluid pump for supplying fluid to die bladder 10. The apparams of claim 5 further including an electrically operated valve for deflating me bladder. 11. Apparams for cycling me lower back of a person dirough a substantial range of lordosis comprising: a force applying apparams including a back engaging surface cyclically movable to increase and descrease force on die lower back diereby to cycle die lower back dirough the range of lordosis; and apparams for adjusting die location of die back engaging surface wim respect to the back of die person. 12. The apparams of claim 11 wherein me adjusting apparams comprises: a bracket including means for securing die bracket to a seat strucmre; and a sleeve including the force applying apparams adapted to slide over die bracket, me sleeve and bracket including at least two spaced apart, cooperating adhering strucmres whereby die position of die sleeve widi respect to die bracket is adjustable. 13. The apparams of claim 12 wherein die bracket is removable from the sleeve allowing die force applying apparams to be used on a substantially horizontal surface. 14. The apparams of claim 12 wherein me adhering strucmres comprise hook and loop elements. 15. The apparams of claim 11 wherein me adjusting apparams comprises: a flexible material surrounding and engaging a rotatable shaft, the flexible material bearing me force applying apparams; and a gripping strucmre affixed to die shaft for rotating me shaft thereby to adjust die location of die force applying apparams. 16. Apparams for cycling me lower back of a person through a substantial range of lordosis comprising: a force applying apparams inlcuding at least two spaced apart back engaging surfaces each cyclically movable to increase and decrease force on die lower back diereby to cycle die lower back through the range of lordosis; and selection logic for selecting one of die at least two spaced apart surfaces for cyclic motion, whereby die location of die back engaging surface is adjustable.

Inventors: HAZARD ROWLAND G, REINECKE STEVEN M, HAZARD, ROWLAND, G., REINECKE, STEVEN, M.
Applicants: ERGOMEDICS INC, ERGOMEDICS, INC.
Application year: 1995
Main classification: A61H1
IPC codes: A61H1, A61H7, A61H23