Patent Description:
Cardiopulmonary resuscitation (CPR) is a well-known and valuable method of first aid used to resuscitate people who have suffered from cardiac arrest. CPR requires repetitive chest compressions to squeeze the heart and the thoracic cavity to pump blood through the body. Artificial respiration, such as mouth-to-mouth breathing or bag mask respiration, is used to supply air to the lungs. When a first aid provider performs manual chest compression effectively, blood flow in the body is about <NUM>% to <NUM>% of normal blood flow.

In efforts to provide better blood flow and increase the effectiveness of bystander resuscitation efforts, various mechanical devices have been proposed for performing CPR. Among the variations are pneumatic vests, hydraulic and electric piston devices as well as manual and automatic belt drive chest compression devices.

Piston-based chest compression systems are illustrated in <CIT>),<CIT>), <CIT>), <CIT>) and <CIT>).

Our own patents, <CIT>);<CIT>);<CIT>); and<CIT>), and <CIT>), show chest compression devices that compress a patient's chest with a belt. Our commercial device, sold under the trademark AUTOPULSE®, is described in some detail in our prior patents, including <CIT>) and <CIT>).

<CIT> describes a cardiac massage device (CMD) having a foldable and rigid support structure, an electric motor incorporated into the support structure and a plate plunger connected to the motor by a driving mechanism. The support structure comprises a length-adjustable base element, a height-adjustable element and a length-adjustable plunger-carrying element. The connection angles between the elements of the support structure can be varied by hinge units. <CIT> describes a cardiopulmonary resuscitation apparatus comprising sternal compression means having a piston for compressing the sternum and thoracic constriction means having a chest band for fastening and constricting the chest when the compression means compresses a patient's chest. The apparatus further comprises length adjusting means for adjusting the length of the chest band according to the size of the patient's chest. <CIT> relates to systems and procedures for treating cardiac arrest. In the resuscitation the victim chest is mechanically compressed and decompressed to stimulate the heart. The victim is induced to inspire and expire against insufflating breathing gas during the chest compression/decompressions.

The invention provides a device for performing mechanical cardiopulmonary resuscitation according to claim <NUM>. More generally, the present disclosure describes devices and methods which provide for a chest compression device using a piston to compress the chest, while using a belt configuration similar to that used for the AutoPulse® chest compression device. Cyclic winding and unwinding of a belt passing through the frame which supports the piston actuates the piston to provide resuscitative chest compressions.

The hybrid chest compression device includes a backboard with a motor and a drive spool housed within the backboard. The motor is operably secured to the drive spool to cyclically wind and unwind the belt which is enclosed within the backboard and the piston support frame and is secured to the drive spool. The piston support frame has two legs and a piston actuator housing and the frame is secured to the backboard forming a channel between the two legs, the backboard and the piston actuator housing to accommodate the patient. The piston is operably housed within the piston actuator housing and the piston is driven by movement of the belt. Two or more sets of guide spindles are located in the backboard and the piston support frame for guiding the belt and forming a belt path through the backboard and the piston support frame. Actuation of the motor results in cyclic rotation and counter-rotation of the motor and corresponding winding and unwinding of the belt on the drive spool to effectuate cyclic extension and retraction of the piston against the patient's chest to perform mechanical chest compressions for cardiopulmonary resuscitation.

<FIG> illustrates the chest compression device fitted on a patient <NUM>. The chest compression device <NUM> applies compressions with the piston <NUM>. The piston is disposed within a housing <NUM> which is supported over the patient with a frame or gantry <NUM> with two legs <NUM> and 7R fixed to a backboard <NUM>. When disposed about the patient, the frame extends over thorax <NUM> of the patient so that the piston is disposed apposing sternum 2A of the patient as shown in <FIG>. Piston <NUM> may include a compression pad <NUM> adapted to contact the patient's chest, directly over the sternum, to impart compressive force on the patient's chest. The chest compression device is controlled using a control system which is operated by a rescuer through interface <NUM>, which may include a display to provide instructions and prompts to a rescuer and includes an input device to accept operating instructions from the rescuer.

As illustrated in <FIG>, piston <NUM> is driven by a belt <NUM> which is tightened and loosened when spooled upon a drive spool <NUM>. The drive spool is mounted in the housing used as the backboard <NUM>. Motor <NUM> within backboard <NUM> is operably connected to drive spool <NUM>. The belt is connected to drive spool <NUM> such that cyclic rotation of motor <NUM> cyclically rotates drive spool <NUM> which spools and unspools belt <NUM> onto and off of drive spool <NUM>. This spooling and unspooling may also be described as winding and unwinding or wrapping and unwrapping. The cyclic spooling and unspooling of belt <NUM> onto and off of drive spool <NUM> cyclically shortens and lengthens the span of belt <NUM> surrounding patient <NUM>. The path or course of belt <NUM>, such as path <NUM>, through backboard <NUM>, frame <NUM> and piston housing <NUM> has a fixed length such that shortening the span of belt <NUM> from span 17A to span 17B (shown in <FIG>) causes belt <NUM> to exert compressive force <NUM> on piston <NUM>. Cyclic spooling and unspooling of belt <NUM> onto and off of drive spool <NUM> causes cyclic exertion of compressive force <NUM> to piston <NUM>, and from piston <NUM> to patient's sternum 2A.

Belt path <NUM> may optionally include guide spindles to control belt <NUM> and belt path <NUM> and minimize friction on the belt when belt <NUM> moves through the frame, backboard and piston housing. For example, upper guide spindles <NUM> and lower guide spindles <NUM> minimize friction and constrain belt path <NUM>. Any suitable number of guide spindles may be provided throughout backboard <NUM>, support frame <NUM> and piston housing <NUM> such as intermediate guide spindles <NUM> which may also be provided within piston housing <NUM>.

To engage a patient in chest compression device <NUM> of <FIG>, chest compression device <NUM> may be slid over patient <NUM> until the patient is oriented with piston <NUM> apposing sternum 2A. Alternatively, chest compression device <NUM> shown in <FIG> may include access opening <NUM> in at least one support leg such as support leg <NUM>. Belt <NUM> has first and second ends 14A and 14B respectively which overlap and are accessible through access opening <NUM>. First and second belt ends 14A and 14B each include cooperating attachment elements such as hook and loop fasteners or other suitable fasteners. Separation of first belt end 14A from second belt end 14B permits support leg <NUM> to be lifted free of backboard <NUM>. Patient <NUM> is then oriented on backboard <NUM>, support leg <NUM> is reengaged to backboard <NUM> with patient <NUM> extending through access opening or channel <NUM>, first and second belt ends 14A and 14B are reconnected to each other and chest compression device <NUM> is ready to provide chest compressions to patient <NUM>.

Chest compression device <NUM> of <FIG> illustrates another configuration for opening the chest compression device to engage a patient such as patient <NUM>. First support leg <NUM>A is attached to backboard <NUM> using any suitable attachment mechanism and first end <NUM>A of belt <NUM> is attached to drive spool <NUM> while belt second end 33B is removably attached to the drive spool to enable insertion of a patient into patient channel <NUM>. Second support leg 31B frictionally engages leg socket <NUM> of backboard <NUM>. Belt second end 33B passes through socket <NUM>, around one or more guide spindles such as guide spindle <NUM>, and is removably attached to drive spool <NUM> using a clip, spline or other suitable attachment means such as clip <NUM>. With belt second end 33B disengaged from drive spool <NUM>, second support leg 31B is disengaged from socket <NUM>. Second support leg 31B with belt second end 33B extending from the leg is moved to enable insertion of patient <NUM> into patient channel <NUM>. When patient <NUM> is properly oriented on backboard <NUM>, belt second end 33B is passed through socket <NUM> and second support leg 31B is inserted into socket <NUM>. Belt second end 33B passes around guide spindle <NUM> and clip <NUM> is then secured to drive spool <NUM> and chest compression device <NUM> is ready to perform mechanical CPR.

Referring now to <FIG>, when a patient is properly oriented within any of chest compression devices <NUM>, <NUM> or <NUM>, activation of the device is accomplished using interface <NUM>. Displays such as display <NUM> provides prompts, alerts and or instructions to an operator. Input controls <NUM> accept operating instructions from the operator. When chest compression is activated in the device, controller <NUM> actuates and controls operation of motor <NUM> and other elements or components of chest compression device <NUM>. Rotation of motor <NUM> rotates drive spool <NUM> which spools and unspools belt <NUM> to cause piston <NUM> to exert compressive force on a patient. Controller <NUM> may include one or more sets of instructions, procedures or algorithms to control actuation and operation of the motor and other elements or components of device <NUM>.

As illustrated in <FIG> and <FIG>, operation of any of chest compression devices <NUM>, <NUM> or <NUM>, results in a controller such as controller <NUM> controlling operation of motor <NUM>. Motor <NUM> which is operably connected to drive spool <NUM> rotates first clockwise, and then counter-clockwise. Alternatively, counter rotation of the drive spool may be accomplished with a releasing clutch and a spring return, a motor driven return or other suitable mechanism. The drive belt such as drive belt <NUM> is operably connected to drive spool <NUM> such that the alternating rotation and counter-rotation first spools or winds the belt onto the drive spool and then unspools or unwinds the belt from the drive spool. The cyclic spooling and unspooling of the belt cyclically shortens and lengthens the span of the belt as discussed above. When the belt span is at its maximum, belt <NUM> and piston <NUM> are in position 43A as illustrated <FIG>. Rotation of the motor and drive spool which spools or winds belt <NUM> onto the drive spool shortens the span of the belt to span 17B and urges piston <NUM> into fully extended position 43B of <FIG>. In position 43B, piston <NUM> compresses patient's thorax <NUM> with compressive force <NUM> applied to sternum 2A. Counter-rotation of drive spool <NUM> releases tension on belt <NUM> and the resilience of the patient's thorax will cause decompression of the thorax which will urge piston <NUM> back into position 43A. Alternatively, any suitable spring such as spring <NUM> may be compressed by the extension of piston <NUM> into position 43B. The force of compressed spring <NUM> and release of tension on belt <NUM> will urge piston <NUM> back into retracted position 43A and may assist in chest decompression.

Whereas claim <NUM> defines a device for performing mechanical cardiopulmonary resuscitation comprising, inter alia, a motor, <FIG> shows an automatic chest compression device <NUM>with a pneumatic drive system as illustrated in our copending <CIT> which is incorporated herein by reference in its entirety. Chest compression device <NUM> includes a backboard <NUM>, with the belt <NUM>, which has a right belt portion 52R and a left belt portion <NUM>. Right and left belt portions <NUM> and 52R extend around vertically oriented spindles <NUM> and 54R and then extend along the superior/inferior (head-to-toe vis-a-vis the patient) axis the of the device to joint <NUM> which secures the belt to actuator rod <NUM> which also extends along the superior/inferior axis of the device to a pneumatic piston <NUM>. The pneumatic piston is operable to pull the rod superiorly (upward relative to the patient) and thereby tighten the band which extends piston <NUM> to compress the patient's chest, and push the rod inferiorly (downward relative to the patient). The pneumatic piston is supplied with fluid through hoses <NUM> and <NUM>, communicating with a pressurized fluid source <NUM> through input hose <NUM> and valve <NUM>. The valve may be controlled through control system <NUM> and interface <NUM>. Using commonly available <NUM> psi (<NUM> atmospheres) air supply, and an actuator with a volume of approximately <NUM> cubic inches (about <NUM> milliliters) or larger, and a stroke of about <NUM> inches (about <NUM>), the piston can pull and push the rod and thus pull and release the straps, such that the compression belt is tightened about the patient at a rate sufficient for CPR and a depth sufficient for CPR (i.e., at resuscitative rate and depth).

The control system may be a computer control system, programmed to control the valve to alternately supply high pressure air to one side of the piston to pull the straps and then supply air to the other side of the piston to release tension on the straps (while in each case venting the other side of the piston), or an electromechanical control system. The control system may be a microprocessor or separate computer system, integrated into the backboard or a separate computer control system located remotely. To provide feedback regarding the effect of compressions, the load plate and load cells shown in our <CIT> may be placed on the upper surface of the platform, such that it is disposed under the patient's thorax when the system is installed on a patient. Also, a compression depth monitor may be used to provide feedback regarding the effect of compressions, as disclosed in out <CIT>.

Claim 1:
A device (<NUM>, <NUM>, <NUM>) for performing mechanical cardiopulmonary resuscitation on a patient comprising:
a backboard (<NUM>, <NUM>, <NUM>);
a motor (<NUM>);
a piston support frame (<NUM>) having two legs (<NUM>, 7R, 31A, 31B) and a piston actuator housing (<NUM>), the piston support frame being secured to the backboard forming a channel (<NUM>) between the two legs, the backboard and the piston actuator housing, wherein one of the two legs can be disengaged from a socket (<NUM>) in the backboard;
a piston (<NUM>) operably housed within the piston actuator housing;
an interface (<NUM>); and
a controller (<NUM>) configured to control actuation and operation of the motor (<NUM>) to effectuate cyclic extension and retraction of the piston against the patient's chest to perform chest compression and assisted decompression during mechanical cardiopulmonary resuscitation, wherein the controller (<NUM>) and interface (<NUM>) are integrated into the backboard (<NUM>, <NUM>, <NUM>).