This invention relates to a CPR mannequin with non-linear chest stiffness.

Cardiopulmonary resuscitation (CPR) is an emergency procedure which is performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person in cardiac arrest. It is indicated in those who are unresponsive with no breathing or abnormal breathing. It may be performed both in and outside of a hospital.

Training of persons in CPR involves the use of mannequins which help in simulating actual conditions which a trainee may have to deal with. Trainees practice CPR on such mannequins in order to keep themselves prepared to deal with real life situations.

The CPR mannequins known to the art have this drawback, namely, that the compressive pressure exerted by the trainee on the chest of the CPR mannequin cannot be equated to the compressive pressure to be exerted by the trainee on the chest of the patient in real life, because the former pressure is found to be "linear" variable while the latter is "non-linear" variable. In other words, the former pressure varies in linear fashion with depth of the compression of the chest of the mannequin, while in reality, the pressure in the latter case increases in non-linear fashion with the depth of compression of the patient's chest. Consequently, the known CPR mannequin will not present itself as a true substitute for the actual patient and the trainee who practices on the mannequin will not find himself (or herself) fully attuned to the task of carrying out CPR in the actual emergent cases with which he (or she) is faced.

It is therefore one of the objects of this invention to propose a CPR mannequin which offers to the trainee a non-linear resistance when the trainee exerts pressure on the chest of the mannequin, thus encountering, during training, real life conditions. Other objects of this invention will be apparent from the following further description. The CPR mannequin with non-linear chest stiffness, according to this invention, is structured to lie horizontally for simulating a person lying flat on his back, the said mannequin comprising a base, a head supported on the base, a humanoid torso separated from the
base, constituting the chest of the mannequin, the torso having markings to indicate the sternum and the ribs of a human being; sensors for measuring compression depth and the rate of compression and or air volume during chest ventilation, said sensors being connected to a system for collecting and analyzing data during CPR training; means for achieving non-linear chest stiffness; and means for achieving multitude of non-linear chest stiffness, or variable chest-stiffness.

This invention will now be described with reference to the accompanying drawings which illustrate a CPR Mannequin and its components according to a preferred embodiment in the following numbered Figures

1. Top view of Mannequin

2. Side view of Mannequin.

3. Sectional view of Mannequin illustrating the air flow measurement and compression distance measurement

4. Sectional view of mannequin showing concentric springs to achieve non-linear springs

5. Various spring setups to realize non-linear chest stiffness

6. Sectional view detailing variable chest realization with pneumatic muscle

The CPR Mannequin is designed to lie horizontally to simulate a person lying flat on his back for CPR administration. The Mannequin shown in Fig. 1, comprises a base and a humanoid torso separated from the base. The base and torso, suitably separated constitute the chest (102) of the mannequin. The torso (103) will have markings to indicate sternum and ribs of a human being. The mannequin will also have a head supported on the base (101).The mechanisms to realize the non-linear chest stiffness will be mounted such that the torso and base of the mannequin are suitably separated. Fig 2 is a side view of Mannequin showing the tiltable head (201), the base plate of the chest (202), the top plate of the chest (203) and a separator (204) to ensure the top and base plates are separated.

The CPR Mannequin may be equipped with sensors for measuring the depth of compression achieved during chest compression and or air volume during chest ventilation while carrying data out. Fig 3 is a sectional View of the CPR Mannequin showing the Head (301), Chest (302) and sensor placement for displacement and airflow measurement. The tube (303) placed in the mouth of the mannequin directs airflow over the velocity sensor setup (304), this provides the air volume for chest ventilation. The displacement measurement is carried out by a LED(307)/LDR(305) setup mounted on the top plate(308) and base plate (309). The LED and LDR are mounted coaxially (306), so that the LED light is directly incident on the LDR.

The sensors can be connected to a system to collect and analyze data on CPR training. The mannequin may also have a motor mounted on the torso or base of the mannequin to provide a reciprocating motion simulating natural breathing movements of the chest.
When administering CPR, to train both chest compression and ventilation, the head is tilted back and any foreign particle in the throat of the mannequin is removed.

Next, air is blown into the mouth of the mannequin for ventilation. The air blown into the mouth is directed by a flexible hose onto the base of the chest of the mannequin where a flow measuring sensor may be mounted.

The next step is the chest compression. The trainee places his palm on the sternum of the mannequin and compresses to a depth of 4 -6cm at the rate of 100 cycles every minute or at a rate predetermined by currently prevalent, applicable medical or military standards.
The compression depth will be measured mechanically or electronically with sensors mounted on the base and torso of the mannequin. The rate of compression may be calculated from sensor data recorded by the system communicating with the sensors.
Fig 4 details variable chest stiffness realization using concentric springs (403, 404, 405, 406) mounted on the base plate of the mannequin (401), separating the top plate and base plate. This is just one of the methods suggested in this document. This and other methods are described in more detail in the following section.

The non-linear stiffness may be realized by one or more of the following methods:
The chest will have 2 or more springs of varying height, diameter and/or stiffness and yield strength mounted concentrically. Fig 5a shows 4 springs of different Inner Diameter/ Outer Diameter and hence differing stiffness. The springs are mounted on the chest. Compression causes the tallest spring to compress. As compression proceeds and the spring compresses to the height of the next tallest spring, the second spring is called into action, increasing the total chest stiffness with the increased depth. This continues until either all the springs are activated or the trainee stops compression, whichever occurs first.

The chest will have 2 or more springs of varying pitch, height and/or stiffness and yield strength stacked one on another. Fig 5b shows 4 springs of nearly equal inner and outer diameters bit different pitch and/or material thus realizing different stiffness for different depths of compression. Chest compression causes the spring with the lowest stiffness to be activated, as compression depth increases, the spring bottoms out causing the spring with the next lowest stiffness to be activated, thus changing stiffness with depth of compression. This continues until either the stiffest spring is activated or the trainee stops compression, whichever occurs first.

The chest may be mounted with conical springs with variable diameter (fig 5 c) and/or pitch (fig 5d). A small initial force provides a noticeable depth of compression, but, the stiffness increases with applied load necessitating a large force to produce the required depth of compression. This is because of the non-linear stiffness of the spring; spring coils with the largest diameter have the lowest stiffness. These are the first to deflect; after a certain load they bottom out, now coils with a smaller diameter deflect, but they have a higher stiffness, hence requiring a larger force to produce the same deflection.

Spring Based Methods require a one or more concentric tube to be mounted on the base of the chest and the torso which slides into the base tube. Fig 5 details the various spring setups described here to realize variable chest stiffness, Fig 5a shows 4 springs of different Inner Diameter/ Outer Diameter and hence differing stiffness. Fig 5b shows stacked springs of different pitch and hence differing stiffness. Fig 5c shows a conical spring of increasing diameter from D1 to Dn and constant pitch p. Fig 5d shows a spring of constant diameter D but increasing pitch from p1 to pn

Figures 6a and 6b show the variable chest stiffness realization with a pneumatic flexible tube. A scissor jack (602) with a PFT (603) is mounted in the chest (601) of the mannequin, between the top plate (604) and base plate (605). Initially the PFT is at its highest compression and hence at the free length of the chest (fig 6a), as compression proceeds the air supply to the PFT is regulated to give a non-linear stiffness increasing with depth of compression. The PFT expands as the chest is compressed (fig 6b). The specific value of compression is realized from a mapping of the supply voltage driving the compressor supplying the PFT to the depth of compression measured by sensors mounted on the base and torso of the mannequin. The supply voltage is dynamically regulated by the compression depth.

We Claim:

1. A CPR mannequin with non-linear chest stiffness, structured to lie horizontally for simulating a person lying flat on his back, the said mannequin comprising chest of a humanoid torso, with or without the base, the torso having markings to indicate the sternum and the ribs of a human being; with or without sensors for measuring compression depth and the rate of compression; means for achieving non-linear chest stiffness;

2. A CPR mannequin as claimed in Claim 1 wherein the said means for achieving non-linear chest stiffness consist of stacked or concentric springs of varying height, diameter, stiffness, pitch and yield strength positioned on or within the torso for providing nonlinear stiffness, on being compressed.

3. A CPR mannequin as claimed in Claim 1 wherein the said means for achieving non-linear chest stiffness consist of conical springs of varying diameter, and or pitch on or within the torso for providing non-linear stiffness, on being compressed.

4. A CPR mannequin as claimed in Claim 1 wherein the said means for achieving non-linear chest stiffness consist of plate springs of varying length, and or pitch on or within the torso for providing non-linear stiffness, on being compressed.

5. A CPR mannequin as claimed in Claim 1 wherein the said means for achieving variable, programmable, or computer controlled nonlinear chest stiffness consist of a pneumatic flexible tube mounted scissor jack positioned on the base of the mannequin while the torso is attached to the top plate of the scissor jack.

6. A CPR mannequin as claimed in Claim 1 wherein the said means for achieving variable, programmable, or computer controlled nonlinear chest stiffness consist of any force resisting device or actuator (example, electric motors, solenoids, magneto-rheological fluids, polymers, shape memory alloy) positioned on the base of the mannequin while the torso is attached to the top plate.

7. A CPR mannequin as claimed in Claim 1 with variable, programmable, or computer controlled non-linear chest stiffness consist of any combination of springs, flexible tubes, actuators for providing non-linear stiffness, on being compressed.