Surgery: kinesitherapy – Kinesitherapy – Device with applicator having specific movement
Reexamination Certificate
1999-01-07
2001-01-09
Yu, Justine R. (Department: 3764)
Surgery: kinesitherapy
Kinesitherapy
Device with applicator having specific movement
C601S044000, C601S107000
Reexamination Certificate
active
06171267
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a method and apparatus for providing automated cardiopulmonary resuscitation (CPR) in the form of closed chest cardiac compression, preferably combined with pulmonary ventilation.
A practical mechanism for automating closed chest cardiac compression was first disclosed in U.S. Pat. No. 3,364,924 assigned to my assignee, Michigan Instruments, Inc. of Grand Rapids, Mich., and has been commercially exploited under the Thumper® Cardiopulmonary Resuscitation System. The system disclosed in U.S. Pat. No. 3,461,861 added the important function of pulmonary ventilation to the Thumper® system by supplying a ventilation cycle intermittently with a number of compression cycles according to the American Heart Association protocol. The waveform of the apparatus disclosed in the '924 patent is shown at C in FIG.
14
. Waveform C generally resembles a damped exponential waveform. This is an improvement over, yet similar to, the sinusoidal waveform shown at M in
FIG. 14
which is produced by manual closed chest cardiac compression.
In a number of articles, including that published by Maier, George W. et al. in Circulation, Vol. 1, 1984, entitled “The Physiology of External Cardiac Massage; High-Impulse Cardio-Pulmonary Resuscitation,” the disclosure of which is hereby incorporated herein by reference, a new form of CPR is proposed under the name “High Impulse CPR.” In high impulse CPR, the waveform more closely resembles a square wave, or impulse, rather than a sinusoidal form. A fast rise in the chest compression stroke that increases the area under the curve, as seen in curve H in
FIG. 14
, applies a greater amount of energy to the patient during the systolic phase. It was discovered that the high energy supplied by the high impulse CPR waveform significantly improved perfusion in the cardiovascular system of the patient. The development of high impulse CPR resulted from studies sponsored by my assignee, Michigan Instruments, Inc.
A commercial embodiment of a high impulse CPR has remained a long felt and unmet need in the art. The exponential acceleration curve necessary to produce the high impulse CPR effect must also be combined with the necessity for controlling the length of the compression stroke. Indeed, once the massage pad, which interfaces the apparatus to the patient, is exponentially accelerated to the selected depth of compression, it must abruptly decelerate and be held at the selected depth during the systolic phase. During the diastolic, or relaxation phase, the apparatus must retract the massage pad with sufficient acceleration to allow the patient's chest to return to its non-compressed state without interference by the apparatus.
The apparatus used to carry out the initial evaluation of high impulse CPR constituted a piston and a cylinder to which a compressed gas could be rapidly supplied and a fixed mechanical stop which limited the extent of the piston travel. While such apparatus was sufficient to demonstrate the benefit of high impulse CPR, it was not commercially viable. The use of a fixed mechanical stop was noisy and made adjustment of the compression stroke rather awkward.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for producing high impulse cardiopulmonary resuscitation (CPR) in a manner which achieves the long felt and unmet need for a commercial device of this type, particularly one that provides an adjustable depth of compression.
A method of performing cardiopulmonary resuscitation, according to an aspect of the invention, includes providing a chamber having an expandable volume and a patient-contacting pad that moves as a function of volume of the chamber and positioning the chamber with respect to the patient to bring the patient-contacting pad to alignment with the patient's chest. A controlled quantity of fluid is supplied to the chamber in order to increase the chamber volume by a controlled amount, thereby compressing the patient's chest during a systolic phase. It has been discovered that the seemingly contradictory requirements of rapidly accelerating the patient contacting pad, thereby compressing the patient's chest in a manner that achieves a controllable extent of compression depth, can be accomplished by this aspect of the invention. In particular, a very rapid acceleration of the compression stroke can be accomplished by rapidly supplying the fluid to the chamber. Control of the extent of compression depth can be achieved by controlling the quantity of the fluid supplied to the chamber.
Preferably, the chamber having an expandable volume is made up of a cylinder enclosing an adjustable piston which is connected with the patient-contacting pad, such as a rod. Most preferably, a compression spring is included in the chamber in order to rapidly return the piston to its retracted position at the beginning of the diastolic or relaxation phase. Indeed, by providing a spring of sufficient spring force, it is possible to provide a retraction force for active reshaping of the chest, as disclosed in my commonly assigned U.S. Pat. No. 5,743,864, the disclosure of which is hereby incorporated herein by reference.
According to a somewhat more detailed aspect of the invention, a cardiopulmonary resuscitation apparatus includes a chamber, a piston in the chamber, and a frame including a first portion adapted to be positioned posteriorly of a patient and a second portion supporting the chamber. The apparatus further includes a pressure source, a control valve assembly that is operative to selectively connect the pressure regulator to the chamber, and a timing circuit.
Preferably, the timing circuit selectively operates the control valve assembly to connect the pressure source to the chamber at the beginning of a systolic phase to accelerate the piston toward the patient to initiate chest compression and to disconnect the pressure source from the chamber and to seal the chamber during the remaining portion of the systolic phase. The pressure source is preferably a pressure regulator adapted to be supplied with a gas under pressure and producing a regulated pressure at an output. Also, preferably, the control valve assembly is operative to connect the pressure regulator output to the chamber. The timing circuit selectively operates the control valve assembly to supply regulated pressure from the pressure regulator output to the chamber for a controllable time period to move the piston to apply chest compression to a patient during a systolic phase.
These and other objects, advantages and features of this invention will become apparent upon review of the following specification in conjunction with the drawings.
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Michigan Instruments, Inc.
Van Dyke Gardner, Linn & Burkhart, LLP
Yu Justine R.
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