Patent Application
20230338233
Hemodynamics is the forward movement of blood. As such, it is required for the maintenance of life in any organism with a separate vascular system. In an intact organism, the vascular system is composed of a pumping mechanism—the heart—and a closed circuit of arteries and veins. Arteries deliver freshly oxygenated blood to the tissues and veins return blood to the heart and lungs for replenishment of oxygen.
The circulatory system is considered to have four components: 1) a pump, 2) an arterial compartment, 3) an organ and tissue compartment, and 4) a venous compartment. Forward blood flow is achieved through a combination of cardiac output and venous return. Additionally:
In the intact organism, the heart achieves circulation means of cardiac output and venous return, the pressure within the arterial compartment being greater than the venous compartment. In the steady-state, each heart beat is similar to any other and incorporates components intended to achieve cardiac output and venous return. Generally, mammals respond to the need for greater cardiac output by means of increasing stroke volume and heart rate.
It is possible to induce forward blood flow to during cardiac arrest by application of external force to the thorax. (Kouwenhoven, Jude, and Knickerbocker 1960; CARDIAC ARREST—The Science and Practice of Resuscitation Medicine 96) Most commonly, this has been achieved by providing anteroposterior compression of the mid-chest in the area of the sternum, usually with a piston like mechanism.
The combination of chest compressions and rescue breathing is called basic life support (BLS). Since its initial adoption, multiple improvements to basic life support have been proposed. Although incremental changes in parameters such as the rates of rescue breathing and chest compression have been widely adopted, (Kleinman et al. 2015) qualitatively different techniques have not become routine. While it has been possible to demonstrate some improvement in outcome in animal models with techniques such as abdominal counterpulsation, (Ralston, Babbs, and Niebauer 1982) circumferential constrict (Halperin et al. 1993) and active decompression, (Cohen, Tucker, Lurie, et al. 1992) the degree of improvement has been insufficient to result in widespread clinical adoption. In almost all cases, changes to basic life support have either a) not been evaluated in clinical trials, b) have failed in clinical trials, or c) have had only modest effectiveness when utilized clinically. Overall, there have not been large increases in the rate of return of spontaneous circulation once cardiac arrest has occurred.
Therefore, there is a significant and important need for improved techniques of cardiopulmonary resuscitation (CPR).
Normal cardiac output in a healthy adult is in the range of 4.7 liters per minute. This output maintains a mean arterial compartment blood pressure of approximately 90 mm Hg. The human heart responds to greater needs for blood flow by increasing rate and the force of contraction.
However, during cardiac arrest, CPR is only able to generate hemodynamics that are a fraction of an intact circulation. Often, they are in the range of 20% of normal cardiac output. (Michael et al. 1984) This large decrease in cardiac output results in mean arterial blood pressures that are often in the range of 25 mm Hg. (Paradis et al. 1989) The low cardiac outputs and arterial compartment pressures result in poor vital organ perfusion, and increased blood transit times. Loss of vasomotor tone in both the atrial and venous compartment acts to exacerbate the loss in hemodynamics. Blood begins to collect in the venous compartment, which raises venous pressures. The motive force for arterial to venous circulation is the difference in pressures between the two compartments. The abnormally low atrial mean pressures and abnormally high venous mean pressures act together to create a low perfusion pressures.
All of these decrements to perfusion and hemodynamics during CPR mean that cardiac output, flow out of the arterial compartment, and return flow from the venous compartment are all only a fraction of native circulation.
In native circulation, cardiac outputs, ventricular stroke volumes, tissue flows, and venous return are generally in equilibrium. Under normal circumstances, one of the vascular compartments does not expand significantly with respect to the other compartments over time frames of minutes. This may not be the case under the extreme low-flow of cardiac arrest and CPR. The relative expansion of the venous compartment may result in inadequate volume on the arterial side of the circulation. This, in turn, may result in impaired cardiac output.
Relative to the volumes of the vascular compartments, the cardiac output during cardiac arrest and CPR is generally inadequate for optimal forward flow and restoration of spontaneous circulation. It has not previously been realized that this inadequacy may be exacerbated by CPR chest compression decompression cycles (CCDCs) of a single type that has been designed with the intention of being optimal overall. Such CCDCs may be a trade-off between compressions optimized for cardiac output (cardiac output optimized CCDCs) versus compressions optimized for venous return (venous return optimized CCDCs).
It may be possible to improve overall forward flow by first performing a series of CCDCs optimized for cardiac output followed by a series optimized for venous return or visa versa. Such an approach might first expand and pressurize the arterial compartment causing improved flow through the tissue compartment and into the venous compartment. If the patient then receives a series of CCDCs optimized for venous return, this might enhance flow back to the heart or thorax and act to optimize the subsequent cardiac output optimized compressions. Such a method may transform the arterial and venous compartments into components of a whole body CPR pump.
For the purposes of clarity, the following terms are used in describing CPR based on movement of the chest or abdomen:
To understand the current invention, it is important to know that, the methods, techniques, components, and enhancements of cardiopulmonary resuscitation based on manipulation of the external chest and/or abdomen may be considered to fall into two broad categories: 1) those that directly create or enhance forward flow (cardiac output), and 2) those that create or enhance venous return.
Mechanistically, it is reasonable to assume that components of the CPR cycle that create or enhance cardiac output act to pressurize the arterial compartment. This will increase flow from the arterial compartment into the tissue compartment. Subsequent increased flow in the tissue compartment will result in increased flow into the venous compartment. The expansion and increased pressure of the venous compartment will enhance flow back to the heart, which is venous return. And finally, enhanced venous return may prime the CPR pump for increased cardiac output and forward-flow on the next cycle.
The mechanistic understanding of CPR hemodynamics is limited by a general lack of agreement as to the actual pump. (Haas et al. 2003) Some authorities believe that the heart continues to function as a pump mechanism, (Bircher, Safar, and Stezoski 1982) while others believe that the thorax becomes functionally the pump during CPR. (Niemann et al. 1980; Weisfeldt, Chandra, and Tsitlik 1981) It is possible that the mechanism of CPR is a combination of cardiac and thoracic pumps, and that the proportional contribution of each mechanism is variable patient to patient.
Methods intended to increase cardiac output during CPR include, but are not limited to (
Methods intended to increase venous return during cardiopulmonary resuscitation include, but are not limited to (
Examples of forward flow cardiac output enhancing techniques include, but are not limited to, standard anteroposterior chest compression and circumferential constriction. (Kouwenhoven, Jude, and Knickerbocker 1960; Halperin et al. 1993) Examples of techniques that may enhance venous return include, but are not limited to, active decompression of the chest (Cohen, Tucker, Lurie, et al. 1992), abdominal counterpulsation (Voorhees, Niebauer, and Babbs 1983), and partial airway obstruction during inhalation—the so called impedance threshold device. (Wolcke et al. 2003)
The improvement in hemodynamics associated with active decompression 3 may be mechanistically mediated by creation of increased negative intrathoracic pressure during the active decompression phase of CPR 10, with resulting enhancement of venous return. Additional enhancement of negative intrathoracic pressure and venous return may be achieved by briefly obstructing the airway during the decompression release phase. (Plaisance et al. 1999) Typically, this is achieved through utilization of a cracking valve mechanism called an impedance threshold device.
In addition to compression and decompression of the chest, compression and decompression of the abdomen, either independently or in a synchronized pattern with the chest compressions, has been proposed as potentially enhancing overall hemodynamics during CPR. (Ralston, Babbs, and Niebauer 1982; Babbs 1984) It is theoretically possible that these abdominal techniques may have independent and variable effects on cardiac output or venous return.
Additionally, alterations in ventilation, either independently or in a synchronized pattern with the chest compressions, has been proposed as potentially enhancing overall hemodynamics during CPR. (Segal 2014) In particular, transient occlusion of the airway during relaxation phase has been demonstrated to enhance negative intrathoracic pressure and venous return. It is theoretically possible that alterations in the parameters of ventilation may have independent and variable effects on cardiac output or venous return.
Previous to this disclosure, all existing methods of CPR have incorporated patterns of CCDC in which each CCDC was intended to be of similar intent to the one before or after. All previous methods have been intended to optimize hemodynamics during CPR by identifying an ideal CCDC optimized overall with respect to both cardiac or thoracic output and venous return, and to use that ideal pattern throughout. Changes to these idealized CCDCs have been limited to force, rate, and location.
All previous devices, methods, and systems have attempted to enhance overall CPR hemodynamic effectiveness only at the level of the single CCDC. It has not previously been taught that overall forward flow may be greater when alternating between single CCDCs or groups of CCDCs that are different with respect to their cardiac output and venous return enhancing components. Alternatively, there is no previous description of a single CCDC or group of CCDCs being intentionally sub-optimal with respect to either cardiac output or venous return so as to enhance the other parameter and overall forward flow.
Previous attempts at improving overall CPR performance have included greater force, greater depth, greater frequency, active forceful decompression, abdominal counterpulsation, and synchronized ventilations, (Berkowitz et al. 1989) among others. Additionally, feedback related to operator performance or patient status has been used to adjust the CCDC patterns. (Abella et al. 2007; Yeung et al. 2009) But importantly, the adjustments in response to feedback have been limited to an increase or decrease in the already chosen CCDC pattern, or a wholesale change to another pattern (i.e. a change from standard CPR to active compression-decompression CPR) not a variable pattern of alternating CCDCs.
The previous universal limitation of CPR chest compressions to one type at any given moment may have reflected a belief that CPR should mimic native circulation, and the assumption that an optimized single CCDC pattern provided the best solution with respect to maximal overall hemodynamics and patient outcome. This assumption is unproven.
Once it has been learned that alternating either single or multiple CCDCs optimized for arterial cardiac output with single or multiple CCDCs optimized for venous return might result in overall improved systemic hemodynamics and patient outcome, mechanisms to design cardiac output and venous return optimized CCDCs may be considered.
Importantly, examination of the list of parameters believed to enhance cardiac output, and the alternative list of parameters believed to enhance venous return demonstrates that some of these parameters are mutually exclusive. In example, consider the possibility that the forces creating cardiac output are greatest during the chest compression phase, and forces creating venous return are greatest during relaxation phase. Of necessity, extending compression phase to augment cardiac output must occur at the expense of venous return during relaxation phase, and vice versa. Thus, it is not be possible to design a single CCDC optimized with both prolonged relative compression and relaxation phases. It may also not be possible to design a single CCDC pattern that optimally pressurizes the arterial compartment and optimally decompresses the venous compartment.
The invention disclosed here relates in general to the field of cardiopulmonary resuscitation (CPR), and more particularly, to a method for improving hemodynamics and clinical outcome.
Devices for providing anteroposterior compression CPR are well known. (McDonald 1982) Generally, these are piston based devices, with the piston held in position anterior to the patient by a structural arm or arch that acts like a gantry.
Devices for providing active anteroposterior decompression are well known. (Cohen, Tucker, Redberg, et al. 1992)
Devices to enhance negative intrathoracic pressure and venous return are well known. (Plaisance et al. 1999)
A method for improving CPR hemodynamics and clinical outcome of patients suffering cardiac arrest and other low-flow states by varying the CCDCs so as to create intervals optimized for differing hemodynamics purposes. In one embodiment, there are alternating phases during which the CCDCs are optimized for cardiac output and others during which they optimized for venous return.
Current recommendations for the treatment of adults in cardiac arrest are that chest compressions be performed at a rate of 100 to 120 compressions per minute to a depth of at least 2 inches. (Kleinman et al. 2015) For the purposes of the figures below, the rate of 100 compressions per minute and a depth of 2 inches will be utilized as standard. At this rate, each CCDC will have a duration of 600 ms and standard compression and relax on phases durations of 300 ms.
A person having ordinary skill in the art will understand that the waveforms in the figures below may equally well represent intrathoracic pressure.
Previous to this disclosure, conventional devices and techniques of CPR were applied with a uniform pattern of CCDCs.
Previous to this disclosure, it has not been taught that overall forward flow and efficacy might be augmented by alternating intervals or phases during which CCDCs are optimized toward different objectives. By way of example, but not limitation, it might be more effective overall to have alternating time intervals during which one phase has CCDCs optimized for cardiac output and another composed of CCDCs optimized for venous return.
Once taught the invention, a person having ordinary skill in the art may appreciate that with this enhancement the major compartments of the circulatory system may not be in continuous equilibrium. Rather, during the phase of the cycle in which the CCDCs are optimized for cardiac output, the arterial compartment may become pressurized relative to the tissue and venous compartments. If this pressure differential moves blood from the arterial compartment to the tissue compartment and then into the venous compartment, the venous compartment may become relatively pressurized. Subsequently, during the phase in which the CCDCs are optimized for venous return, the venous compartment would be drained with increased returned blood flow to the heart.
Under this alternating pattern CPR (AP-CPR), a pattern may be established in which there is sequential volume expansion and pressurization of first the arterial compartment, then the tissue compartment and finally the venous compartment. As such, the arterial and venous compartments may be considered components of a systemic pumping mechanism rather than simply conduits. Flow within the tissues may take on a more sinusoidal pattern.
As a result of alternating between cardiac-output optimized CCDCs and venous-return optimized CCDCs, the overall hemodynamic efficacy, for example the minute-volume of blood flow through an organ of interest, is improved relative to what could be achieved by either of the two types of CCDCs alone.
In implementing such a preferred embodiment, a practitioner of ordinary skill in the art would know that CCDCs optimized for cardiac output would include, but are not limited to CCDCs of:
A person having ordinary skill in the art, may additionally appreciate that alterations in the abdomen and/or ventilations may adjunctively augment overall hemodynamics during CCDCs optimized for cardiac output. These alterations may be synchronized with specific alterations in the cardiac output or venous return optimized CCDCs.
In implementing such a preferred embodiment, a practitioner of ordinary skill in the art would also know that CCDCs optimized for venous return would include, but are not limited to CCDCs of:
A person having ordinary skill in the art, may additionally appreciate that alterations in the abdomen and/or ventilations may adjunctively augment overall hemodynamics during CCDCs optimized for venous return. These alterations may be synchronized with specific alterations in the venous return optimized CCDCs.
In an alternative specific embodiment, a practitioner of ordinary skill would produce a method in which there are alternating pairs of CCDCs, one cycle optimized for cardiac output, a second cycle optimized for venous return (
In an alternative specific embodiment, a practitioner of ordinary skill would produce a method in which there are alternating time intervals composed of multiple CCDCs, one interval composed of multiple cycles optimized for cardiac output, a second phase composed of multiple cycles optimized for venous return (
Once taught this invention, a person of ordinary skill in the art, would understand that any one of a number of ratios between cardiac output enhanced CCDCs and venous return enhanced CCDCs are possible. Additionally, this ratio may be adjusted dynamically based on feedback of the patient's status.
In an alternative specific embodiment, a practitioner of ordinary skill would produce a method in which there are repeating time intervals composed of multiple CCDCs, each repeating interval composed of CCDCs that transition from cycles optimized for cardiac output to cycles optimized for venous return.
In an alternative specific embodiment, a practitioner of ordinary skill would produce a method in which there are repeating intervals composed of multiple CCDCs, each repeating interval composed of multiple CCDCs cycles that transition from cycles optimized for venous return to cycles optimized for cardiac output.
In an alternative specific embodiment, a practitioner of ordinary skill would produce a method in which the CCDCs are optimized for cardiac output through incorporation of one or more selected from the group consisting of: greater compressive force, greater compressive speed, greater depth of compression, more frequent compressions, prolonged compression phase relative to relaxation, lessened active decompression, decreased force of decompression, decreased speed of decompression, shortened decompression phase.
In an alternative specific embodiment, a practitioner of ordinary skill would produce a method in which the CCDCs are optimized for venous return through incorporation of one or more selected from the group consisting of: greater active decompression, increased force of decompression, increased speed of decompression, lengthened decompression phase, lessened compressive force, lessened compressive speed, lessened depth of compression, prolonged decompression phase.
Alternatively, CCDCs may be provided that transition incrementally from ones that are solely intended to enhance venous return through CCDCs that blend venous return and cardiac output enhancing characteristics to CCDCs that are solely intended to enhance cardiac output. The oscillation through this cycle would be alternated with a time period that is itself optimized empirically or through feedback to enhance overall system forward flow.
For purposes of illustration and not limitation, a practitioner of ordinary skill in the art would, once taught the invention, be able to construct particular preferred embodiments wherein:
There are components of the invention that, while sufficient, are interchangeable within the context of the invention. With the benefit of the present disclosure, a practitioner skilled in the art would know which specific embodiments of these components to incorporate in optimizing performance of the invention.
Once it is understood and appreciated that the invention disclosed herein is for a method to improve CPR hemodynamics and the clinical outcome of patients suffering cardiac arrest, the usefulness will be manifest to anyone with ordinary skill in the art.
The non-obviousness of the invention herein disclosed is demonstrated by the complete absence of its description, appreciation or discussion in the medical or intellectual property literature. Additionally, a number of large commercial enterprises produce devices for mechanical CPR; despite extensive research and development enterprises, none of these companies have disclosed or developed methods or systems such as disclosed herein.
Previous methods and systems have attempted to enhance overall CPR hemodynamic effectiveness at the level of the single compression. Extensive review of the medical/patent literature has revealed no description of a method or system in which any single CPR compression/decompression is intentionally made sub-optimal with respect to its effect on arterial side forward flow so as to enhance venous side forward flow—essentially proving that the methods described herein have not previously been envisioned.
Once it is understood and appreciated that the invention disclosed herein is for a method to improve the efficacy of CPR delivered or controlled by electrical and/or mechanical devices, it will be immediately appreciated that the methods described are critical components of the relevant structures within these devices or methods.
Once taught the invention by means of this specification, a person of ordinary skill would be able to adapt known techniques and devices that provide chest compression by way of motor or pneumatic driven pistons or belts such that their standard control systems direct the device to provide CCDCs that are alternatively cardiac output and venous return enhancing as described. These CCDCs have been described in similar sufficient detail.
It will be understood that many changes in the details, materials, steps and arrangements of elements, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art without departing from the scope of the present invention.
Since many modifications, variations and changes in detail can be made to the described embodiments of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents.
Now that the invention has been described,
| Number | Date | Country | |
|---|---|---|---|
| 62365461 | Jul 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15657078 | Jul 2017 | US |
| Child | 18341686 | US |
