Method to increase the efficacy of cardiopulmonary resuscitation by means of alternating phases during which the physical characteristics of chest compression are varied so as to increase overall forward blood flow

Abstract

A method to increase the overall hemodynamic efficacy of cardiopulmonary resuscitation (CPR) by alternating between chest compression-decompression cycles optimized to either cardiac output or venous return. The phases of cardiac output and venous return enhancement may themselves by adjusted in their duration and character. The method may enhance mechanical and manual techniques delivered to the anterior or circumferential chest, and be synchronized to adjunctive techniques such as airway, ventilatory or abdominal therapies.

Claims

1. A method to increase the overall hemodynamic efficiency of external chest compressions performed during cardiopulmonary resuscitation on a patient comprising: applying two or more chest compression-decompression cycles (CCDCs) to the patient suffering from cardiac arrest, wherein applying the two or more CCDCs to the patient includes applying a first set of CCDCs optimized to increase a cardiac output blood flow in the patient suffering from cardiac arrest and applying a second set of CCDCs optimized to increase a venous return blood flow in the patient suffering from cardiac arrest; wherein the first set of CCDCs optimized for the cardiac output blood flow is performed alternately with the second set of CCDCs optimized for the venous return blood flow to enhance hemodynamic efficiency, wherein applying the two or more CCDCs results in return of spontaneous circulation for the patient suffering from cardiac arrest; wherein optimizing the first set of CCDCs to increase the cardiac output blood flow includes the first set of CCDCs being different from standard CCDCs by greater compressive force, greater compressive speed, greater compression depth, more frequent compressions, prolonged compression phase relative to relaxation phase, and shorter relaxation phase, wherein optimizing the second set of CCDCs to increase the venous return blood flow includes the second set of CCDCs being different from standard CCDC's by adding active decompression, increased force of active decompression, increased speed of active decompression, lessened compressive force, lessened compressive speed, lessened compression depth, addition of impedance airway devices, and a prolonged decompression phase; wherein standard CCDC's have a compression depth of 2 inches, a compression phase duration of 300 ms, a relaxation phase duration of 300 ms, and no active decompression.

2. The method according to claim 1, wherein a ratio of time intervals of the first set of CCDCs and the second set of CCDCs is not equal.

3. The method according to claim 1, wherein the first set of CCDCs optimized for the cardiac output blood flow comprises a first interval of multiple CCDCs and the second set of CCDCs optimized for the venous return blood flow comprises a second interval of multiple CCDCs.

4. The method according to claim 1, wherein an incremental transition occurs from the first set of CCDCs optimized for the cardiac output blood flow to the second set of CCDCs optimized for the venous return blood flow.

5. The method according to claim 1, wherein a speed of decompressions of at least one of the first set of CCDCs and the second set of CCDCs is adjusted based on a biomarker measurement obtained from the patient.

6. The method according to claim 1, wherein a pattern of transition from the first set of CCDCs optimized for the cardiac output blood flow to the second set of CCDCs optimized for the venous return blood flow includes a third set of CCDCs that transition from the first set to the second set, wherein the third set is adjusted based on a biomarker measurement obtained from the patient.

7. The method according to claim 2, the ratio of the first set to the second set is 3 to 2.

8. The method according to claim 1, wherein CCDCs, or their respective phases, are further enhanced by phasic manipulation of the abdomen.

9. The method according to claim 1, wherein CCDCs, or their respective phases, are further enhanced by phasic alteration in ventilation pattern or pressures.

10. The method according to claim 1, wherein the CCDCs, or their respective phases, are further enhanced by phasic alteration in the patient's body position or a portion of the patient's body chosen from a list that includes the head, neck, chest, abdomen, arms or legs.

11. A method of forcing circulation of blood out from a patient's heart and back in to the patient's heart during cardiac arrest before return of spontaneous circulation (ROSC), the method comprising: alternating between at least two different types of chest compression-decompression cycles (CCDCs), wherein alternating between at least two different types of CCDCs comprises: applying an outflow set of CCDCs to the patient, wherein the outflow set of CCDCs force blood out of the heart and out to bodily extremities; and applying a return flow set of CCDCs to the patient wherein the return flow set of CCDCs pull blood back to the heart from the veins; wherein the outflow set of CCDCs to force blood out of the heart and out to bodily extremities includes the outflow set of CCDCs being different from the return flow set of CCDCs by greater compressive speed, greater compression depth, decreased force of active decompressions, decreased speed of active decompressions, and wherein the return flow set of CCDCs to pull blood back into the heart from the veins includes the return flow set of CCDCs being different from the outflow set of CCDCs by increased speed of active decompression, increased force of active decompression, lessened compressive speed, and lessened compression depth.

12. A method of forcing circulation of blood out from a patient's heart and back in to the patient's heart during cardiac arrest comprising: alternating between at least two different types of chest compression-decompression cycles (CCDCs), wherein alternating between at least two different types of CCDCs comprises: applying a first set of CCDCs to the patient that increase pressure in an arterial compartment of the patient; and applying a second set of CCDCs to the patient that decrease pressure in a venous compartment of the patient; wherein the first set of CCDCs that increase pressure in the arterial compartment includes the first set of CCDCs being different from the second set of CCDCs by greater compressive speed, greater compressive force, greater compression depth, more frequent compressions, prolonged compression phase relative to relaxation phase, addition of thoracic constriction, decreased force of active decompression, decreased speed of active decompressions, and shortened decompressive phase, and wherein the second set of that decrease pressure in the venous compartment includes the second set of CCDCs being different from the first set of CCDCs by adding active decompression, increased speed of active decompression, increased force of active decompression, lessened compressive force, lessened compressive speed, and lessened compression depth, addition of impedance airway devices, and a prolonged decompression phase.

13. The method according to claim 12, wherein alternating between the first set of CCDCs that increase pressure in the arterial compartment and the second set of CCDCs that decrease pressure in the venous compartment further comprises decreasing the pressure of the venous compartment below the pressure of the arterial compartment, thereby facilitating the flow of blood out to the extremities and back to the heart.

14. The method according to claim 12, wherein applying the second set of CCDCs that decrease pressure in the venous compartment of the patient further comprises overcoming the presence of inertial resistance to flow so that blood is pulled from the surrounding tissues back towards the heart.

15. The method according to claim 12, wherein alternating between the first set of CCDCs that increase the pressure in the arterial compartment and the second set of CCDCs that decrease pressure in the venous compartment further comprises increasing blood flow to result in return of spontaneous circulation (ROSC) in patients with no native circulation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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 2015) For the purposes of the figures below, the rate of 100 compressions per minute and a dep 2 inches will be utilized as standard. At this rate, each CCDC will have a duration of 600 ms and standard compression and relaxation phases durations of 300 ms.

(2) A person having ordinary skill in the art will understand that the waveforms in the figures below may equally well. represent intrathoracic pressure.

(3) FIG. 1—Idealized chest displacement during standard mechanical chest compressions (two compressions and one intervening relaxation)

(4) FIG. 2—Chest displacement during standard manual chest compressions (two compressions and one intervening relaxation)

(5) FIG. 3—Chest displacement during mechanical CPR, CCDC's enhanced for cardiac output relative to venous return. Specifically illustrated are: a greater force/speed/depth of compression (slope down) 6, a greater duration of compression 8, and a shorter durations of relaxation 9 (two compressions and one intervening relaxation)

(6) FIG. 4—Chest displacement during mechanical CPR, CCDC's enhanced for venous return relative to cardiac output. Specifically illustrated are: active decompression (slope up) 3, relaxation phase chest wall location above baseline 11, and longer durations of relaxation 12. (two compressions and a relaxation)

(7) FIG. 5: Chest displacement during mechanical CPR, alternating CCDC's enhanced for cardiac output and CCDC's enhanced for venous return (1 CCDC:1 CCDC ratio)

(8) FIG. 6: Chest displacement during mechanical CPR, alternating CCDC's enhanced for cardiac output and CCDC's enhanced for venous return (3 CCDC:3 CCDC ratio)

(9) FIG. 7: Chest displacement during mechanical CPR, alternating CCDC's enhanced for cardiac output and CCDC's enhanced for venous return (3 CCDC:1 CCDC ratio)

DETAILED DESCRIPTION

(10) Previous to this disclosure, conventional devices and techniques of CPR were applied with a uniform pattern of CCDCs.

(11) 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.

(12) 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.

(13) 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.

(14) 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.

(15) 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:

(16) 1. Greater compressive force/speed than a previous target which may have been otherwise recommended or set for compressive force/speed. For example, the speed and/or force of compression may be increased, or the time interval of the chest compression relaxation phase 9 to less than 100 milliseconds while maintaining force unchanged. Additionally, greater than standard compression depths may be used (i.e. 2.0-2.4 inches) 7. Hence, the force applied to the chest to reach a target range of 2.0-2.4 inches may be greater during a time interval of less than 100 milliseconds in comparison to a time interval of 100 milliseconds or longer. The application of such force during compression may result in greater cardiac output of blood from the heart to the arterial compartment.

(17) 2. Greater depth of compression than a previous target which may have otherwise been recommended or set for compression depth 7. For example, the target compression depth that would normally be set to a recommended standard compression depth of 2.0-2.4 inches may be increased to a range of compression depths of 2.4-4 inches. By compressing to a greater depth than the typically recommended 2.0-2.4 inches, more blood would be expected to be output from the heart to the surrounding tissues.

(18) 3. More frequent compressions than a previous target which may have otherwise been recommended or set for compression rate. For example, the target compression rate that may typically be set to a standard rate of 100-120 compressions per minute may be increased to a range of compression rate of 120-200 compressions per minute. Compressing the chest at such an increased rate may result in an overall larger volume of blood being output from the heart to surrounding tissues than would otherwise be the case at lower rates of compression.

(19) 4. Shortened relaxation phase 9 as compared to conventional time intervals 5 for the relaxation phase of a chest compression. For example, the time interval of the relaxation/decompression phase, may be decreased from a standard duration of approximately 400 milliseconds to a duration of 1-300 milliseconds. Shortening the duration of the relaxation/decompression may allow for a subsequent chest compression to be initiated sooner, resulting in increased overall rate and/or force/pressure on the chest of the patient to move blood forward.

(20) 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.

(21) 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:

(22) 1. Active decompression, involving the upward forceful decompression of the anterior of the chest. Such an upward forceful action resulting in a greater negative intrathoracic pressure within the chest cavity that results in enhanced venous return from surrounding tissues back to the heart.

(23) 2. Increased force/speed active decompression as compared to typical decompression. For example, the speed at which the anterior of the chest is forcefully pulled upward may be increased by lowering the time interval of the decompression to less than 100 milliseconds for a standard compression depth of 2.0-2.4 inches. The application of a relatively greater upward force on the anterior of the chest due to the increased speed of the active decompression phase would lead to an increased magnitude of negative intrathoracic pressure, resulting in improved venous return of blood to the heart from the surrounding tissues.

(24) 3. Prolonged decompression phase 12 to provide increased opportunity for movement of blood back to the heart. For example, the time interval of the relaxation/decompression may be increased from a standard duration of approximately 400 milliseconds to a duration of 400-1500 milliseconds. This increase in duration may allow for enhanced negative intrathoracic pressure generated during active decompression to sufficiently overcome the presence of inertial resistance to flow such that blood is effectively able to be pulled from the surrounding tissues back toward the heart.

(25) 4. Airway occlusion during decompression to restrict unnecessary air from entering into the chest cavity during decompression. For example, a valve such as that provided by the ResQPOD impedance threshold device manufactured by ZOLL Medical Corporation may be placed in the airway of the patient, (Jenkins et al. 2015) obstructing air from entering until a predetermined cracking pressure is achieved. By occluding the passage of air during the decompression phase, the effects of negative intrathoracic pressure on venous return are further enhanced.

(26) 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.

(27) 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 (FIG. 5).

(28) 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 (FIGS. 6,7).

(29) 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 CCDC's and venous return enhanced CCDC's are possible. Additionally, this ratio may be adjusted dynamically based on feedback of the patient's status.

(30) 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.

(31) 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.

(32) 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.

(33) 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.

(34) 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.

(35) 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:

(36) 1. The ratio of the time intervals is one to one.

(37) 2. The ratio of the time intervals is not one to one.

(38) 3. The duration of the time intervals is equal.

(39) 4. The duration of the time intervals is not equal.

(40) 5. The duration or ratio patterns of the two time intervals is adjusted based on a biomarker measurement obtained from the patient that assists in determining hemodynamic efficacy.

(41) 6. The pattern of transition from CCDCs optimized for cardiac output to CCDCs optimized for venous return is adjusted based on a biomarker measurement obtained from the patient that assists in determining hemodynamic efficacy.

(42) 7. The cardiopulmonary resuscitation is provided by circumferential or partial circumferential constriction and relaxation.

(43) 8. The CCDCs are provided by a mechanical device.

(44) 9. The CCDCs are provided by an automated chest compression device.

(45) 10. The ratio or sequence of CCDCs is variable based on feedback of patient status.

(46) 11. The cardiac output enhancing CCDCs, or their respective phases, are further enhanced by phasic manipulation of the abdomen.

(47) 12. The venous output enhancing CCDCs, or their respective phases, are further enhanced by phasic manipulation of the abdomen.

(48) 13. The cardiac output enhancing CCDCs, or their respective phases, are further enhanced by phasic alteration in ventilation pattern or pressures.

(49) 14. The venous output enhancing CCDCs, or their respective phases, are further enhanced by phasic alteration in ventilation pattern or pressures.

(50) 15. The cardiac output enhancing CCDCs, or their respective phases, are further enhanced by phasic alteration in the patient's body position or a portion of the patient's body chosen from a list that includes the head, neck, chest, abdomen, arms or legs.

(51) 16. The venous output enhancing CCDCs, or their respective phases, are further enhanced by phasic alteration in the patient's body position or a portion of the patient's body chosen from a list that includes the head, neck, chest, abdomen, arms or legs.

(52) 17. The alternating CCDCs and the phases of alternating CCDCs are provided by manually applied compressions in which the person providing chest compressions is assisted in the provision of cardiac output enhancing CCDCs and venous return enhancing CCDCs by biomarker and performance feedback.

(53) 18. The patients whole body is accelerated intermittently and in a manner synchronized to specific portions of the CCDCs such that cardiac output or venous return are further enhanced.

(54) 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.

Usefulness of the Disclosed Invention

(55) 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.

Non-Obviousness and No Prior Art

(56) 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.

(57) 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.

Critical Component

(58) 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.

Sufficiency of Disclosure

(59) 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.

Modifications

(60) 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.

(61) 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.

(62) Now that the invention has been described,

(63) Other Publications Incorporated in the Current Application by Reference Abella, B. S., D. P. Edelson, S. Kim, E. Retzer, H. Myklebust, A. M. Barry, N. O'Hearn, T. L. Hoek, and L. B. Becker. 2007. ‘CPR quality improvement during in-hospital cardiac arrest using a real-time audiovisual feedback system’, Resuscitation, 73: 54-61. Babbs, C. F. 1984. ‘Preclinical studies of abdominal counterpulsation in CPR’, Ann. Emerg. Med, 13: 761-63. Berkowitz, I. D., T. Chantarojanasiri, R. C. Koehler, C. L. Schleien, J. M. Dean, J. R. Michael, M. C. Rogers, and R. J. Traystman. 1989. ‘Blood flow during cardiopulmonary resuscitation with simultaneous compression and ventilation in infant pigs’, Pediatr. Res, 26: 558-64. Bircher, N., P. Safar, and S. W. Stezoski. 1982. ‘Do Intrathoracic Pressure Fluctuations or Heart Compression Move Blood During External Cardiopulmonary Resuscitation?(Abst)’, Anesthesiology, 3: S150. CARDIAC ARREST—The Science and Practice of Resuscitation Medicine. 96. (Williams & Wilkins: Baltimore). Cohen, T. J., K. J. Tucker, K. G. Lurie, R. F. Redberg, J. P. Dutton, K. A. Dwyer, T. M. Schwab, M. C. Chin, A. M. Gelb, and M. M. Scheinman. 1992. ‘Active compression-decompression. A new method of cardiopulmonary resuscitation. Cardiopulmonary Resuscitation Working Group [see comments]’, JAMA, 267: 2916-23. Cohen, T. J., K. J. Tucker, R. F. Redberg, K. G. Lurie, M. C. Chin, J. P. Dutton, M. M. Scheinman, N. B. Schiller, and M. L. Callaham. 1992. ‘Active compression-decompression resuscitation: a novel method of cardiopulmonary resuscitation’, Am. Heart J, 124: 1145-50. Haas, T., W. G. Voelckel, V. Wenzel, H. Antretter, A. Dessl, and K. H. Lindner. 2003.‘Revisiting the cardiac versus thoracic pump mechanism during cardiopulmonary resuscitation’, Resuscitation, 58: 113-6. Halperin, H. R., J. E. Tsitlik, M. Gelfand, M. L. Weisfeldt, K. G. Gruben, H. R. Levin, B. K. Rayburn, N. C. Chandra, C. J. Scott, and B. J. Kreps. 1993. ‘A preliminary study of cardiopulmonary resuscitation by circumferential compression of the chest with use of a pneumatic vest’, N. Engl. J. Med, 329: 762-68. Jenkins, C., K. Brinkley, H. Alford, K. Costello, N. Korkow, D. Johnson, and L. V. Fulton. 2015. ‘Effects of the ResQPOD on Kinetics, Hemodynamics of Vasopressin, and Survivability in a Porcine Cardiac Arrest Model’, Mil Med, 180: 1011-6. Kleinman, M. E., E. E. Brennan, Z. D. Goldberger, R. A. Swor, M. Terry, B. J. Bobrow, R. J. Gazmuri, A. H. Travers, and T. Rea. 2015. ‘Part 5: Adult Basic Life Support and Cardiopulmonary Resuscitation Quality: 2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care’, Circulation, 132:S414-35. Kouwenhoven, W. B., J. R. Jude, and G. G. Knickerbocker. 1960. ‘Closed Chest Cardiac Massage’, JAMA, 173: 1064-67. McDonald, J. L. 1982. ‘Systolic and mean arterial pressures during manual and mechanical CPR in humans’, Ann Emerg. Med, 11: 292-95. Michael, J. R., A. D. Guerci, R. C. Koehler, A. Shi, J. Tsitlik, N. C. Chandra, E. Niederm, M. C. Rogers, R. J. Traystman, and M. L. Weisfeldt. 1984. ‘Mechanisms by which epinephrine augments cerebral and myocardial perfusion during cardiopulmonary resuscitation in dogs’, Circ, 69: 822-35. Niemann, J. T., J. Rosborough, M. Hausknecht, D. Brown, and J. M. Criley. 1980. ‘Cough-CPR: documentation of systemic perfusion in man and in an experimental model: a “window: to the mechanism of blood flow in external CPR’, Crit Care. Med, 8: 141-46. Paradis, N. A., G. B. Martin, M. G. Goetting, J. M. Rosenberg, E. P. Rivers, T. J. Appleton, and R. M. Nowak. 1989. ‘Simultaneous aortic, jugular bulb, and right atrial pressures during cardiopulmonary resuscitation in humans. Insights into mechanisms [see comments]’, Circ, 80: 361-68. Plaisance, P., K. G. Lurie, E. Vicaut, F. Adnet, J. L. Petit, D. Epain, P. Ecollan, R. Gruat, P. Cavagna, J. Biens, and D. Payen. 1999. ‘A comparison of standard cardiopulmonary resuscitation and active compression-decompression resuscitation for out-of-hospital cardiac arrest. French Active Compression-Decompression Cardiopulmonary Resuscitation Study Group’, N. Engl. J. Med, 341: 569-75. Ralston, S. H., C. F. Babbs, and M. J. Niebauer. 1982. ‘Cardiopulmonary resuscitation with interposed abdominal compression in dogs’, Anesth. Analg, 61: 645-51. Segal, N. 2014. ‘Intermittent positive-pressure ventilation, chest compression synchronized ventilation, bilevel ventilation, continuous chest compression, active compression decompression, and impedance threshold device-the complexity of ventilation during cardiopulmonary resuscitation’, Crit Care Med, 42: 480-81. Voorhees, W. D., M. J. Niebauer, and C. F. Babbs. 1983. ‘Improved oxygen delivery during cardiopulmonary resuscitation with interposed abdominal compressions’, Ann. Emerg. Med, 12: 128-35. Wang, C. H., M. S. Tsai, W. T. Chang, C. H. Huang, M. H. Ma, W. J. Chen, C. C. Fang, S. C. Chen, and C. C. Lee. 2015. ‘Active Compression-Decompression Resuscitation and Impedance Threshold Device for Out-of-Hospital Cardiac Arrest: A Systematic Review and Metaanalysis of Randomized Controlled Trials’, Crit Care Med, 43: 889-96. Weisfeldt, M. L., N. C. Chandra, and J. Tsitlik. 1981. ‘Increased intrathoracic pressure—not direct heart compression-causes the rise in intrathoracic vascular pressures during CPR in dogs and pigs’, Crit Care. Med, 9: 377-78. Wolcke, B. B., D. K. Mauer, M. F. Schoefmann, H. Teichmann, T. A. Provo, K. H. Lindner, W. F. Dick, D. Aeppli, and K. G. Lurie. 2003. ‘Comparison of standard cardiopulmonary resuscitation versus the combination of active compression-decompression cardiopulmonary resuscitation and an inspiratory impedance threshold device for out-of-hospital cardiac arrest’, Circulation, 108: 2201-05. Yeung, J., R. Meeks, D. Edelson, F. Gao, J. Soar, and G. D. Perkins. 2009. ‘The use of CPR feedback/prompt devices during training and CPR performance: A systematic review’, Resuscitation, 80: 743-51.