A new cardiopulmonary resuscitation method using only rhythmic abdominal compression A preliminary report B

Transcription

1 American Journal of Emergency Medicine (2007) 25, Original Contribution A new cardiopulmonary resuscitation method using only rhythmic abdominal compression A preliminary report B Leslie A. Geddes ME, PhD, DSc a,, Ann Rundell PhD a, Aaron Lottes BCh, MBA, PhD a, Andre Kemeny MS b, Michael Otlewski BS b a Weldon School of Biomedical Engineering, Purdue University, W Lafayette, IN 47907, USA b Basic Medical Sciences, Purdue University, W Lafayette, IN 47907, USA Received 13 December 2006; revised 27 March 2007; accepted 3 April 2007 Abstract This article introduces 2 new cardiopulmonary resuscitation (CPR) concepts: (1) the use of only rhythmic abdominal compression (OAC) to produce blood flow during CPR with ventricular fibrillation and (2) a new way of describing coronary perfusion effectiveness, namely, the area between the aortic and right atrial pressure curves, summed over 1 minute, the units being millimeters of mercury per second. We call this unit the coronary perfusion index (CPI). True mean coronary perfusion pressure is CPI/60. We also relate CPI during CPR with ventricular fibrillation to the CPI for the normally beating heart in the same animal, obtained before each experiment. This 11-pig (25-35 kg) study compares the CPI for standard chest-compression CPR and that obtained with OAC-CPR. The coronary perfusion ratio for OAC-CPR compared with standard chest-compression CPR was 1.6 ± 0.73 (P =.024). In other words, OAC-CPR produced 60% more coronary perfusion than standard chest-compression CPR, with no damage to visceral organs Elsevier Inc. All rights reserved. 1. Introduction Only abdominal compression (OAC) cardiopulmonary resuscitation (CPR) is a new CPR technique (in contrast to the AHA [1]) in which blood flow during ventricular fibrillation (VF) is produced by rhythmic compression of the abdominal organs. Bard [2] reported that the abdominal organs contain approximately 25% of the total blood volume. Rhythmic Supported by the Purdue Trask Fund. Corresponding author. Tel.: ; fax: address: geddes@ecn.purdue.edu (L.A. Geddes). compression of this vascular bed can produce substantial CPR blood flow during VF, as we will demonstrate. The first objective of this study was to determine the amount of coronary perfusion obtainable with OAC-CPR during VF compared with the coronary perfusion with the normally beating heart in the same animal. A second objective was to determine coronary perfusion during VF using standard chest-compression CPR and to compare it with the coronary perfusion for the normally beating heart in the same animal. A third objective was to compare the OAC-CPR ratios with the ratios obtained with standard chest-compression CPR. This latter comparison was /$ see front matter 2007 Elsevier Inc. All rights reserved. doi: /j.ajem

2 New CPR methods designed to quantitate the superiority of OAC-CPR over standard chest-compression CPR. By using OAC-CPR, the risk of rib fractures is eliminated. Rib fractures, although not fatal, do occur with standard CPR [3-5]. They are painful, slow to heal, and change the chest-recoil elasticity, making it slower to recoil during the decompression cycle. 2. Methods and materials All studies were approved by the Purdue Animal Care and Use Committee. In this investigation, 11 isofluraneanesthetized pigs (25-35 kg) were used. All animals were sedated with an injection of 100 mg Telazol, 50 mg xylazine, and 50 mg ketamine; were intubated; and breathed oxygen. A catheter was inserted into the left femoral artery and advanced to the aortic (Ao) arch for measurement of Ao pressure. A catheter was inserted into the right jugular vein and advanced to the right atrium for measurement of right atrial (RA) pressure. These catheters were then connected to high-fidelity pressure transducers (COBE, Denver, CO). During VF, repeated series of 30 abdominal compressions (100 lb, at 100/min) were followed by 2 deep breaths. The electrocardiogram, Ao and RA pressure, end-tidal CO 2, and SaO 2 were monitored continuously. Ventricular fibrillation was induced electrically with a right ventricular, bipolar catheter electrode. Rhythmic abdominal compression was applied with the Thumper (Michigan Instruments, Grand Rapids, MI) connected to a contoured abdominal compression plate. The contoured abdominal compression force was 100 lb at 100/min with a duty cycle of 50%. These parameters were derived from preliminary studies. The same parameters were used for standard chest-compression CPR with the Thumper. Defibrillation was accomplished with transchest electrodes. If, after defibrillation, sinoatrial node arrest or atrioventricular block occurred, to rescue the animals, the ventricles were paced with the right ventricular catheter electrode. The Tukey statistical method was used to confirm differences in blood pressure gradients between the 2 types of CPR, as well as the normally beating heart before each type of CPR. Significance was concluded at P b interposed abdominal compression, and active compressiondecompression CPR), both Ao and RA pressures are varying; and the peaks and valleys of each curve occur at slightly different times, making the subtraction difficult and the interpretation of the results complex. To circumvent this problem, we define the coronary perfusion index (CPI) as the area between the Ao and RA pressure curves summed over 1 minute, the units being millimeters of mercuryseconds. True mean CPP is CPI/60. The following examples will illustrate the meaning of this new concept. Fig. 1A shows records of Ao and RA pressure for the normally beating heart. The area between the 2 curves, summed over 1 minute, is the CPI. In this example, it is 2545 mm Hg-s. Fig. 1B shows the same pressures with VF and standard chest-compression CPR (100/min and 100 lb) in the same animal. In this case, the CPI was 248 mm Hg-s. In other words, the coronary perfusion was 248/2669 or 9% of that with the beating heart. The X in Fig. 1B identifies the times when RA pressure exceeds Ao pressure Coronary perfusion index During CPR with VF, it is necessary to have an adequate flow of oxygenated blood through the coronary arteries so that, after defibrillation, the ventricles will beat forcibly. Coronary blood flow is proportional to the difference between Ao and RA pressure; this quantity is called the coronary perfusion pressure (CPP). Typically selected values of CPP (or its mean value) during the decompression phase are used as an indicator of the efficacy of CPR. However, during different forms of CPR with VF (such as OAC, Fig. 1 A, The Ao and RA pressures in the normally beating heart. B, The same pressures with standard chest-compression CPR. The times when RA pressure exceeds Ao pressure are identified by X. C, The same pressures in the same animal during OAC-CPR (rate = 100/min, force 100 lb, duty cycle 50%).

3 788 L.A. Geddes et al. Fig. 1C shows the same 2 pressures with VF and OAC- CPR (100/min and 100 lb). In this case, the CPI was 645 mm Hg-s. In other words, the coronary perfusion was 645/2545, or 25% of that for the beating heart, that is, about 2.5 times greater than that with standard chest-compression CPR. Note that in Fig. 1B (standard CPR), there are instances (X) when RA pressure exceeds Ao pressure, indicating retrograde coronary flow. In Fig. 1C (OAC-CPR), RA pressure was almost always less than Ao pressure, resulting in coronary flow during almost all of the abdominal compression and decompression cycles. Use of the CPI is very convenient and applicable to all CPR methods. Whereas current calculations of CPP evaluate only the efficacy of the CPR during the decompression phase and require choosing a point in time for subtraction, CPI computes the pressure difference across the compression and decompression phases to eliminate phase-shift errors encountered with CPR techniques and includes a 1-minute time. This indicates that CPI is a better unit to describe coronary perfusion. It merely requires recording Ao and RA pressure simultaneously and continuously and entering these data into a digital computer for area processing, which takes a very short time. We believe that the CPI is an excellent tool for evaluating the effectiveness of all CPR methods to provide coronary perfusion Abdominal compression plate (the home plate) To facilitate the rhythmic application of force evenly to the abdomen, we created a contoured wooden applicator that fits over the abdomen just beyond the lower border of the rib cage as shown in Fig. 2. Because of its unique shape, it has been called the home plate, the term being derived from the baseball home plate. We have built a model that is easily coupled to the pneumatically driven Thumper (Michigan Table 1 Only abdominal compression CPR CPI Pig Beating heart OAC CPI CPI ratio Average SD Instruments); this application is shown in Fig. 2 and permits quantitative control of force. 3. Results Fig. 1C shows a typical record of Ao and RA pressure with OAC-CPR. Table 1 shows the CPI values for the beating heart and those for OAC-CPR for the 11 animals. Table 1 also shows the ratios of OAC CPI to the beating heart CPI ratios; the average is 0.24 ± In other words, the mean coronary perfusion with OAC-CPR was 24% of that when the heart was beating normally. Note that each animal served as its own control. Table 2 shows the CPI values for the normally beating heart and those obtained with VF and standard chestcompression CPR. The average ratio (CPI for standard CPR with VF to the CPI with the beating heart) is 0.17 ± In other words, standard chest-compression CPR provided 17% Fig. 2 Abdominal compression plate, called the home plate (H), and its application to the pig abdomen used with the pneumatically driven Thumper.

4 New CPR methods Table 2 Standard CPR CPI Pig Beating heart Standard CPR CPI CPI Ratio Average SD of the beating heart coronary perfusion. Only abdominal compression CPR provided 0.24/0.17 = 1.40 times that produced by standard chest-compression CPR, that is, OAC- CPR provided 40% more coronary perfusion than with standard chest-compression CPR during VF. Table 3 presents another method of comparing the effectiveness of coronary perfusion for the 2 methods (standard CPR and OAC-CPR). For each method are listed the CPI ratios compared with the beating heart values for each animal. The right-hand column in Table 3 shows the individual OAC-CPR/standard CPR ratios. The mean value was 1.60 ± In other words, OAC-CPR provides 60% more coronary perfusion than standard chest-compression CPR. 4. Discussion Table 3 Ratio of OAC-CPR CPI to standard CPR CPI Pig Standard CPR CPI OAC-CPR CPI OAC/Standard ratio Average 1.60 SD 0.73 The idea of using OAC to pump blood during CPR with VF originated with Ralston et al [6] who reported interposed abdominal compression with standard chestcompression CPR. They found that CPR blood flow was doubled. It was therefore logical to explore the potential of rhythmic OAC without chest compression, which became the subject of this study. Although it is true that CPP is proportional to the difference between Ao and RA pressure, not all investigators use the same Table 4 Algorithms used to compute CPP Investigator Year Species Method Halperin et 1993 Human Diastolic Ao RA al [7] Xavier et al 2003 Pig Diastolic Ao RA [8] Raessler et al [9] 1988 Dog Diastolic Ao RA and systolic Ao RA Cohen et al [10] 1992 Dog Diastolic MAP diastolic mean RA Lurie et al [11] 2001 Pig Diastolic Ao RA (time Niemann et al [12] 1982 Dog Mid-diastolic Ao RA and peak systolic Ao RA Niemann et al [13] 1985 Dog Computer integrated mean, peak systolic Ao RA, and peak Cairns and Niemann [14] [15] [16] [17] diastolic Ao RA 1998 Dog End-diastolic Ao RA 1989 Human Diastolic Ao RA 1990 Human Ao RA (toward the end of diastole, for 5 consecutive cycles and average) 1991 Human Ao RA (toward the end of diastole, for 5 consecutive cycles and average) 1980 Dog AV (MAP CVP mean) and SAP 1981 Dog MAP and SAP Bircher et al [18] Bircher and Safar [19] Sanders et al 1984 Dog Diastolic Ao RA [20] Sanders et al 1985 Human Mid-diastolic Ao RA [21] Noc et al 1994 Rat Diastolic Ao RA (time [22] Tang et al 1997 Pig Mid-diastolic Ao RA (averaged [23] with all the preceding beats for 1 min prior) Klouche et 2002 Pig Ao RA (time coincident, al [24] recorded continuously, reported Fries et al [25] every 30 s) 2006 Pig Peak diastolic Ao RA (time Systolic = during compression Diastolic = during decompression MAP indicates mean arterial pressure; CVP, central venous pressure; SAP, systolic arterial pressure; AV, atrioventricular. 789

5 790 L.A. Geddes et al. algorithm to compute this difference. Table 4 summarizes the methods used by various investigators. Because different algorithms were used, it is difficult to compare and evaluate the published values. The algorithms used to date do not recognize the fact that during the compression cycle, RA pressure exceeds Ao pressure, as shown as X in Fig. 1B (standard CPR). This is why we chose to compute CPP by measuring the area between the Ao and RA pressure curves over several cycles and representing it over 1 minute, which we call the CPI. True mean CPP is CPI/ Rib fractures Although not a serious problem, rib fractures do occur; OAC-CPR eliminates this adverse effect. Lederer et al [3] compared the ability of chest radiographs to identify rib fractures in 19 out-of-hospital CPR subjects and compared the result with autopsy findings. Radiographs identified fractures in 9 of 19, and autopsy reports identified 19 of 19. Black et al [4] reviewed the autopsy reports of 1823 deaths for rib cage fractures; all had CPR before death. Rib fractures were found in 37% of the female and 36% of the male subjects. The incidence of rib fractures increased with age. Hoke and Chamberlain [5] reviewed the published literature to identify the incidence of rib and sternal fractures. They stated that such fractures rarely cause damage to internal organs Summary In summary, OAC-CPR eliminates the possibilities of rib fractures. It also provides substantially more coronary perfusion than standard chest-compression CPR. With OAC-CPR, Ao pressure exceeds RA pressure during almost the entire compression-decompression cycle, thereby providing a high coronary perfusion. With standard chest-compression CPR, there is some retrograde coronary flow because RA pressure exceeds Ao pressure during a portion of the compression-decompression cycle. In this preliminary study, we have found no evidence of damage to visceral organs. References [1] American Heart Association (AHA). Supplement to circulation 2005;112(Suppl 114): [2] Bard P. Medical physiology. 11th ed. St Louis: CV Mosby; [3] Lederer W, Mair D, Ralston SH, et al. Rib and sternal fractures associated with out-of-hospital CPR. Resuscitation 2004;60: [4] Black CJ, Busuttil A, Robertson C. Chest wall injuries following CPR. Resuscitation 2004;63: [5] Hoke RS, Chamberlain D. Skeletal chest injuries secondary to CPR. Resuscitation 2004;61: [6] Ralston SH, Babbs CH, Neibauer MJ. Cardiopulmonary resuscitation with interposed abdominal compression in dogs. Anesth Analg 1982;61: [7] Halperin HR, Tsitlik JE, Gelfand M, et al. A preliminary study of cardiopulmonary resuscitation by circumferential compression of the chest with use of a pneumatic vest. N Engl J Med 1993;329(11): [8] Xavier L, Kern KB, Berg RA, et al. Comparison of standard CPR versus diffuse and stacked hand position interposed abdominal compression-cpr in a swine model. Resuscitation 2003;59: [9] Raessler KL, Kern KB, Sanders AB, et al. Aortic and right atrial systolic pressures during cardiopulmonary resuscitation: a potential indicator of the mechanism of blood flow. Am Heart J 1988;115: [10] Cohen TJ, Tucker KJ, Redberg RF, et al. Active compressiondecompression resuscitation: a novel method of cardiopulmonary resuscitation. Am Heart J 1992;124: [11] Lurie KG, Voelckel WG, Zielinski T, et al. Improving standard cardiopulmonary resuscitation with an inspiratory impedance threshold valve in a porcine model of cardiac arrest. Anesth Analg 2001;93: [12] Niemann JT, et al. Coronary perfusion pressure during experimental cardiopulmonary resuscitation. Ann Emerg Med 1982;11(3): [13] Niemann JT, et al. Predictive indices of successful cardiac resuscitation after prolonged arrest and experimental cardiopulmonary resuscitation. Ann Emerg Med 1985;14(6): [14] Cairns CB, Niemann JT. Hemodynamic effects of repeated doses of epinephrine after prolonged cardiac arrest and CPR: preliminary observations in an animal model. Resuscitation 1998;36: [15] Paradis NA, Martin GB, Goetting MG, et al. Simultaneous aortic, jugular bulb, and right atrial pressures during cardiopulmonary resuscitation in humans. Circulation 1989;80: [16] Paradis NA, Martin GB, Rivers EP, et al. Coronary perfusion pressure and the return of spontaneous circulation in human cardiopulmonary resuscitation. JAMA 1990;263(8): [17] Paradis NA, Martin GB, Rosenberg J, et al. The effect of standard- and high-dose epinephrine on coronary perfusion pressure during prolonged cardiopulmonary resuscitation. JAMA 1991;265(9): [18] Bircher N, Safar P, Stewart R. A comparison of standard, MAST - augmented, and open-chest CPR in dogs. Crit Care Med 1980;8 (3): [19] Bircher N, Safar P. Comparison of standard and new closed-chest CPR and open-chest CPR in dogs. Crit Care Med 1981;9(5): [20] Sanders AB, Ewy GA, Taft TV. Prognostic and therapeutic importance of the aortic diastolic pressure in resuscitation from cardiac arrest. Crit Care Med 1984;12(10): [21] Sanders AB, Ogle M, Ewy GA. Coronary perfusion pressure during cardiopulmonary resuscitation. Am J Emerg Med 1985;3:11-4. [22] Noc M, Weil MH, Sun S, et al. Spontaneous gasping during cardiopulmonary resuscitation without mechanical ventilation. Am J Respir Crit Care Med 1994;150: [23] Tang W, Weil MH, Schock RB, et al. Phased chest and abdominal compression-decompression. Circulation 1997;95: [24] Klouche K, Weil MH, Sun S, et al. Stroke volumes generated by precordial compression during cardiac resuscitation. Crit Care Med 2002;30: [25] Fries M, Tang W, Chang YT, et al. Microvascular blood flow during cardiopulmonary resuscitation is predictive of outcome. Resuscitation 2006;71: