Chapter 22: CPR and ACLS Updates

Cardiac arrest is the abrupt cessation of cardiac pump function which leads to death, but in some cases can be reversible by a prompt intervention in the form of cardiopulmonary resuscitation (CPR).¹ In- and out-of-the-hospital cardiac arrest remains a substantial public health problem and a leading cause of death in many parts of the world.² In the United States and Canada, approximately 350,000 people/year suffer a cardiac arrest (approximately half of them in-hospital) and receive attempted resuscitation; approximately 25% of these present with pulseless ventricular arrhythmias.^3,4 Cardiac-arrest victims who present with ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT) have a substantially better outcome compared with those who present with asystole or pulseless electrical activity (PEA).⁴ Emergency systems that can immediately and effectively implement life support measurement can achieve witnessed VF cardiac arrest survival of almost 50%.⁵ However, there is a dramatic variation in the survival rates across various systems of care, with the most successful systems reporting survival rates five times higher than the least successful.³

The survival rate and the quality of life (specially measured as a neurological performance) after a cardiac arrest have also changed over time; for example, the US survival rates for hospitalized patients with cardiac arrest improved from 30.4% in 2001 to 42.2% in 2009 as per the US National In-Patient Sample, a national hospital discharge database.⁶ It is important to understand that CPR outcomes are significantly influenced by the underlying pathology and the initial cardiac rhythm at the time of the cardiac arrest. In a nutshell, survival is best for patients with VT or VF.

It is an integrated and coordinated system, starting from initial responders (including both medical professionals and bystanders) to in-hospital caregivers, functioning as a comprehensive whole that will produce the highest likelihood of achieving the desired survival to discharge from hospital outcome. However, research has shown that several factors prevent bystanders from taking action; including fear that they will perform CPR incorrectly, fear of legal liability, and fear of infection from performing mouth-to-mouth.⁷ But a hospital setting does not have these inhibitory factors; hence, hospital personnel have tools in the form of the knowledge about CPR guidelines and resources to fight against cardiac arrest.

Resuscitation is one of the most widely studied topics in medicine. It has been known and practiced since 1740 when performance of mouth-to-mouth resuscitation for drowning victims was recommended by the Paris Academy of Science.⁸ As of December 2013, there were close to 19,000 related references cited in PubMed, with new changes being recommended every few years in how CPR should be administered; so it is important to keep ourselves updated with the latest knowledge and practice of the art of CPR. The American Heart Association (AHA), in cooperation with the International Liaison Committee on Resuscitation, leads the research and management guidelines for CPR. The latest guidelines available for CPR were established in 2010⁷ after an extensive evidence evaluation process that included 356 resuscitation experts from 29 countries who reviewed and analyzed the available literature during the 36-month period before the 2010 Consensus Conference. The experts produced 411 scientific evidence reviews on 277 topics in resuscitation and emergency cardiovascular care. The purpose of this chapter is to review the fundamentals of these recommendations, to emphasize the new changes made in 2010, and review the evidence-base literature that support these guidelines.

Upon review of the history of CPR, the earliest recorded reference to artificial breathing is in the Old Testament, in the book of Kings, where the prophet Elisha restored the life of a boy through a technique that included placing his mouth on the mouth of the child.⁸ Around the 1700s, there was a large number of drowning deaths in the Rhine river near Paris, and even though there were case reports and references to mouth to mouth resuscitation for many years before this, it was not until the 1740s that the technique became well known after the Paris Academy of Science's official recommendation of mouth-to-mouth resuscitation for drowning victims.⁸ In 1891, Dr Friedrich Maass performed the first equivocally documented chest compression on a human.⁸ This resuscitation technique was rediscovered in the 1940s during the polio epidemic in Minneapolis by the anesthesiologist James Elam.⁹

The three most important contributors to modern CPR are Doctors Zoll, Safar, and Kouwenhoven.¹⁰ Safar in the1950s investigated techniques for airway management and showed that the optimal position for CPR was with the patients' neck extended, mandible supported, in order to insert the oropharyngeal tube to deliver oxygen; Zoll performed and recorded the first successful closed chest human defibrillation in a man with syncope and VF; and Kouwenhoven in 1950s to 1960s developed a closed chest cardiac massage and external defibrillation. Later in the 1960s, Safar et al¹¹ published a paper showing circulatory efficacy of closed-chest cardiac massage and postulated that rhythmic sternal pressure must be accompanied by intermittent positive-pressure ventilation.

In 1960, Dr Kouwenhoven, in association with Drs Knickerbocker and Jude, documented 14 patients who survived cardiac arrest with the application of closed chest cardiac massage¹²; that same year, at the meeting of the Maryland Medical Society in Ocean City, the combination of chest compressions and rescue breathing was introduced.¹³ Two years later, in 1962, direct-current, monophasic waveform defibrillation was described, and in 1966, the AHA developed the first CPR guidelines, which have been followed by periodic updates.¹⁴ Since then, the AHA has maintained a program to acquaint physicians with closed chest cardiac resuscitation; this program is the forerunner of CPR training for the general public.

In 1979, the concept of Advanced Cardiovascular Life Support (ACLS) was introduced during the Third National Conference on CPR, and in the 1990s, Early Public Access Defibrillation programs were developed with goal in mind of providing training, resources, and the ability of the general public to become proactive and integral in the successful resuscitation of sudden cardiac arrest victims.¹⁵ It was not until 2005 that the International Consensus on Emergency Cardiovascular Care (ECC) and CPR Science with Treatment Recommendations (CoSTR) Conference produced the 2005 AHA guidelines for CPR and ECC.⁷

Two studies published just before the 2005 International Consensus Conference documented the poor quality of CPR performed in both out-of-and in-hospital resuscitations;^16,17 addressing this, changes in the compression-ventilation ratio and in the defibrillation sequence (from 3 stacked shocks to 1 shock followed by immediate CPR) were recommended to minimize interruptions in chest compressions.⁷ Since 2005, as mentioned earlier, it is more clear that after CPR with early, noninterrupted chest compressions and early defibrillation and ACLS, the best survival chance is for patients with VT or VF. To follow, we will review the major changes from 2010 AHA guidelines for CPR and ECC,⁷ and some of the studies behind these recommendations.

Traditionally, basic life support (BLS) has three components: achieving a patent airway, delivering lung inflations via mouth to mouth or bag-mask to mouth, and promoting circulation with chest compressions. Studies have demonstrated improved outcomes after out-of-hospital cardiac arrest (OHCA), particularly from shockable rhythms when there are minimal interruptions in compressions without excessive ventilation.^5,18,19 In order to prevent wasting time on potentially improper airway maneuvers, the most recent AHA guidelines recommend a significant change in BLS sequence.

Reasoning: High-quality CPR is the cornerstone of a system of care that can optimize outcomes beyond return of spontaneous circulation (ROSC), where return to a prior quality of life and functional state of health is the ultimate goal. The newest development in the 2010 AHA Guidelines for CPR and ECC is a change in the BLS sequence of steps from “A-B-C” (Airway, Breathing, Chest compressions) to “C-A-B” (Chest compressions, Airway, Breathing) for adult patients. As explained in the AHA guidelines, the A-B-C sequence could be reason why fewer people in cardiac arrest received bystander CPR. A-B-C starts with the most difficult and time consuming set of tasks: positioning the patient's head correctly, opening the airway, achieving a mouth to mouth seal, and delivering rescue breaths. Also there may be hesitancy on part of a rescuer's willingness to provide mouth-to-mouth resuscitation. By changing to C-A-B sequence, chest compressions will be initiated sooner and ventilation only minimally delayed until the first cycle of chest compressions is completed. The only exception to this sequence is in drowning victims and newborn patients where conventional CPR must be done.

In a prospective, population-based, observational study involving patients with emergency responder resuscitation attempts from 1998 through 2003, Iwami et al¹⁸ found that 1 year survival with favorable neurologic outcome was similar for bystander-initiated cardiac-only resuscitation (4.3%; odds ratio [OR], 1.72; 95% confidence interval [CI], 1.01-2.95) and conventional CPR for most adult OHCAs.

Olasveengen et al²⁰ did a retrospective, observational study between 2003 and 2006 in all nontraumatic cardiac arrest adult patients treated by the community-run emergency medical service (EMS) in Oslo, Norway in which they measured outcomes for patients receiving Standard basic life support (S-BLS), compared with patients receiving only continuous chest compression (CCC). They found that there were no differences in outcomes between the two patient groups, with 13% discharged with a favorable outcome for the S-BLS group and 10% in the CCC group (P = 0.85). Similarly, there was no difference in survival subgroup analysis of patients presenting with initial VF/VT after witnessed arrest, with 29% and 28% patients discharged from hospital in the S-BLS and CCC groups, respectively (P = 0.97).

Reasoning: “Look, listen, and feel” is an inconsistent and time-consuming practice. In a study by Rupert et al²¹ four different populations were tested for their ability to assess breathlessness: EMS personnel, physicians, medical students, and laypersons. Only 55.6% of all participants showed correct diagnostic skills. They concluded that this diagnostic procedure takes more time than recommended in international guidelines and checking for breathing was shown to be mostly inaccurate and unreliable. Professional as well as lay rescuers may be unable to accurately determine the presence or absence of adequate or normal breathing in unresponsive victims because the airway is not open or because the victim has occasional gasps.

1. A “chest compression rate of at least 100/min” is now recommended, different from the “approximately 100/min” recommended in 2005.

   Reasoning: The number of chest compressions per minute is an important factor for attaining ROSC. Studies show that delivery of more frequent compressions is associated with better survival. A prospective observational study by Abella¹⁷ showed that in-hospital chest-compression rates were below published resuscitation recommendations; suboptimal compression rates were correlated with poor ROSC.

2. “Chest compression depth of at least 2 in (5 cm),” different from the “approximately 2 in” recommended in 2005.

   Reasoning: Chest compression delivers blood flow and oxygen to heart and brain. Studies show that rescuers often do not push hard enough. Steil et al²² found suboptimal compression depth in half of patients by 2005 guideline standards and in almost all patients by 2010 standards; a strong association between increased compression depth and higher survival outcomes was found.

3. If a bystander is not trained in CPR, it is recommended he/she perform hands-only CPR with the emphasis to push fast and hard at the center of the chest. AHA 2005 guidelines did not provide different recommendations for trained versus untrained rescuers. However, according to the N2010 AHA recommendations, the trained rescuer should perform cardiac compression and give breaths.

   Reasoning: During the past 5 years, there has been an effort to simplify CPR recommendations and emphasize the fundamental importance of high-quality CPR. For most adults with OHCA, bystander CPR with chest compression only (Hands-Only CPR) appears to achieve outcomes similar to those of conventional CPR (compressions with rescue breathing).^18,19 However, for children, conventional CPR is superior. Hands only CPR is easier for an untrained person. Studies written above^19,20 show hands only CPR to be as effective as conventional CPR.

4. The new guidelines do not recommend routine use of cricoid pressure.

   Reasoning: Cricoid pressure may impede ventilation and it can delay or prevent placement of an advanced airway, and some aspiration can still occur despite cricoid pressure. It is also difficult to train rescuers in using this maneuver. A study by Li et al²³ showed that cricoid pressure impedes insertion of, and ventilation through the ProSeal laryngeal mask airway in anesthetized, paralyzed patients.

ACLS is an extension of BLS and is implemented by a team which can provide advanced therapeutic care. At the time of the 2010 International Consensus Conference, there was still insufficient data to demonstrate that any drugs or mechanical CPR devices improve long-term outcomes after cardiac arrest. So the 2010 AHA Guidelines for CPR and ECC continue to emphasize that the foundation of successful ACLS is good BLS, beginning with prompt high-quality CPR with minimal interruptions, and for VF/pulseless VT, attempted defibrillation within minutes of collapse.⁷ The new recommendations focus on the Post–Cardiac Arrest Care, as comprehensive multidisciplinary care that begins with recognition of cardiac arrest and continues after ROSC, through hospital discharge and beyond.

1. Continuous quantitative waveform capnography is a major new Class I recommendation for intubated adults throughout the periarrest period. It should be used for confirming tracheal tube placement and for monitoring CPR quality and detecting return of spontaneous circulation, based on end-tidal carbon dioxide values.

   Reasoning: Blood has to circulate through the lungs for carbon dioxide to be exhaled and measured, so capnography can be used for monitoring the effectiveness of chest compressions. Inadequate chest compressions, failing cardiac output, or rearrest causes decreased end tidal carbon dioxide. Grmec²⁴ studied adult patients intubated by an emergency physician in the field, with tube position confirmed by auscultation, infrared capnometry, and infrared capnography. He concluded that capnography is the most reliable method to confirm endotracheal tube placement in emergency conditions in the prehospital setting

2. Atropine is not recommended for Pulseless electrical activity (asystole) while adenosine is recommended in the initial diagnosis and treatment of stable, undifferentiated, monomorphic tachycardia.

   Reasoning: Evidence suggests that routine use of Atropine for PEA/Asystole is unlikely to have therapeutic benefit.⁷ Adenosine is safe and efficient and so recommended for aforementioned tachycardia.²⁵ The effects of atropine were assessed in 7448 adults with nonshockable rhythm from the SOS-KANTO study; they found that administration of atropine had no long-term neurological benefit in adults with OHCA due to nonshockable rhythm and concluded that atropine is not useful for adults with PEA.²⁶

3. Post–Cardiac arrest care to improve survival for victims of cardiac arrest admitted to hospital after return of spontaneous circulation. It should include cardiopulmonary and neurologic support, therapeutic hypothermia, and percutaneous coronary interventions when indicated; EEG for the diagnosis of seizures, monitored frequently in a comatose patient after ROSC; optimizing cardiopulmonary function and vital organ perfusion after ROSC; transportation to an appropriate hospital or critical-care unit with a comprehensive post–cardiac arrest treatment system of care; identification of and intervention for acute coronary syndromes; anticipation, treatment, and prevention of multiple organ dysfunction.

   Reasoning: Systematically organized multidisciplinary treatment programs for post–cardiac arrest (in- or out-of-hospital) patients may improve survival to hospital discharge outcomes among victims who attain ROSC.²⁷ Coordinated programs focusing on optimizing neurologic, metabolic, and hemodynamic function have shown some promise when deployed in an integrated system of care. As of now, the individual effects of such therapies have not been conclusively studied, but there is emerging evidence that use of such therapies may effectively improve outcomes. Studies have shown possible benefit of therapeutic hypothermia after cardiac arrest and that organized post–cardiac arrest care may improve survival to hospital discharge. Study done by hypothermia study group²⁸ found that therapeutic mild hypothermia increased the rate of a favorable neurologic outcome and reduced mortality for in-hospital patients who had been successfully resuscitated after cardiac arrest due to VF. It is recommended that post–cardiac arrest patient treated with therapeutic hypothermia be monitored for clinical neurologic signs using electrophysiological studies, biomarkers, and imaging where available, at 3 days after cardiac arrest, to be used for prognostication.

The steps in BLS (shown in Figure 22–1) and ACLS (shown in Figure 22–2) are shown as algorithms to be followed.

Evidence-based medicine is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients; the practice of evidence-based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research.²⁹ Resuscitation research is particularly challenging because it must be scientifically rigorous, while confronting ethical, regulatory, and public relations concerns that arise; life or death scenarios presented by the need for CPR make it impossible to receive informed consent from the patient. Regulatory requirements, community notification, and consultation requirements often impose expensive and time-consuming demands that may not only delay important research, but also render it cost prohibitive, with little significant evidence that these measures effectively address the concerns about research.³⁰ The following are some more recent and perhaps controversial topics/studies that arise when discussing evidence base CPR recommendations.

Identifying the most accurate and relevant post–cardiac arrest outcomes to measure is a major challenge that requires further research. The most used measurements are survival to hospital discharge, or neurologically intact survival to discharge. Caution is advised, for example, when considering limiting care or withdrawing life-sustaining therapy because the predictors of neurological recovery currently in use have not been validated for patients who are treated with therapeutic hypothermia.

Hollenberg et al¹⁹ conducted a study during a 14 year time period (1992-2005) in Sweden describing changes in 1-month survival in patients given CPR after OHCA. He found improved survival rates over that time period; factors that potentially contributed to the improved survival rate were an increase in emergency medical crew-witnessed cases (from 9% in 1992 to 15% in 2005 [P < 0.01]) and, to a lesser degree, an increase in bystander CPR (from 31% in 1992 to 50% in 2005 [P < 0.01]).

Hinchey et al⁵ did an observational multiphase before-after cohort study to assess survival from OHCA in adult patients with cardiac arrest managed by emergency responders. They concluded that in the context of a community-wide focus on resuscitation, the sequential implementation of 2005 AHA guidelines for compressions, ventilations, and induced hypothermia significantly improved survival after cardiac arrest.

CPR Quality

Minimizing the interval between stopping chest compressions and delivering a shock (ie, minimizing the preshock pause) improves the chances of shock success and patient survival.³¹

Edelson et al³² did a study on internal medicine residents at a university hospital who attended weekly debriefing sessions of the prior week's resuscitations, reviewing CPR performance transcripts obtained from a CPR-sensing and feedback-enabled defibrillator. Compared with the control period, the mean (SD) ventilation rate decreased (13 [7]/min vs 18 [8]/min; P < 0.01) and compression depth increased (50 [10] vs 44 [10] mm; P < 0.01), among other CPR improvements. These changes correlated with an increase in the rate of ROSC in the RAPID (Resuscitation with Actual Performance Integrated Debriefing) group (59.4% vs 44.6%; P < 0.05). They concluded that the combination of RAPID and real-time audiovisual feedback improved CPR quality compared with the use of feedback alone and was associated with an increased rate of ROSC. Survival from cardiac arrest depends on early recognition of the event and immediate activation of emergency response system, but equally critical is the quality of CPR delivered.

Five main components of high performance CPR have been identified: chest compression fraction (proportion of time chest compressions are administered in each minute of CPR), chest compression rate, chest compression depth, chest recoil, and ventilation.³³

CPR Devices

Several devices to provide effective CPR have been the focus of recent clinical trials. To date, no adjunct has consistently been shown to be superior to standard conventional (manual) CPR for out-of-hospital BLS, and no device other than a defibrillator has consistently improved long-term survival from OHCA.

Integration of AEDs into a system of care is critical in the Chain of Survival in public places outside of hospitals. To give the victim the best chance of survival, 3 actions must occur within the first moments of a cardiac arrest: activation of the EMS system, provision of CPR, and operation of a defibrillator.⁷ An area of continued interest is whether delivering a longer period of CPR before defibrillation improves outcomes in cardiac arrest. Early studies showed improved survival when 1.5 to 3 minutes of CPR preceded defibrillation for patients with cardiac arrest for more than 5 minutes duration prior to EMS arrival, but more recent trials did not improved outcomes.⁷

Transcutaneous pacing has also been the focus of several recent trials. In the current 2010 AHA recommendations, pacing is not generally recommended for patients in asystolic cardiac arrest since randomized controlled trials indicate no improvement in rate of admission to hospital or survival to hospital discharge when pacing was attempted in patients with cardiac arrest in the prehospital or in-hospital (ED) setting.⁷

Medications Used During CPR

A meta-analysis of 5 randomized trials³⁴ showed no statistically significant differences between vasopressin and epinephrine for ROSC, 24-hour survival, or survival to hospital discharge.

It is appropriate to administer a 1-mg dose of epinephrine IV/IO every 3 to 5 minutes during adult cardiac arrest or one dose of vasopressin 40 U IV/IO may replace either the first or second dose of epinephrine in the treatment of pulseless arrest.⁷

Hypothermia

Therapeutic hypothermia is one intervention that has been shown to improve outcome for comatose adult victims of witnessed OHCA when the presenting rhythm was VF.²⁸ Since 2005, nonrandomized studies with concurrent controls or historic controls have indicated the possible benefit of hypothermia following in- and out-of-hospital cardiac arrest from all other initial rhythms in adults. Holzer's study found 53% survival with favorable neurological outcome in the endovascular cooling group, compared to 34% in the control group (OR 2.15, 95% CI, 1.38 to 3.35; P < 0.05).³⁵ Therapeutic hypothermia is a “game changer,” changing the specificity of neurological prognostication decision rules that were previously established from studies of post–cardiac arrest patients not treated with hypothermia.

Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is a form of external cardiopulmonary life support (ECLS). Its goal is supporting the body's circulation in the absence of an adequately functioning cardiac pump. The initiation of ECLS and the management of a patient on ECLS require highly trained personnel and specialized equipment. ECLS has been associated with improved survival rates when compared with conventional CPR in patients less than 75 years old with potentially correctable conditions in case series and observational studies for in-hospital and OHCA sufferers. Although there are no randomized studies that compare ECLS with conventional CPR for patients in cardiac arrest, there are data from several case series that demonstrate the feasibility and safety of ECLS in highly specialized centers,³⁶ but, as of this writing, there is not enough evidence to recommend the routine use of ECLS in this population.

Study by Thiagarajan³⁷ showed that ECMO used to support CPR rescued one third of patients in whom death was otherwise certain; improved survival was found in association with patient diagnosis, absence of severe metabolic acidosis before ECMO support, and uncomplicated ECMO course.

In a study by Lamhaut L et al³⁸ published in 2013, prehospital ECMO (PH-ECLS) was implemented by a PH-ECLS team for refractory cardiac arrest in 7 patients with a witnessed cardiac arrest, with CPR initiated within the first 5 minutes, and absence of severe comorbidities. This pilot study suggests that PH-ECLS performed by nonsurgeons is potentially safe and feasible. Further studies are needed to confirm the time saved by this strategy and its potential effect on survival.

Ethical Issues

1. Should resuscitative efforts be started? Ethical issues associated with CPR start with the question as to whether or not to initiate resuscitation as some patients might prefer palliative care without heroic measures to prolong life; advance directives play a very important role in these matters, and if an advance directive in the form of a living will is not available then a health care proxy or surrogate decision maker is helpful. Acknowledgment of a verbal or written do-not-attempt-resuscitation order may decrease the number of futile resuscitation attempts; however, there is insufficient evidence to support this without further validation.

2. When should resuscitative efforts stop? The final decision to stop resuscitative efforts often is not simple; clinical judgment and respect for patients' and their families' wishes must enter into decision making. Research addressing issues related to the appropriate termination of resuscitative efforts is limited. Goto et al³⁹ performed a study with Japanese database on patients with OHCA. The main outcome measures were specificity, positive predictive value (PPV), and area under the receiver operating characteristic curve for the new developed termination of resuscitation (TOR) rule for emergency department physicians. They validated that the TOR rule consisting of 3 prehospital variables (no prehospital ROSC, unshockable initial rhythm, and unwitnessed by bystanders) had a more than 99% PPV of very poor outcome. However, the implementation of this new rule in other countries or EMS systems requires further validation studies.

3. Should family be present during CPR? Jabre P et al⁴⁰ enrolled 570 relatives of patients who were in cardiac arrest and were given CPR by 15 pre-hospital EMS units that were randomly assigned either to systematically offer the family member the opportunity to observe CPR (intervention group) or to follow standard practice regarding family presence (control group). The primary end point was the proportion of relatives with post-traumatic stress disorder-related symptoms on day 90; secondary end points included the presence of anxiety and depression symptoms, the effect of family presence on medical efforts at resuscitation, the well-being of the health care team, and the occurrence of medico-legal claims. They concluded that family presence during CPR was associated with positive results on psychological variables and did not interfere with medical efforts, increase stress in the health care team, or result in medico-legal conflicts. Some other studies indicate that no clear conclusion is derived from studies done so far and more studies have to be done in this area.

4. Organ donation. Because of the growing need for transplant tissue and organs, all provider teams who treat postarrest patients should also plan and implement a system of tissue and organ donation that is timely, effective, and supportive of family members for that subset of patients in whom brain death is confirmed or for organ donation after cardiac arrest.

The 2010 AHA guidelines recommend education to improve the effectiveness of resuscitation.⁷ The recommendations include frequent practicing of skills; training of teamwork and leadership skills; formal training in CPR techniques, including compression-only (Hands-Only) in CPR to potential bystander rescuers; training in dispatcher instructions over the telephone by EMS providers. Recommended educational tools include high-quality medical simulators, videos, and written tests accompanied with a performance assessment.

The art of resuscitation has developed over thousands of years. The guidelines for resuscitation have had significant updates and as strong evidence-based studies continually provide the medical community with more information, methods used in resuscitative efforts may likely evolve further to improve patient outcomes. Extensive training and education of nonmedical staff in BLS and medical staff in BLS and ACLS is necessary so that we properly implement them. Simulation training on mannequins, for example, is one tool that can aid in the application of these guidelines effectively. Extensive studies have been done on CPR techniques but more research has to be done on the ethical and other aspects of CPR. We have come a long way in our understanding of what life-saving measures work best, and further understanding and evolution of CPR practices most likely will improve our ability to effectively save lives through CPR.