RESUSCITATION OF PATIENTS WITH COVID-19 — Interim guidelines for the performance of cardiopulmonary resuscitation (CPR) in patients with COVID 19-related illness have been published by the American Heart Association (AHA) in collaboration with several other major medical organizations. These guidelines and associated algorithms for basic life support (BLS) and advanced cardiac life support (ACLS) can be accessed using the following link and graphic: AHA interim guidelines for COVID-19 patients (algorithm 1). These guidelines should be used for all patients with an unknown etiology of cardiac arrest.
Systems and procedures should be in place to minimize any time delays in providing life-saving interventions. Tasks and modifications for clinicians emphasized in the COVID 19-related guidelines include the following:
●Don personal protective equipment (PPE) according to local guidelines and availability before beginning CPR.
●Minimize the number of clinicians performing resuscitation; use a negative-pressure room whenever possible; keep the door to the resuscitation room closed if possible.
●May use a mechanical device, if resources and expertise are available, to perform chest compressions on adults and on adolescents who meet minimum height and weight requirements.
●Use a high-efficiency particulate air (HEPA) filter for bag-mask ventilation (BMV) and mechanical ventilation.
●Emphasize early intubation performed by the provider most likely to achieve first-pass success (table 1); use video laryngoscopy if resources and expertise available; stop chest compressions while intubation is performed (ideally, this should be performed during the two-minute rhythm check as quickly as possible to minimize no-flow time).
●Use a supraglottic airway (or bag-valve-mask with tight seal, two-person thenar technique) if intubation is delayed; avoid excessive ventilation rate or pressure (ie, avoid hyperventilation and squeeze the bag gently).
●Avoid prolonged resuscitation efforts: consider the extremely high mortality of adult COVID-19 patients in cardiac arrest and consider lapses in infection control and associated risks during high-stress medical emergencies.
INTRODUCTION — Cardiopulmonary resuscitation (CPR) as we recognize it today was developed in the late 1950s and 1960s. Elam and Safar described the technique and benefits of mouth-to-mouth ventilation in 1958 [1]. Kouwenhoven, Knickerbocker, and Jude subsequently described the benefits of external chest compressions [2], which in combination with mouth-to-mouth ventilation form the basis of modern CPR. External defibrillation, first described in 1957 by Kouwenhoven [3], has since been incorporated into basic life support (BLS) resuscitation guidelines.
BLS consists of cardiopulmonary resuscitation and, when available, defibrillation using automated external defibrillators (AED). The keys to survival from sudden cardiac arrest (SCA) are early recognition and treatment, specifically, immediate initiation of excellent CPR and early defibrillation.
This topic review will discuss the critical facets of BLS in adults for clinicians as presented in the guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care published jointly by the International Liaison Committee on Resuscitation, American Heart Association, and European Resuscitation Council [4-11]. Advanced cardiac life support (ACLS) and other related topics, such as airway management and BLS for infants and children, are presented separately. (See "Advanced cardiac life support (ACLS) in adults" and "Basic airway management in adults" and "Pediatric basic life support (BLS) for health care providers".)
EPIDEMIOLOGY AND SURVIVAL — The exact incidence of sudden cardiac arrest (SCA) in the United States is unknown, but estimates vary from 180,000 to over 450,000 annually [12,13]. In North America and Europe, the estimated incidence falls between 50 to 100 per 100,000 in the general population [14]. The most common etiology of SCA is ischemic cardiovascular disease resulting in the development of lethal arrhythmias. Resuscitation is attempted in up to two-thirds of people who sustain SCA.
Despite the development of cardiopulmonary resuscitation (CPR), electrical defibrillation, and other advanced resuscitative techniques over the past 50 years, survival rates for SCA remain low. While early, properly performed CPR improves outcomes, not performing CPR or low-quality performance are important factors contributing to poor outcomes [15-19]. Multiple studies assessing both in-hospital and prehospital performance of CPR have shown that trained health care providers consistently fail to meet basic life support (BLS) guidelines [20,21]. The epidemiology and etiology of SCA are discussed in greater detail separately. (See "Overview of sudden cardiac arrest and sudden cardiac death" and "Pathophysiology and etiology of sudden cardiac arrest".)
RESUSCITATION GUIDELINES — The Guidelines for Cardiopulmonary Resuscitation (CPR) and Emergency Cardiovascular Care (CPR-ECC Guidelines) are based upon an extensive review of the clinical and laboratory evidence performed by the International Liaison Committee on Resuscitation (ILCOR) and are published jointly by ILCOR, the American Heart Association (AHA), and the European Resuscitation Council (ERC). The Guidelines and algorithms are designed to be simple, practical, and effective (algorithm 2). Updates to the guidelines are published periodically, including treatment recommendations [4,8-11,22,23]; the current version of the AHA basic life support (BLS) algorithm can be accessed here (AHA BLS algorithm).
Key concepts for BLS — Important concepts and practices in the CPR-ECC Guidelines for BLS include:
●Recognize sudden cardiac arrest (SCA) as soon as possible by noting unresponsiveness or absent/gasping breathing (often described as breathing that does not look normal). Mistakenly interpreting agonal respirations as a sign of stable breathing rather than cardiac arrest is likely a major contributor to delays in treatment (CPR and early defibrillation) and thereby to poor outcomes.
●For the lay rescuer, initiate CPR as soon as the patient is thought to be in cardiac arrest. Performing CPR on an unresponsive patient who is not in cardiac arrest has few adverse consequences [24], while not performing CPR on a patient who is in cardiac arrest is likely to contribute to a poor outcome.
●Health care providers may perform a carotid pulse check for no longer than 10 seconds prior to initiating CPR in an unresponsive patient. Again, it is far better to err on the side of initiating CPR if there is any question of pulselessness.
●Perform excellent CPR – "push hard, push fast" (but not too hard nor too fast) – with continuous attention to the quality of chest compressions, and to the frequency of ventilations.
●Minimize interruptions in CPR.
●Use an automated external defibrillator as soon as one is available.
●Activate emergency medical services or the cardiac arrest team as soon as possible
Patient survival in SCA depends primarily upon immediate initiation of excellent CPR and early defibrillation [25,26].
Phases of resuscitation — Many researchers in resuscitation consider there to be three distinct phases of cardiac arrest: the electrical phase, the hemodynamic phase, and the metabolic phase [25]. The emphasis of treatment varies according to the phase.
Electrical phase — The electrical phase is defined as the first 4 to 5 minutes of arrest in patients in ventricular fibrillation (VF). Immediate DC cardioversion is needed to optimize survival of these patients. Performing excellent chest compressions while the defibrillator is readied also improves survival [26]. Excellent chest compressions should be started immediately upon recognizing SCA and continued until just before defibrillation is performed. When using an automatic defibrillator, the rescuer must listen and adhere to all prompts coming from the device. In situations in which a manual defibrillator is used, we recommend the following sequence:
●Charge the defibrillator during active compressions.
●Once charged, stop compressions only briefly to confirm the rhythm; if shockable rhythm is present, deliver the shock.
●Resume CPR immediately if the patient is in a non-shockable rhythm or after the shock is delivered.
Hemodynamic phase — The hemodynamic or circulatory phase, which follows the electrical phase, consists of the period from 4 to 10 minutes after SCA, during which patients with VF-mediated SCA may remain in VF. Early defibrillation remains critical for survival in patients found in VF.
It remains unclear whether it is beneficial during the hemodynamic phase to delay defibrillation in order to perform 2 to 3 minutes of CPR. Randomized trials have reached inconsistent conclusions:
●In one trial, investigators randomly assigned 200 patients with out-of-hospital VF arrest to receive immediate defibrillation or 3 minutes of CPR prior to defibrillation [27]. Among cases with ambulance response times over 5 minutes, patients treated with CPR prior to defibrillation had higher rates of survival to hospital discharge than those immediately defibrillated (22 versus 4 percent, odds ratio [OR] 7.4, 95% CI 1.6-34.3). In contrast, among cases with a rapid ambulance response, patient outcomes did not differ.
●A similar trial of 202 patients found no statistically significant increase in survival to hospital discharge with 3 minutes of CPR prior to defibrillation, regardless of ambulance response time (17 versus 10 percent, p = 0.16) [28].
●A third trial treated 256 patients with out-of-hospital cardiac arrest using immediate defibrillation or 90 seconds (rather than 3 minutes) of CPR followed immediately by defibrillation [29]. There was no significant difference in survival to hospital discharge (4.2 versus 5.1 percent, odds ratio [OR] 0.81, 95% CI 0.25-2.6). Although subgroup analysis was not planned for this study, no differences in survival were noted in the two treatment groups based upon ambulance response time.
The CPR-ECC Guidelines state that there is insufficient evidence to determine whether a period of CPR prior to defibrillation is beneficial in all cases of SCA. A meta-analysis of the randomized trials described above concluded that either approach is reasonable [30], while other meta-analyses with variable inclusion criteria have emphasized the conflicting nature of the evidence [31,32].
While it is essential to provide excellent CPR until the defibrillator is attached to the patient and charged and to resume excellent compressions immediately after the shock is delivered, we believe there is insufficient evidence of benefit to justify delaying defibrillation in order to perform chest compressions for any predetermined period. For EMS systems that do advocate this approach, clinicians should consider both patient downtime and their own response time when deciding whether to postpone defibrillation to provide CPR. As an example, it would be reasonable to perform 2 minutes of excellent CPR prior to defibrillation for patients with an unwitnessed cardiac arrest and fine VF whose down time is thought to exceed 3 to 5 minutes. However, it is equally reasonable to defibrillate fine VF as soon as the defibrillator is in place, without performing CPR for any prespecified period, as there is no conclusive evidence that this approach is harmful.
Metabolic phase — Treatment of the metabolic phase, defined as greater than 10 minutes of pulselessness, is primarily based upon postresuscitative measures, including hypothermia therapy. If not quickly converted into a perfusing rhythm, patients in this phase generally do not survive. (See "Initial assessment and management of the adult post-cardiac arrest patient".)
Recognition of cardiac arrest — Rapid recognition of cardiac arrest is the essential first step of successful resuscitation. According to the CPR-ECC Guidelines, the rescuer who witnesses a person collapse or comes across an apparently unresponsive person should check to be sure the area is safe before approaching the victim and then confirm unresponsiveness by tapping the person on the shoulder and shouting: "are you all right?". If the person does not respond, the rescuer calls for help, activates the emergency response system, and initiates excellent chest compressions. Mobile telephones are an important means for activating EMS. Many emergency dispatch centers have adopted protocols for dispatchers to contemporaneously instruct untrained lay rescuers to perform CO-CPR in order to enhance survival.
The CPR-ECC Guidelines emphasize that even well-trained professionals can have difficulty determining if pulses are present or breathing is adequate in unresponsive patients. A knowledgeable clinician may check for a carotid pulse; however, no more than 10 seconds should be spent assessing pulselessness. The same criteria for establishing apnea is used by both lay rescuers and health care providers and should be performed in parallel with the pulse check. If the unresponsive patient is not breathing normally, the patient should be considered apneic. The key principle is not to delay the initiation of CPR in patients who require it. The most recent version of the AHA basic life support (BLS) algorithm can be accessed here (AHA BLS algorithm) [4,23].
After assessing responsiveness, health care providers should quickly check the patient's pulse. While doing so, it is reasonable for the health care provider to visually assess the patient's respirations. It is appropriate to assume the patient is in cardiac arrest if there is absent or any abnormal breathing (eg, gasping) or if a pulse cannot be readily palpated within 10 seconds. In general, it is considered more prudent, when uncertainty exists, to perform CPR on an unresponsive person not in cardiac arrest than to withhold CPR from one who is in cardiac arrest.
Chest compressions
Performance of excellent chest compressions — Chest compressions are the most important element of cardiopulmonary resuscitation (CPR) [33-36]. Coronary and cerebral perfusion pressure and return of spontaneous circulation (ROSC) are maximized when excellent chest compressions are performed [37,38]. The mantra of the CPR-ECC Guidelines was: "push hard and push fast on the center of the chest" (algorithm 2) [4,26]. Although this is easy to learn and remember, subsequent guidelines have added upper limits (no greater than 120 per minute) to what is considered “hard” and “fast” when performing chest compressions. The most recent version of the basic life support (BLS) algorithm can be accessed here (AHA BLS algorithm) [4,23].
The following goals are essential for performing excellent chest compressions:
●Maintain the rate of chest compression at 100 to 120 compressions per minute [39,40]
●Compress the chest at least 5 cm (2 inches) but no more than 6 cm (2.5 inches) with each down-stroke [40]
●Allow the chest to recoil completely after each down-stroke (it should be easy to pull a piece of paper from between the rescuer's hand and the patient's chest just before the next down-stroke)
●Minimize the frequency and duration of any interruptions
To perform excellent chest compressions, the rescuer and patient must be in optimal position. This may require movement of the patient or bed, adjustment of the bed's height, or the use of a step-stool so the rescuer performing chest compressions is appropriately positioned. The patient must lie on a firm surface. This may require a backboard if chest compressions are performed on a bed [41-43]. If a backboard cannot be used, the patient should be placed on the floor. All efforts to deliver excellent CPR must take precedence over any advanced procedures, such as tracheal intubation or vascular access.
The rescuer places the heel of one hand in the center of the chest over the lower (caudad) portion of the sternum and the heel of their other hand atop the first (picture 1). The rescuer's own chest should be directly above their hands. This enables the rescuer to use their body weight to compress the patient's chest, rather than just the muscles of their arms, which may fatigue quickly.
It is imperative that each facet of performing excellent chest compressions be continually reassessed and corrections made throughout the resuscitation. Resuscitation teams may believe that compressions are being performed appropriately when in fact they are inadequate and cerebral perfusion is compromised, thereby reducing the chance for neurologically intact survival [44].
An inadequate rate of chest compression reduces the likelihood of ROSC and neurologically intact survival following sudden cardiac arrest (SCA) [37,39,45,46]. Rates as high as 125 compressions per minute have been beneficial [39]. The CPR-ECC Guidelines recommend a rate of at least 100 compressions per minute but not more than 120. Audiovisual tools that provide immediate feedback may help rescuers maintain adequate rates [47].
Animal and observational clinical studies suggest that chest compressions of proper depth (at least 5 cm) play an important role in successful resuscitation [48-50]. In addition, full chest recoil between down-strokes generates the greatest negative intrathoracic pressure, resulting in enhanced cardiac preload and higher coronary perfusion pressures [51]. According to the CPR-ECC Guidelines, rescuers are better at allowing full recoil when they receive immediate automated feedback on CPR performance and if they remove their hands slightly but completely from the chest wall at the end of each compression [47].
Inadequate compression and incomplete recoil are more common when rescuers fatigue, which can begin as soon as 1 minute after beginning CPR [26]. The CPR-ECC Guidelines suggest that the rescuer performing chest compressions be changed every two minutes whenever more than one rescuer is present. Interruptions in chest compressions are reduced by changing the rescuer performing compressions at the two-minute interval when the compressions should cease for rhythm assessment, and the patient is defibrillated if needed. However, if the rescuer is unable to perform adequate compressions, it is best to swap rescuers immediately so perfusing compressions are maintained.
Minimizing interruptions — Interruptions in chest compressions during CPR, no matter how brief, result in unacceptable declines in coronary and cerebral perfusion pressure and worse patient outcomes [35,45,52-58]. The most common reasons for prolonged interruptions in chest compressions are rhythm checks, changes in the clinician performing chest compressions, incorrect use of mechanical chest compression devices, and tracheal intubation [59].
Once compressions stop, up to 1 minute of continuous, excellent compressions may be required to achieve sufficient perfusion pressures [60]. Two minutes of continuous CPR should be performed following any interruption [61,62]. The coordination of chest compressions and ventilation during CPR is discussed below. (See 'Ventilations' below.)
Rescuers must ensure that excellent chest compressions are provided with minimal interruption; rhythm analysis without compressions should only be performed at preplanned intervals (every 2 minutes). Such interruptions should not exceed 10 seconds, except for specific interventions, such as defibrillation. (See 'Pulse checks and rhythm analysis' below.)
When using an automatic external defibrillator (AED), the rescuer must follow the prompts provided by the defibrillator. The AED will advise rescuers not to touch the patient while it assesses the patient's cardiac rhythm. If the patient is in a non-shockable rhythm, the AED will instruct the rescuer to resume excellent CPR. The AED will reassess the rhythm every two minutes. If it identifies a shockable rhythm at any two-minute interval, it will charge the defibrillator and advise the rescuer to deliver a shock, followed by immediate CPR. Rescuers cannot change this sequence when using an AED (or a monitor/defibrillator in the AED mode) unless they actively change the monitor/defibrillator to manual mode.
When using a monitor/defibrillator in manual mode, rescuers should continue performing excellent chest compressions while charging the defibrillator until just before they are ready to deliver a single shock as indicated, and excellent compressions should resume immediately after shock delivery or after the rescuer determines that no shock is indicated. Rescuers will need to keep track of time when manually operating the monitor/defibrillator so they perform a rhythm check at two-minute intervals. Rescuers should not take extra time to assess pulse or breathing prior to defibrillation. No more than three to five seconds should elapse between stopping chest compressions and shock delivery or identification of a non-shockable rhythm. Pulse checks, if necessary, should occur during planned interruptions in compressions. If a single lay rescuer is providing CPR, excellent chest compressions should be performed continuously without ventilations. (See 'Compression-only CPR (CO-CPR)' below.)
Multiple studies of trained rescuers support the importance of uninterrupted chest compressions:
●One prospective study reported improved survival among out-of-hospital cardiac arrest patients treated with minimally interrupted cardiac resuscitation [63]. This study was performed as urban and rural EMS and Fire personnel in Arizona were being trained in the approach advocated by the AHA 2005 BLS Guidelines, which were the first to emphasize continuous chest compressions with minimal interruption. Survival among patients rescued by personnel trained according to the 2005 Guidelines was 5.4 percent (36 out of 668) compared to 1.8 percent (4 out of 218) among those treated according to earlier BLS guidelines (odds ratio [OR] 3.0; 95% CI 1.1-8.9).
●A retrospective observational study compared survival rates and neurologic outcomes in two groups of rural patients who sustained out-of-hospital cardiac arrest [36]. The first group was treated between 2001 and 2003 according to the 2000 CPR-ECC Guidelines (standard compressions and ventilations), while the second group was treated between 2004 and 2007 according to the 2005 Guidelines (compression-only CPR without ventilations). Among 92 patients in the first group, 18 survived of whom 14 (15 percent) were neurologically intact. Of the 89 patients in the second group, 42 survived of whom 35 (39 percent) were neurologically intact. Similar subsequent studies have replicated these results [55,64].
For patients receiving high-quality CPR from trained emergency medical personnel, the use of continuous chest compressions (ie, ventilations are performed without interrupting CPR) may not improve outcomes. In a cluster-randomized trial involving 114 emergency medical service (EMS) agencies, 1129 of 12,613 patients (9.0 percent) treated with continuous chest compressions survived to hospital discharge, compared to 1072 of 11,035 patients (9.7 percent) treated with standard CPR, consisting of cycles of 30 chest compressions interrupted briefly to provide 2 ventilations (difference 0.7 percent; 95% CI -1.5 to 0.1) [62]. Neurologic outcome among survivors also did not differ significantly between groups. As noted in the accompanying editorial, the mean chest compression fraction (percentage of each minute during resuscitation when compressions were being performed) was quite high in both groups, and thus essentially neither group experienced major interruptions in CPR [65]. The CPR-ECC Guidelines suggest a chest compression fraction of at least 60 percent.
Compression-only CPR (CO-CPR) — When multiple trained personnel are present, the simultaneous performance of continuous excellent chest compressions and proper ventilation using a 30:2 compression to ventilation ratio is recommended by the AHA for the management of sudden cardiac arrest (SCA) [4,23,66]. The importance of ventilation increases with the duration of the arrest. (See 'Ventilations' below and 'Phases of resuscitation' above.)
However, if a sole lay rescuer is present or multiple lay rescuers are reluctant to perform mouth-to-mouth ventilation, the CPR-ECC Guidelines encourage the performance of CPR using excellent chest compressions alone, and the results of several randomized trials support this approach [4,23,66-68]. The Guidelines further state that rescuers should not interrupt excellent chest compressions to palpate for pulses or check for the return of spontaneous circulation and should continue CPR until an AED is ready to defibrillate, EMS personnel assume care, or the patient wakes up. Note that CO-CPR is not recommended for children or arrest of noncardiac origin (eg, near drowning). (See "Pediatric basic life support (BLS) for health care providers".)
For many would-be rescuers, the requirement to perform mouth-to-mouth ventilation is a significant barrier to the performance of CPR [21]. This reluctance may stem from fear of contracting a communicable disease, although the risk of transmission for non-respiratory diseases is extremely low [69,70]. It may also be due to anxiety about performing CPR correctly. CO-CPR circumvents these problems, potentially increasing the willingness of bystanders to perform CPR. Resuscitation of patients with known or possible infection with COVID-19 is discussed separately. (See 'Resuscitation of patients with COVID-19' above.)
Evidence directly comparing bystander CO-CPR with conventional CPR using a 30:2 ratio of compressions to ventilation is limited to one large observational study which suggests improved survival when conventional CPR is performed [71]. Randomized trials of bystander CPR that have compared CO-CPR to conventional CPR with a 15:2 ratio have shown that CO-CPR increases survival to hospital discharge, but evidence is lacking to show favorable neurologic outcomes with good quality of life following bystander CO-CPR. Nevertheless, we support CO-CPR when personnel to perform conventional CPR with a 30:2 ratio are not available. (See "Prognosis and outcomes following sudden cardiac arrest in adults", section on 'Chest compression-only CPR'.)
Monitoring of chest compression quality — Aside from early defibrillation of VF or pVT cardiac arrest, the quality of CPR is the most important intervention affecting outcome. In the author's experience, even in the hands of experienced medical professionals, CPR quality is variable at best and frequently inadequate. It would be reasonable to assume that monitoring of chest compression quality would improve neurologically intact survival, but data are inconclusive. Despite this, we recommend employing available monitoring techniques provided they do not cause excessive discontinuation of compressions.
During in-hospital cardiac arrest (IHCA), CPR quality can be monitored in several ways. In addition to close observation by other knowledgeable clinicians providing real-time correction to rescuers, chest compression quality can be monitored by three means:
●Mechanical devices that provide real-time feedback of chest compression rate and depth and of adequate chest recoil
●End-tidal carbon dioxide (ETCO2) measurement, which reflects the quality of chest compressions
●Diastolic blood pressure measurement using invasive arterial pressure monitoring
A 2020 ILCOR systematic review found that most studies of monitoring during CPR did not find a significant association between real-time feedback and improved patient outcomes, but reported no evidence of harm [24]. One randomized trial reported a 25.6 percent increase in survival to hospital discharge from IHCA with audio feedback on compression depth and recoil (54 versus 28.4 percent) [72]. An analysis of data from the American Heart Association's Get With The Guidelines Resuscitation registry showed a higher likelihood of ROSC (OR 1.22; 95% CI 1.04–1.34) when CPR quality was monitored using ETCO2 or diastolic blood pressure (requiring invasive arterial pressure monitoring) [73].
A 2018 systematic review of studies of ETCO2 as a prognostic indicator following SCA found variable results, but in general 10 mmHg or less was associated with poor outcomes, while measurements above 20 mmHg were associated with higher rates of ROSC [74]. This suggests that targeting chest compressions to an ETCO2 ≥20 mmHg may be useful. The role of ETCO2 for prognosis during resuscitation of SCA is reviewed in greater detail separately. (See "Carbon dioxide monitoring (capnography)", section on 'Clinical applications for intubated patients'.)
Invasive arterial blood pressure monitoring may help to guide resuscitation efforts. The use of diastolic blood pressure monitoring during cardiac arrest was associated with higher ROSC, but there are inadequate human data to suggest a specific measurement threshold.
Ventilations — During the initial phase of SCA, when the pulmonary alveoli are likely to contain adequate levels of oxygen and the pulmonary vessels and heart likely contain sufficient oxygenated blood to meet markedly reduced demands, the importance of compressions supersedes ventilations [75-77]. Consequently, the initiation of excellent chest compressions is the first step to improving oxygen delivery to the tissues (algorithm 2). This is the rationale behind the compressions-airway-breathing (C-A-B) approach to SCA advocated in the CPR-ECC Guidelines [26]. The most recent version of the AHA basic life support (BLS) algorithm can be accessed here (AHA BLS algorithm) [23].
In some circumstances, continuing excellent compression-only CPR may be preferable to adding ventilations, especially when lay rescuers are performing the resuscitation. However, in patients whose cardiac arrest is associated with hypoxia, it is likely that oxygen reserves have already been depleted, necessitating the performance of excellent standard CPR with ventilations. (See 'Chest compressions' above and 'Compression-only CPR (CO-CPR)' above.)
Properly performed ventilations become increasingly important as pulselessness persists. In this, the metabolic phase of resuscitation, clinicians must continue to ensure that ventilations do not interfere excessively with the cadence and continuity of chest compressions. The techniques used in basic airway management are discussed in greater detail separately. (See 'Phases of resuscitation' above and "Basic airway management in adults".)
Proper ventilation for adults includes the following:
●Give two ventilations after every 30 compressions, discontinuing compressions during the ventilations for patients without an advanced airway [71]
●Give each ventilation over no more than one second
●Provide only enough tidal volume to observe the chest rise (approximately 500 to 600 mL, or 6 to 7 mL/kg)
●Avoid excessive ventilation (rate or volume)
●Give one asynchronous ventilation every 8 to 10 seconds (6 to 8 per minute) to patients with an advanced airway (eg, supraglottic device, endotracheal tube) in place
Although the Guidelines recommend 10 breaths per minute, we believe 6 to 8 breaths are adequate in the low-flow state during cardiac resuscitation of adults. However, the key point is to avoid excessive ventilation.
Asynchronous implies ventilations need not be coordinated with chest compressions. Ventilations should be delivered in as short a period as possible, not exceeding one second per breath, while avoiding excessive ventilatory force. Only enough tidal volume to confirm initial chest rise should be given. This approach promotes both prompt resumption of compressions and improved cerebral and coronary perfusion.
Excessive ventilation, whether by high-ventilatory rates or increased volumes, must be avoided. Positive pressure ventilation raises intrathoracic pressure which causes a decrease in venous return, pulmonary perfusion, cardiac output, and cerebral and coronary perfusion pressures [78]. Studies in animal models have found that over-ventilation reduces defibrillation success rates and decreases overall survival [35,61,79-81].
Despite the risk of compromised perfusion, professional rescuers routinely over-ventilate patients. One study of prehospital resuscitation reported that average ventilation rates during CPR were 30 per minute, while a study of in-hospital CPR revealed ventilation rates of more than 20 per minute [20,78]. It is imperative that the rate and volume of ventilations be continually reassessed, and corrections made throughout the resuscitation. Resuscitation teams often believe that ventilations are being performed effectively when in fact they are not (usually due to poor bag-mask-ventilation technique), resulting in inadequate cerebral perfusion and reducing the patient's chance for a neurologically intact survival.
Defibrillation — The effectiveness of early defibrillation in patients with VF and short "downtimes" is well supported by the resuscitation literature and early defibrillation is a fundamental recommendation of the CPR-ECC Guidelines [25,82]. As soon as a defibrillator is available, providers should assess the cardiac rhythm and, when indicated, perform defibrillation as quickly as possible. With the exception of excellent CPR, there is no intervention (eg, intubation, placement of intravenous catheter, administration of medication) that has been found to have a morbidity or mortality benefit greater than rhythm assessment and defibrillation in VF/ventricular tachycardia (VT) cardiac arrest.
For BLS, a single shock from an automated external defibrillator (AED) is followed immediately by the resumption of excellent chest compressions. For advanced cardiac life support, a single shock is recommended regardless of whether a biphasic or monophasic defibrillator is used. The effectiveness of double sequential defibrillation (performing two defibrillation attempts in rapid succession) remains unproven, and the advanced cardiac life support (ACLS) guidelines suggests that this approach not be used routinely. (See "Advanced cardiac life support (ACLS) in adults", section on 'Pulseless ventricular tachycardia and ventricular fibrillation'.)
Biphasic defibrillators are preferred because of the lower energy levels needed for effective cardioversion. Biphasic defibrillators measure the impedance between the electrodes placed on the patient (figure 1) and adjust the energy delivered accordingly. Rates of first shock success are reported to be approximately 85 percent [83-85]. (See "Basic principles and technique of external electrical cardioversion and defibrillation".)
The CPR-ECC Guidelines recommend using the energy levels suggested by the manufacturer of the device [86]. We recommend that all defibrillations for patients in cardiac arrest be delivered at the highest available energy in adults (generally 360 J for a monophasic defibrillator and 200 J for a biphasic defibrillator). This approach reduces interruptions in CPR and is implicitly supported by a study in which out-of-hospital cardiac arrest patients randomly assigned to treatment with escalating energy using a biphasic device showed higher conversion and termination rates for ventricular fibrillation than those assigned to treatment with fixed lower energy [87]. (See "Advanced cardiac life support (ACLS) in adults", section on 'Pulseless patient in sudden cardiac arrest'.)
Controversy exists about the possible benefit of delaying defibrillation in order to perform excellent chest compressions for a predetermined period (eg, 60 to 120 seconds). This issue is discussed separately. (See 'Hemodynamic phase' above.)
Pulse checks and rhythm analysis — It is essential to minimize delays and interruptions in the performance of excellent chest compressions. Therefore, cardiac rhythm analysis should only be performed during a planned interruption at the two-minute interval following a complete cycle of cardiopulmonary resuscitation (CPR). Even short delays in the initiation or brief interruptions in the performance of CPR can compromise cerebral and coronary perfusion pressure and decrease survival. Following any interruption, sustained chest compressions are needed to regain pre-interruption rates of blood flow. (See 'Chest compressions' above.)
Even among clinicians, wide variation exists in the ability to determine pulselessness accurately and efficiently [88]. Therefore, the AHA BLS Guidelines recommend that untrained rescuers begin CPR immediately, without a pulse check, as soon as they determine a patient is unresponsive with abnormal respirations. Health care providers must not spend more than 10 seconds checking for a pulse and should start CPR immediately if no pulse is felt or it is indeterminate. The author advocates that clinicians use end-tidal carbon dioxide monitoring when available to determine the presence of return of spontaneous circulation, which reduces interruptions in CPR by obviating the need for pulse checks. (See 'Recognition of cardiac arrest' above and "Carbon dioxide monitoring (capnography)", section on 'Return of spontaneous circulation'.)
The CPR-ECC Guidelines recommend that CPR be resumed without a pulse check, after any attempt at defibrillation, regardless of the resulting rhythm. Data suggest that the heart does not immediately generate effective cardiac output after defibrillation, and CPR may enhance post-defibrillation perfusion [27,85,89-91].
One observational study of 481 cases of cardiac arrest found that rhythm reanalysis, repeated shocks, and post-shock pulse checks resulted on average in a 29-second delay in restarting chest compressions [92]. Post-shock pulse checks were of benefit in only 1 of 50 patients.
COMPLICATIONS OF CPR — Injuries caused by cardiopulmonary resuscitation (CPR) have long been a concern. Although more frequent when incorrect technique is employed, injuries from chest compressions can occur despite excellent technique. Evidence is limited, and precise rates are not known, but potential injuries may include [93-96]:
●Rib and sternal fractures
●Cardiac and pulmonary contusions
●Pneumo- and hemothorax
●Intra-abdominal trauma
Despite the possibility of such complications, the risk of withholding potentially lifesaving treatment from a patient in cardiac arrest is far exceeded by the potential benefit of brain-saving resuscitation. For patients who regain spontaneous circulation, clinicians should be aware of potential complications, particularly those that may impede acute management, such as pneumothorax.
Observational studies have looked at the incidence of chest compression-induced complications, including the following:
●A retrospective forensic autopsy study (n = 88) reported an incidence of 26.7 percent for rib fractures (86 percent in the midclavicular line and with a slight right-sided predominance), 17.4 percent for sternal fractures, and 18.2 percent for soft tissue injury [93]. This was consistent with prior reports. Although no injury was considered lethal, 35 percent were considered severe, 48 percent moderate, and 16 percent mild. Severity was based on proximity to the heart, number of fractured ribs, anticoagulation status, and medical history that increased the risk associated with complications. When a physician was present at the resuscitation, there was a trend toward more severe complications.
●A study of chest computed tomography (CT) performed within 24 hours on survivors of nontraumatic cardiac arrest (n = 43) assessed the relationship between the duration of manual CPR and CPR-related injuries [94]. In this study, all patients developed bilateral lung contusions (95.3 percent dependent-type) and rib fractures (8.4 fractures per patient, majority anterior). There was no correlation between duration of CPR and lung contusion; however, there appeared to be a correlation among the number of rib fractures, duration of CPR, and age over 70. Sternal fractures were identified in 72.1 percent of cases, increasing in frequency with prolonged CPR duration; 65.1 percent had pleural effusions/hemothorax, 9.3 percent pneumothorax, and 44.2 percent retrosternal hematoma. No abdominal injuries were identified.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Basic and advanced cardiac life support in adults".)
SUMMARY AND RECOMMENDATIONS
●The most recent version of the AHA basic life support (BLS) algorithm appears in the following table (algorithm 2) or can be accessed here (AHA BLS algorithm). Important practices described in the CPR-ECC Guidelines are summarized below.
●Chest compressions – Chest compressions are the most important element of cardiopulmonary resuscitation (CPR) (picture 1). Interruptions in chest compressions during CPR, no matter how brief, result in unacceptable declines in coronary and cerebral perfusion pressure. The CPR mantra is: "push hard and push fast (but not too hard nor too fast) on the center of the chest." The critical performance standards for CPR include (see 'Chest compressions' above):
•Maintain the rate of chest compression at 100 to 120 compressions per minute
•Compress the chest at least 5 cm (2 inches) but no more than 6 cm (2.5 inches) with each down-stroke
•Allow the chest to recoil completely between each down-stroke
•Minimize the frequency and duration of any interruptions
●Compression-only CPR (CO-CPR) – The appropriate use of CO-CPR is as follows (see 'Compression-only CPR (CO-CPR)' above):
•When multiple trained personnel are present, the simultaneous performance of continuous excellent chest compressions and proper ventilation with a 30:2 compression to ventilation ratio is recommended for the management of sudden cardiac arrest (SCA).
•If a sole lay rescuer is present or multiple lay rescuers are reluctant to perform mouth-to-mouth ventilation, the CPR-ECC Guidelines encourage the performance of CPR using chest compressions alone. Lay rescuers should not interrupt chest compressions to palpate for pulses and should continue CPR until an automated external defibrillator (AED) is ready to defibrillate, EMS personnel assume care, or the patient wakes up. Note that CO-CPR is not recommended for children or arrest of noncardiac origin (eg, near drowning).
●Ventilations – As pulselessness persists in patients with sudden cardiac arrest (SCA), the importance of performing ventilations increases. The CPR-ECC Guidelines suggest a compression to ventilation ratio of 30:2. Each ventilation should be delivered over no more than one second while compressions are withheld during this time. Ventilations must not be delivered with excessive force; only enough tidal volume to confirm chest rise should be given. Avoid excessive ventilation from high rates or increased volumes, which can compromise cardiac output. The effective use of a bag-mask-ventilator is a learned procedure, is best done with two people, and requires practice to maintain proficiency. (See 'Ventilations' above.)
●Compression-ventilation ratio – In adults, the CPR-ECC Guidelines recommend that CPR be performed at a ratio of 30 excellent compressions to two ventilations until an advanced airway has been placed. There is mounting evidence that early tracheal intubation results in worse outcomes; however, following placement of an advanced airway, excellent compressions are performed continuously, and asynchronous ventilations are delivered approximately 6 to 8 times per minute. (See 'Ventilations' above.)
●Defibrillation – Early defibrillation is critical to the survival of patients with ventricular fibrillation. The CPR-ECC Guidelines recommend a single defibrillation in all shocking sequences. In adults, we suggest defibrillation using the highest available energy (generally 200 J with a biphasic defibrillator and 360 J with a monophasic defibrillator) (Grade 2C). Compressions should not be stopped until the defibrillator has been fully charged. (See 'Defibrillation' above.)
●Phases of resuscitation – There are three phases of sudden cardiac arrest. The electrical phase comprises the first 4 to 5 minutes and requires immediate defibrillation. The hemodynamic phase spans approximately minutes 4 to 10 following SCA. Patients in the hemodynamic phase benefit from excellent chest compressions to generate adequate cerebral and coronary perfusion and immediate defibrillation. The metabolic phase occurs following approximately 10 minutes of pulselessness; few patients who reach this phase survive. (See 'Phases of resuscitation' above.)
●Instruction – All health care providers should receive standardized training in CPR and be familiar with the operation of AEDs.
