I-26 Circulation December 13. 2005 confined spaces (LoE 6). 59. 160CPR-friendlydeflatable environment or is a trauma patien need of surgical mattresses have been studied, and they do not provide an intervention. CPR is better and has fewer interruptions when adequate surface on which to perform chest compressions the resuscitation is conducted where the patient is found (LOE6.161.162 Allow the chest wall to recoil completely after each The rescuer should compress the lower half of the victims compression. In studies of CPR in humans 66 and pigs, 167 ternum in the center (middle) of the chest, between the incomplete chest wall recoil was common, particularly when nipples. 163 The rescuer should place the heel of the hand on rescuers were fatigued. 182 Incomplete recoil during BLS CPR the sternum in the center(middle)of the chest between the s associated with higher intrathoracic pressures, decreased nipples and then place the heel of the second hand on top of coronary perfusion, and decreased cerebral perfusion(LOE the first so that the hands are overlapped and parallel (LOE 6: 6).167 CPR instruction should emphasize the importance of Class Ila). 63-165 allowing complete chest recoil between compressions. 66 Depress the sternum approximately 17 to 2 inches(ap- Manikin 6s and animal studies 70, 183 suggest that with duty oximately 4 to 5 cm)and then allow the chest to return to cycles(the compression part of the cycle)of 20% to 50% its normal position. Complete chest recoil allows venous coronary and cerebral perfusion increase as the chest com- return to the heart, is necessary for effective CPR, and should pression rate increases up to 130 to 150 compressions per be emphasized in training( Class IIb). 66. 167 Compression and minute(LOE 6). 170, 183 A duty cycle of 50% is recommended chest recoil/relaxation times should be approximately equal because it is easy to achieve with practice. 68 Rescuer fatigue may lead to inadequate compression rates hospital 72 and in-hospital settings, 7340% of chest compres or depth. Significant fatigue and shallow compressions are sions were of insufficient depth. Rescuers should practice to seen after I minute of CPR, although rescuers may deny that ensure good chest compressions and should relieve on fatigue is present for >5 minutes(LOE 6). 182 When 2 or more another every few minutes to reduce the contribution of rescuers are available, it is reasonable to switch the compres- fatigue to inadequate chest compression depth and rate( sor about every 2 minutes(or after 5 cycles of compressions There insufficient evidence from human studies to made to accomplish this switch in <5 seconds(Class IIb).If identify a single optimal chest compression rate. Animall74 the 2 rescuers are positioned on either side of the patient, one and human 75. 176 studies support a chest compression rate of rescuer will be ready and waiting to relieve the"working >80 compressions per minute to achieve optimal forward compressor"every 2 minutes blood flow during CPR. We recommend a compression rate compression force was gauge of about 100 compressions per minute( Class Ila). adequate if it generated a palpable carotid or femoral pulse Two human observational studies 72, 173 showed that inter- ut a venous pulse may be felt during CPR in the absence of ruptions of chest compressions were common. In these effective arterial blood flow 110, 184 The available evidence studies of healthcare provider CPR, no chest compressions suggests that blood flow is optimized by using the recom were provided for 24% to 49% 173.7of total arrest time. mended chest compression force and duration and maintain- Interruption of chest compressions in animal models ing a chest compression rate of approximately 100 compres ssociated with reduced sions per minute. 70 and the more frequent or prolonged the interruption, the lower the mean coronary perfusion pressure. In 3 animal studies Compression-Ventilation Ratio frequent or prolonged interruptions in chest compressions ventilation ratio of 30: 2 is recommended and were associated with reduced return of spontaneous circula- further validation of this guideline is needed(Class tion(ROSC), reduced survival rates, and reduced postresus- Ila). 150. 151.180.185-187 In infants and children(see Part II citation myocardial function(LOE 6). 13, 174, 178, 179 Some ani Pediatric Basic Life Support"), 2 rescuers should use a ratio mal studies suggest that continuous chest compressions wit of 15: 2(Class IIb). minimal or no interruptions produce higher survival rates This 30: 2 ratio is based on a consensus of experts rather than standard CPR (LOE 6). 51, 179-l8I These guidelines than clear evidence. It is designed to increase the number of ommend that all rescuers minimize interruption of chest compressions, reduce the likelihood of hyperventilation, min compressions for checking the pulse, analyzing rhythm, or imize interruptions in chest compressions for ventilation, and performing other activities( Class Ila) simplify instruction for teaching and skills retention. A Lay rescuers should continue CPR until an AED arrives, manikin study suggests that rescuers may find a compression the victim begins to move, or EMS personnel take over CPR ventilation ratio of 30: 2 more tiring than a ratio of 15: 2. 18 ( Class Ila). Lay rescuers should no longer interrupt chest Further studies are needed to define the best method for to check for signs of circulatio coordinating chest compressions and ventilations during CPR Healthcare providers should interrupt chest compressions as and to define the best compression-ventilation ratio in terms infrequently as possible and try to limit interruptions to no of survival and neurologic outcome in patients with or longer than 10 seconds except for specific interventions such without an advanced airway in place as insertion of an advanced airway or use of a defibrillator Once an advanced airway is in place, 2 rescuers no longer Class Ila). deliver cycles of CPR(ie, compressions interrupted by pauses a We strongly recommend that patients not be moved while for ventilation). Instead, the compressing rescuer should give PR is in progress unless the patient is in a dangerou continuous chest compressions at a rate of 100 per minuteconfined spaces (LOE 6).159,160 “CPR-friendly” deflatable mattresses have been studied, and they do not provide an adequate surface on which to perform chest compressions (LOE 6).161,162 The rescuer should compress the lower half of the victim’s sternum in the center (middle) of the chest, between the nipples.163 The rescuer should place the heel of the hand on the sternum in the center (middle) of the chest between the nipples and then place the heel of the second hand on top of the first so that the hands are overlapped and parallel (LOE 6; Class IIa).163–165 Depress the sternum approximately 11⁄2 to 2 inches (ap￾proximately 4 to 5 cm) and then allow the chest to return to its normal position. Complete chest recoil allows venous return to the heart, is necessary for effective CPR, and should be emphasized in training (Class IIb).166,167 Compression and chest recoil/relaxation times should be approximately equal (Class IIb).168–171 In studies of chest compression in out-of￾hospital172 and in-hospital settings,173 40% of chest compres￾sions were of insufficient depth. Rescuers should practice to ensure good chest compressions and should relieve one another every few minutes to reduce the contribution of fatigue to inadequate chest compression depth and rate (see below). There is insufficient evidence from human studies to identify a single optimal chest compression rate. Animal174 and human175,176 studies support a chest compression rate of
80 compressions per minute to achieve optimal forward blood flow during CPR. We recommend a compression rate of about 100 compressions per minute (Class IIa). Two human observational studies172,173 showed that inter￾ruptions of chest compressions were common. In these studies of healthcare provider CPR, no chest compressions were provided for 24% to 49%172,173,177 of total arrest time. Interruption of chest compressions in animal models is associated with reduced coronary artery perfusion pressure, and the more frequent or prolonged the interruption, the lower the mean coronary perfusion pressure. In 3 animal studies frequent or prolonged interruptions in chest compressions were associated with reduced return of spontaneous circula￾tion (ROSC), reduced survival rates, and reduced postresus￾citation myocardial function (LOE 6).113,174,178,179 Some ani￾mal studies suggest that continuous chest compressions with minimal or no interruptions produce higher survival rates than standard CPR (LOE 6).151,179–181 These guidelines rec￾ommend that all rescuers minimize interruption of chest compressions for checking the pulse, analyzing rhythm, or performing other activities (Class IIa). Lay rescuers should continue CPR until an AED arrives, the victim begins to move, or EMS personnel take over CPR (Class IIa). Lay rescuers should no longer interrupt chest compressions to check for signs of circulation or response. Healthcare providers should interrupt chest compressions as infrequently as possible and try to limit interruptions to no longer than 10 seconds except for specific interventions such as insertion of an advanced airway or use of a defibrillator (Class IIa). We strongly recommend that patients not be moved while CPR is in progress unless the patient is in a dangerous environment or is a trauma patient in need of surgical intervention. CPR is better and has fewer interruptions when the resuscitation is conducted where the patient is found. Allow the chest wall to recoil completely after each compression. In studies of CPR in humans166 and pigs,167 incomplete chest wall recoil was common, particularly when rescuers were fatigued.182 Incomplete recoil during BLS CPR is associated with higher intrathoracic pressures, decreased coronary perfusion, and decreased cerebral perfusion (LOE 6).167 CPR instruction should emphasize the importance of allowing complete chest recoil between compressions.166 Manikin168 and animal studies170,183 suggest that with duty cycles (the compression part of the cycle) of 20% to 50%, coronary and cerebral perfusion increase as the chest com￾pression rate increases up to 130 to 150 compressions per minute (LOE 6).170,183 A duty cycle of 50% is recommended because it is easy to achieve with practice.168 Rescuer fatigue may lead to inadequate compression rates or depth. Significant fatigue and shallow compressions are seen after 1 minute of CPR, although rescuers may deny that fatigue is present for
5 minutes (LOE 6).182 When 2 or more rescuers are available, it is reasonable to switch the compres￾sor about every 2 minutes (or after 5 cycles of compressions and ventilations at a ratio of 30:2). Every effort should be made to accomplish this switch in 5 seconds (Class IIb). If the 2 rescuers are positioned on either side of the patient, one rescuer will be ready and waiting to relieve the “working compressor” every 2 minutes. In the past sternal compression force was gauged as adequate if it generated a palpable carotid or femoral pulse. But a venous pulse may be felt during CPR in the absence of effective arterial blood flow.110,184 The available evidence suggests that blood flow is optimized by using the recom￾mended chest compression force and duration and maintain￾ing a chest compression rate of approximately 100 compres￾sions per minute.170 Compression-Ventilation Ratio A compression-ventilation ratio of 30:2 is recommended and further validation of this guideline is needed (Class IIa).150,151,180,185–187 In infants and children (see Part 11: “Pediatric Basic Life Support”), 2 rescuers should use a ratio of 15:2 (Class IIb). This 30:2 ratio is based on a consensus of experts rather than clear evidence. It is designed to increase the number of compressions, reduce the likelihood of hyperventilation, min￾imize interruptions in chest compressions for ventilation, and simplify instruction for teaching and skills retention. A manikin study suggests that rescuers may find a compression￾ventilation ratio of 30:2 more tiring than a ratio of 15:2.182 Further studies are needed to define the best method for coordinating chest compressions and ventilations during CPR and to define the best compression-ventilation ratio in terms of survival and neurologic outcome in patients with or without an advanced airway in place. Once an advanced airway is in place, 2 rescuers no longer deliver cycles of CPR (ie, compressions interrupted by pauses for ventilation). Instead, the compressing rescuer should give continuous chest compressions at a rate of 100 per minute IV-26 Circulation December 13, 2005