Good morning, everyone. This is Dr. Balala. I'm currently an associate professor at Texas A&M University and University of Texas Medical Branch at Driscoll Health System. I'm currently serving as research advisor and founding chair of research task force and as a pediatric intensivist at Driscoll Children's Hospital. I'm truly honored to be invited to present on CPR, especially optimal chest compression depth in pediatric CPR. I'm thankful to the system Congress organizers for inviting me to present on this important topic. I would like to acknowledge exceptional contributions of my mentors, Drs. Robert Burr and Vinay Natkarni in the field of cardiac arrest and CPR. This is the list of my prior funding, and currently I do not have any conflict of interest or financial disclosure. The objectives of today's talk are discuss about external cardiac massage, discuss about chest compressions, especially high-quality deep chest compressions, discuss about CPR-related injuries, and discuss about future directions. The development of cardiopulmonary resuscitation has been achieved by a combination of small contributions by multiple investigators. The reintroduction of closed chest cardiac massage by William Covenhaven, Guy Knickerbocker, and James Jude changed the outcomes of patients with cardiac arrest profoundly. Since Covenhaven, Jude, and Knickerbocker first introduced the closed chest compression in 1960, the optimal rate and depth for chest compressions have been evaluated by numerous physicians. Based on evidence that deeper compression depths have shown better outcomes compared to shallower compression depths, the 2010 International CPR Guidelines recommended that rescuers should perform chest compressions over 5 cm depth in adults. Too shallow compression depth can reduce cardiac output and coronary perfusion pressure, which can impede survival from sudden cardiac arrest. This is the flow diagram of Adult Resuscitation Guideline, which was released in 2010. The guideline emphasized monitoring the quality of CPR and provision of a high-quality CPR by pushing hard, pushing fast, and allowing full recoil. In next few slides, we will go through the details of high-quality CPR, especially why deeper chest compressions are important. Closed chest compression, a crucial factor during cardiopulmonary resuscitation, affects cardiac output and coronary perfusion pressure and can directly affect victim's survival. Henry Halperin and co-investigators conducted experiments in dogs and demonstrated a good correlation between normalized myocardial perfusion pressure and applied sternal force for manual CPR, and also a good correlation between normalized cerebral perfusion pressure and applied sternal force for manual CPR. Neonatal resuscitation guidelines recommend chest compressions to be delivered to a depth of approximately one-third of anterior-posterior chest diameter. Buckner and co-investigators conducted a study aimed at investigating the hemodynamic effects of different chest compression depths in a neonatal piglet model. Chest compressions were performed with an automated CC machine with 33%, 40%, and 25% AP chest diameter in all piglets in same order for a duration of 3 minutes each. Eight newborn piglets, aged 1 to 3 days, weighing 1.7 to 2.3 kg, were included in the study. Asphyxiated blood flow and systolic blood pressure were the highest using a CC depth of 40% AP chest diameter, i.e., 19.3 ± 7.5 ml per kg per minute and 58 ± 32 mm mercury. The study concluded that CC depth influences hemodynamic parameters in asphyxiated newborn piglets during cardiopulmonary resuscitation. The highest cerebral blood flow and systolic blood flow were achieved using a CC depth of 40% AP chest diameter. When I was a fellow at Children's Hospital of Philadelphia, I was fortunate to work with giants of resuscitation science, Drs. Veena Natkarni and Robert Burke. We conducted CPR experiments on swine model of asphyxia VF cardiac arrest. The animals which were used corresponded to adolescent pediatric anatomy and physiology. Although the American Heart Association recommended that providers compress chest more than or equal to 50 mm during cardiopulmonary resuscitation, scientific data in the literature suggested that providers achieved only about 33 mm compression depth during actual resuscitations. We hypothesized that outcomes will improve when chest compressions were targeted to a goal of 51 mm compared to 33 mm, the usual care, during an asphyxial VF model of cardiac arrest. In our experiments, 8 female 3-month-old pigs, approximately 30 kg each, were intubated and anesthetized with isofurin and fentanyl and subjected to a 7-minute of asphyxia followed by induction of ventricular fibrillation. Using a CPR-recorded defibrillator, manual CPR was performed at a rate of 100 per minute, ventilation rate of 6 per minute, and FIOT of 100% for 10 minutes before first defibrillation attempt. Arterial blood pressure and entiral CO2 were measured continuously. Physiologic variables and cardiac output were recorded at baseline and 30-second pre-VF. Variables were randomized into two groups, chest compression guided to a target of 33 mm with standard ACLS-based epinephrine dosing or chest compressions guided to a target of 51 mm with standard ACLS epinephrine dosing. Analysis was performed using generalized estimated equations. The primary outcome variables were arterial blood pressure and entiral CO2. There was no difference between groups for physiologic variables or cardiac outputs at baseline or 30-second before VF. Average delivered chest compression depths were 30 mm and 47 mm in two groups respectively. Other CPR quality variables and epinephrine dosing were similar. Systolic blood pressure and entiral CO2 were significantly higher with 51 mm cc depth as compared to 33 mm cc depth. In short, chest compression targeted to 51 mm improved systolic arterial blood pressure and entiral CO2 in an asphyxial VF model. In this particular study by Li and co-investigators, CPR was performed on two pigs with a CPR machine commencing one minute after the heart was stopped. Four CPR modes were used with compression rate of 60 or 100 compressions per minute and compression depth of 3 or 5 cm. The CPR machine was equipped with a load cell for measuring compression force and a potentiometer for measuring compression depth. The measurement results obtained from the sensor were used to calculate the frequency components. The compression force and depth data were used to calculate the mechanical power of the CPR machine and mechanical impedance of the thoracic cavity. Changes in enteral CO2, coronary perfusion pressure, carotid blood flow and right atrial pressure were measured during performance of CPR. There was a good correlation between CPR power and change in right atrial pressure and that between compression force and cerebral blood flow. In another set of experiments, Buckner and co-investigators aimed at examining the optimal AP depth which would reduce the time to return of spontaneous circulation and improve survival during chest compressions. They hypothesized that asphyxiated neonatal piglets receiving chest compression resuscitated with 40% AP chest depth compared to 33%, 25% or 12.5% will have reduced time to return of spontaneous circulation and improved survival. Newborn piglets were anesthetized, intubated, instrumented and exposed to 45-minute normal capnic hypoxic event followed by asphyxia and cardiac arrest. Piglets were randomly allocated to four intervention groups, anterior-posterior 12.5% depth, 25% depth, 33% depth or 40% depth. Chest compressions were performed using an automated chest compression machine with a rate of 90 per minute. Hemodynamic and respiratory parameters, applied compression force and chest compression depth were continuously measured. The median time to return of spontaneous circulation was 600 sec, 135 sec, 85 sec and 116 sec for 12.5%, 25%, 30% and 40% depth groups respectively. All piglets achieved raw skin 33% and 40% depth groups. Arterial blood pressure, CVP, carotid blood flow, applied compression force, thyroid volume and minute ventilation increased with increasing AP chest depth during chest compression. The study concluded that time to return of circulation and survival were similar between 25%, 33% and 40% AP depths while 12.5% AP depth did not result in return of spontaneous circulation or survival. Hemodynamic and respiratory parameters improved with increased AP diameter, suggesting improved organ perfusion and oxygen delivery with 33% and 40% AP diameter. To evaluate association between CPR quality and hemodynamic measurements during in-hospital pediatric cardiac arrest, Dr. Sutton and co-investigators at CHOP hypothesized that AHA recommended CPR rate and depth targets would be associated with systolic blood pressure more than or equal to 80 mmHg and diastolic blood pressure more than or equal to 30 mmHg. In children and adolescents less than 18 years of age who suffered a cardiac arrest with an invasive arterial catheter in place, a CPR monitoring defibrillator collected CPR data which was synchronized to arterial blood pressure tracings. Chest compression depths were corrected for matrisc deflection. Generalized least squares regression estimated the association between blood pressure and CPR quality treated as continuous variables. Mixed effects logistic regression estimated the association between systolic blood pressure more than 80 mmHg and diastolic blood pressure more than or equal to 30 mmHg. It was 111 per minute, AHA depth was achieved in 26.2% of chest compressions, systolic blood pressure more than 80 mm was attained in 60% compressions and diastolic more than 30 in 61% compressions. Exceeding rate more than 100 per minute and depth more than 38 mm was associated with systolic blood pressure more than or equal to 80 mm mercury and diastolic blood pressure more than or equal to 30 mm mercury. The study concluded that AHA quality targets i.e. rate more than or equal to 100 per minute and depth more than or equal to 38 mm were associated with systolic blood pressures more than or equal to 80 mm mercury and diastolic blood pressure more than or equal to 30 mm mercury during CPR injection. In this particular study, authors found suboptimal compression depth in half of the patients by 2005 guidelines and almost all by 2010 guidelines. The authors found a strong association between survival outcomes and increased compression depth but no clear evidence to support or refute 2010 recommendation of more than 50 mm. Chest compressions during cardiopulmonary resuscitation are not sufficiently effective in many circumstances. Mechanical chest compressions could be more effective than manual chest compressions but there are no studies comparing techniques in children. In an experimental model of a sphyxial cardiac arrest, 50 piglets were randomized to receive either manual compressions or mechanical compressions using a periodic piston chest compression device. Mean arterial pressure, arterial blood gas and enteral CO2 values were measured at 3, 9, 18 and 24 minutes after the beginning of resuscitation. There were no significant differences in mean arterial pressure, diastolic arterial pressure, arterial blood gas and enteral CO2 between chest compression techniques during CPR. Survival rate was higher in manual compression than in mechanical compression group. In the mechanical compression group there was a non-significant higher incidence of hemorrhage through the endotracheal tube. Three anthropometric studies have shown that the pediatric chest can be compressed to one-third AP diameter without damaging intrathoracic organs. An observational study found an improvement in rates of ROSC and 24-hour survival when at least 60% of 30-second epochs of CPR achieve an average chest compression depth greater than 5 cm for in-hospital cardiac arrest. Remember that mattress component does affect the CPR depth and overall CPR quality. CPR mode is available on some hospital beds to stiffen the mattress during CPR. Mannequin models indicate that mattress compression ranges between 12% and 57% of total compression depth with softer mattresses being compressed the most. This can lead to a reduced sternal displacement and a reduction in effective chest compression depth. Mannequin studies and one pediatric case series showed that effective compression depth can be achieved even on a soft surface providing the CPR provider increases overall compression depth to compensate for mattress compression. Meta-analysis of six studies showed a 3 mm improvement in chest compression depth associated with backboard use when CPR was performed on a mannequin placed on a mattress or bed. Helvo et al. reported that intra-organ injuries were more frequent among arrest patients by the rescuer group who performed two deep chest compressions compared to the group who performed less deep chest compressions. Excessively forceful chest compressions can cause various mechanical complications such as rib, sternal or clavicular fractures, flail chest, lung damage or pneumothorax, pneumomediastinum, hemothorax, lung contusion, abdominal injuries such as liver lack or splenic lack. In some cases critical cardiovascular complications including coronary artery dissection ruptures, myocardial rupture and aortic dissection have been reported. Overall cardiac injury from CPR is directly induced by deep chest compressions therefore maintaining optimal compression depth during CPR is very important to prevent these deadly complications. Some studies have investigated optimal compression depth to prevent serious complications from too deep compressions. However there is a lack of evidence for optimal chest compression depth for infants and children therefore guidelines are not being well established for these populations. The 2005 AHA guidelines recommend an optimal compression depth between 1 third and 1 half of the thoracic depth for infants and children. The 2010 guidelines changed the optimal depth guidelines to over 1 third of thoracic depth for infants approximately 4 centimeter and children approximately 5 centimeter. Although the 2005 guideline of 1 half of thorax depth was dropped in 2010 guideline this new guidelines still allow of the thorax depth to be permeable compression depth because this guideline only mentions the lower limit of optimal compression depth. To review the evidence on the incidence of rib and sternal fractures after conventional closed chest compression in the treatment of cardiac arrest in adults and children and after active compression decompression CPR Hoke and co-authors conducted systematic review. Reports on conventional CPR in adults suggest an incidence of rib fractures ranging from 1 13 to 97 percent and of sternal fractures from 1 to 43 percent. Reports on CPR in children suggest an incidence of rib fractures of 0 to 2 percent and no sternal fractures. ACD CPR has been reported as causing rib fractures in 4 to 87 percent and sternal fractures in 0 to 93 percent of cases. In infants and toddlers manual CPR rarely causes skeletal chest injuries. In adults sternal fractures occur in an at least one-fifth and rib fractures as well as rib and or or sternal fractures in at least 1 third of the patients during conventional CPR. There is no compelling evidence to show that an increased complication rate is associated with ACD CPR. Rib or sternal fractures are unlikely to increase mortality as they rarely cause severe internal organ damage. In this report the authors described two rare cases of intra-abdominal bleeding following cardiac compressions. The first case was 29 year old female with massive pulmonary embolism. Following CPR due to cardiac arrest she showed signs of intra-abdominal bleeding. A liver lack was found and sutured. The patient passed away due to massive PE. The second patient was a 62 year old female suffering from cardiac arrest due to drowning at sea. CPR was performed in situ. At presentation to the ER she showed signs of intra-abdominal bleeding. The origin of the was found to be vessels of the lesser curvature of stomach which were ligated. Regarding the first patient PE has already been described as a cause of liver laceration in CPR due to stasis and liver enlargement. The second case is the first report of gastric vessel injury without gastric rupture or laceration and pneumoperitoneum. Complications of CPR should not represent a drawback to performing cardiac compressions. Parenchymatic injuries have been related to inappropriate technique of chest compressions during basic life support. Therefore it is important for the providers to refresh the knowledge of performing CPR and be very cautious about the positioning of the hand in respect to the sternum. This particular study aimed to investigate the potential association of CPR related thoracic and abdominal injuries and compression depth measured with an accelerometer. The authors analyzed the autopsy records, CT scans or chest radiographs of 170 adults suffering in-hospital cardiac arrest at Tempere University Hospital during period 2009-2011 and the goal was to look at association of chest compression and iatrogenic injuries. The quality of manual compressions during CPR was recorded on a Philips HeartStart MRX QCPR defibrillator. Patients were 110 males and 60 females. Injuries were found in 36% of male and 23% of female patients. Among males, CPR related injuries were associated with deeper mean and peak compression depths. No such association was observed in women. The frequency of injuries in mean compression depth less than 5, 5-6 and more than 6 cm was 28%, 27% and 49% respectively. Of all patients with 27% sustained rib fractures, 11% sternal fracture and 8 patients had hematoma or rupture in myocardium. In addition, authors observed 1 laceration of the stomach without bleeding, 1 ruptured spleen, 1 mediastinal hemorrhage and 2 pneumothoraxes. The authors concluded that the number of iatrogenic injuries in male patients was associated with chest compressions during cardiopulmonary resuscitation. Also, number of chest injuries increased as the measured compression depth exceeded 6 cm. While there is an increased risk of complications with deeper compressions, it is important to realize that the injuries were by and large minimal. A systematic review and pooled analysis of CPR-associated cardiovascular and thoracic injuries showed that incidence of reported CPR-associated cardiovascular and thoracic wall injuries varies widely. CPR with active compression-decompression devices has a higher reported incidence of cardiopulmonary injuries. Bedside ultrasound may be a useful adjunct to assess risk stratified patients to identify serious or life-threatening CPR-associated injuries. In this study, investigators reviewed a total of 280 consecutive chest CT scans in permuted blocks of 20 for each of 14 age divisions between 0 and 8 years. External and internal AP depths were measured at midsternum and residual chest depth was calculated at simulated 1 third and 1 half AP compressions. After a simulated compression calculation, 1 half external AP depth cc would result in a residual internal depth of less than 10 mm for 94% of children 3-8 months. For a 1 third external AP chest compression, only 0.4% of children 3-8 years had a calculated residual internal depth less than 10 mm. In short, by using CT reconstruction estimates of chest dimensions across the developmental spectrum from 0 to 8 years of age, the investigators demonstrated that a simulated cc targeting approximately 1 third external AP chest depth seems radiographically appropriate for children aged 3 months to 8 years, whereas simulated cc targeting approximately 1 half AP chest depth seems radiographically to be too deep, resulting in residual internal chest depth less than 10 mm for most patients of this age. This study aimed to compare optimal chest compression depth for infants and children with that of adults when the simulated compression depth was delivered according to the guidelines. A total 467 consecutive CT chest in 93 infants, 110 children and 264 adults were reviewed. The AP diameter and compressible depth or the compressible diameter for infants and children were measured at internipple level and at mid-lower half of spine for adults. Compression ratio to compression depth was calculated at simulated 1 fourth, 1 third and 1 half AP compressions in infants and children and simulated 5 and 6 cm compressions in adults. In adults, the compression ratio to compression depth at simulated 5 and 6 cm compression depth were 42% and 50% respectively. In children and infants, the compression ratio to compression depth at 1 third chest compression were 50% and 52% respectively and at half chest compression, compression ratio were 83% and 78% respectively. The compression ratio to compression depth of 4 cm in infants and 5 cm in children were 75% and 63% respectively. The compression ratio to compression depth for children and infants were significantly higher than in adults. The compression ratio to compression depth of 4 cm in children was almost similar to that of 6 cm compression depth in adults. The study concluded that current pediatric guidelines for compression depth are too deep compared to those in adults. The investigators suggested using 1 third of anteroposterior chest diameter or about 4 cm in children and less than 4 cm in infants. In this particular study, Li and co-investigators went on to determine whether chest compression depth of at least 1 third of AP diameter of the chest and about 5 cm is appropriate for children of all age groups via chest CT scan. The AP diameter of the chest, anterior chest wall diameter and compressible diameter were measured at lower half of sternum for patients between 1-18 years using chest CT. Among children aged 1-7 years, compressing 5 cm was deeper than 1 third AP diameter. Also, among children aged 1-5 years, 5 cm did not leave a residual depth of 1 cm potentially causing intrathoracic injury. In short, current pediatric resuscitation guidelines of chest compression depth for children were too deep for younger children aged 1-7 years. In this particular study, Li and co-investigators aimed to find a better indicator of CC depth which maximizes CC depth while also minimizing injury. Chest CT images of patients aged 8 years and younger were measured for external diameter and internal diameter i.e. distance between internal surface of anterior chest wall and anterior surface of vertebral body at the midway of the lower half of sternum. Compressible depth was defined as 1 cm short of internal diameter. The investigators determined that up to 10% estimated risk of overcompression is acceptable and approximated a quantile regression line for 10th percentile for compressible depth on external diameter. A total of 426 images were analyzed. The new indicator had a slope of 0.5 and an intercept of –1.9 cm. Compared to ⅓ external diameter, the new indicator would provide deeper chest compressions with average difference of 2 cm without increasing risk of overcompression. Chest compression of 4 or 5 cm would provide deeper chest compression compared to the new indicator. However, its overcompression risk was too high. Chest compression of ½ external diameter – 1 finger breadth maximizes CC depth without increasing overcompression in pediatric population. This study included 349 pediatric patients 1 to 9 years old who had a CT chest. The study found that a chest compression depth of ⅓ AP diameter might be more appropriate than the 5 cm depth chest compression for younger, but ⅓ AP diameter might induce deep compressions greater than an upper limit of compression depth for adults in older Korean children. Another CT scan study assessing a heterogeneous Asian population showed that in settings whereby chest compression depths can be accurately measured, compression at current recommended chest compression of approximately 4 cm in infants and 5 cm in young children could result in potential for overcompression. This study was created to assess whether a 30 mm depth of chest compression is sufficient and safe for neonatal cardiopulmonary resuscitation. The study concluded that a 30 mm depth could be appropriate for sufficient and safe neonatal resuscitation. Shallower chest compressions should be considered in preterm babes. The premise of this particular study was that neonatal resuscitation program guidelines recommend chest compression depth of ⅓ AP diameter. Appropriateness of this recommendation has not been rigorously assessed. AP internal and external chest depth, heart dimensions, and non-cardiac thoracic tissue depth were measured from neonatal chest CTs. Using these measurements, residual internal chest depth, remaining depth of chest between sternum and spine after external compression was calculated for compression depth of ⅓, ⅓, and ⅓ AP chest depth. Compression sufficient to compress the chest less than 10 mm residual internal chest depth was defined as overcompression. The study concluded that mathematical modeling based upon neonatal chest CT scan dimensions suggests that NRP chest compression recommendation of ⅓ AP chest depth should be more effective than ⅓ compression depth and safer than ⅓ AP compression depth. In conclusion, chest compressions are cornerstone of resuscitation. Deep chest compressions are associated with improved hemodynamic and overall outcomes as compared to shallow compressions. CPR related injuries to chest and internal organs are not uncommon and majority are not fatal. Very deep chest compressions can potentially cause injuries to chest and internal organs. Current evidence regarding optimal CC depth in different age groups is not conclusive. It is fair to state that CC depth of ⅓ AP diameter is optimal and safe in most neonates, infants, and children. CC depth of 5 cm is optimal and safe in most adolescents and adults, whereas compression depth more than 6 cm is likely to be associated with chest injuries and internal injuries. Thank you so much.

CPR

chest compression depth

high-quality CPR

optimal compression depths

CPR-related injuries

resuscitation efforts

ongoing research