Since the introduction of the cardiopulmonary resuscitation (CPR) ABC sequence (airway patency, breathing, and circulation) in the late 1960s (1), traditional bystander CPR according to these guidelines has saved lives. Recently the reappraisal of mouth-to-mouth ventilation (2,3) has been widely criticized (4), and some studies have identified important disadvantages of mouth-to-mouth ventilation, including gastric insufflation and less cycle time spent on effective chest compression (5). When no endotracheal tube is in place, assisted-ventilation maneuvers are often associated with aspiration of gastric contents. This aspiration may cause adult respiratory distress syndrome and pneumonia (6). These adverse effects should not be expected if life support measures are provided solely by medical professionals (7,8).
Additional unintended and unanticipated consequences or complications of external chest compressions have been described in medical literature (9,10). The most frequently reported complications are skeletal injuries and injuries of the gastrointestinal (lacerations, ruptures, hemorrhage) and cardiopulmonary systems (lacerations, hemorrhage, pneumohemothorax, pneumomediastinum, and myocardial or tracheal rupture). These studies are mainly based on autopsy findings in nonsurviving cardiac arrest patients.
The aim of this prospective review was to discover whether bystander CPR increases the incidence of mouth-to-mouth ventilation-associated adverse effects (i.e., aspiration, gastric insufflation) and complications caused by external cardiac massage by means of chest radiograph on admission to the emergency department in primarily successful resuscitated cardiac arrest patients.
From July 1997 to June 1999, data were prospectively collected on patients admitted to the department of emergency medicine at a university hospital after cardiac arrest that had occurred before or during hospitalization. Data collection was performed according to the recommended guidelines for uniform reporting of data on out-of-hospital cardiac arrests (11). The procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation and with the Helsinki Declaration of 1975, as revised in 1983.
Patients eligible for inclusion had a witnessed, nontraumatic, normothermic cardiac arrest. Sufficient circulatory function on admission after primary successful resuscitation was obligatory. Patients with any first electrocardiogram-recorded arrest rhythm and any presumed etiology of cardiac arrest were eligible, except patients with asphyxial arrest caused by airway obstruction, water submersion, or preceding respiratory symptoms.
Vienna, the city where the study was performed, has a population of about 1.6 million, spread over an area of approximately 400 km2. Courses in basic life support are compulsory for taxi drivers, policemen, and medical professionals applying for a driver’s license. Approximately 16,000 people (1% of the population) receive basic life support training in Vienna every year. Emergency medical technicians are not permitted to perform advanced cardiac life support procedures. The ambulances are dispatched as a single tier. Patients with cardiac arrest are either successfully resuscitated and brought to hospital or declared dead by the emergency physician and left at the scene. Treatment in the field, as well as in the hospital, was performed according to the American Heart Association guidelines for basic and advanced cardiac life support and postresuscitation care. At the hospital, all patients received standard intensive care treatment.
Cardiac arrest was defined as the absence of both spontaneous respiration and palpable pulses. Return of spontaneous circulation was defined as return of palpable arterial pulse (11). Acute care consisted of basic and advanced cardiac life support performed by the ambulance service or in-hospital emergency nursing staff and physicians according to standard protocol (12). The interval from the time of collapse (the presumed time of cardiac arrest) to basic life support was defined as the “no-flow duration,” and the interval from the beginning of life support until the return of spontaneous circulation was called the “low-flow duration.”
For analysis we assigned the patients to three groups: 1) patients who received bystander basic life support (Bystander group)—this group consisted of patients who received basic life procedures performed by laypersons; 2) patients who did not receive bystander basic life support before advanced life support was started (ALS group); and 3) patients who did not receive external chest compressions because restoration of spontaneous circulation could be achieved within 1 min (Early Defibrillation group). This group consisted of patients with ventricular fibrillation caused by myocardial infarction that could be terminated after a maximum of three countershocks.
Cerebral function, expressed in terms of cerebral performance category, was assessed prospectively on arrival at the emergency department and at regular intervals after the return of spontaneous circulation. Cerebral performance category is based on the Glasgow outcome performance categories (13). A cerebral performance category of 1 or 2 reflects a favorable functional neurologic recovery, whereas a cerebral performance category of 3, 4, or 5 represents unfavorable functional neurologic recovery. The neurologic result is described as the best cerebral performance category achieved within 6 mo.
For assessment of basic life support-associated complications, conventional chest radiographs in the supine position that used standardized variables (kilovolts and milliamperes, depending on patient size and weight) were performed within 1 h after admission. All chest radiographs were read independently by two radiologists skilled in thoracic radiology and emergency imaging. Both readers were blinded to all clinical and patient data. A consensus decision was obtained in case of differing results (14,15). Chest radiographs were reviewed with special regard to the following findings.
- 1. Soft tissue alterations (e.g., emphysema, edema, tumors).
- 2. Skeletal findings, especially rib fractures.
- 3. Findings suggestive of extra luminal air and gastric insufflation.
- 4. Pneumothoraces.
- 5. Parenchymal opacities evocative of aspiration.
- 6. Signs indicative of adult respiratory distress syndrome.
Radiologically-proven suspicion of aspiration was defined as a segmental consolidation with positive air bronchogram in typical location, i.e., both lower lobes or the middle lobe.
Data are given as the median and interquartile range unless otherwise specified. For comparison of continuous data between groups, the Mann-Whitney U-test was used. A P value <0.05 was considered statistically significant.
Within the study period, 224 consecutive patients who were having or had had cardiac arrest were admitted to the emergency department. Of these, 173 patients (77%) were eligible. The median age was 58 yr (51, 71), and 126 patients (73%) were men. The median body weight was 80 kg (71, 85) in the Bystander group, 80 kg (70, 90) in the ALS group, and 75 kg (70, 85) in the Early Defibrillation group, with no differences among groups.
Cardiac arrest-specific data are given in Table 1. The no-flow duration in the Early Defibrillation group is caused by life support’s being initiated immediately after cardiac arrest by emergency medical personnel. Table 2 presents differences in laboratory variables on admission among groups. Table 3 shows the frequencies of basic life support-associated complications assessed by chest radiograph.
Within a 6-month follow-up period, 88 patients (51%) died (Group 1, 33 patients [56%]; Group 2, 50 patients [52%]; and Group 3, 5 patients [28%]), and 10 patients (6%) suffered from unfavorable functional neurologic recovery (Group 1, two patients [3%], Group 2, eight patients [8%], and Group 3, no patients). Six months after restoration of spontaneous circulation, 74 (43%) patients were alive with favorable neurologic function (Group 1, 24 patients [41%]; Group 2, 38 patients [40%]; and Group 3, 13 patients [72%]).
Bystander basic life support had no effect on the number of CPR-related injuries in patients surviving cardiac arrest, as assessed by chest radiograph on hospital admission. The incidence of mouth-to-mouth ventilation-associated adverse effects, such as aspiration and gastric insufflation, and the number of external chest compression-related injuries were independent of whether patients received life support by laypeople or by medical professionals only.
In patients receiving bystander CPR, many assisted-ventilation maneuvers were initiated until endotracheal intubation was performed (Table 1). This did result in a notable number of ventilation-associated adverse effects, such as a moderate or severe degree of gastric insufflation and suspected aspiration of gastric contents, but the distribution of these results did not differ among groups (Table 3). It seems that even very carefully provided life support measures by medical professionals could not prevent such adverse effects (6,7).
The number of rib fractures (8%) seems relatively small (Table 3). This can be explained by the fact that our patients were cardiac arrest survivors, and chest radiograph, rather than autopsy, was the chosen method for assessing complications. In addition, radiographs taken in the supine position may detect only a few rib fractures.
Concerns about mouth-to mouth ventilation and its adverse effects in the recent medical literature (2,3) led us to perform this study. We tried to detect a possible difference in the incidence of CPR-related adverse effects as assessed by means of chest radiograph on hospital admission in cardiac arrest survivors who did or did not receive bystander basic life support. The harmful effects of therapeutic interventions in primary successfully resuscitated cardiac arrest victims are routinely analyzed, not only via autopsy but also clinically. Therefore, putting such findings into the perspective of a more thorough evaluation is justified because this might have importance, not only for the continuing discussion about the design of basic life support, but also for daily clinical and academic routine (16). Because it is feasible neither to perform chest radiographs in the field nor to perform autopsy in every patient, we excluded patients who did not live until reaching the emergency department. Even a study based on radiologic criteria plus autopsy evidence would be of limited value. The two groups would be inherently different regarding the circumstances of the cardiac arrest.
Mouth-to-mouth ventilation can have deleterious side effects, such as gastric insufflation with consecutive regurgitation and aspiration, leading to pneumonia and possibly lethal adult respiratory distress syndrome (6). During cardiac arrest and CPR, pulmonary compliance decreases. Increased inspiratory pressure, which is needed to inflate the lung and lower esophageal sphincter tone and which usually prevents regurgitation, may decrease. These are all factors that could increase the risk for gastric insufflation. Above all, there was evidence that regurgitation occurs after the stomach is insufflated with air (17–19). The number of severe gastric insufflation and suspicion of aspiration events is quite large in our patients, at nearly 20%, and did not significantly differ among groups (Table 3). Obviously, the number of ventilation side effects was not increased by mouth-to-mouth ventilation performed by laypeople. This observation could still encourage bystanders to perform ventilation maneuvers or at least help to alleviate the fear of it. Even the report by Hallstrom et al. (3), in which survival among patients with out-of-hospital cardiac arrest was similar, whether untrained bystanders performed CPR by chest compression alone or by chest compression and mouth-to-mouth ventilation, does not suggest a benefit from mouth-to-mouth ventilation. In addition, their (3) findings did not answer the question of how airway patency might have influenced the results. Therefore, all potential bystanders should be informed about steps A and B of the new recommendations by the American Heart Association (16).
Misplaced airways, dental and lip injuries, larynx and tracheal injuries, and gastric dilation and rupture (20), as well as pneumothorax and interstitial emphysema, are described as unintended results of ventilation and intubation (21). Injuries of the upper respiratory system were not observed in our patients, and pneumothoraces were found infrequently in groups with and without bystander basic life support (Table 3). External chest compressions could have injurious consequences. Most of the findings in the literature are based on autopsy series. Specifically, external chest compressions can result in fractures of the sternum (9%), ribs (19%), cartilage, and cervical spine; lacerations of liver, spleen, and lung; hemothorax; and cardiac contusion (6,9,10).
Our results demonstrate that mouth-to-mouth ventilation and external chest compression were performed by a relatively large number of bystander rescuers. This number, however, cannot be compared with previous reports (22,23) on bystander action, because a potential selection bias might have occurred by excluding the nonsurviving patients from our analysis. However, no study has shown an increased mortality rate caused by bystander basic life support efforts. On the contrary, basic life support performed by laypeople in patients suffering from out-of-hospital cardiac arrest significantly improves outcome (23). Therefore, we think our conclusions based on the selected study population are important.
The difficulties of conducting clinical studies in patients who have had cardiac arrest (especially difficulties in acquiring comparable groups) are well known. We tried to minimize this problem by using an internationally recognized protocol (11). In addition, the calculation of the no-flow duration is an estimate and cannot be quantified accurately. To minimize the imprecision of the exact time of recognition of collapse, personal interviews of the witnesses were done concerning the beginning of CPR attempts and when emergency medical attention was given. Because only one person was responsible for collecting data, we assume that our findings are reasonably accurate. The long delay until the low-flow duration in the Bystander group as compared with the ALS group can be explained by the fact that 35 collapses among the 96 patients in ALS group were witnessed by emergency medical personnel, and restoration of spontaneous circulation was achieved within a very short period (Table 1).
Reliance on a single chest radiograph as a measure of adverse consequences may be a problem, particularly at an early stage. We chose chest radiography as a referring method because it has become a proven and well established tool in intensive care medicine for detecting the most important pathologies that may occur in cardiac arrest survivors (14,15).
The aim of this prospective study was not to describe rare but serious abdominal lesions and complications assessed by clinical follow-up (i.e., development of pneumonia or acute respiratory distress syndrome or length of intensive care unit stay), further imaging methods (i.e., ultrasonography or computed tomography scan), or laboratory tests. Further studies with larger groups of patients should be performed concerning the adverse effects of CPR, including the analysis of the above-mentioned factors.
The number of CPR-related injuries in patients surviving cardiac arrest (aspiration, gastric insufflation or emphysema, rib fractures, pneumothorax) assessed by means of chest radiograph on hospital admission were independent of whether patients received life support by laypeople or medical professionals only. These data may be valuable in motivating laypeople to perform basic life support. However, investigations of prospectively collected data with a larger number of patients should be done to confirm our findings.
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