1. Introduction Cardiopulmonary resuscitation (CPR) using high-quality chest compressions is required in order to improve the chance of restoring spontaneous circulation.1–3 4–6 4,7 4,8
In Taiwan, health care is provided under the reimbursement systems of the National Health Insurance to ensure decreased economic hindrances to health care access. Emergency departments (EDs) then become overcrowded, indicating overuse, which leads to huge challenges such as an increase of patient number, and disease severity and complexity. Facing a high demand for timely treatment, emergency physicians actually practice under tremendous workload and pressure. When an OHCA patient is sent to the ED, a CPR team (at least 4 medical professionals, according to the Basic Life Support and Advanced Cardiovascular Life Support guidelines9,10 mechanical chest compression (MeCC) device, offer treatment, and record data, was introduced in recent years, but the outcomes of cardiac arrest studies vary. Additionally, whether the use of MeCC reduces human power for CPR is of interest because it would indicate whether the staff power is sufficient to support other functions in the ED. We conducted this retrospective study to preliminarily evaluate the MeCC device prior to a larger clinical study.
The purposes of the study were to describe the outcome during a limited period in the emergence room (ER) in nontraumatic OHCA patients treated with standard CPR followed by MeCC or MaCC in a municipal hospital ED of Kaohsiung, Taiwan, and to investigate if the use of MeCC decreased human power demands for CPR without compromising patient care in the human power-demanding EDs.
2. Methods This retrospective study conducted at the ED of one medical university-affiliated municipal hospital was approved by the hospital's institutional review board. During a period of 4 years (April 2010–December 2013), patients with OHCA of presumed cardiac etiology were enrolled. This period was divided into two parts according to the use of MeCC (May 2012–December 2013) with standard CPR or MaCC (April 2010–April 2012). Exclusion criteria included age under 18 years, trauma, pregnancy, hypothermia, intoxication, hanging and drowning, return of spontaneous circulation (ROSC) prior to arrival at the ED, and other reasons, such as terminal illness. An MeCC device (Life-Stat 1008 Cardiopulmonary Resuscitator; Michigan Instruments, Inc., Michigan, USA) was introduced to the ED of our hospital in April 2012. Prior to that, chest compressions were delivered manually only for all OHCA patients. These patients (in the MaCC group) were therefore used as a control group.
Situated in South Taiwan, Kaohsiung is second in size only to the capital Taipei in the north. The emergency medical services (EMS) system in Kaohsiung serves about 2.7 million inhabitants in an area of 3000 km2 . Ambulances are dispatched for each call judged to relate to a life-threatening state of health. All OHCA patients are treated according to the American Heart Association and the International Liaison Committee on Resuscitation guidelines, such as Basic Life Support and/or Advanced Cardiovascular Life Support guidelines.9,10
All data were collected from the ED of our hospital and were confirmed by the data obtained from the EMS dispatch notes. Further medical data of patients admitted alive to the hospital were collected from hospital records. The primary endpoint of the study was ROSC following resuscitation and treatment, while the secondary endpoints were survival to hospital admission and medical human power demands for CPR.
The distribution of variables is given as mean ± standard deviation and percentages. For comparison of continuous variables between groups, Student t test was used. For comparison between groups of dichotomous variables, Fisher's exact test was used. In the multivariate analyses, logistic regression was used. A p value < 0.05 was regarded as significant.
3. Results During a period of 45 months, 455 patients who suffered from OHCA were enrolled in this study. Among these patients, 51 patients who met various exclusion criteria were excluded. The most frequent exclusion criterion was ROSC (12 cases) prior to arrival at ED. As a result, 404 patients were evaluated (216 in the MeCC group and 188 in the control group).
The patients were relatively old (mean age of 66.33 years and 64.59 years in the MeCC and the control groups, respectively), and almost two-thirds were male. About half of the patients had a history of coronary artery disease, and approximately one-third had a history of heart failure, pulmonary disease, and diabetes. There were no differences in terms of age, sex, or underlying diseases. No significant differences were also found between groups with respect to the time needed to transport the patients to the ED and first recorded electrocardiogram rhythm (Table 1 ). Regarding the delay resulting from calling the EMS to transport the patients to the ED, the greatest proportion of patients were sent to our ED within 10 minutes for both groups (69.0% vs. 70.7%, p = 0.676). The proportion of patients found in ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT) was not significantly different between groups as well (8.3% vs. 6.9%, p = 0.597).
Table 1: Demographic data of patients.
As shown in Table 2 , both ROSC (33.3% vs. 27.1%, p = 0.154) and the number of patients who survived hospitalization (22.2% vs. 17.6%, p = 0.229) increased after MeCC was used with standard CPR at the ED, however without significant differences.
Table 2: Study endpoints.
Several factors were simultaneously considered to find independent predictors of survival to hospitalization. The factors included age, sex, previous medical history, arrival at ER within 10 minutes, initial rhythm (VF/pulseless VT), MeCC/MaCC, and ROSC. Independent predictors of survival to hospitalization are listed, in order of significance, in Table 3 . The chance of survival to hospitalization increased 4.37 times if the patients had VF/pulseless VT as the initial rhythm and approximately 468 times if they had ROSC. Age, sex, previous medical history, arrival at ER within 10 minutes, and MeCC/MaCC were not found to be independent predictors of survival to hospitalization in the present analysis.
Table 3: Independent predictors of survival to hospitalization.
When an OHCA patient was sent to the ED, at least four medical professionals were needed when there was no MeCC device—one for MeCC, one for respiratory support (Ambu), one for prompt treatment and medical recording, and one for instruction. As fatigue occurred soon after the start of CPR, these four persons took turns performing MeCCs every 2 minutes during the minimum request of 30 minutes of CPR suggested by the Advanced Cardiovascular Life Support guideline. However, when the MeCC device was introduced, only two medical professionals were needed to instruct, keeping records, and offer treatments. The MeCC device performed chest compressions without fatigue and provided respiratory support. This resulted in a ratio of 2:4 for the human power demand for CPR between the MeCC group and MaCC group.
4. Discussion In this study, there was no difference in the early survival after OHCA between patients treated with MeCC and those treated with MaCC. However, several factors might explain the survival to hospitalization that was observed.
During May 2012–December 2013, 216 OHCA patients received MeCC. In this group, we found relatively older patients, fewer women, and the higher rate of survival to hospitalization.
Recent studies reveal a survival-to-hospitalization rate of 21–25% after OHCA and a larger proportion (38%) of patients who survived hospitalization if the study sample included only those experiencing cardiac arrests.1,4
The chance of survival to hospitalization was slightly higher when the patients received MeCC. It is only possible to speculate about the reasons for those findings. The prehospital protocol of CPR begins with MaCC and defibrillation when possible. If the patient does not receive ROSC upon arrival at the ED, the next step at the ED is to apply the mechanical device and subsequently begin intubation and intravenous treatments. All survivors had received ROSC after MeCC was used.
Whether MeCC improved the outcome after OHCA was not confirmed in our study. Several studies have also concluded insufficient delivery of MeCC in both quality and quantity.1,5,8 11,12 13–16
With regard to the patient characteristics, i.e., age, sex, previous medical history, and arrival at ER within 10 minutes, there were no unexpected findings. People in a better-educated society appear to call the EMS sooner.17
With the passage of every minute after a cardiac arrest, VFs have increasingly converted to nonshockable rhythms,17 18,19 1,20
This study has several limitations. The study site was an urban university-affiliated ED. The study's single-center retrospective study design might limit its generalizability. In addition, the quality of CPR was not measured and evaluated in the study. A large-scale, well-designed prospective study is needed to better test the outcomes of MeCC for OHCA patients in an ED.
In conclusion, in this study of nontraumatic OHCA patients, we found no difference in early survival between standard CPR performed with MeCC and that performed with MaCC. With regard to MeCC, there are benefits for the working environment of ED, although our conclusion is unable to assert that MeCC contributed to the increase in survival to hospitalization. However, the use of the MeCC device appears to promote staff availability without waiving patient care in the human power-demanding EDs of Taiwan hospitals.
Acknowledgments The authors would like to express their gratitude to the EMS personnel in the city of Kaohsiung, Taiwan. We also wish to thank Mr Richard H. Davis, MA, a second-language teacher, for his gratuitous assistance with the English editing of this manuscript. The study was approved by the hospital's institutional review board (KMUH-IRB-20140119).
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