DOI: https://doi.org/10.21203/rs.3.rs-2501124/v1
Although the resuscitation guidelines consider mechanical chest compressions acceptable for cardiopulmonary resuscitation (CPR) in unstable settings, the efficacy of automated chest compression devices for out-of-hospital cardiac arrest (OHCA) patients according to treatment time period remains unclear. We assessed the effectiveness of automated chest compression devices depending on time of admission based on frequency of iatrogenic chest injuries, duration of in-hospital resuscitation efforts, and clinical outcomes among OHCA patients.
We conducted a retrospective historical control study of OHCA patients in Japan between April 1, 2015 and March 31, 2022. Patients were divided according to time of admission; wherein day- and night-time were considered as duration between 07:00–22:59 and 23:00–06:59, respectively. These patients were then divided into two categories based on in-hospital cardiopulmonary resuscitation (IHCPR) device used: manual chest compression (mCC) group and automatic chest compression devices (ACCD) group. Univariate and multivariate ordered logistic regression models adjusted for pre-hospital confounders were used to evaluate the impact of ACCD use during IHCPR on outcomes [IHCPR duration, CPR-related chest injuries, and clinical outcomes] in day- and night-time groups.
A total of 1,101 patients with OHCA (day-time, 809; night-time, 292) formed our study population. Of these, 215 (26.6%) and 104 (35.6%) patients underwent ACCD during IHCPR in day-and night-time groups. Multivariate model showed significant association of ACCD use with outcomes of in-hospital resuscitation, including higher rates of return of spontaneous circulation, lower incidence of CPR-related chest injuries, longer in-hospital resuscitation duration, survival to Emergency Department and hospital discharge, and survival with good neurological outcome to hospital discharge, only in the night-time group.
Patients who underwent ACCD during in-hospital resuscitation at night had a significantly longer duration of in-hospital resuscitation, lower incidence of CPR-related chest injuries, and better outcomes.
Out-of-hospital cardiac arrest (OHCA) is a public health problem throughout the world, including Japan. [1, 2] Although cardiopulmonary resuscitation (CPR) is essential to save patients with OHCA, it is well known that CPR could result in iatrogenic chest injuries, such as pneumothorax or rib fractures. Chest injuries could in turn result in ineffective chest compressions because failure of thoracic compliance causes interruption of the cycle of positive and negative pressure. [3] It has also been reported that patients who experienced OHCA and received CPR during night-time had shorter resuscitation durations, higher incidence of CPR-related chest injuries, and lower survival rate, [4] in comparison to day-time CPR. [5]
High-quality chest compressions are a pivotal part of resuscitation, and the effectiveness of manual chest compressions depends on the endurance of the resuscitation team. To resolve these issues, mechanical chest compression devices were developed to maintain chest compression at appropriate rates and depths, and the devices reportedly produce non-inferior outcomes (compared to manual compressions) in terms of mortality and neurological outcomes after OHCA. [6] Although the Emergency Cardiovascular Care (ERC) and American Heart Association (AHA) resuscitation guidelines consider mechanical chest compressions to be acceptable for CPR in unstable settings, [7, 8] no reports have examined the efficacy of automated chest compression devices on the basis of treatment time period. Thus, this study aimed to evaluate the effectiveness of automated chest compression devices among patients with OHCA depending on the time of admission to the emergency department (ED) ( day-time or night-time) in terms of outcomes of in-hospital cardiopulmonary resuscitation (IHCPR) duration, frequency of iatrogenic chest injuries, rates of return of spontaneous circulation (ROSC), along with survival and neurological outcomes.
This single-center retrospective control study was conducted at a tertiary emergency critical care center (Tokyo, Japan), which receives approximately 170 patients with OHCA every year. The medical records of OHCA patients transferred to our center between April 1, 2015, and March 31, 2022, were surveyed. The staffing shift during the study period was generally provided as follows: (i) day-time (> 2 board-certified emergency physicians, 3 medical interns, and 3 nurses) and (ii) night-time (1 board-certified emergency physician, 3 medical interns, and 2 nurses). Procedures and medications were equally available at all times. Pre-hospital factors were recorded as similar between day- and night-times, as the Japanese emergency service (EMS) system ensures constant quality assessment of pre-hospital care (including holidays). The method of chest compressions on arrival of patients at the ED was formally changed at the study center on May 1, 2020, at which point automated mechanical compression replaced manual compression. During the study period, CPR and post-cardiac arrest care (including targeted temperature management) were provided consistently in accordance with the 2015 or 2020 AHA Guidelines for CPR and European Resuscitation Council (ERC).
This study complied with the principles of the 1964 Declaration of Helsinki and its amendments. The study protocol was approved by the ethics committee of Tokyo Medical and Dental University Hospital of Medicine (M2022-249). The need for informed consent was waived due to the retrospective nature of the study. All patient data were retrospectively collected from electronic medical charts and anonymized before statistical analyses.
This study included consecutive OHCA patients who were transferred to the Tokyo Medical and Dental University Hospital between April 1, 2015, and March 31, 2022. We excluded patients who were less than 18 years old, had do-not-attempt-resuscitation orders, experienced cardiac arrest due to trauma, received open-chest CPR, did not undergo chest computed tomography (CT) examination, or had missing or insufficient data regarding the study variables (i.e., lack of information regarding CPR duration, witnessed status, or initial rhythm). In addition, patients were excluded if they had received CPR from an automated chest compression device after arrival to the ED before May 1, 2020, regardless of the setting, as this study aimed to evaluate whether the quality of CPR performed by emergency medical staff was comparable to mechanical chest compression devices. Patients who were not suitable for mechanical CPR (e.g., those with severe cachexia, morbid obesity, and chest wall deformity) were also excluded from the study.
The Lund University Cardiac Assist System 3 (LUCAS 3, Stryker, Kalamazoo, MI, USA) was used as the mechanical chest compression device at our hospital for in-hospital resuscitation after May 1, 2020. LUCAS 3 is a piston-based device that provides active compression and decompression via a suction cup placed at the center of the chest.
The following data were collected retrospectively from medical records: age, sex, ED admission time, presence or absence of a witness to cardiac arrest, presence or absence of bystander CPR before the arrival of paramedics’ at the scene, shockable rhythm status, cause of cardiac arrest, whether or not ROSC was achieved, IHCPR duration, out-of-hospital CPR (OHCPR) duration, and patient status at the time of hospital discharge (i.e., survival or death). We also used the patients’ medical records and 64-slice CT imagery to collect data regarding CPR-related chest injuries (i.e., rib fractures, sternal fractures, pleural effusion/hemothorax, or pneumothorax). Our hospital has a general policy of routinely performing CT after CPR to identify the cause of cardiac arrest in non-traumatic cases. CT findings were interpreted by ≥ 2 board-certified emergency physicians and one radiologist.
OHCA was defined as cardiac arrest that occurred out-of-hospital, during which the patient was unresponsive to stimulation, gasping or not breathing, and had carotid arteries that were not palpable for a maximum assessment interval of 10 seconds, as described previously. [9] Based on the hospitals’ shift schedules and the results of previous studies, [9, 10] we divided the patients into two groups on the basis of when they were admitted to the ED: during day-time (07:00–22:59) or night-time (23:00–06:59).
OHCPR duration was defined as the interval between EMS dispatch and ED arrival in cases with bystander CPR, [11] or as the interval between EMS arrival at the scene and ED arrival in cases without bystander CPR.
IHCPR duration was defined as the interval between ED arrival and termination of resuscitation or ROSC. [12] For this study, ROSC was defined as the return of spontaneous circulation that lasted at least 5 min. We defined CPR-related chest injuries as rib fractures, sternal fractures, pleural effusion/hemothorax, or pneumothorax, as described previously. [5]
The primary outcomes of this study were defined as rate of ROSC, frequency of CPR-related chest injuries, and duration of IHCPR. We defined secondary outcomes as rate of survival to ED discharge, rate of survival to hospital discharge, and rate of survival with good neurological outcomes to hospital discharge. Cerebral Performance Category (CPC) scores were used to classify neurological outcomes into five stages:1) full recovery or mild disability, 2) moderate disability but independent in activities of daily living, 3) severe disability with dependence for support in activities of daily living, 4) persistent vegetative state, and 5) death. CPC scores of 1 or 2 indicated good neurological outcomes, while CPC scores of 3 or 4 implied poor outcomes. [13]
Categorical variables were reported as numbers (percentages), while continuous variables were reported as means (standard deviation) or medians (interquartile range), as appropriate.
We divided the enrolled patients on the basis of whether they were admitted to the ED during day-time or night-time, and further divided them into two categories based on the IHCPR device used: the manual chest compression (mCC) group (from April 1, 2015, to April 31, 2020) and automatic chest compression device (ACCD) group (from May 1, 2020, to March 31, 2022). First, we used a multivariate ordered logistic regression model to evaluate the interaction between in-hospital ACCD use and admission time for the outcomes to evaluate whether the effect of in-hospital ACCD use was affected by admission time. We incorporated age, sex, witnessed status, bystander CPR status, initial rhythm (shockable or not), cause of cardiac arrest, and OHCPR duration as explanatory variables in the multivariate model, which were clinically plausible and well-known confounders in previous epidemiologic studies. Second, we used univariate and multivariate ordered logistic regression models to evaluate the impact of ACCD use during IHCPR on outcomes in the day- and night-time groups, respectively.
All statistical analyses were performed using the R software (version 4.1.1; R Foundation for Statistical Computing, Vienna, Austria). Moreover, we used a command to add statistical functions that are frequently used in biostatistics. All reported p values were two-sided, and p values < 0.05 were considered statistically significant.
The patient selection process identified a total of 1,101 patients with OHCA, including 809 day-time cases (73.5%) and 292 night-time cases (26.5%). Day-time OHCA cases involved 215 patients (26.6%) who underwent automated chest compression devices during IHCPR, while night-time cases comprised 104 patients (35.6%) (Fig. 1). The baseline characteristics of the day- and night-time groups are summarized in Table 1. Age and proportion of females between the day- and night-time groups were similar. The night-time group had relatively lower rates of witnessed OHCA, bystander CPR, and shockable initial rhythm, along with relatively longer duration of OHCPR. Table 2 provides the baseline characteristics of each patient group divided according to admission time and IHCPR device. No significant differences were observed between the mCC and ACCD groups in the context of rates of witnessed OHCA, bystander CPR, shockable initial rhythm, or duration of OHCPR in both day- and night-time groups.
|
Day-time group, N = 809 |
Night-time group, N = 292 |
p value |
|
|---|---|---|---|
|
Age, median [IQR] |
68 [56–81] |
66 [52–80] |
0.483 |
|
Female, n (%) |
239 (29.5) |
90 (30.8) |
0.393 |
|
Witnessed, n (%) |
308 (38.1) |
65 (22.3) |
< 0.001 |
|
Bystander CPR, n (%) |
191 (23.6) |
43 (14.7) |
0.014 |
|
Shockable Initial rhythm, n (%) |
129 (15.9) |
36 (12.3) |
0.003 |
|
Cardiogenic, n (%) |
163 (20.1) |
58 (19.9) |
0.321 |
|
OHCPR duration, mean min [IQR] |
29 [23–35] |
37 [28–42] |
< 0.001 |
|
Abbreviations; IQR, interquartile range; CPR, cardiopulmonary resuscitation; OHCPR, out-of-hospital cardiopulmonary resuscitation |
|||
Table 2. Baselines characteristics of each patient group according to admission time and device of IHCPR
|
Day-time group, N = 809 |
Night-time group, N = 292 |
||||||
|
mCC group N = 594 |
ACCD group N = 215 |
p value |
mCC group N = 188 |
ACCD group, N = 104 |
p value |
||
|
Age, median [IQR] |
68 [55–81] |
65 [57–83] |
0.395 |
65 [48–79] |
65 [59–79] |
0.683 |
|
|
Female, n (%) |
180 (30.3) |
59 (27.4) |
0.543 |
59 (31.4) |
31 (29.8) |
0.793 |
|
|
Witnessed, n (%) |
236 (39.7) |
72 (33.5) |
0.106 |
44 (23.4) |
21 (20.2) |
0.261 |
|
|
Bystander CPR, n (%) |
149 (25.1) |
42 (19.5) |
0.111 |
28 (14.9) |
15 (14.4) |
0.391 |
|
|
Shockable Initial rhythm, n (%) |
90 (15.1) |
39 (18.1) |
0.277 |
24 (12.8) |
12 (11.5) |
0.754 |
|
|
Cardiogenic, n (%) |
115 (19.4) |
48 (22.3) |
0.171 |
37 (19.7) |
21 (20.2) |
0.791 |
|
|
OHCPR duration, mean min [IQR] |
28 [23–35] |
29 [24–36] |
0.261 |
34 [26–40] |
35 [31–42] |
0.231 |
|
|
Abbreviations; IQR, interquartile range; IHCPR, in-hospital cardiopulmonary resuscitation; CPR, cardiopulmonary resuscitation; OHCPR, out-of-hospital cardiopulmonary resuscitation; mCC, manual chest compression; ACCD, automatic chest compression devices |
|||||||
The results of univariate analyses are summarized in Table 3. In the day-time group, no significant differences were observed in IHCPR duration and rate of chest injuries between the mCC and ACCD groups. However, in the night-time group, the ACCD group had significantly longer IHCPR duration (median 27 min vs. 34 min) and a lower incidence of chest injuries (59.6% vs. 39.4%), compared to the mCC group. There were no significant differences in the rates of ROSC, survival to ED discharge, survival to hospital discharge, and survival with good neurological outcomes to hospital discharge between the mCC and ACCD groups in the day-time group. However, in the night-time group, the ACCD group had a significantly higher rate of ROSC (26.6% vs. 33.7%), survival to ED discharge (16.0% vs. 23.1%), survival to hospital discharge (6.9% vs. 12.5%), and survival with good neurological outcome at hospital discharge (4.3% vs. 8.7%).
|
Outcomes |
Day-time group N = 809 |
Night-time group N = 292 |
||||
|---|---|---|---|---|---|---|
|
mCC N = 594 |
ACCD N = 215 |
P value |
mCC N = 188 |
ACCD N = 104 |
P value |
|
|
ROSC, n (%) |
191 (32.2) |
78 (37.1) |
0.031 |
49 (26.6) |
35 (33.7) |
< 0.001 |
|
Chest injuries, n (%) |
202 (34.0) |
81 (37.7) |
0.328 |
112 (59.6) |
41 (39.4) |
< 0.001 |
|
IHCPR duration, min [IQR] |
35 [28–39] |
34 [27–38] |
0.762 |
27 [24–32] |
34 [28–38] |
< 0.001 |
|
Survival to ED discharge, n (%) |
108 (18.2) |
42 (19.5) |
0.271 |
30 (16.0) |
24 (23.1) |
< 0.001 |
|
Survival to hospital discharge, n (%) |
51 (8.6) |
22 (10.2) |
0.106 |
13(6.9) |
13 (12.5) |
< 0.001 |
|
Survival with good neurological outcome to hospital discharge, n (%) |
39 (6.6) |
16 (7.4) |
0.214 |
8 (4.3) |
9 (8.7) |
0.021 |
|
Abbreviations; ROSC, return of spontaneous circulation; IHCPR, in-hospital cardiopulmonary resuscitation; IQR, interquartile range; ED, emergency department; mCC, manual chest compression; ACCD, automatic chest compression devices |
||||||
In the entire study cohort, p values for interaction term of admission time categories (day-time or night-time group) and in-hospital ACCD use were < 0.001, which indicated a significant intra-group difference in terms of the impact of in-hospital ACCD use on clinical outcomes (Additional File 1). Table 4 presents the results of multivariate analysis regarding the impact of in-hospital ACCD use on outcomes in day- and night-time groups. After adjusting for confounding factors, we found a significant association between night-time in-hospital ACCD use and longer IHCPR duration, lower chest injury rate, higher rate of ROSC, survival to ED discharge, survival to hospital discharge, and survival with good neurological outcome at hospital discharge. However, we did not observe a significant impact of in-hospital ACCD use on clinical outcome in the day-time group.
|
Day-time group |
Night-time group |
|||||
|---|---|---|---|---|---|---|
|
AOR [95% CI] |
AD [95% CI] |
P value |
AOR [95% CI] |
AD [95% CI] |
P value |
|
|
ROSC |
0.66 [0.24–1.42] |
- |
0.354 |
1.14 [1.05–1.37] |
- |
< 0.001 |
|
Chest injuries |
0.78 [0.51–1.21] |
- |
0.431 |
0.41 [0.30–0.81] |
- |
< 0.001 |
|
IHCPR duration |
- |
-1.2 [-2.1-0.9] |
0.526 |
- |
6.1 [4.5–7.5] |
< 0.001 |
|
Survival to ED discharge |
0.81 [0.43–1.42] |
- |
0.651 |
1.13 [1.04–1.27] |
- |
< 0.001 |
|
Survival to hospital discharge |
0.89 [0.51–1.52] |
- |
0.472 |
1.10 [1.03–1.21] |
- |
< 0.001 |
|
Survival with good neurological outcome to hospital discharge |
0.94 [0.53–1.48] |
- |
0.235 |
1.09 [1.04–1.12] |
- |
0.002 |
|
Abbreviations; ACCD, automatic chest compression devices; IHCPR, in-hospital cardiopulmonary resuscitation; AOR, adjusted odds ratio; AD, adjusted difference; ED, emergency department; CI, confidence interval; ROSC, return of spontaneous circulation |
||||||
First, this was a retrospective observational study conducted at a single hospital with a limited sample size; thus, there was a risk of residual confounding and type II error. Second, detailed reasons (s) for termination of resuscitation in the ED were not always available. Third, we did not consider the impact of Coronavirus disease 2019 (COVID-19) pandemic on OHCA epidemiology. Although the COVID-19 pandemic did not appear to affect OHCA incidence or outcomes in our region (Tokyo, Japan), [14] OHCA studies from Europe and United States reporting outcome events during the COVID-19 pandemic were consistent and documented lower rates of ROSC, less frequent survival to hospital admission, lower survival to hospital discharge, and worse neurological outcomes. [15, 16] Finally, although Utstein has recommended defining ROSC as return of spontaneous circulation for ≥ 30 s, [17] this study defined ROSC as return of spontaneous circulation for ≥ 5 min, based on the absence of 30-s interval clinical data in the hospitals’ electronic medical record systems.
In this retrospective control study, we evaluated the impact of in-hospital ACCD use on the clinical outcomes of 1101 patients with OHCA, according to the time of admission. The present study revealed that the ACCD group had longer in-hospital resuscitation duration and lower incidence of CPR-related chest injuries compared to the mCC group in the night-time OHCA cases, even after adjusting for pre-hospital confounding factors. Notably, we found a higher impact of in-hospital ACCD use on survival and neurological outcomes in the night-time group than in the day-time group. These results suggest that the quality of CPR may be superior when using ACCD for in-hospital resuscitation compared to manual chest compression at night.
In contrast to several recent randomized clinical trials (RCTs), [18, 19] systematic reviews, and meta-analyses, [20, 21] our results demonstrated improved survival rates with mechanical CPR compared to manual CPR controls in limited situations. The relatively small sample size in the present study might explain these differences. Another possible explanation could be related to the Japanese EMS system which has restrictions on the decision to terminate resuscitation in the field. [22, 23] For example, the in-hospital survival rate in the present study was 9.0%, which was much lower compared to the previously reported rates. [18, 19]
The quality of manual chest compressions depends on several factors such as practitioner’s skill, environment, along with mental and physical strength; and this effectiveness could vary depending on the individual. [24] Fatigue and exhaustion of the practitioners due to prolonged CPR leads to decrease in the effectiveness of CPR. Therefore, it might be difficult to maintain high-quality CPR (i.e., appropriate hand position, depth, and rate) during night-time resuscitation. Mechanical compression devices have been invented to solve these problems generated from manual chest compression to standardize the CPR process and quality, and to increase the effectiveness of chest compression. [25] ACCD has been reported to produce non-inferior outcomes (vs. chest compressions performed by healthcare providers) in terms of survival rate and neurological outcomes after OHCA. Moreover, ACCD minimizes pauses during transport, thereby, allowing rescuers to focus on advanced life support. [6] Although the International Liaison Committee on Resuscitation’s (ILCOR) acknowledged the use of mechanical devices in situations where high-quality manual chest compressions may be impractical or dangerous to rescuers, [26] routine use of automated chest compression devices has not yet been recommended. [6] Furthermore, use of mechanical devices has also been reportedly associated with an increased risk of chest injuries. [27, 28] However, these findings should be interpreted with caution as they are prone to selection bias. Moreover, the quality of manual chest compression delivered, as the comparator group, is generally not recorded.
Delivery of high-quality manual chest compressions over a prolonged period is an aerosol-generating procedure that can be physically exhausting. The published AHA and ERC guidelines, [29, 30] recommend that manual chest compressions should be replaced with mechanical CPR devices to reduce the number of rescuers in settings with protocols in place and expertise in use. LUCAS3 was implemented at various stages of resuscitation and designed to minimize CPR interruptions. Therefore, a protocol requiring device implementation at a particular point of care may produce different results. For example, device application for patients who required procedures, such as catheterization or chest tubes, showed modestly beneficial results. Furthermore, in situations where high-quality manual chest compressions cannot be safely delivered, such as COVID-19 cases or during night-time, using a mechanical device could be a reasonable clinical approach. [31]
The findings of the present study are strengthened by the fact that all included patients underwent CT examinations, which allowed detection of CPR-related chest injuries. The two study periods had similar settings regarding treatment guidelines, and staffing. Furthermore, to the best of our knowledge, our study was the first to report that using a mechanical device for in-hospital resuscitation could also be a better clinical approach during night-time, in addition to the aforementioned unstable situations.
This retrospective control study revealed that OHCA patients who underwent in-hospital resuscitation using an automated chest compression device at night had significantly longer duration of in-hospital resuscitation, significantly lower incidence of CPR-related chest injuries, and significantly better clinical and neurological outcomes. Further large-scale research is necessary to confirm the results of this study.
OHCA: Out-of-hospital cardiac arrest
IHCPR: In-hospital cardiopulmonary resuscitation
OHCPR: Out-of-hospital cardiopulmonary resuscitation
mCC: Manual chest compression
ACCD: Automatic chest compression devices
CPR: Cardiopulmonary resuscitation
ERC: Emergency cardiovascular care
AHA: American Heart Association
ED: Emergency department
ROSC: Return of spontaneous circulation
ERC: European resuscitation council
CT: Computed tomography
LUCAS: Lund University Cardiac Assist System
CPC: Cerebral performance category
Ethics approval and consent to participate: This study complied with the principles of the 1964 Declaration of Helsinki and its amendments. The study protocol was approved by the ethics committee of Tokyo Medical and Dental University Hospital of Medicine (M2022-249). The need for informed consent was waived due to the retrospective nature of the study.
Consent for publication: Not applicable.
Availability of data and materials: The datasets analyzed in this study are not publicly available due to privacy issues, but are available from the corresponding author upon reasonable request.
Competing interests: The authors declare that they have no competing interests.
Funding: Not applicable.
Authors’ contributions: WT, AE, KM, and YO participated in the study conception and design, data collection, and drafting of the manuscript. All authors read and approved the final manuscript.
Acknowledgements: We thank all the included patients and their families, as well as the physicians, nurses, paramedics, and other staff for performing CPR and assisting with data acquisition.