a b s t r a c t

Objectives: This study aimed to evaluate the association between prehospital airway type and oxygenation and ventilation in out-of-hospital cardiac arrest (OHCA).

Methods: This retrospective observational study included OHCA patients who visited the emergency departments (EDs) between October 2015 and June 2021. The study groups were categorized according to the prehospital airway type: Endotracheal intubation , Supraglottic airway , or bag-valve-mask ventilation (BVM). The primary outcome was good oxygenation: partial pressure of oxygen (PaO2) >= 60 mmHg on the first arterial blood gas test. The secondary outcome was good ventilation: partial pressure of carbon dioxide (PaCO2) <= 45 mmHg. Multivariate logistic regression was conducted to calculate the adjusted odds ratio (AOR) and 95% confidence interval (CI).

Results: A total of 7,372 patients were enrolled during the study period: 1,819 patients treated with BVM, 706 with ETI, and 4,847 who underwent SGA. In multivariable logistic regression analysis for good oxygenation outcomes, the ETI group showed a higher AOR than the BVM group (AOR [95% CIs]: 1.30 [1.06-1.59] in ETI and 1.05 [0.93-1.20] in SGA groups). Regarding good ventilation, the ETI group showed a higher AOR, and the SGA group showed a lower AOR compared to the BVM group (AOR [95% CIs] 1.33 [1.02-1.74] in the ETI and 0.83 (0.70-0.99) in the SGA groups). There was no significant difference in survival to discharge.

Conclusions: ETI was significantly associated with good oxygenation and good ventilation compared to BVM in patients with OHCA, particularly during longer transports. This should be taken into consideration when deciding the prehospital advanced airway management in patients with OHCA.

(C) 2022

1. Introduction

Out-of-hospital cardiac arrest (OHCA) is a serious burden worldwide with high Morbidity and mortality rates [1,2]. Annually, 74.3 per 100,000 people in the United States and 48.7 per 100,000 people in South Korea experience OHCA [3,4]. Several studies have been conducted to improve survival outcomes, including early recognition of cardiac arrest, early cardiopulmonary resuscitation (CPR), and Early defibrillation [5-10]. However, the incidence of OHCA continues to increase, and mortality is still high in South Korea [11,12].

* Corresponding author at: Department of Emergency Medicine, Seoul National University College of Medicine and Hospital, 101, Daehak-ro, Jongno-gu, Seoul 03080, Republic of Republic of Korea.

E-mail addresses: [email protected] (K.H. Kim), [email protected] (S.D. Shin).

hypoxic-ischemic brain injury occurs when the Blood supply to the brain is stopped after cardiac arrest, resulting in an interruption of oxygen supply [13]. It is the leading cause of mortality and long-term neurologic disability after OHCA [14,15]. Wang et al. reported that abnormal oxygen (partial pressure of oxygen <60 mmHg) and carbon dioxide levels (partial pressure of carbon dioxide >50 mmHg) in arterial blood gas are associated with the prognosis of OHCA [16]. Youn-Jung et al. predicted that partial pressure of carbon dioxide (PaCO2) in ABG identified during OHCA could predict Ischemic injury and mortality [17].

The American Heart Association (AHA) recommends maintaining a patent airway and providing adequate Ventilation and oxygenation during cardiopulmonary resuscitation (CPR) [18]. Advanced airway management in OHCA is the core treatment for emergency medical service (EMS) providers [19,20]. Early advanced airway placement has been demonstrated to increase the probability of return of spontaneous circulation (ROSC) in witnessed patients with OHCA [21], and a delay in

https://doi.org/10.1016/j.ajem.2022.12.021

0735-6757/(C) 2022

advanced airway management was associated with decreased neurolo- gic recovery among patients with OHCA [22]. However, the association between advanced prehospital airway and oxygenation and ventilation in OHCA has not been well studied.

We hypothesized that advanced prehospital airway management would more likely show a lower probability of hypoxemia and hyper- capnia in patients with OHCA. This study aimed to evaluate the associa- tion between prehospital airway type and oxygenation and ventilation during emergency department (ED) visits for OHCA.

1. Methods
   1. Study design and setting

We conducted a multicenter retrospective observational study based on the Korean Cardiac Arrest Research Consortium (KoCARC) registry between October 2015 and June 2021. It is a collaborative research network that was developed to perform studies in the field of OHCA resuscitation and to strengthen research cooperation. Since October 2015, KoCARC investigators have prospectively collected standardized data of OHCA patients from the EDs of 32 hospitals in South Korea registered as KoCARC research hospitals. In each hospital, OHCA is treated according to the recent American Heart Association guidelines, and ABG analysis is performed as soon as possible to assess the patient’s condition and identify correctable causes for all patients, even during CPR.

The Korean EMS system is a fire-based public system with two EMS provider classifications, namely level-1 and level-2 emergency medical technicians , which is comparable to advanced emergency technician (AEMT) and emergency technician (EMT) levels in the US. A level-1 EMT can provide advanced life support procedures, including administration of intravenous fluids, placement of prehospital advanced airways, including Endotracheal tubes or Supraglottic airways, and administration of limited medications under direct medical oversight.

According to the Korean Emergency Medical Service Act, which delineates the responsibilities and rights of Emergency medical service providers, level-1 EMT qualification is obtained by graduating from the EMT school (a 3- to 4-year curriculum) of a university or college. To become an EMT, they must also pass a national certification examina- tion composed of written and skills tests. EMT schools have specific curricula for advanced airway management, including six courses and 147 education hours. The National Fire Service Academy, to which level-1 EMTs can apply for recruitment, has online and offline learning classes for EMTs. An advanced airway management class is included in the lifesaving technique course provided by national or provincial fire service academies for skill enhancement.

EMS providers cannot declare death or stop CPR in the field unless ROSC occurs. Therefore, all patients with OHCA are transported to the EDs while receiving CPR in an ambulance, if there is no prehospital ROSC. Mandatory medical education is provided to enhance knowledge and skills, and is composed of yearly 4-h didactic sessions and compre- hensive Clinical training courses every other month at an ED. Central fire services (CFSs) have internal regulations for level-1 EMTs to ensure that a single advanced airway management attempt may be performed in a 30-s interval, and two attempts at the most, can be made on the scene. The standard operating protocol recommends the use of bag-valve- mask ventilation with an oral or nasal airway. End-tidal carbon dioxide monitoring, which could potentially impact the hypercarbia of patients, is recommended, but is not routinely used in OHCA in South Korea. Ambulance crews are usually composed of 2-3 members (level-1 EMT, level-2 EMT, and first responder).

• 1. Study population

Patients with suspected medical OHCA admitted to the participating EDs between October 2015 and June 2021 were included in the study.

We excluded inter-hospital transport cases, pediatrics, non-EMS users, OHCA witnessed in ambulance, cases in which CPR was not continued in the ED (death on arrival, do-not-resuscitate order, or ED arrival with sustained ROSC from the field), patients with missing ABG values, and extreme EMS time variables (response interval, scene interval, or transport interval over 1 h).

• 1. Outcome measures

The primary outcome was good oxygenation at the time of ED visit, defined as a partial pressure of oxygen (PaO2) level >= 60 mmHg in the initial ABG performed at the ED [16]. The secondary outcome was good ventilation at the time of ED visit, defined as a partial pressure of carbon dioxide (PaCO2) level <= 45 mmHg in the initial ABG performed at the ED. Survival to discharge was used as the tertiary outcome.

• 1. Variables and measurements

The main exposure was the prehospital airway type, conducted by EMS personnel. Prehospital airway type was defined as either endotra- cheal intubation (ETI) or Supraglottic airway insertion before hospital arrival. The study groups were categorized as ETI, SGA, or bag-valve-mask ventilation (BVM). Demographic findings and clinical information were collected and categorized as follows: year, age group (under 45, 45-65, and greater than 65 years), sex, past medical history (hypertension, diabetes mellitus, heart disease, and pulmonary disease), residential area (metropolitan or non-metropolitan), place of arrest (public or private), witnessed status, provision of bystander CPR, Automated external defibrillator application by a bystander, EMS response interval (elapsed time interval between call to EMS and EMS scene arrival), EMS scene interval (elapsed time interval between EMS scene arrival and EMS departure to hospital), EMS transport interval (elapsed time interval between EMS depar- ture to hospital and EMS arrival at hospital), prehospital initial electrocardiogram rhythm (ventricular fibrillation or pulseless ven- tricular tachycardia, pulseless electrical activity, and asystole), pre- hospital defibrillation and mechanical CPR device application by EMS, prehospital intravenous placement and epinephrine adminis- tration by EMS, multitier response of EMS, transient ROSC in the field, and first ABG obtained following ED arrival (pH, PaO2, and PaCO2).

• 1. Statistical analysis

A descriptive analysis was performed to analyze the distribution of demographics and clinical findings of the study population. Continuous variables were compared using the Wilcoxon rank sum test and cate- gorical variables were compared using the chi-squared test with Bonferroni adjustment for multiple comparisons. To determine the associations between prehospital airway type and outcomes, adjusted odds ratios (AORs) with 95% confidence intervals (CIs) were calculated using a multivariable logistic regression analysis with the BVM group as a reference after adjusting for year of arrest, age, sex, pulmonary disease history, residential area (metropolitan), place of arrest (public), witness, bystander CPR, EMS response interval, scene interval, multitiered response, prehospital mechanical CPR, initial prehospital electrocardio- gram (ECG) rhythm, and transient ROSC in the field. Additionally, the ETI group was used as a reference to compare the ETI and SGA groups. Since a prolonged period after cardiac arrest may affect hypoxemia and hypercapnia, the prehospital interval was calculated (response interval + scene interval + transport interval) and categorized into three quantiles (shorter than 27 min, 27-33 min, and over 33 min) for subgroup analysis. All statistical analyses were performed using SAS version 9.4 (SAS Institute Inc., Cary, NC, USA) and R, version 3.5 (R Foundation for Statistical Computing, Vienna, Austria).

Fig. 1. Patient flow.

OHCA, out-of-hospital cardiac arrest; KoCARC, Korean Cardiac Arrest Research Consortium; EMS, emergency medical services; DOA, death on arrival; DNR, do-not-resuscitate order; ED, emergency department; ROSC, return of spontaneous circulation; ABG, arterial blood gas.

1. Results

Among 15,368 patients with OHCA who were admitted to EDs and participated in the KoCARC study from October 2015 to June 2021, 7372 were included in the final analysis. We excluded inter-hospital transport (n = 697), pediatrics (n = 328), non-EMS users (n = 626), witnessed in ambulance (n = 1052), CPR not conducted in the ED (n = 1505), missing ABG values (n = 3722), and extreme EMS time variables (n = 66) (Fig. 1).

Table 1 shows the demographics and clinical findings of the study groups. Initial ABG analysis showed differences according to the study groups; the mean PaO2 in the initial ABG was 42.7 mmHg in ETI,

41.8 mmHg in SGA, and 38.3 mmHg in BVM. The Mean PaCO2 in initial ABG was 75.0 mmHg in ETI, 81.0 mmHg in SGA, and 78.0 mmHg in BVM. Survival to discharge was 3.8% for ETI, 5.1% for SGA, and 6.8% for BVM patients (Table 1).

A multivariable logistic regression model was used to assess the association between prehospital airway type of OHCA and study outcomes. In the multivariable logistic regression analysis for good oxygenation (PaO2 >= 60 mmHg), the ETI group showed a significantly higher AOR than the BVM group, with a statistically significant differ- ence; AOR (95% CIs): 1.30 (1.06-1.59) in ETI, and 1.05 (0.93-1.20) in

SGA groups. ETI demonstrated a similar association for good ventilation (PaCO2 <= 45 mmHg), but SGA showed lower probability; AOR (95% CIs):

1.33 (1.02-1.74) in ETI, and 0.83 (0.70-0.99) in SGA. There was no

statistically significant difference in survival to discharge; AOR (95% CIs): 1.04 (0.75-1.34) in ETI and 1.00 (0.85-1.18) in SGA groups

(Table 2). Additional subgroup analysis was conducted to evaluate the effect size of prehospital airway type according to Prehospital time intervals. The ETI group showed a significantly higher probability of good oxygenation over 33 min of prehospital intervals (Table 3).

1. Discussion

We found significant associations between prehospital airway type and oxygenation and ventilation in the initial ABG analysis of ED visits for EMS-treated adult OHCAs. Compared to BVM, ETI showed a higher probability of good oxygenation and good ventilation, but SGA was negatively associated with good ventilation. The association appears prominent with a longer prehospital time of >33 min. However, there was no significant difference between prehospital airway type and survival to discharge.

ETI is usually considered a definite airway management technique that positions the tube within the trachea, facilitating more controlled oxygen delivery, and the cuff of the tube is intended to protect the lungs from vomit aspiration [23,24]. In this study, oxygenation and ventilation were improved based on the strength of ETI. However, the application of ETI has many technical difficulties and requires consider- able experience and education [25,26]. SGA is a convenient technology that is widely used as an alternative to ETI for OHCA [27,28]. During the study period, the proportion of SGA insertions by EMS providers tended to increase. SGA malpositioning is known to result in severe air leakage and airway obstruction, potentially causing negative patient outcomes [29].

We estimated that the effect of prehospital airway type would vary according to the prehospital time interval. Specifically, it was hypothe- sized that oxygenation and ventilation were more likely to deteriorate because of airway obstruction due to malpositioning of SGA as time passed in the prehospital phase [30]. In addition, we assumed that it would take time for the effect of Gas exchange by prehospital airway management to be reflected. The results of our study showed that a prehospital time interval of over 33 min is a critical period in which ETI predominantly affects gas exchange. In Asian countries, approxi- mately 30-35 min is generally the median prehospital time [31,32]. It was probably difficult to maintain the proper position of the airway within a moving ambulance, especially in patients who underwent SGA. In our study, the Survival outcomes were not significantly different between ETI and BVM, similar to that observed in a recent large-scale clinical trial [33]. The BVM group showed a more favorable characteris- tic and a higher survival rate for certain reasons, including resuscitation time bias, which limits the clarification of the association between prehospital airway type and survival. In addition, it is suspected that CPR quality may not be sustained during advanced procedures, which has been indicated as the reason why advanced airway management showed no difference in clinical outcomes [34]. Whether prehospital advanced airway management is provided seemed to depend predom- inantly on the characteristics of OHCA, which would affect the associa- tion. We analyzed patients who were not witnessed and stayed over 9 min at the scene, and found a higher odds of survival outcome in the ETI group; AOR (95% CIs): 2.18 (0.79-6.04) in ETI and 1.81

(0.86-3.78) in SGA.

oxygen supplementation and outcomes in patients with OHCA have been previously studied. Generally, greater Tissue oxygenation during cardiac arrest shows a greater likelihood of ROSC and is associated

Demographics and clinical findings according to prehospital airway type.

	Total		BVM		ETI		SGA	p-value
	N (%)		N (%)		N (%)		N (%)
Total	7372		1819 (24.7)		706 (9.6)		4847 (65.7)
Demographics
Year 2015-2016	589 (8.0)		272 (15.0)?,??		60 (8.5)??		257 (5.3)	<0.01
2017	1006 (13.6)		362 (19.9)?,??		79 (11.2)??		565 (11.7)
2018	1538 (20.9)		511 (28.1)?,??		160 (22.7)??		867 (17.9)
2019	1682 (22.8)		339 (18.6)?,??		193 (27.3)??		1150 (23.7)
2020-2021	2557 (34.7)		335 (18.4)?,??		214 (30.3)??		2008 (41.4)
Age, years	72 (59-81)		72 (59-81)?		75 (64-81)??		72 (59-81)	<0.01
Age group, years -44	508 (6.9)		126 (6.9)?,??		39 (5.5)??		343 (7.1)	<0.01
45-64	2014 (27.3)		523 (28.8)?,??		146 (20.7)??		1345 (27.7)
65-	4850 (65.8)		1170 (64.3)?,??		521 (73.8)??		3159 (65.2)
Gender, Male	4828 (65.5)		1159 (63.7)		468 (66.3)		3201 (66.0)	0.18
Past medical history HTN	2475 (33.6)		547 (30.1)?,??		268 (38.0)		1660 (34.2)	<0.01
DM	1798 (24.4)		369 (20.3)?,??		193 (27.3)??		1236 (25.5)	<0.01
Heart disease	1287 (17.5)		259 (14.2)?,??		138 (19.5)		890 (18.4)	<0.01
Pulmonary disease	451 (6.1)		102 (5.6)		55 (7.8)		294 (6.1)	0.11
Metropolitan	4601 (62.4)		945 (52.0)?,??		637 (90.2)??		3019 (62.3)	<0.01
Public	1228 (16.7)		309 (17.0)		101 (14.3)		818 (16.9)	0.20
Witnessed	4173 (56.6)		1123 (61.7)?,??		360 (51.0)??		2690 (55.5)	<0.01
Bystander CPR	4070 (55.2)		846 (46.5)?,??		415 (58.8)??		2809 (58.0)	<0.01
Bystander AED	82 (1.1)		25 (1.4)		8 (1.1)		49 (1.0)	0.45
EMS Variable Response interval, min, median (IQR)	7 (6-9)		7 (5-9)?,??		7 (5-9)??		7 (6-9)	<0.01
Scene interval, min, median (IQR)	15 (12-19)		12 (9-16)?,??		17 (14-21)??		16 (12-20)	<0.01
Transport interval, min, median (IQR)	7 (5-10)		7 (5-10)?		6 (5-9)??		7 (5-10)	0.02
multi-tiered response	3803 (51.6)		417 (22.9)?,??		543 (76.9)??		2843 (58.7)	<0.01
Prehospital initial ECG rhythm								0.62
VF or pulseless VT	1026 (13.9)		246 (13.5)		89 (12.6)		691 (14.3)
PEA	1651 (22.4)		397 (21.8)		167 (23.7)		1087 (22.4)
Asystole	4695 (63.7)		1176 (64.7)		450 (63.7)		3069 (63.3)
Defibrillation	1458 (19.8)		348 (19.1)		142 (20.1)		968 (20.0)	0.72
Mechanical CPR	1809 (24.5)		160 (8.8)?,??		413 (58.5)??		1236 (25.5)	<0.01
IV assessment	4936 (67.0)		798 (43.9)?,??		636 (90.1)??		3502 (72.3)	<0.01
Epinephrine	1519 (20.6)		131 (7.2)?,??		225 (31.9)??		1163 (24.0)	<0.01
Transient ROSC at the field	386 (5.2)		80 (4.4)		34 (4.8)		272 (5.6)	0.12
Outcome
pH in initial ABG, median, (IQR)	6.9 (6.8-7.0)	6.9 (6.8-7.0)??		6.9 (6.8-7.0)??		6.9 (6.8-7.0)		<0.01
PaO2 in initial ABG, mmHg, median, (IQR)	41.1 (20.6-68.9)	38.3 (19.1-70.3)		42.7 (23.0-70.0)		41.8 (20.9-68.1)		0.13
PaCO2 in initial ABG, mmHg, median, (IQR)	79.6 (59.0-101.6)	78.0 (56.1-100.0)??		75.0 (54.6-98.7)??		81.0 (61.2-102.3)		<0.01
72 h survival	1132 (15.4)	334 (18.4)?,??		91 (12.9)		707 (15.6)		0.04

BVM, bag-valve mask ventilation; ETI, endotracheal intubation; SGA, supraglottic airway; HTN, hypertension; DM, diabetes mellitus; CPR, cardio-pulmonary resuscitation; AED, automated external defibrillator; RTI, response time interval; STI, scene time interval; TTI, transport time interval; ECG, electrocardiogram; VF, ventricular fibrillation; VT, ventricular tachycardia; PEA, pulseless electrical activity; IV, intravenous; ROSC, return of spontaneous circulation; pH; power of hydrogen ion; ABG, arterial blood gas; PaO2, partial pressure of oxygen; PaCO2, partial pressure of carbon dioxide.

* Bonferroni-adjusted p-value <0.05 compared with the ETI group.

?? Bonferroni-adjusted p-value <0.05 compared with the SGA group.

Table 2

Multivariable logistic regression analysis according to prehospital airway type of OHCA.

Outcomes	n/N (%)	Univariable analysis		Multivariable analysisa		Multivariable analysisb
		OR (95% CI)		Adjusted OR (95% CI)		Adjusted OR (95% CI)
Good oxygenation BVM	581/1819 (31.9)	1.00		1.00		NA
ETI	251/706 (35.6)	1.18 (0.98-1.41)		1.30 (1.06-1.59)		1.00
SGA	1550/4847 (32.0)	1.00 (0.89-1.12)		1.05 (0.93-1.20)		0.81 (0.68-0.97)
Good ventilation BVM	281/1819 (15.4)	1.00	1.00		NA
ETI	120/706 (17.0)	1.12 (0.89-1.42)	1.33 (1.02-1.74)		1.00
SGA	569/4847 (11.7)	0.73 (0.62-0.85)	0.83 (0.70-0.99)		0.63 (0.50-0.79)
72-Hour Survival BVM	334/1819 (18.4)	1.00	1.00		NA
ETI	91/706 (12.9)	0.66 (0.51-0.85)	1.04 (0.75-1.34)		1.00
SGA	707/4847 (15.6)	0.76 (0.66-0.88)	1.00 (0.85-1.18)		1.00 (0.77-1.29)

OHCA, out-of-hospital cardiac arrest; OR, odds ratio; CI, confidence intervals; BVM, bag-valve mask ventilation; ETI, endotracheal intubation; SGA, supraglottic airway; multivariable model was adjusted with year or arrest, age group, sex, pulmonary disease history, metropolitan, public, witnessed status, bystander CPR, RTI, STI, multi-tiered EMS, prehospital mechanical CPR, Prehospital initial ECG rhythm, and Transient ROSC at the field.

Model ^a,b used same statistical analysis with different references.

Table 3

Multivariable logistic regression analysis for oxygenation and ventilation according to prehospital airway type by prehospital time of OHCA.

Prehospital time < 27 min Prehospital time 27-33 min Prehospital time >= 34 min

	N (%)	Adjusted OR (95% CIs)		N (%)	Adjusted OR (95% CIs)		N (%)	Adjusted OR (95% CIs)
Good oxygenation
BVM	266 (33.2)	1.00		160 (31.3)	1.00		155 (30.6)	1.00
ETI	57 (33.3)	1.08 (0.74-1.58)		93 (33.9)	1.26 (0.90-1.79)		101 (38.7)	1.46 (1.02-2.09)
SGA	445 (33.1)	1.03 (0.84-1.26)		547 (33.9)	1.18 (0.93-1.48)		558 (29.5)	0.94 (0.74-1.19)
Good ventilation
BVM	147 (18.4)	1.00	70 (13.7)		1.00	64 (12.6)		1.00
ETI	32 (18.7)	1.28 (0.80-2.04)	40 (14.6)		1.12 (0.71-1.78)	48 (18.4)		1.57 (0.97-2.54)
SGA	190 (14.1)	0.84 (0.64-1.09)	213 (13.2)		0.98 (0.71-1.33)	166 (8.8)		0.70 (0.49-0.98)

OHCA, out-of-hospital cardiac arrest; OR, odds ratio; CI, confidence intervals; BVM, bag-valve mask; ETI, endotracheal intubation; SGA, supraglottic airway. Multivariable model was adjusted with year or arrest, age group, sex, pulmonary disease history, metropolitan, public, witnessed status, bystander CPR, RTI, STI, multi-tiered EMS, prehos- pital mechanical CPR, Prehospital initial ECG rhythm, and Transient ROSC at the field.

with a lower mortality rate [31,32]. In contrast, hyperoxia may have a harmful effect by increasing the production of Reactive oxygen species in cerebral tissue [33]. We attempted to determine whether prehospital advanced airway management was related to hyperoxia. The cutoff of PaO2 was varied in 10 mmHg increments, and statistical significance for the association between higher PaO2 and ETI was found only at 50 mmHg and 60 mmHg (Supplement 1).

The results of this study showed that Prehospital ETI is associated with good oxygenation and ventilation in OHCA patients. EMS providers could consider ETI for oxygenation in select patients whose prehospital interval is estimated to be relatively longer. To clarify the effect of the type of prehospital advanced airway management on organ perfusion and survival outcomes, additional investigations on organ damage and large-scale clinical studies with selective OHCA are needed.

• 1. Limitations

This study has several limitations. First, the missing ABG values in the population were excluded. Most of these patients died without ABG analysis, which could have significantly affected the results. Second, the main exposure in our study was the prehospital airway type, which was confirmed at the participating EDs. In the database, the timing of airway insertion, the number of trials, and whether the prehospital airway type was changed at the scene when the proce- dure failed were not collected. In addition, it was not confirmed whether the normal position was maintained upon arrival at the ED. Patients with first-attempt success were probably clinically different from those with multiple unsuccessful attempts. In addi- tion, if information regarding the Quality of CPR had been collected, the effect on survival outcomes would have been clarified more clearly. Third, the main outcome of our study was the initial ABG analysis performed at the ED. The ABG analysis test time differed for each patient, but could not be adjusted because the exact time point of the test was not collected. We believe that there would be no significant difference since all the participating hospitals tried to retrieve ABG immediately after the patient’s arrival; however, the lack of standardized ABG collection time is also a limitation. Hyperoxia and hypercarbia are known to have detrimental effects on clinical outcomes, but they were not evaluated due to the sample size. Additionally, the normal range of blood oxygen and carbon dioxide levels vary according to various published guidelines [18,35]. We defined this based on the normal value of the study insti- tute, but this could be limited in generalizability. Fourth, since patients who achieved ROSC early in the resuscitative phase were more likely to have favorable outcomes and less likely to receive prehospital advanced airway management, we excluded OHCA patients admitted to the ED with ROSC status, but the results could be biased. Association between ETI and outcomes were not signifi- cantly changed after excluding any prehospital ROSC, (n = 6986); AOR (59% CIs): 1.28 (1.04-1.58) for good oxygenation, 1.32

(0.99-1.74) for good ventilation, and 1.08 (0.64-1.82) for survival to discharge. Additional analysis of patients with ROSC at ED arrival was conducted to compare the characteristics of the cohort and sim- ilar trends were observed; median (interquartile range, IQR): 135.6 (72.5-237.0) mmHg in the ETI, 98.4 (70.0-163.4) mmHg in the SGA, and 91.3 (65.0-154.) mmHg in the BVM groups (Supplement 2). Korean EMS implemented a multi-tier response system around 2017 and a designated advanced life support program around 2020. Changes in the system may have altered the performance and compliance of advanced airway management differently. Fifth, our study was a retrospective observational study, so there may be unmeasured bias. Finally, this study cannot be generalized because it was conducted in a country where the EMS setting is based on the scoop and run model.

1. Conclusion

Among OHCA patients, the ETI group had a significantly higher probability of good oxygenation and good ventilation than the BVM group. Conversely, the SGA group was more likely to show hypoxemia and hypercapnia than the ETI group. Further studies are needed to clarify the effect on organ damage according to the type of prehospital advanced airway management technique.

Disclaimer

The study was approved by the institutional review boards (IRBs) of each participating institution before data collection (IRB No. H-1401- 090-550). The KoCARC registry was registered at clinicaltrials.gov (protocol NCT03222999).

Funding Acknowledgement

There is nothing to declare.

CRediT authorship contribution statement

So Ra Song: Writing – review & editing, Writing – original draft, Investigation, Formal analysis, Data curation, Conceptualization. Ki Hong Kim: Writing – review & editing, Writing – original draft, Visual- ization, Supervision, Investigation, Formal analysis, Conceptualization. Jeong Ho Park: Writing – review & editing, Validation, Supervision, Resources, Project administration, Methodology. Kyoung Jun Song: Writing – review & editing, Supervision, Resources, Project administra- tion, Methodology. Sang Do Shin: Writing – review & editing, Supervision, Resources, Methodology.

Declaration of Competing Interest

No authors have other relationships, conditions, or circumstances that present potential conflicts of interest.

Acknowledgements

We would like to acknowledge and thank to investigators from all participating hospitals of KoCARC:

Woon Yong Kwon (Seoul National University Hospital), Sang Kuk Han, Phil Cho Choi (Kangbuk Samsung Medical Center), Sang O Park, Jong Won Kim (Konkuk University Medical Center), Han Sung Choi, Jong Seok Lee (Kyung Hee University Hospital), Sung Hyuk Choi, Young Hoon Yoon (Korea University Guro Hospital), Su Jin Kim, Kap Su Han (Korea University Anam Hospital), Min Seob Sim, Gun Tak Lee (Samsung Medical Center), Shin Ahn (Asan Medical Center), Jong Whan Shin, Hui Jai Lee (SMG-SNU Boramae Medical Center), Keun Hong Park, Hahn Bom Kim (Seoul Medical Center), In Cheol Park, Yoo Seok Park (Yonsei University Severance Hospital), Tae Young Kong (Yonsei University Gangnam Severance Hospital), Chu Hyun Kim (Inje Univer- sity Seoul Paik Hospital), Youngsuk Cho (Hallym University Kangdong Sacred Heart Hospital), Gu Hyun Kang, Yong Soo Jang (Hallym Univer- sity Kangnam Sacred Heart Hospital), Tai Ho Im, Jae Hoon Oh (Hanyang University Seoul Hospital), Seok Ran Yeom, Sung Wook Park (Pusan National University Hospital), Jae Hoon Lee (Dong-A University Hospi- tal), Jae Yun Ahn (Kyungpook National University Hospital), Kyung Woo Lee, Tae Chang Jang (Daegu Catholic University Medical Center), Jae-hyug Woo (Gachon University Gil Medical Center), Woon Jeong Lee, Seon Hee Woo (The Catholic University of Korea Incheon St. Mary’s Hospital), Sung Hyun Yun, Jin Won Park (Catholic Kwandong University International St. Mary’s Hospital), Sun Pyo Kim, Yong Jin Park (Chosun University Hospital), Jin Woong Lee, Wonjoon Jeong (Chungnam National University Hospital), Sung Soo Park, Jae Kwang Lee (Konyang University Hospital), Ryeok Ahn, Wook Jin Choi (Ulsan University Hospital), Young Gi Min, Eun Jung Park (Ajou University Hospital), You Hwan Jo, Joong Hee Kim (Seoul National University Bundang Hospi- tal), In Byung Kim, Ki Ok Ahn (Myongji Hospital), Han Jin Cho (Korea University Ansan Hospital), Seung Cheol Lee, Sang Hun Lee (Dongguk University Ilsan Hospital), Young Sik Kim (Bundang Jesaeng Hospital), Jin Sik Park (Sejong Hospital), Dai Han Wi (Wonkwang University Sanbon Hospital), Ok Jun Kim, Min Woo Kang (Cha University Bundang Medical Center), Sang Ook Ha, Won Seok Yang (Hallym University Pyeongchon Sacred Heart Hospital), Soon Joo Wang, Hang A Park (Hallym University Dongtan Sacred Heart Hospital), Jun Hwi Cho, Chan Woo Park (Kangwon National University Hospital), An Mu Eob, Tae Hun Lee (Hallym University Chuncheon Sacred Heart Hospital), Sang Chul Kim, Hoon Kim (Chungbuk National University Hospital), Han Joo Choi, Chan Young Koh (Dankook University Hospital), Hyung Jun Moon, Dong Kil Jeong (Soonchunhyang University Cheonan Hospital), Tae Oh Jung, Jae Chol Yoon (Chonbuk National University Hospital), Seung Yong Lee, Young Tae Park (Dongguk University Gyeongju Hospital), Jin Hee Jeong, Soo Hoon Lee (Gyeongsang National University Hospital), Ji Ho Ryu, Mun Ki Min (Pusan National University Yangsan Hospital), Won Kim, Yi Sang Moon (Cheju Halla General Hospital), Sung Wook Song, Woo Jung Kim (Jeju National University Hospital), Joon-myoung Kwon, Eui Hyuk Kang (Mediplex Sejong Hospital), Sang Chan Jin, Tae-kwon Kim (Keimyung University Dongsan Medical Center), Hyuk Joong Choi (Hanyang University Guri Hospital), Seong Chun Kim (Gyeongsang National University Changwon Hospital), In Soo Cho (Hanil General Hospital).

To steering committee, comprised of following individuals:

Sung Oh Hwang (Chair, Wonju Severance Christian Hospital), Hyuk Jun Yang (Advisory Committee, Gachon University Gil hospital), Sung Phil Chung (Data Safety and Management Board, Yonsei University Gangnam Severance Hospital), Sung Woo Lee (Security and Monitoring Board, Korea University Anam hospital), Seung Sik Hwang

(Epidemiology and Prevention Research Committee, Seoul National University), Gyu Chong Cho (Community Resuscitation Research Committee, Hallym University Kangdong Sacred Heart Hospital), Hyun Wook Ryoo (Emergency Medical Service Resuscitation Research Committee, Kyungpook National University Hospital), Kyoung Chul Cha (Hospital Resuscitation Research Committee, Wonju Severance Christian Hospital), Won Young Kim (Hypothermia and Post- Resuscitation Care Research Committee, Asan Medical Center), Sang Hoon Na (Cardiac Care Resuscitation Research Committee, Seoul National University Hospital), Young Ho Kwack (pediatric resuscitation Research Committee, Seoul National University hospital).

To member of Secretariat: Sun Young Lee (Seoul National University Hospital), and Sung Kyung Kim (Seoul National University Hospital).

To National Fire Agency for providing prehospital EMS data.

And to Korean Association of Cardiopulmonary Resuscitation (KACPR) for support.

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi. org/10.1016/j.ajem.2022.12.021.

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