a b s t r a c t

Introduction and purpose: The end-tidal carbon dioxide measurement is accepted as the gold standard method for assessing cardiopulmonary resuscitation (CPR) efficacy. In recent studies, the use of Carotid Doppler ultrasonography has become widespread in showing CPR efficacy. In the present study, the carotid blood flow measurement was compared with ETCO₂ measurement and an evaluation was made of whether this method could be used as an alternative method to capnography in the assessment of CPR efficacy.

Material and method: This study was conducted on patients who presented at the Emergency Department (ED) with non-traumatic arrest or began to suffer from arrest during emergency service follow-up. The main carotid artery peak systolic velocity (PSV), end diastolic velocity (EDV) and time-dependent mean flow velocity (MNV), and ETCO₂ values were measured and recorded after the 100th chest pressure of the CPR cycle and the results were statistically analyzed.

Results: The mean age of the patients was 54.5 +- 12.3 years and 65.6% of the patients were male. The mean values of patients measured from the carotid artery during the CPR were PSV 67.1 +- 17.3, EDV 16.3 +- 4.5, MNV 25.5 +-

8.1 and ETCO₂ 22.2 +- 8.1. A significant difference was found between in-hospital and out-of-hospital arrests in terms of patient outcome (return of spontaneous circulation (ROSC) and death) (p b 0.05). The mean ETCO₂ values of those who died were found to be lower than those of the ROSC group (p b 0.05). Although there was a positive and low-level of correlation between the EtCO2 values and PSV values, and a positive and very low- level of correlation between the EDV and MNV values of all patients, these correlations were not statistically sig- nificant. (p N 0.05). Conclusion: A low correlation was found between the PSV and ETCO2 values. With effective CPR, the results close to carotid blood flow in normal healthy individuals were obtained. However, the study showed that carotid blood flow measurement results during CPR were not as valuable as ETCO2 in demonstrating CPR efficacy.

(C) 2018

Introduction

Advances in emergency medical science have increased the rate of reanimated patients after cardiopulmonary resuscitation (CPR). Al- though different results have been obtained in other studies conducted, the rate of discharge from hospital after CPR is between 1% and 16% in general. Each year, 450,000 sudden cardiac deaths occur in the United States with an average survival rate of less than 5% [1,2].

* Corresponding authors.

E-mail addresses: [email protected] (G. Yilmaz), [email protected] (B. Caglar).

end-tidal CO2 monitoring has been used in modern anes- thesiology and reanimation units since the early 1980s and has been an important component of cardiopulmonary resuscitation and critical patient monitoring in emergency services in recent years. This method has been used to validate endotracheal intubation, to assess CPR efficacy and as a sign of spontaneous circulation as defined in the guidelines [3]. Existing cardiopulmonary resuscitation goals have focused primarily on the chest compressions and ventilation from hemodynamically mea- sured cardiopulmonary resuscitation. Hemodynamic information ob- tained from the measurement of blood flow of large vessels using ultrasonography (USG) allows objective evaluation of the effectiveness of chest compressions [4,5]. There have been studies on the feasibility of

https://doi.org/10.1016/j.ajem.2018.01.022

0735-6757/(C) 2018

measuring carotid blood flow with Doppler USG in evaluating CPR effi- cacy [6]. However, further studies are needed on this subject.

The purpose of this study was to compare the carotid blood flow measurement with the ETCO2 measurement in the evaluation of cardio- pulmonary resuscitation efficacy and to evaluate the usability of this method as an alternative to capnography.

Materials and method

This prospective clinical trial was performed in a 6-month period in 2016 in the Health Sciences University Izmir Bozyaka Training and Re- search Hospital Emergency Medicine Clinic. Before beginning the study, approval was obtained from the Local Ethics Committee.

The study included 32 non-traumatic patients aged between 18 and 65 years comprising those who presented with cardiopulmonary arrest to the emergency service and those who began to suffer from cardiopul- monary arrest during assessment in the emergency service and underwent endotracheal intubation.

Victims of trauma, patients aged b 18 years or N 65 years, pregnant women, patients with carotid stenosis or plaque history (including ca- rotid operation history), patients sustaining return of spontaneous cir- culation ROSC by CPR before the USG measurement, patients who could not be measured within the first 5 cycles of the CPR, patients with gastrointestinal system (GIS) bleeding and hypovolemia such as advanced dehydration were not included in the study.

Cardiopulmonary resuscitation was performed for 2 min with a rate of 100-120 compressions per minute, as described in the American Heart Association (AHA) 2015 Guide to Advanced Cardiac Life Support. Patients in the first 5 cycles of CPR were included in the study. The first 5 cycle measurements were considered to be more accurate because the ETCO₂ value was thought to be affected by rib fractures and impaired thoracic expansion in later cycles of the CPR. The measurements were taken after the 100th chest press of the relevant cycle and recorded when they reached the highest values in that cycle. The concurrent main carotid peak systolic velocity (PSV), end diastolic velocity (EDV) and time dependent mean flow velocity (MNV) values and ETCO2 values during the CPR were recorded for these patients.

Measurement of carotid blood flow was performed by measuring the main PSV, EDV, and MNV in a transverse or longitudinal position with a 10 MHz Linear probe using Esaote brand Mylab 30 gold model USG in the right main carotid tract, lateral to the trachea and medial to the sternocleidomastoidium muscle. The study was carried out by emergency physician with over 3 years of experience who had received advanced USG course training.

The ETCO2 values were measured by means of concurrent EMMA brand capnometer and by the mainstream method and recorded on the data collection form.

Statistical analysis was performed using the SPSS 15.0 program for Windows. The descriptive criteria were presented as mean and percent- age distribution. The conformity of the data to normal distribution was assessed with the Kolmogorov-Smirnov test. The Student’s t-test was used to determine the mean differences between the groups in cases when the parametric conditions were met, and the Mann Whitney U test was used when these conditions were not met. Kruskal-Wallis anal- ysis was applied for more than two groups, the Pearson Chi-Square test was used to compare the differences between the percentages, and the Fisher’s Exact test was used when needed. Pearson Correlation Analysis was used to evaluate the correlations. A value of p b 0.05 was accepted as statistically significant.

Results

The age, gender, comorbid diseases, cardiac rhythm at the time of admission, arrest patterns, carotid measurement values and ETCO2 values of the patients were documented.

Of the 32 patients included in the study, 11 were female and 21 were male. The mean age of the patients was 54.5 +- 12.3 years. The most common comorbid diseases were diabetes mellitus and hyperten- sion (HT). The patients presented at ED most frequently with the com- plaints of asystole (n = 24, 75.0%), followed by pulseless electrical activity (n = 6,18.8%) and ventricular fibrillation (VF) (n = 2, 6.3%), re- spectively. Of the applications, 10 (31.2%) were from within the hospital and 22 (68.8%) were from outside the hospital. In arrest patients from outside the hospital, the mean duration of out-of-hospital arrest was

15.9 +- 11.2 min (median = 10). The values of the patients measured from the carotid during CPR were PSV 67.1 +- 17.3, EDV 16.3 +- 4.5, and MNV 25.5 +- 8.1. The mean ETCO₂ value of the patients was 22.2

+- 8.1. The general characteristics of the 32 patients included in the study are shown in (Table 1).

A statistically significant difference was determined between the in- hospital and out-of-hospital arrests in terms of patient outcome (return of spontaneous circulation = ROSC or Death) (p b 0.05) (Table 2).

No statistically significant correlation was determined when the mean values of PSV, EDV, and MNV were compared in patients with the outcomes of ROSC and death (p N 0.05). The mean ETCO₂ value of the death group (19.1 +- 7.8) was determined to be significantly lower than that of the ROSC group (26.3 +- 6.5) (p b 0.05) (Table 3).

When the correlation between the ETCO₂ values and the PSV, EDV, MNV values is examined, there was a low and positive correlation be- tween the ETCO₂ values and the PSV values, and a very low and positive correlation between the ETCO₂ and the EDV and MNV values. However, none of the correlations were statistically significant (p N 0.05) (Table 4).

A statistically significant positive correlation was determined be- tween the PSV and MNV values (p b 0.05) (Table 4).

A statistically significant positive correlation was determined be- tween the EDV and MNV values (p b 0.05) (Table 4).

As a result of the ROC analysis, it was seen that ETCO₂ values had di- agnostic value in predicting that adequate circulation was ensured, when the PSV value, assumed to provide adequate circulation, was taken as 60 (AUC:0.81. 95% CI: 0.62-0.99. p b 0.05). The recommended limit value for this is 20.5 (with 81% sensitivity, 91% selectivity) (AUC = area under the curve) (Image 2).

Discussion

ETCO₂ measurement is currently used as the gold standard method to show the efficacy of CPR. Another method that can be used in addi- tion to the ETCO₂ measurement is to measure the intra-arterial diastolic

Table 1

General characteristics of the patients

Number (%) Mean +- SD

Mean age (years) 54.5 +- 12.3

Gender

Female 11 (34.4)

Male 21 (65.6)

Additional disease

Diabetes mellitus = DM 10 (31.2)

Hypertension = HT 10 (31.2)

Rhythm at the time of application

Asystole	24 (75.0%)
Pulseless electrical activity	6 (18.8%)
Ventricular fibrillation = VF	2 (6.3%)
Arrest pattern In-hospital	10 (31.2%)
Out-of-hospital	22 (68.8%)
Out-of-hospital arrest stay length	15.9 +- 11.2 (median = 10)
PSV	67.1 +- 17.3
EDV	16.3 +- 4.5
MNV	25.5 +- 8.1
ETCO2	22.2 +- 8.1

Table 2

Comparison of the ROSC and DEATH situations in terms of the place where the arrest occurred.

of 20 mmHg and above and the ROSC rate [14]. As a result of other stud- ies in literature, the 2010 AHA guidelines suggested the use of ETCH₂ monitoring to validate the endotracheal intubation site, to demonstrate

ROSC N (%)

Death N (%)

p Value

the efficacy of chest compressions (b 10 mmHg if insufficient) and as the ROSC criterion (N 40 mmHg for adequate cardiac output) [3]. As new in-

in-hospital arrest 8 (80) 2 (20) 0.008

Out-of-hospital arrest 6 (27.3) 16 (72.7)

Table 3

Comparison of PSV, EDV, MNV and ETCO₂ averages of those with the outcomes of ROSC and Death.

formation in the 2015 AHA guidelines, it was stated that if the ETCO₂ value cannot be increased to 10 mmHg despite 20 min of CPR in intubated patients, termination of the CPR may be considered [15]. The results of the present study show similarity to the data related to ETCO₂ in both the 2010 and the 2015 AHA guidelines.

The mean values of the main carotid artery were found to be 67 (55-106) cm/s for PSV and 18 (12-27) cm/s for EDV in the study by

ROSC mean +- SD		Death p Value Mean +- SD		Adeyinka A. et al., entitled “Applicability of the Measurements of Carotid Artery Blood Flow during CPR”. The PSV values in the same study were
Mean PSV Mean EDV	70.5 +- 17.5 16.3 +- 4.2	64.5 +- 17.1 16.2 +- 4.9	0.51 0.84	close to the PSV values (28.6-178.4) in normal healthy individuals [16, 17]. In the present study, the mean values of the main Carotid arteries
Mean MNV	24.7 +- 9.3	26.1 +- 7.2	0.49	were found to be 67.1 +- 17.3 cm/s for PSV and 16.3 +- 4.5 cm/s for
ETCO2	26.3 +- 6.5	19.1 +- 7.8	0.01	EDV. The values in the present study were similar to those of both
				Adeyinka A. et al., and the PSV values of normal healthy individuals

pressure [7]. Studies have shown that carotid artery blood flow mea- surement is a feasible method for demonstrating the CPR quality [6]. To the best of our knowledge, there has been no study in which carotid blood flow has been assessed with ETCO₂.

The reason for evaluating patients under 65 years of age in the study was because of the increased risk of atherosclerosis in advanced age, im- paired chest elasticity affecting chest compressions with older age, ca- rotid artery stenosis and stroke risk at an older age. Studies conducted to assess the risk of atherosclerosis have shown that 65 years of age should be considered as a threshold value for vascular events such as stroke and acute myocardial infarction [8,9,10,11].

In the present study, the ROSC rate of the in-hospital arrest cases was found to be statistically significantly higher than that of the out-of- hospital arrest cases (p = 0.008). Similarly, Tomruk et al. showed that the ROSC of in-hospital cardiac arrest cases was statistically significantly higher (p b 0.001) [12]. It is considered that the higher rate of reanima- tion in in-hospital arrest cases is due to people witnessing the cases, early onset of chest pressure, faster access to advanced cardiac life sup- port, and quicker detection of underlying causes and Reversible causes. In a study by Cheskes S. et al. of 842 cardiopulmonary arrest cases, it was found that the CPR quality was not affected by out-of-hospital car- diac arrest distance and duration when performed by well-trained health personnel [13]. The present study also showed that the effect of mean duration of out-of-hospital arrest on the ROSC and Death rates

was not statistically significant (p = 0.61).

In the present study, the mean ETCO₂ of those who died (19.1 +- 7.8) was significantly lower than that of patients with the outcome of ROSC (26.3 +- 6.5) (p b 0.05). Lui et al. investigated the predictability of ETCO2 in ensuring ROSC during CPR in 178 non-traumatic out-of-hospital ar- rest patients and based it on two values of 10 mmHg and 20 mmHg for ROSC patients. High specificity was determined between the values

Table 4

Correlation of the ETCO_2. PSV, EDV, MNV values with each other.

	PSV correlation	EDV correlation	MNV correlation	ETCO2 correlation
	coefficient	coefficient	coefficient	coefficient
	(p value)	(p value)	(p value)	(p value)
PSV	-	0.19	0.66	0.31
		(0.28)	(0.01)	(0.09)
EDV	0.19	-	0.39	0.14
	(0.28)		(0.03)	(0.44)
MNV	0.66	0.39	-	0.17
	(0.01)	(0.03)		(0.35)
ETCO2	0.31	0.14	0.17	-
	(0.09)	(0.44)	(0.35)

(28.6-178.4). The present study is important because it shows that ef- fective CPR can ensure a carotid blood flow close to that of a normal healthy individual.

In the present study, correlations between the ETCO₂ values and the PSV, EDV, MNV values measured by main carotid artery Doppler USG were not statistically significant (p N 0.05). This may have been due to a small number of cases or situations that may have affected the ETCO₂ values. If the number of cases were to be increased, it is thought that a statistically significant relationship could be found between these values.

There was a positive and low-level of correlation between the ETCO2 values and PSV values, and a positive and very low-level of correlation between the EDV and MNV values. When the required PSV value for ad- equate circulation was taken as 60 cm/s in the ROC curve, it was deter- mined that ETCO₂ values had diagnostic value in predicting adequate circulation. This relationship between the PSV and ETCO₂ suggests that sufficient carotid blood flow can be achieved with the increased ETCO₂ value during CPR. Thus, carotid blood flow measurement during CPR may be an indirect guide for providing cerebral perfusion. However, the present study showed that the ETCO₂ measurement, the gold stan- dard, was more appropriate in showing CPR efficacy, and carotid Dopp- ler USG measurements were not sufficient in this respect (see also Image 1).

There was a statistically significant positive correlation between the PSV and MNV values (0.66-p = 0.01) and a significant positive correla- tion between the EDV and MNV values (0.39-p = 0.03) when evaluat- ing the adequacy of carotid blood flow. To the best of our knowledge, there has been no previous study in literature which has evaluated the correlation of the carotid measurement values with each other.

The limitations of this study are the low number of cases, the depen- dence of the USG on the individual, the difficulty of measuring during CPR, and the need for a certain period of time to reach and measure USG during CPR. Another limitation is the lack of use of carotid intima media thickness measurement, which is an important marker in the de- termination of vascular incident risk and is used to evaluate the carotid blood flow.

Conclusion

The results of this study showed a low-level of correlation be- tween the PSV and ETCO₂ values. With effective CPR, the results were close to carotid blood flow in normal healthy individuals. How- ever, it was observed that carotid blood flow measurement results during CPR did not show the efficacy of CPR as much as the ETCO₂ values. There is a need for further studies with more and larger series of cases on this topic.

Image 1. USG image showing the carotid Doppler measurement values of a patient during CPR.

Conflict of interest

The limitations of this study are the low number of cases, the depen- dence of the USG on the individual, the difficulty of measuring during CPR, and the need for a certain period of time to reach and measure USG during CPR. Another limitation is the lack of use of carotid intima

Image 2. ROC CURVE BETWEEN THE ETCO₂ AND PSV.

media thickness measurement, which is an important marker in the de- termination of vascular incident risk and is used to evaluate the carotid blood flow.

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