Signa Vitae. 2023; 19(6): 67-72. doi: 10.22514/sv.2023.102
Original Research

Femoral artery collapse ratio as an indicator of chest compression quality during cardiopulmonary resuscitation in a porcine cardiac arrest model

Mun Ki Min1, Dae Sup Lee1, Min Jee Lee1, Mo Se Chun1, Seung Woo Shon1, Tae Kyu Hyun1, Ji Ho Ryu1,*,

1Department of Emergency Medicine, Pusan National University School of Medicine, 50612 Busan, Republic of Korea

*Corresponding Author(s):pnuem@pusan.ac.kr (Ji Ho Ryu)

History Submitted: 08 December 2022 | Accepted: 01 March 2023 | Published: 08 November 2023
Copyright:  ©2023  The Author(s). Published by MRE Press.
This is an open access article under the CC BY 4.0 license (https://creativecommons.org/licenses/by/4.0/).

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Abstract

Cardiopulmonary resuscitation (CPR) quality is crucial for improving patient survival rates after cardiac arrest. This study aimed to investigate the usefulness of femoral artery collapse ratio (systolic diameter/diastolic diameter ratio) measurement using M-mode ultrasound versus end-tidal carbon dioxide (ETCO2) for the assessment of high-quality CPR in a porcine cardiac arrest model. A total of 10 male mongrel pigs (age range, 16–20 weeks; weight, 45–50 kg) were used. After anesthesia, the carotid artery was dissected and exposed. The animals were instrumented with an arterial catheter in the exposed carotid artery to monitor arterial blood pressure. Cardiac arrest was induced by injecting potassium chloride (KCl, 40 equivalents of weight). The animals underwent chest compression using a mechanical device, and the chest compression depth and ETCO2 were measured using a defibrillator. To obtain hemodynamic information, two investigators performed an ultrasound examination on both femoral arteries. One examiner measured the femoral peak systolic velocity (PSV), while the other measured the diameters of the femoral artery (systolic diameter and diastolic diameter) in a transverse or longitudinal position using the M-mode of the linear ultrasound probe. As the compression depth increased, ETCO2, femoral artery diameter, collapse ratio (systolic diameter/diastolic diameter), and blood flow increased; however, PSV decreased. The ETCO2 and collapse ratio were positively correlated. The femoral artery collapse ratio, measured using the M-mode ultrasound, could be an alternative and simple method to evaluate high-quality CPR.

Keywords:Porcine;Ultrasound;Chest compression;Carbon dioxide;Cardiopulmonary resuscitation
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Cite this article

Mun Ki Min, Dae Sup Lee, Min Jee Lee, Mo Se Chun, Seung Woo Shon, Tae Kyu Hyun, Ji Ho Ryu. Femoral artery collapse ratio as an indicator of chest compression quality during cardiopulmonary resuscitation in a porcine cardiac arrest model. Signa Vitae. 2023; 19(6): 67-72. doi: 10.22514/sv.2023.102

1. Introduction

High-quality cardiopulmonary resuscitation (CPR) is an important factor in improving the survival rate of patients with cardiac arrest. Exhaled end-tidal carbon dioxide (ETCO2) and diastolic arterial pressure monitoring are used to confirm high-quality CPR; therefore, the American Heart Association and European Resuscitation Council guidelines recommend monitoring of these parameters for high-quality CPR after endotracheal intubation [1, 2, 3].

If the partial pressure of exhaled end-tidal carbon dioxide (PETCO2) is maintained at ≥10 mmHg or diastolic arterial pressure is maintained at ≥20 mmHg during CPR, there is a high chance of return of spontaneous circulation (ROSC) [1, 2].

Currently, ETCO2 measurement is a non-invasive and simple method for estimating organ perfusion during CPR. In addition, ETCO2 reflects cardiac output and the effectiveness of chest compression in CPR and has a positive correlation with the cardiac index, coronary and cerebral perfusion pressure, and ROSC [4, 5, 6, 7, 8, 9, 10, 11]. Ultrasound is also useful for differentiating the cause of shock or cardiac arrest during CPR in the intensive care unit (ICU) or emergency department (ED). Therefore, we thought that ultrasound could be an alternative to the quality of CPR and thus compared ETCO2 and ultrasound to evaluate high-quality CPR in a porcine cardiac arrest model. The hypothesis was that the quality of chest compression could be assessed by measuring the hemodynamic parameters in the femoral artery using ultrasound. Moreover, ETCO2 is believed to be correlated with the femoral artery collapse ratio (systolic diameter/diastolic diameter ratio) during chest compressions. Therefore, this study aimed to compare ETCO2 verus hemodynamic parameters (i.e., systolic diameter, diastolic diameter, peak velocity, collapse ratio) measured using ultrasound to evaluate high-quality CPR in a porcine cardiac arrest model. To the best of our knowledge, this is the first study that does not have similar findings; therefore, its findings are novel and of significance.

2. Materials and methods

2.1 Anesthesia/instrumentation

A total of 10 male mongrel pigs (aged 16–20 weeks, weighing 45–50 kg) were premedicated and anesthetized with intramuscular injections of alphaxalone (2 mg/kg) and xylazine (2 mg/kg). After intubation, anesthesia was maintained with isoflurane inhalation (2–3%), and vecuronium (0.1 mg/kg) was injected via the auricular vein. Volume-controlled ventilation was provided at a tidal volume (Vt) of 6–7 mL/kg.

After anesthesia, the carotid artery was dissected and exposed. The animals were instrumented with an arterial catheter in the exposed carotid artery to monitor the arterial blood pressure (BeneVision N 15 monitor, Mindray, China). Electrocardiography (ECG) and PETCO2 were monitored using a monitor defibrillator (X series; ZOLL Medical, Chelmsford, MA, USA). Chest compression depth was measured using a defibrillator with an integral accelerometer-based chest compression sensor. Fasting animals were given an initial fluid bolus of 20 mL/kg warm balanced electrolyte solution and, then, warm normal saline was administered at 5–10 mL/kg/h.

To obtain hemodynamic information, one investigator performed an ultrasound examination of the femoral arteries before cardiac arrest, and ultrasound was maintained during arrest.

2.2 Intervention

Cardiac arrest was induced by injecting potassium chloride (KCl, 40 equivalents of weight). After injection of KCl, the ventilator was disconnected. Arrest was confirmed by ECG monitoring and femoral blood flow using ultrasound performed before cardiac arrest.

The animals underwent mechanical chest compression using the Easy Pulse® device (Schiller, Medizintechnik GMBH, Feldkirchen, Germany). During chest compressions, the pigs were ventilated with a guideline-based ventilation regimen (Vt-8–10 mL/kg, fraction of inspired oxygen (FiO2)-1.0, and respiratory rate-10 breaths per minute (min)). CPR was continued for 8 min, and 1 mg epinephrine was administered every 4 min. If ventricular fibrillation continued after 4 min, defibrillation (200 J, biphasic) was performed.

2.3 Measurements and statistical analysis

Chest compression depth was measured using a defibrillator with an integral accelerometer-based chest compression sensor (X series; ZOLL Medical, Chelmsford, MA, USA). ECG and PETCO2 were measured using a monitor defibrillator.

Systolic blood pressure (SBP), mean blood pressure (MBP), and diastolic blood pressure (DBP) were measured using the arterial catheter in the exposed carotid artery. To obtain hemodynamic information, two investigators performed ultrasound examinations of both femoral arteries. One examiner measured the femoral peak systolic velocity (PSV), while the other measured diameters of the femoral artery (diameter during systole (SD) and diastole (DD)) in transverse or longitudinal positions using a 10 M-Hz linear probe and Sonosite brand X-porte model ultrasound. The systolic and diastolic diameters were measured using M-mode ultrasound (Fig. 1). The diameter ratio (SD/DD) was calculated to measure the degree of change in the diameter. Two examiners measured femoral blood flow during cardiac arrest (from 1 min before the arrest). The volume flow rate refers to the volume of fluid that passes per unit time and is defined as the product of velocity and cross-sectional area. Therefore, the blood flow rate was calculated by multiplying the PSV and the cross-sectional area of the femoral artery during systole (Flow = PSV × (SD/2)2).

Measurement of systolic and diastolic diameter of femoral artery by M-mode ultrasound. SD, systolic diameter; DD, diastolic diameter.

Fig. 1.Measurement of systolic and diastolic diameter of femoral artery by M-mode ultrasound. SD, systolic diameter; DD, diastolic diameter.

PSV, diameter, and PETCO2 were measured for the first 2 min. The thoracic pressure decreased due to several factors (rib fracture, impaired thoracic expansion, etc.) in later cycles of CPR, which may have affected the PSV, diameter, flow, and PETCO2. CPR was performed for 8 min to check ROSC; however, there was no ROSC.

Sample sizes were calculated based on a correlation analysis between compression depth, PSV, and blood flow rate. The sample size was 138 on calculation with a correlation coefficient of 0.3, α error of 0.5, and power of 0.95, based on previous studies. As chest compressions were performed approximately 200 times and CPR was performed for 2 min, 10 pigs were considered to be a sufficient sample size for verification.

Data were analyzed using the PASW statistical software package for Windows, version 27 (IBM Corp., Armonk, NY, USA), and standard descriptive summaries appropriate for the underlying distribution of the variables were calculated. The normality of the distribution of continuous variables was assessed using the Shapiro-Wilk test. To determine the relationship between compression depth and blood flow, a correlation analysis was performed with PSV, femoral artery diameter, flow rate, and depth. To determine the relationship between PETCO2 and blood flow, a correlation analysis was performed with PSV, femoral artery diameter, flow rate, and PETCO2. Multivariate linear regression was performed for the statistically significant variables. As the variables did not have a normal distribution, a correlation analysis was performed using bivariate analysis with Spearman’s correlation coefficient. Statistical significance was defined as a two-tailed p-value of < 0.05.

3. Results

A total of 10 experiments were performed. The chest compression depth was 3.29 ± 0.52 cm and SBP, MBP, and DBP were as follows: 88.86 ± 33.03, 41.14 ± 13.16, and 17.67 ± 13.16 mmHg, respectively. PETCO2 was 33.01 ± 16.77 mmHg. PSV was 59.29 ± 26.46 cm s−1, SD was 2.16 ± 1.02 cm, DD was 1.02 ± 0.92 cm, and collapse ratio (SD/DD ratio) was 2.78 ± 1.55. The blood flow rate was 76.60 ± 65.33 cm3/s (Table 1).

In the correlation analysis, as the compression depth increased, PETCO2, femoral artery diameter, femoral artery collapse ratio, and blood flow increased; however, the PSV decreased. Depth affected the diameter and PSV. PSV decreased because of the enlarged systolic diameter (Table 2). As the diameter increased, the PSV decreased; however, the blood flow rate increased owing to the enlarged diameter. As PETCO2 increased, the PSV, systolic diameter, and blood flow rate decreased. As the collapse ratio (SD/DD) and compression depth increased, the ETCO2 increased (Tables 2 and 3).

Multivariable linear regression analysis revealed that the collapse ratio and blood pressure (SBP, MBP, DBP) were correlated with ETCO2 (R = 0.959, R2adj = 0.916, p < 0.001) (Table 4).

Table 1.General characteristics.
VariablesMean ± SD*
Compression depth (cm)3.29 ± 0.52
Arterial blood pressure (mmHg)
SBP88.86 ± 33.03
MBP41.14 ± 13.16
DBP17.67 ± 13.16
PETCO2 (mmHg)33.01 ± 16.77
Peak systolic velocity (cm/s)59.29 ± 26.46
Systolic diameter (SD, cm)2.16 ± 1.02
Diastolic diameter (DD, cm)1.02 ± 0.92
Collapse Ratio (SD/DD)2.78 ± 1.55
Blood flow rate (cm3/s)76.60 ± 65.33
SD*, standard deviation; SBP, systolic blood pressure; MBP, mean blood pressure; DBP, diastolic blood pressure; PETCO2 partial pressure of end-tidal carbon dioxide.
Table 2.Correlation with depth and variables.
VariableSpearman’s correlation coefficientp-value
PETCO20.507<0.001
Peak systolic velocity−0.341<0.001
Systolic diameter (SD)0.465<0.001
Diastolic diameter (DD)0.1100.002
Collapse ratio (SD/DD)0.176<0.001
Blood flow rate0.1250.001
PETCO2, partial pressure of end-tidal carbon dioxide.
Table 3.Correlation with ETCO2 and variables.
VariableSpearman’s correlation coefficientp-value
Compression depth0.507<0.001
Peak systolic velocity−0.158<0.001
Systolic diameter (SD)−0.0260.554
Diastolic diameter (DD)−0.347<0.001
Collapse ratio (SD/DD)0.386<0.001
Blood flow rate−0.203<0.001
SBP−0.210<0.001
MBP0.240<0.001
DBP0.1040.048
ETCO2, end-tidal carbon dioxide; SBP, systolic blood pressure; MBP, mean blood pressure; DBP, diastolic blood pressure.
Table 4.Multivariable linear regression for predicting ETCO2.
VariableB95% CIβtp-value
Compression depth1.898−0.269–4.0650.0431.7250.086
Peak systolic velocity−0.018−0.071–0.0356−0.020−0.6740.501
Systolic diameter (SD)0.594−2.798–3.9870.0420.3450.345
Diastolic diameter (DD)1.096−2.825–5.0170.0890.5510.582
Collapse ratio (SD/DD)7.9357.208–8.6620.99321.492<0.001
SBP−0.948−1.275–−0.621−1.337−5.713<0.001
MBP2.6031.651–3.5561.2105.386<0.001
DBP−1.674−2.336–−1.012−1.277−4.981<0.001
*R2adj = 0.916, p < 0.001. ETCO2, end-tidal carbon dioxide; CI, confidence interval; SBP, systolic blood pressure; MBP, mean blood pressure; DBP, diastolic blood pressure.

4. Discussion

As mentioned in the Introduction section, ETCO2 measurement is essential for assessing the CPR quality. Several studies have been conducted on ETCO2 during CPR in animal models. In one study, ETCO2 was significantly lower during right lung ventilation than during ventilation of both the lungs and ventilation of the left lung [12]. Another study reported that ETCO2 during extracorporeal cardiopulmonary resuscitation may be predictive of the extent of brain or kidney damage [13, 14].

Several studies have examined the relationship between ETCO2 and ROSC. According to one study, the higher the ETCO2, the higher was the probability of ROSC in patients with out-of-hospital cardiac arrest [15]. Another study reported that the probability of ROSC increases when ETCO2-guided algorithm CPR is performed [16]. However, ROSC was not associated with an increased ventilation rate during CPR, as reported in a previous study [17]. In our study, the association between ETCO2 and ROSC was not evaluated because cardiac arrest takes a long time in the asphyxial model, and porcine vessels tend to collapse easily due to their relatively small diameter compared to human vessels, making it difficult to measure the vessel. Therefore, cardiac arrest was induced by injecting KCl. It was believed that ROSC would not be possible in a model of cardiac arrest caused by KCl administration.

Point-of-care ultrasound (POCUS) is routinely used as a diagnostic screening device in acute care conditions, such as blunt trauma, undifferentiated shock in the ICU or ED, and assessment of reversible causes of cardiac arrest and ROSC during CPR [1, 2, 18, 19]. However, one systematic review reported uncertainty in the diagnostic accuracy of POCUS for identifying reversible causes of cardiac arrest and suggested that further study is needed [20].

Several studies have used the carotid artery to compare CPR quality using POCUS. Two studies reported that sonographic blood flow measurement of the carotid artery is a non-invasive and useful method for ensuring high-quality CPR during chest compression [21, 22]; however, one study reported a weak correlation between PSV and ETCO2 values in CPR [23].

Sonographic measurements of the carotid artery may interfere with CPR to a certain extent. Therefore, we believe that the femoral artery is an appropriate site for sonographic measurement without CPR interruption. Furthermore, as the diameter of the blood vessel changes with the amount of blood flow during chest compression, the femoral artery collapse ratio can be an important method of assessment; thus, it can be used to evaluate high-quality CPR. There is one comparative study on manual palpation and femoral artery Doppler ultrasound as a method to determine ROSC [24]. However, this is the first study to evaluate CPR quality using sonographic measurement of the femoral artery diameter. ETCO2, systolic and diastolic diameter, femoral collapse ratio, and blood flow rate were positively correlated with the compression depth, whereas the PSV was negatively correlated. We judged that there was a negative correlation between the PSV and better chest compression, greater blood flow rate, increased femoral artery diameter, and decreased PSV. The compression depth, collapse ratio, MBP, and DBP were positively correlated with ETCO2 in Spearman’s correlation; however, DBP was negatively correlated in multivariable regression. There may be problems with the number of samples and technical measurement of the device, but the exact reason is unknown, and additional research is needed in future.

We used a mechanical chest compression device to maintain regular chest compression rate and depth. The animals underwent mechanical chest compressions using the Easy Pulse®device. This device is a mixed-type combination of piston and compression band. Mean chest compression depth was 3.29 ± 0.52 cm in our study. This is attributed to differences in the anatomy of the chest compared with that of humans and the type of mechanical compression device used. Several CPR guidelines have recommended a chest compression depth of 5–6 cm [1, 25]. The chest compression depth in our study was relatively shallow compared with that mentioned in the recommended guidelines. These guidelines emphasize the role of only compression depth of the sternum for chest compression. In the present study, deeper compression of the sternum may not have increased the intrathoracic pressure or blood flow. Considering this, it may be necessary to discuss only the compression depth of the sternum. One porcine model of cardiac arrest reported that relatively shallow chest compressions have similar hemodynamic effects with fewer complications than standard compression depth [26].

This study has some limitations. First, the results from this study are not directly applicable to patients with clinical cardiac arrest because this study was conducted on animals. Second, spontaneous circulation was not restored because the administration of KCl induced cardiac arrest. However, our study is of great importance because it is the first study to evaluate high-quality CPR using a method that has never been examined before.

5. Conclusions

The femoral artery collapse ratio measured using the M-mode of POCUS could be an alternative and simple method for evaluating high-quality CPR. Further research in humans is needed in the future for its application to clinical settings.

Abbreviations

DBP, Diastolic blood pressure; DD, Diastolic diameter; ECPR, Extracorporeal cardiopulmonary resuscitation; ED, Emergency department; ICU, Intensive care unit; MBP, Mean blood pressure; POCUS, Point-of-care ultrasound; PSV, Peak systolic velocity; ROSC, Return of spontaneous circulation; SBP, Systolic blood pressure; SD, Systolic diameter.

Availability of data and materials

The data used to support the findings of this study are available from the corresponding author upon request.

Author contributions

JHR—Conceptualization, supervision; MSC and DSL—methodology; MJL—validation; TKH, MKM and MSC—formal analysis; JHR, MKM, MSC and SWS—investigation; MKM—data curation; MKM and JHR—writing-original draft preparation; SWS and JHR—writing-review and editing. All authors have read and agreed to the published version of the manuscript.

Ethics approval and consent to participate

This study was approved by Pusan National University Yangsan Hospital (PNUYH)’s the Institutional Animal Care and Use Committee (approval no. 2021-031-A1C0(0)).

Acknowledgment

We would like to thank Editage (https://www.editage.co.kr/) for English language editing.

Funding

This research was funded by the National Research Foundation of Korea (NRF) grant, funded by the Korean government (MSIT), grant number NRF-2021R1F1A1063029.

Conflict of interest

The authors declare no conflict of interest.

References

Merchant RM, Topjian AA, Panchal AR, Cheng A, Aziz K, Berg KM, et al. Part 1: Executive summary: 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2020; 142: S337–S357.

[Google Scholar]

Soar J, Böttiger BW, Carli P, Couper K, Deakin CD, Djärv T, et al. European resuscitation council guidelines 2021: adult advanced life support. Resuscitation. 2021; 161: 115–151.

[Google Scholar]

Link MS, Berkow LC, Kudenchuk PJ, Halperin HR, Hess EP, Moitra VK, et al. Part 7: Adult advanced cardiovascular life support: 2015 American Heart Association guidelines update for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2015; 132: S444–S464.

[Google Scholar]

Sandroni C, De Santis P, D’Arrigo S. Capnography during cardiac arrest. Resuscitation. 2018; 132: 73–77.

[Google Scholar]

Weil MH, Bisera J, Trevino RP, Rackow EC. Cardiac output and end-tidal carbon dioxide. Critical Care Medicine. 1985; 13: 907–909.

[Google Scholar]

Sanders AB, Atlas M, Ewy GA, Kern KB, Bragg S. Expired PCO2 as an index of coronary perfusion pressure. The American Journal of Emergency Medicine. 1985; 3: 147–149.

[Google Scholar]

Lewis LM, Stothert J, Standeven J, Chandel B, Kurtz M, Fortney J. Correlation of end-tidal CO2 to cerebral perfusion during CPR. Annals of Emergency Medicine. 1992; 21: 1131–1134.

[Google Scholar]

Kolar M, Križmarić M, Klemen P, Grmec S. Partial pressure of end-tidal carbon dioxide successful predicts cardiopulmonary resuscitation in the field: a prospective observational study. Critical Care. 2008; 12: R115.

[Google Scholar]

Sheak KR, Wiebe DJ, Leary M, Babaeizadeh S, Yuen TC, Zive D, et al. Quantitative relationship between end-tidal carbon dioxide and CPR quality during both in-hospital and out-of-hospital cardiac arrest. Resuscitation. 2015; 89: 149–154.

[Google Scholar]

Murphy RA, Bobrow BJ, Spaite DW, Hu C, McDannold R, Vadeboncoeur TF. Association between prehospital CPR quality and end-tidal carbon dioxide levels in out-of-hospital cardiac arrest. Prehospital Emergency Care. 2016; 20: 369–377.

[Google Scholar]

Touma O, Davies M. The prognostic value of end tidal carbon dioxide during cardiac arrest: a systematic review. Resuscitation. 2013; 84: 1470–1479.

[Google Scholar]

Ryu DH, Jung YH, Jeung KW, Lee BK, Jeong YW, Yun JG, et al. Effect of one-lung ventilation on end-tidal carbon dioxide during cardiopulmonary resuscitation in a pig model of cardiac arrest. PLOS ONE. 2018; 13: e0195826.

[Google Scholar]

Ölander C, Vikholm P, Lindblom R, Schiller P, Hellgren L. Extracorporeal cardiopulmonary resuscitation guided by end-tidal carbon dioxide—a porcine model. Journal of Cardiovascular Translational Research. 2022; 15: 291–301.

[Google Scholar]

Ölander C, Vikholm P, Schiller P, Hellgren L. End-tidal carbon dioxide impacts brain and kidney injury in experimental extracorporeal cardiopulmonary resuscitation (ECPR). Shock. 2021; 55: 563–569.

[Google Scholar]

Javaudin F, Her S, Le Bastard Q, De Carvalho H, Le Conte P, Baert V, et al. Maximum value of end-tidal carbon dioxide concentrations during resuscitation as an indicator of return of spontaneous circulation in out-of-hospital cardiac arrest. Prehospital Emergency Care. 2020; 24: 478–484.

[Google Scholar]

O’Brien CE, Santos PT, Kulikowicz E, Adams S, Lee JK, Hunt EA, et al. Use of an end-tidal carbon dioxide-guided algorithm during cardiopulmonary resuscitation improves short-term survival in paediatric swine. Resuscitation Plus. 2021; 8: 100174.

[Google Scholar]

Ruiz de Gauna S, Gutiérrez JJ, Ruiz J, Leturiondo M, Azcarate I, González-Otero DM, et al. The impact of ventilation rate on end-tidal carbon dioxide level during manual cardiopulmonary resuscitation. Resuscitation. 2020; 156: 215–222.

[Google Scholar]

Stengel D, Leisterer J, Ferrada P, Ekkernkamp A, Mutze S, Hoenning A. Point-of-care ultrasonography for diagnosing thoracoabdominal injuries in patients with blunt trauma. Cochrane Database of Systematic Reviews. 2018; 12: CD012669.

[Google Scholar]

Stickles SP, Carpenter CR, Gekle R, Kraus CK, Scoville C, Theodoro D, et al. The diagnostic accuracy of a point-of-care ultrasound protocol for shock etiology: a systematic review and meta-analysis. CJEM. 2019; 21: 406–417.

[Google Scholar]

Reynolds JC, Nicholson T, O’Neil B, Drennan IR, Issa M, Welsford M. Diagnostic test accuracy of point-of-care ultrasound during cardiopulmonary resuscitation to indicate the etiology of cardiac arrest: a systematic review. Resuscitation. 2022; 172: 54–63.

[Google Scholar]

Koch M, Mueller M, Warenits AM, Holzer M, Spiel A, Schnaubelt S. Carotid artery ultrasound in the (peri-)arrest setting—a prospective pilot study. Journal of Clinical Medicine. 2022; 11:469.

[Google Scholar]

Adedipe AA, Fly DL, Schwitz SD, Jorgenson DB, Duric H, Sayre MR, et al. Carotid doppler blood flow measurement during cardiopulmonary resuscitation is feasible: a first in man study. Resuscitation. 2015; 96: 121–125.

[Google Scholar]

Yilmaz G, Silcan M, Serin S, Caglar B, Erarslan Ö, Parlak İ. A comparison of carotid doppler ultrasonography and capnography in evaluating the efficacy of CPR. The American Journal of Emergency Medicine. 2018; 36: 1545–1549.

[Google Scholar]

Schwartz BE, Gandhi P, Najafali D, Gregory MM, Jacob N, Helberg T, et al. Manual palpation vs. femoral arterial doppler ultrasound for comparison of pulse check time during cardiopulmonary resuscitation in the emergency department: a pilot study. The Journal of Emergency Medicine. 2021; 61: 720–730.

[Google Scholar]

Olasveengen TM, Semeraro F, Ristagno G, Castren M, Handley A, Kuzovlev A, et al. European resuscitation council guidelines 2021: basic life support. Resuscitation. 2021; 161: 98–114.

[Google Scholar]

Liang L, Li Z, Chen R, Liu S, Zhou T, Jiang L, et al. Compression depth of 30 mm has similar efficacy and fewer complications versus 50 mm during mechanical chest compression with miniaturized chest compressor in a porcine model of cardiac arrest. Journal of Thoracic Disease. 2021; 13: 5788–5798.

[Google Scholar]