Introduction
Cardiac arrest (CA) is a medical emergency that can lead to death if not treated immediately. Cardiopulmonary resuscitation (CPR) is a lifesaving measure that improves survival rates after CA (Vural et al., 2017). Patients admitted to the intensive care units (ICUs) are at risk of CA due to their critical clinical conditions (Katircioglu et al., 2023). The incidence of ICU-CPR is approximately 40 in 1,000 admissions overall and approximately 10 in 1,000 admissions after the day of ICU admission (Zajic et al., 2022).
Patient monitoring and invasive and semi-invasive treatments are performed in the ICU (Marshall et al., 2017). Due to the breadth of services they provide, ICUs can be likened to small hospitals within larger hospitals that deliver life-saving care to patients in critical condition. This life-saving care results from the interaction among healthcare providers, patients, and medical equipment (Vaillancourt et al., 2011). The ICU is known as the performance control bottleneck in the hospital, and compliance with standards in this unit is of utmost importance. ICU nurses perform many important tasks, one of the most important of which is the management of patients with CA (Seethala et al., 2010).
CA is defined as the cessation of the heart’s pumping function, resulting in the cessation of cardiac output. Following CA, the patient loses consciousness after 15 seconds and breathing stops after 30-60 seconds, and a decreased level of consciousness along with loss of pulse and blood pressure occurs immediately after CA (Morley, 2007). 
CPR is one of the most important in-hospital interventions to save the lives of patients who have suffered cardiopulmonary arrest (Elshal et al., 2021). It is a set of measures that, following cardiopulmonary arrest, attempts to artificially restore blood circulation and respiration until the patient’s spontaneous blood flow returns. This set of measures is known as basic and advanced cardiac life support (Kim et al., 2020).
In the United States, approximately 2.2 million people require CPR annually, of which approximately 350,000 undergo CPR, many of whom die and many others suffer irreversible damage (Anderson et al., 2014). The survival and discharge rate after cardiopulmonary arrest in the United States has been reported to be 16.5% (Go et al., 2013). 
The quality of CPR plays a critical role in improving CPR outcomes and patient survival. Chest compressions are the most important factor in improving the quality of CPR. Chest compressions need to be performed at the correct depth (5–6 cm) and rate (100–120 per minute) (Singh et al., 2022; Jaberi et al., 2011). Therefore, numerous efforts have been made to ensure the effectiveness of chest compressions (Xu et al., 2021; Jung et al., 2022). Chest compressions are the most important element of CPR. Coronary and cerebral blood pressure and ROSC are maximized when quality chest compressions are performed (Savastano et al., 2021). All efforts to provide quality CPR should take precedence over any advanced procedures, such as endotracheal intubation or vascular access (Peberdy et al., 2009). The quality of chest compressions is the most important intervention affecting outcomes. During CA, the quality of chest compressions can be assessed using a variety of methods that are commonly available in hospitals (Morley, 2007). For example, a CPR meter can be placed between the rescuer’s hand and the patient’s chest to check the rescuer’s chest compression performance for correct depth and rate, increasing the number of correct chest compressions (Kim et al., 2020; Picard et al., 2021). The CPR meter, a compact hand-held device developed by Laerdal Medical, has been designed to provide real-time feedback on the quality of chest compressions during CPR. The device measures key parameters, including a compression rate between 100–120 compressions per minute (±3/min), a compression depth of at least 50 mm (±10%), and chest recoil with a release force of less than 2.5 kg. Its dimensions are approximately 154×64×28 mm, allowing easy placement on the patient’s chest during CPR efforts (Buléon et al., 2016). 
Some studies have explored the impact of CPR feedback devices on resuscitation outcomes. A recent systematic review and meta-analysis of randomized controlled trials conducted by Lin et al. found that the use of CPR feedback devices in resuscitation training significantly improved the depth and rate of chest compressions (Lin et al., 2025; Pothitakis et al., 2011). Furthermore, a study by Buléon et al. using a CPR meter in a simulation setting showed a significant improvement in chest compression quality, suggesting its potential to enhance rescuer performance (Buléon et al., 2013). 
While the use of CPR feedback devices has been widely studied, with some research suggesting a positive impact on resuscitation quality and ROSC, other systematic reviews have reported conflicting results or a lack of significant effect on patient outcomes. For instance, in a systematic review and meta-analysis by Wang et al., the pooled results did not confirm the positive effects of the CPR feedback device, meaning that despite improvements in chest compression quality, there was no conclusive evidence of a positive effect of feedback devices on patient survival and neurological outcomes (Wang et al., 2020). This inconsistency in the literature highlights the ongoing need for further research, especially considering the variability in healthcare systems and patient populations across different regions. 
Therefore, this study aimed to determine the effect of real-time CPR feedback using a CPR meter on ROSC in critically ill patients admitted to the ICU.

Materials and Methods 
Design, setting, and sample
This single-blinded, two-arm parallel randomized clinical trial was conducted from January 2023 to October 2024 at the Iraqi-Korean Critical Care Specialty Hospital in Baghdad, Iraq. 
 Participants were patients requiring CPR admitted to the ICU. Inclusion criteria included patients between 18 and 80 years of age with CA of non-traumatic origin. Patients who died or whose resuscitation was terminated by the resuscitation team were excluded from the study. 
Based on the results of Krikscionaitiene et al. (2013), and given a type I error probability of 0.05 and a power of 0.8, the sample size was determined to be 35 patients in each group. To eliminate the effect of the resuscitator’s role, an attempt was made to include nurses in a fixed ICU where they do not usually move to other wards. Also, since this was done across different shifts and patients were randomly assigned to groups, this effect was partially controlled. The recruitment process is shown in Figure 1. 

Patients were initially recruited from the ICU, based on the inclusion criteria. To ensure a robust randomization process and minimize selection bias, a block randomization design with variable block sizes (e.g. 4 and 6) was employed to randomly assign patients to either the intervention or control groups using the Sealed Envelope website. This method helps maintain a balanced number of participants in each group throughout the study Selection bias may be further reduced by using random block sizes and keeping the investigator blind to the size of each block (Efird, 2011). 

Intervention 
The study objectives were first explained to the participants’ families and an informed consent was received by each of them. Then, a checklist of demographic information of eligible patients admitted to the ICU was completed. The experimental group underwent CPR using the relevant device, and the control group received routine care without the use of the feedback device.
ROSC components were measured and evaluated in these patients five times during CPR (5, 10, 15, 20, and 30 minutes after the start of CPR). ROSC refers to the rate of pulse, blood pressure, and ETCO2 (at the beginning of cardiac resuscitation, a capnograph was connected to the patient’s endotracheal tube by the nurse, and the assigned nurse recorded the patient’s ETCO2 levels).

Data collection 
The primary data collection tools used in this study included a CPR meter for the intervention group and a researcher-developed Utstein guideline checklist for recording ROSC key components (blood pressure, pulse, and ETCO2) in both groups. The Utstein style guidelines, developed by International Liaison Committee on Resuscitation (ILCOR), standardized reporting of CA and CPR outcomes (Nolan et al., 2019).
To ensure the validity of the checklist, its content was reviewed and approved by a panel of experts in nursing and emergency medicine at Shahed University, Tehran, Iran. The panel evaluated the checklist’s items for relevance, clarity, and comprehensiveness. Additionally, the irst author trained the assigned nurses to use the checklist and CPR meter to standardize data collection procedures. The inter-rater reliability of the checklist was also assessed among the researchers, yielding a high degree of agreement (Kappa coefficient 0.6-0.8).

Data analysis 
SPSS 24 was used for data analyses. The Kolmogorov-Smirnov test was used to examine the normal distribution of quantitative variables. An independent t-test was used to compare quantitative variables (e.g. age, CPR time) between the two groups, and a chi-square test was used to compare qualitative variables (e.g. gender, underlying disease, heart rhythm when CPR is started, and work shift) between the two groups. To compare the percentage of ROSC between the two groups, the chi-square test was also performed. Additionally, a repeated measures ANOVA was used to examine the mean changes in ROSC components, including systolic blood pressure, pulse rate, and ETCO2, across the intervention period (at 5, 10, 15, 20, and 30 minutes after the start of CPR). At this stage, the analyst was blinded to the data belonging to the intervention and control groups.

Results 
Comparison of demographic and clinical characteristics of the experimental and control groups are summarized in Table 1.


The mean age of the patients in the intervention and control groups was 59.35±6.14 and 58.1±6.09 years, respectively. Statistical analysis revealed no significant difference between the two groups regarding demographic and clinical characteristics (P>0.05). The results of this study showed that the percentage of patients achieving sustained ROSC after 30 minutes of resuscitation was higher in the intervention group (17.55%) compared to the control group (14.35%), indicating that a better outcome was achieved in the intervention group.
Within-group comparison showed a significant difference in the blood pressure, pulse rate, and ETCO2 in both groups at the time interval of five minutes to 30 minutes after the start of CPR. Between-group comparison showed that systolic blood pressure was not significantly different between the intervention and control groups at five minutes (P=0.09); however, a significant difference was observed at minutes 10 (P=0.032), 15 (P=0.017), 20 (P=0.005), and 30 (P=0.001). Pulse rate was not significantly different at 5 minute (P=0.12), but a significant difference was found between the groups at minutes 10 (P=0.035), 20 (P=0.042), 20 (P=0.012), and 30 (P=0.001). ETCO2 was not significantly different between the groups at minutes 5 (P=0.68), 15 (P=0.95), and 20 (P=0.88). However, a significant difference was noted at minutes 10 (P=0.047) and 30 (P=0.001) (Table 2).



Discussion
This study aimed to evaluate the effect of CPR feedback to nurses using a CPR meter on ROSC in patients undergoing CPR admitted to the ICU. According to the findings of the present study, 30 minutes after the start of CPR, ROSC in patients undergoing CPR in the intervention group was superior to that in the control group, as indicated by higher systolic blood pressure and ETCO2 levels.
Effective chest compression remains the cornerstone of successful CPR and is vital for survival and good neurological recovery (Kovacs et al., 2015). As such, the quality of chest compression remains a focal point of international guidelines (Ayala et al., 2014). 
Both compression rate and depth are critically important; compression rates below 75 or above 125 compressions per minute are associated with a decreased likelihood of ROSC, which indicates a poorer outcome. Moreover, the use of proper compression force and depth is essential to minimize CPR-associated injuries (Kovacs et al., 2015).
Several CPR adjunct devices have been developed to improve the consistency and quality of chest compressions (Miller et al., 2014; Pozner et al., 2011). As an example and consistent with the results of the present study, another study showed that the use of the Cardio First Angel™ CPR feedback device improved the adherence to published CPR guidelines and CPR quality, and was associated with increased rates of ROSC (Vahedian-Azimi et al., 2016). 
A study by Lampe et al. at Northwell Health established a time-dependent function correlating carotid blood flow during CPR with the response to varying chest compressions. The aim of this study was to optimize CPR parameters in real time and thus maximize carotid blood flow, by predicting the carotid blood flow generated by subsequent chest compressions (Lampe et al., 2020). 
Currently, patient outcomes after CA remain poor. We found that the average ROSC increased, consistent with previous studies reporting rates between 13% and 72%. Breuer-Kaiser et al. showed that although the use of CPR feedback devices is not routine, their use is associated with improved ROSC rates. However, no significant effect was found on ROSC at hospital admission, highlighting the need for further research (Breuer-Kaiser et al., 2024).
One of the main limitations of this study is the relatively small sample size and its conduction within a single clinical setting, which may limit the generalizability of the findings. In the intervention group, adherence to cardiac resuscitation guidelines significantly increased with the use of the CPR meter, which likely reflects the positive impact of this device. However, the possible role of other unmeasured factors in this improvement cannot be entirely ruled out. Future studies should aim to control for these variables and further clarify the precise effect of the device.

Conclusion
The findings of this study highlight the potential benefits of incorporating CPR feedback devices into clinical practice to enhance the quality of resuscitation efforts. By improving adherence to CPR guidelines and supporting timely physiological assessments, these devices can contribute to better patient management during CA. Future research should focus on larger, multicenter trials to confirm these benefits and to evaluate long-term patient outcomes, thereby guiding evidence-based implementation of CPR feedback technology.

Ethical Considerations
Compliance with ethical guidelines
This research was approved by the Ethics Committee of University of Baghdad, Baghdad, Iraq (code: Ref18843, 14.01.2024). The patients’ families were informed about the study’s aim, the voluntary nature of patient participation, and the right to withdraw from the study at any time. Informed consent was obtained from the legal guardian of each patient before data collection. All steps of this study involving human participants were conducted in accordance with the ethical principles of the Declaration of Helsinki.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.

Authors' contributions
Conceptualization: Bahman Aghaie, Alice Khachian, Alaa Jawad Kadhim, Ali Khosravi Zad, and Zahra Hezbiyan; Methodology and supervision: Bahman Aghaie, Alice Khachian, and Alaa Jawad Kadhim; Validation: Bahman Aghaie, Alice Khachian, Alaa Jawad Kadhim, Mina Abolfazli, Reza Norouzadeh, and Zahra Hezbiyan; Investigation: Bahman Aghaie, Alice Khachian, Alaa Jawad Kadhim, Mina Abolfazli, and Zahra Hezbiyan; Visualization: Bahman Aghaie, Alice Khachian, Alaa Jawad Kadhim, and Mina Abolfazli; Resources: Reza Norouzadeh; Writing the original draft: Bahman Aghaie, Alice Khachian, Alaa Jawad Kadhim, Mina Abolfazli, and Ali Khosravi Zad; Review and editing: Mina Abolfazli and Reza Norouzadeh; Final approval: All authors.

Conflict of interest
The authors declared no conflict of interest.

Acknowledgments
The authors are grateful to the participants who took part in this study.


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