Introduction
Generally, when first responders think of an out-of-hospital cardiac arrest (OHCA), they typically imagine optimal lighting conditions, timing, or resources. In reality, OHCA can occur at any time and in the most unexpected places. For this reason, the European Resuscitation Council, (ERC; Niel, Antwerpen, Belgium) within its recommendations Reference Olasveengen, Semeraro and Ristagno1 dedicates a chapter to special circumstances, such as drowning. Reference Lott, Truhlář and Alfonzo2
However, there doesn’t seem to be any recommendations for conducting cardiopulmonary resuscitation (CPR) under low-light conditions, as may occur at night. Considering that approximately 50% of the time world-wide is spent in darkness, this is a relevant issue globally. It is also unclear in what situations an emergency could occur and whether lifeguards could be the first responders to a cardiac arrest at night. The truth is, aquatic spaces are a viable environment for OHCA occurrences, and this is not limited to daytime hours. In recent years, lifeguards also monitor events during the night (eg, beach concerts or nighttime pool parties at hotels), and as a result, they may face the challenge of performing CPR under deficient or even non-existent lighting conditions. An important factor for the prognosis of a person with cardiac arrest is the quality of CPR. Reference Gräsner, Wnent and Herlitz3
As it is unknown whether training and preparation under optimal conditions transfer to situations of low visibility, the aim of this study was to evaluate the feasibility of performing CPR at night under two different conditions, in darkness with ambient light and with the additional illumination of a headlamp, as well as to determine the quality of the maneuver.
Materials and Methods
Design
This was a crossover, randomized pilot study in a simulated scenario.
Participants
University students from the Bachelor’s Degree in Physical Activity and Sport Sciences at the University of Vigo (Spain) were invited to participate. As inclusion criteria, all participants were required to hold official lifeguard certification and have undergone CPR training in the month prior to their participation in the study. The lifeguard certification, in addition to addressing aspects related to drowning prevention and rescue techniques, also covers prehospital treatment using resuscitation techniques. Before participating in the study, each subject signed an informed consent form. This study complies with the ethical principles of the Helsinki Declaration and has been approved by the Ethics Committee of Faculty of Education and Sport Sciences of the University of Vigo (code 11-170123).
Procedures
Rolling Refresh—All participants underwent a 30-minute CPR re-training session based on the current recommendations of the ERC Reference Olasveengen, Semeraro and Ristagno1 utilizing a pocket mask for ventilation. Furthermore, during the three months prior to the study, all participants had undergone at least one weekly, one-hour CPR training session.
CPR Tests at Night Under Different Lighting Conditions—Each lifeguard performed two five-minute CPR tests, also based on the ERC guidelines Reference Olasveengen, Semeraro and Ristagno1 following a 30:2 ratio for chest compressions (CCs) to ventilation. The ventilation was administered using mouth-to-pocket mask technique (Laerdal; Stavanger, Norway). The order of the tests was determined by block-controlled randomization (lifeguards were grouped into blocks of four and were randomly assigned balanced sequences [ABBA, BAAB, ABAB, or BABA] using the RAND function in Excel [Microsoft Corp.; Redmond, Washington USA]), and both tests were conducted in the darkness of the night with a 30-minute break between them to prevent fatigue (Figure 1). All tests were conducted on the same day at Mogor Beach, Pontevedra, Spain (Figure 2). The actual light intensity was not measured.
Flow Chart Design.
Abbreviation: CPR, cardiopulmonary resuscitation.
Cardiopulmonary Resuscitation (CPR) Tests and Their Location.
Abbreviation: CPR, cardiopulmonary resuscitation.
The conditions were (Figure 2):
-
HeadlampCPR – Total darkness with headlamp illumination. The lifeguard wears a headlamp (Headlight Cready; Barcelona, Spain) on their forehead in the lifeguard station, which is in complete darkness.
-
NightCPR – Natural nighttime environment at the beach, with the ambient light provided by the moon and a lamppost, without additional lighting from the lifeguard, in the external area of the lifeguard station.
Variables
The quality of resuscitation was recorded using the QCPR Training App (Laerdal) connected to the Resusci Anne QCPR manikin (Laerdal). The quality parameters of CPR are based on the current guidelines of ERC Reference Olasveengen, Semeraro and Ristagno1 : CCs at five-to-six centimeters depth, rate of 100-120 CCs/minute, with complete chest recoil, and no CC interruptions. Effective ventilations are 500-600ml of air. The ratio was 30:2 (CC:ventilations). The variables were: quality of CPR for each participant (%); number of CCs (#); mean depth (mm); mean rate (CCs/minute), and number of effective ventilations (#), as assessed with the QCPR Training App. At the end of each test, subjective effort perception was assessed with the modified Borg’s scale of 10 points. Reference Borg4
Data Analysis
Statistical analysis was conducted with the software IBM SPSS Statistics (v. 21 for Windows; IBM Corp.; Armonk, NY, USA). Shapiro-Wilk test was used to check the assumption of normality of the data distribution for the quantitative variables, considering that a variable followed a normal distribution if the value of the test was greater than 0.05. The data were described using the median and interquartile range (IQR). As each participant performed the simulation with and without the headlamp, comparisons between the two groups were analyzed by mean difference (MD) as calculated for paired variables. Variables with data following a normal distribution were compared based on the resuscitation technique using a paired t-test for related samples. For all comparisons, effect sizes (ES) and its 95% confidence interval (CI) were calculated in accordance with Cohen’s d test. For variables whose data did not follow a normal distribution, comparisons were made based on the test using the Wilcoxon rank sum test for related samples. In the case of significant outcomes, effect size and its 95% confidence interval were calculated in accordance with Rosenthal’s r test. Effect size was classified as follows when Cohen’s d test was performed: trivial (< 0.2), small (0.2 - 0.5), moderate (0.5 - 0.8), large (0.8 - 1.3), and very large (≥ 1.3). Effect size was classified as follows when Rosenthal’s r test was performed: small (0.1 - 0.3), moderate (0.3 - 0.5), and large (> 0.5). Categorical variables were described using absolute and relative frequencies, with significance defined as P = .05 for all outcomes.
Results
The participants were 19 lifeguards (13 male; 68%) with a median age of 21 years (IQR: 20 – 22), a weight of 73kg (IQR: 61 – 80), and a height of 1.73m (IQR: 1.70 – 1.76).
The Shapiro-Wilk test showed that the variables number of CCs (NightCPR: P = .13; HeadlampCPR: P = .31); mean depth of CCs (NightCPR: P = .22; HeadlampCPR: P = .10), and mean rate of CC (NightCPR: P = .08; HeadlampCPR: P = .87) followed a normal distribution, while the variables quality of CPR (NightCPR: P = .02; HeadlampCPR: P < .001), number of effective ventilations (NightCPR: P = .23; HeadlampCPR: P = .001), and perception of effort (NightCPR: P = .13; HeadlampCPR: P = .04) did not.
The overall quality of CPR was a median of 96% (IQR: 94 - 99) in the NightCPR test and 97% (IQR: 94 - 99) in the HeadlampCPR test, with no statistically significant differences between conditions (MD = 0; 95%CI, 3 – 1; Z = -0.31; P = .76). No statistically significant differences were observed between tests in CPR variables except for number of CCs (NightCPR: 402, IQR 392 – 418 versus HeadlampCPR: 411, IQR: 393 – 420; MD = -8 [95%CI, -15 – 0]; P = .041) and mean rate of CCs (NightCPR: 110 CCs/minute; IQR 108 – 113 versus HeadlampCPR: 113 CCs/minute; IQR: 111 – 115; MD = -3 [95%CI, -5 – -1]; P = .008); Table 1.
Quality of CPR (N = 19). Degrees of freedom for all analyses: 18
Note: * Paired t-test for comparisons and Paired Cohen’s d test for effect size with 95% confidence interval; † Paired Wilcoxon test for comparisons and Rosenthal’s r test for effect size with 95% confidence interval. Degrees of freedom for all analyses: df = 18.
Abbreviations: CPR, cardiopulmonary resuscitation; CC, chest compressions; NightCPR, natural night environment; HeadlampCPR, total darkness with headlamp.
On the other hand, no significant differences were observed in the perception of effort, with the HeadlampCPR test presenting a median of 5.0 (IQR: 2.5 – 5.0) and the NightCPR test a median of 4.0 (IQR: 2.5 – 5.0; MD = -1 [95%CI, -1 – 0]; P = .18).
Discussion
This study aimed to assess the feasibility of performing CPR at night using a headlamp versus ambient light without additional illumination. The main findings were:
-
1. Trained lifeguards achieved a good overall quality of CPR both in the darkness of the night and in complete darkness with headlamp illumination.
-
2. In both nighttime conditions, the depth of CCs was excessive.
The lack of significant differences in the overall quality of CPR between the groups using headlamp illumination and those relying solely on ambient light suggests that, in terms of CPR quality, the use of a headlamp may not be essential during nighttime interventions when responders are well-trained in resuscitation. The differences found between conditions in the compression rate do not have clinical implications because both groups performed compressions at a rate between 100 and 120 compressions per minute as established by the guidelines. Reference Olasveengen, Semeraro and Ristagno1
Despite compromised visibility, participants demonstrated remarkable skill both in performing CCs and rescue ventilations. The combination of both techniques is essential for maintaining tissue oxygenation in a person experiencing cardiac arrest and improving their chances of survival. Reference Gräsner, Wnent and Herlitz3,Reference Yan, Gan and Jiang5,Reference Wnent, Tjelmeland and Lefering6 Ventilations take on essential prominence in situations where combating hypoxia is paramount, such as in cases of drowning. Reference Bierens, Abelairas-Gomez and Barcala Furelos7,Reference Bierens, Bray and Abelairas-Gomez8 Although the ventilation technique is more complex than CCs, Reference Newell, Grier and Soar9 in this study with lifeguards, good effectiveness was achieved in ventilations performed with a pocket mask. These results are presumably due to the high level of skill of the rescuers, who were experts in treating drowning victims Reference Bierens, Abelairas-Gomez and Barcala Furelos7,Reference Szpilman, de Barros Oliveira, Mocellin and Webber10 and highly qualified to perform the mouth-to-pocket mask ventilation technique. Reference Adelborg, Dalgas, Grove, Jørgensen, Al-Mashhadi and Løfgren11
However, despite the good quality of CPR recorded, the excessive depth of CCs in both conditions suggests a need for greater attention to resuscitation technique in nighttime interventions, to improve patient outcomes and minimize the risk of injury. It is unclear whether reduced visibility may have influenced the excessive depth of CCs, or the same participants would have achieved a more appropriate depth under daylight conditions. Excessive depth in CC is an important quality factor in resuscitation because it could increase patient injuries such as rib fractures, sternal fractures, or lung injuries. Reference Gao, Sun and Yuan12,Reference Van Wijck, Prins, Verhofstad, Wijffels and Van Lieshout13
Furthermore, an excess depth of CCs in prolonged resuscitation would also be expected to cause greater rescuer fatigue, potentially resulting in a decrease in CPR quality. Reference Barcala-Furelos, Abelairas-Gomez, Romo-Perez and Palacios-Aguilar14 And although the participants reported a fatigue level of four or five out of 10 that did not affect the overall quality of resuscitation, it would be expected that with a more ergonomic CC technique, efficiency could be improved and high-quality CPR could be prolonged. The incorporation of training using a smart simulator that provides real-time feedback on depth, Reference Gugelmin-Almeida, Tobase, Polastri, Peres and Timerman15 including low visibility scenarios, could help address this aspect of resuscitation quality and encourage rescuers to maintain an appropriate depth during emergencies.
The ERC, in its chapter on Basic Life Support in special circumstances, addresses the management of cardiac arrests that present additional challenges, such as limited space (eg, on an airplane), adverse maritime conditions (eg, on a boat), or situations with crowds (eg, sporting events). Reference Lott, Truhlář and Alfonzo2 These guidelines do not include specific recommendations on how to address OHCA in low-visibility nighttime environments, despite the fact that this type of emergency may be common at night. Reference Mottlau, Andelius, Gregersen, Malta Hansen and Folke16,Reference Lin, Shi, Wang and Liang17 Based on the results of this pilot study, while participants demonstrated an overall good quality of CPR, they exhibited a tendency to perform CCs that were excessively deep. This indicates that managing cardiac arrests in the darkness of night may present specific challenges that could impact the quality of CPR. Further research is needed to explore various nighttime visibility conditions in order to develop specific recommendations guiding the management of cardiac arrests in low-light environments within clinical guidelines.
In the event of a cardiac arrest in a dark environment, it seems reasonable to recommend not delaying the initiation of CPR, as it can be performed with good quality and additional lighting from a headlamp does not appear essential. It is important to note that this study focused on CPR techniques: CCs and ventilations with a pocket mask. However, managing a cardiac arrest involves other skills, such as the ABC approach (airway, breathing, circulation) and the use of an automated external defibrillator (AED), Reference Perkins, Graesner and Semeraro18 for which it is still unclear whether better illumination, for example, through the use of a headlamp, could improve performance compared to conducting the intervention in darkness.
Implications for Practice
Based on the results of this study, lifeguards operating in nighttime environments should not delay the initiation of CPR, whether or not they have additional lighting (eg, a headlamp). Furthermore, they should focus their CPR training on low-visibility circumstances, utilizing their usual lighting equipment such as headlamps, to ensure high-quality resuscitation, with particular emphasis on avoiding excessive CC depth. These same implications may be applicable to other first responder groups who may find themselves needing to respond to emergencies during the night, such as Emergency Medical Services personnel, firefighters, police officers, or security personnel at events and public venues. Finally, these findings should be considered for future updates to clinical guidelines, particularly concerning resuscitation in nighttime and low-visibility environments.
Limitations
This study has some limitations. Firstly, it is a pilot study, so investigations with larger sample sizes would provide broader evidence on the effectiveness of CPR in nighttime conditions and would allow for narrower confidence intervals for effect size. Secondly, the study is based on simulations using manikins, and although skills in simulation are often transferable to real situations, they may not fully reflect the complexities and challenges of a real emergency. Thirdly, the study focused on a specific type of nighttime lighting and participants, which does not fully address the variability in low-light conditions that rescuers may encounter in practice, nor does it consider their ability to perform CPR under daylight conditions. Finally, the study was conducted with a specific type of participant, namely lifeguards with very good resuscitation training, so caution should be exercised when extrapolating the results to other populations.
Conclusions
Cardiopulmonary resuscitation in nighttime conditions is feasible, and lifeguards are able to perform it with good quality both in darkness and with the use of a headlamp. The use of additional lighting with a headlamp does not appear to be essential for resuscitation. Attention to technique during nighttime interventions is necessary to prevent excessive CC depth. In the event of a nighttime emergency, it is recommended that first responders initiate resuscitation maneuvers regardless of whether they have additional lighting.
Conflicts of interest/funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The authors declare no conflicts of interest.
Acknowledgments
Thanks to the Universidade de Vigo for the support provided to carry out this research.
Author Contributions
Conceptualization: Silvia Aranda-García, Roberto Barcala-Furelos, María Fernández-Méndez, Martín Barcala-Furelos, and Santiago Martínez-Isasi.
Data Curation: Roberto Barcala-Furelos, Martín Otero-Agra, and Martín Barcala-Furelos.
Formal Analysis: Martín Otero-Agra.
Investigation: Silvia Aranda-García, María Fernández-Méndez, Martín Otero-Agra, Silvia San Román-Mata, and Santiago Martínez-Isasi.
Methodology: Silvia Aranda-García, Roberto Barcala-Furelos, María Fernández-Méndez, Silvia San Román-Mata, and Santiago Martínez-Isasi.
Software: Martín Otero-Agra.
Project Administration: Roberto Barcala-Furelos and Santiago Martínez-Isasi.
Resources: Roberto Barcala-Furelos and María Fernández-Méndez.
Supervision: Roberto Barcala-Furelos and Santiago Martínez-Isasi.
Validation: Silvia Aranda-García, Roberto Barcala-Furelos, María Fernández-Méndez, Martín Barcala-Furelos, and Santiago Martínez-Isasi.
Roles/Writing - Original Draft: Silvia Aranda-García.
Writing - Review & Editing: Silvia Aranda-García, Roberto Barcala-Furelos, and María Fernández-Méndez.
