Cardiopulmonary resuscitation (CPR) is essential in the management of cardiorespiratory arrest (CA) to improve survival rates. High-quality chest compressions are the primary intervention to maintain circulation and oxygenation of vital organs during cardiac arrest, making them a key determinant in CPR effectiveness. Guidelines emphasize that the quality of chest compressions is a critical factor in the effectiveness of basic life support (BLS). To ensure efficacy, a compression rate of 100 to 120 per minute is recommended, with a depth of at least 5 cm but not exceeding 6 cm, proper arm and hand alignment, full chest recoil after each compression, minimal interruptions during CPR, and rescuer rotation every 2 minutes to prevent performance decline due to fatigue. As we can see, these guidelines refer to performing compressions using the upper limbs. However, it is essential to acknowledge that some individuals have physical limitations that may impair their ability to apply effective force with their upper limbs (e.g., amputations, fractures, neuromuscular dysfunctions). This presents important challenges regarding accessibility and inclusive CPR training. In addition, the use of the lower extremities has been proposed as an alternative to potentially reduce rescuer fatigue, although evidence regarding its effectiveness and impact on physiological fatigue is still limited. There are studies comparing chest compressions performed with the hands (Hands Method, HMM) and with the feet (Foot Method, FMM); however, these studies have certain limitations and a limited number of participants. Although the quality of CPR was lower when using the feet technique, the results were positive. However, to date, no specific guidelines have been established on how to perform CPR using the feet (Foot CPR), and it remains unclear whether the position of the feet on the chest or whether compressions are performed with or without shoes are variables that influence compression quality. Furthermore, during CPR, it is recommended to rotate rescuers every 2 minutes when two or more rescuers are available due to fatigue associated with the procedure. Current evidence suggests that CPR is most effectively performed in the kneeling position, rather than standing or using a stool, due to the lower levels of fatigue in this position. Traditionally, exercise-induced fatigue is assessed using subjective perception of exertion (RPE), performance monitoring (e.g., power or speed), or biochemical markers (e.g., blood lactate). More recently, heart rate variability (HRV) has been proposed as a valuable tool for assessing the autonomic nervous system response to exercise stress and quantifying physiological fatigue. After exercise, especially if it is intense or prolonged, the body experiences significant physiological stress. This stress affects multiple systems, including the cardiovascular and autonomic nervous systems. Post-exercise fatigue is a complex sensation involving muscular, metabolic, and neuronal factors. Therefore, HRV becomes a valuable biomarker. Numerous studies have shown a correlation between decreased HRV and the subjective perception of fatigue after exercise. People with lower heart rate variability (HRV) after exercise tend to report higher levels of fatigue. HRV analysis provides an objective and physiological measure of the stress the body experiences after short-duration, high-intensity exercise, such as that performed during resuscitation. Therefore, measuring HRV after 2 minutes of chest compressions can indicate the degree of exercise-induced physiological fatigue, which could vary depending on the technique used (Hands-on CPR \[H-CPR\] vs. Feet-on CPR \[F-CPR\]). Efforts to improve outcomes should focus on optimizing the chain of survival through training in Basic Life Support and Automated External Defibrillation (BLS + AED). Offering these courses to the general population presents significant challenges in terms of accessibility and implementation of comprehensive and inclusive training. The objective of our randomized simulation study using mannequins, with a population of Basic Life Support students, was to compare the quality of chest compressions and the fatigue produced by this technique, in compressions performed with the hands and with the foot.
This is a single-center, randomized, crossover, controlled study conducted in the Skills Laboratory of the Faculty of Medicine and Health Sciences, Campus Clínic. Each participant will act as their own control, performing chest compressions with both hands and their foot. The order of compression method (hand or foot) will be randomly assigned, and participants will subsequently perform the alternative method they did not initially complete. Participants will be enrolled in a Basic Life Support and Automated External Defibrillation (BLS+AED) course from the Catalan Resuscitation Council - European Resuscitation Council. Data collection will be consecutive and open-label. Variable-size block randomization, generated using statistical software, will be used to ensure balanced assignment of participants to the study groups while maintaining unpredictability. To implement this randomization, the R programming language will be used, widely used in scientific research and statistical analysis due to its robustness and reliability. R offers specialized tools for this type of randomization, ensuring a rigorous, transparent, and reproducible process. We will use the R package blockrand, specifically designed for efficient and controlled block randomization. Primary objectives: To compare the depth of uninterrupted chest compressions (without ventilation) delivered over a 2-minute period during a simulated cardiac arrest on the floor, using either the hands (HM) or feet (FM). To assess CPR-associated fatigue in the two groups using: Subjective measures: Rating of perceived exertion (Borg score). Direct objective measures: Use of a wearable health monitoring device (abdominal strap-based) to measure rescuer heart rate variability (HRV), a parameter correlated with fatigue during CPR. Indirect objective measures: heart rate and oxygen saturation. Data will be collected using the SkillReporter® app (Laerdal Medical®) during 2 minutes of continuous chest compressions on a Resusci Anne QCPR manikin, a certified medical-grade abdominal strap (Movesense®), and a pulse oximeter.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
NONE
Enrollment
128
Performing chest compressions on a mannequin using the foot
Performance of standard chest compressions with the upper limbs.
Facultad de Medicina de La Universidad de Barcelona
Barcelona, BARCELONA, Spain
MEAN CHEST COMPRESSION DEPTH
Data will be collected using the SkillReporter® application (Laerdal Medical®) during 2 minutes of continuous chest compressions on a Resusci Anne QCPR manikin. Primary Variable: Mean chest compression depth: To compare the mean depth of uninterrupted chest compressions (without ventilations) performed over a 2-minute period during a simulated cardiac arrest on the floor using the hands (HM) or the feet in both positions (FM-S and FM-T).
Time frame: One day
DFA α1 (DETRENDED FLUCTUATION ANALYSIS - α1)
DFA α1 - Short-term scaling exponent from Detrended Fluctuation Analysis (DFA) is a nonlinear HRV metric derived from detrended fluctuation analysis, representing short-term fractal scaling behavior of RR intervals. Assesses fractal-like correlation properties of heart rate time series over short time scales. It provides insights into the complexity and self-regulation of autonomic control. Values closer to 1.0 indicate healthy, adaptable systems, while deviations may suggest altered autonomic regulation. Change in heart rate variability (HRV), measured before and after performing the two minutes of CPR using a certified medical-grade abdominal band device (Movesense®). HRV is a non-invasive indicator of autonomic nervous system (ANS) activity and is known to be affected by physical fatigue and physiological stress.
Time frame: One day
OVERALL COMPRESSION SCORE
Overall compression score (%): A variable created by Laerdal Medical® reflecting how closely CPR performance aligns with ERC Guidelines. Deviations reduce the score from 100%. The score incorporates depth, rate, incomplete release, number of compressions per cycle, and hand/foot positioning.
Time frame: One day
TOTAL NUMBER OF COMPRESSIONS
Total number of compressions will be collected using the SkillReporter® application (Laerdal Medical®) during 2 minutes of continuous chest compressions on a Resusci Anne QCPR manikin
Time frame: One day
COMPRESSION / DESCOMPRESSION RATIO
This variable refers to the ratio between the duration of the downward chest compression and the upward chest recoil (decompression). Compression/decompression ratio will be collected using the SkillReporter® application (Laerdal Medical®) during 2 minutes of continuous chest compressions on a Resusci Anne QCPR manikin
Time frame: One day
CORRECT COMPRESSION DEPTH
Correct compression depth (%): percentage of chest compressions with a depth between 5 and 6 cm. Data will be collected using the SkillReporter® application (Laerdal Medical®) during 2 minutes of continuous chest compressions on a Resusci Anne QCPR manikin
Time frame: One day
COMPRESSION RELEASE
Compression release (%) refers to the percentage of chest compressions in which full chest recoil was achieved. Compression release (%) will be collected using the SkillReporter® application (Laerdal Medical®) during 2 minutes of continuous chest compressions on a Resusci Anne QCPR manikin
Time frame: One day
MEAN COMPRESSION RATE
Mean compression rate refers to the average number of chest compressions delivered per minute (cpm). Data will be collected using the SkillReporter® application (Laerdal Medical®) during 2 minutes of continuous chest compressions on a Resusci Anne QCPR manikin
Time frame: One day
CORRECT HANDS/FEET POSITION
Correct hand/feet position (%): Correct Hand/Feet Position (%) refers to the percentage of chest compressions performed with the hands or feet placed correctly Data will be collected using the SkillReporter® application (Laerdal Medical®) during 2 minutes of continuous chest compressions on a Resusci Anne QCPR manikin
Time frame: One day
TOTAL NUMBER OF BREAKS
Total number of breaks: The total count of pauses or interruptions during chest compressions Data will be collected using the SkillReporter® application (Laerdal Medical®) during 2 minutes of continuous chest compressions on a Resusci Anne QCPR manikin
Time frame: One day
BORG SCALE
The Borg Scale measures perceived exertion or subjective intensity of effort during chest compressions. The Borg scale will be used before and after compressions to assess perceived fatigue in all groups.
Time frame: One day for each participant (3 weeks in total).
STANDARD DEVIATION OF NN INTERVALS (SDNN)
SDNN (Standard Deviation of NN intervals): Reflects overall heart rate variability (HRV) by measuring the standard deviation of all normal-to-normal (NN) intervals. It indicates general autonomic activity and long-term components of variability. Change in heart rate variability (HRV), measured before and after performing the two minutes of CPR using a certified medical-grade abdominal band device (Movesense®). HRV is a non-invasive indicator of autonomic nervous system (ANS) activity and is known to be affected by physical fatigue and physiological stress.
Time frame: One day
ROOT MEAN SQUARE OF SUCCESSIVE DIFFERENCES (RMSSD)
RMSSD (Root Mean Square of Successive Differences): Represents the short-term heart rate variability (HRV by calculating the square root of the mean squared differences between adjacent NN intervals. It is primarily influenced by parasympathetic (vagal) activity. Change in heart rate variability (HRV), measured before and after performing the two minutes of CPR using a certified medical-grade abdominal band device (Movesense®). HRV is a non-invasive indicator of autonomic nervous system (ANS) activity and is known to be affected by physical fatigue and physiological stress.
Time frame: One day
LOW FREQUENCY (LF)
Low Frequency (LF) refers to the power of heart rate variability (HRV) within the frequency range of 0.04 to 0.15 Hz in spectral (frequency-domain) analysis. This means it reflects oscillations in heart rate that occur every 7 to 25 seconds.Represents a combination of sympathetic and parasympathetic modulation, commonly associated with baroreflex activity. Change in heart rate variability (HRV), measured before and after performing the two minutes of CPR using a certified medical-grade abdominal band device (Movesense®). HRV is a non-invasive indicator of autonomic nervous system (ANS) activity and is known to be affected by physical fatigue and physiological stress.
Time frame: One day
HIGH FREQUENCY (HF)
High Frequency (HF) refers to the power of heart rate variability within the frequency range of 0.15 to 0.40 Hz in spectral (frequency-domain) analysis. This corresponds to oscillations in heart rate occurring approximately every 2.5 to 7 seconds, which are strongly linked to respiratory activity. HF (High Frequency, 0.15-0.40 Hz): Reflects parasympathetic activity and is related to respiratory sinus arrhythmia. Change in heart rate variability (HRV), measured before and after performing the two minutes of CPR using a certified medical-grade abdominal band device (Movesense®). HRV is a non-invasive indicator of autonomic nervous system (ANS) activity and is known to be affected by physical fatigue and physiological stress.
Time frame: One day
LOW FREQUECY (LF) /HIGH FREQUENCY (HF) RATIO
The LF/HF ratio is the ratio of Low Frequency (LF) power to High Frequency (HF) power in the spectral analysis of heart rate variability (HRV). LF/HF Ratio Indicates the balance between sympathetic and parasympathetic nervous system activity. An increased ratio may reflect sympathetic dominance. Change in heart rate variability (HRV), measured before and after performing the two minutes of CPR using a certified medical-grade abdominal band device (Movesense®). HRV is a non-invasive indicator of autonomic nervous system (ANS) activity and is known to be affected by physical fatigue and physiological stress.
Time frame: One day
JT/RR ratio
The JT/RR ratio is the ratio between the JT interval and the RR interval on an ECG. Change in heart rate variability (HRV), measured before and after performing the two minutes of CPR using a certified medical-grade abdominal band device (Movesense®). HRV is a non-invasive indicator of autonomic nervous system (ANS) activity and is known to be affected by physical fatigue and physiological stress.
Time frame: One day
SpO₂
SpO₂: Oxygen saturation measured by a portable digital pulse oximeter before and after 2 min of chest compressions
Time frame: one day
PULSE RATE
Pulse rate: Number of heartbeats per minute (bpm), measured via pulse waveform by a portable digital pulse oximeter before and after 2 minutes of chest compressions.
Time frame: one day
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