A randomized cross-over study assessed the metabolic and performance differences in CPR performed on a hard surface versus a standard hospital mattress. The study was conducted at West Texas A&M University between January and June 2020, following approval from the university’s Institutional Review Board (IRB approval number 2020-05).

Thirty-four participants (17 males and 17 females), aged between 19 and 27 years (mean age ± SD: 23 ± 2.1 years), were recruited from the College of Nursing and Health Sciences. Inclusion criteria required participants to have current certification in Basic Life Support (BLS) from the American Heart Association and be physically capable of CPR for extended periods. Exclusion criteria included any musculoskeletal injuries or medical conditions that could be exacerbated by physical exertion.

Before participation, all individuals provided written informed consent and completed a health questionnaire to screen for contraindications to vigorous physical activity.

Participants were randomized to begin CPR either on the hard surface or the hospital mattress to control for any order effects. Each participant performed two CPR sessions, one on each surface, separated by a rest period of at least 30 minutes to prevent fatigue carryover.

CPR was performed on a Resusci Anne QCPR manikin (Laerdal Medical, Stavanger, Norway), providing real-time compression depth and rate feedback. The manikin was placed either directly on the floor (hard surface condition) or on a standard hospital mattress positioned on a hospital bed adjusted to a standard working height (mattress condition).

Participants performed continuous chest compressions for a total of 24 minutes per session, following the AHA guidelines for compression-only CPR to focus solely on the compression component. To simulate a realistic resuscitation scenario and manage physical exertion, participants alternated roles every 2 minutes, mimicking standard CPR practice where rescuers switch to prevent fatigue (AHA, 2020). However, in this study, since only the compressions were being assessed, participants alternated with brief rest periods required to switch positions.

These measurements were taken using a VO₂ Master Analyzer (VO₂ Master Health Sensors, Inc., Vernon, British Columbia, Canada), a portable device that analyzes your breathing to assess how well your heart and lungs work during exercise.

The feedback system integrated into the Resusci Anne manikin recorded compression depth and rate. The device’s data logging capabilities allow the collection of average values over the entire session.

Participants rated their perceived exertion using the Borg Rating of Perceived Exertion (RPE) Scale (6–20 scale) at the midpoint (12 minutes) and upon completion (24 minutes) of each CPR session (Borg, 1982).

Data were analyzed using SPSS Statistics for Windows, version 25.0 (IBM Corp., Armonk, NY, USA). Paired t-tests were performed to compare physiological and performance variables between the hard surface and mattress conditions. The level of statistical significance was set at p < 0.05. Data are presented as mean ± standard deviation (SD).

Thirty-four participants completed the study without any adverse events. The mean age was 23 ± 2.1 years, with a mean body mass index (BMI) of 22.5 ± 2.3 kg/m².

The higher heart rates and oxygen consumption observed during CPR on the mattress condition indicate more significant cardiovascular and metabolic stress on the providers. This aligns with previous research suggesting that CPR is a physically demanding activity, and factors that increase exertion may lead to an earlier onset of fatigue (Chung et al., 2012; Ock et al., 2011). The increased ventilatory equivalents (Ve/VO₂) and decreased fraction of expired oxygen (FeO₂) further suggest that rescuers work less efficiently on a compliant surface, potentially due to the additional effort required to achieve adequate chest compression.

The significant reduction in compression depth when CPR was performed on the mattress is of particular concern. Compression depth is directly associated with increased ROSC and survival rates (Idris et al., 2015; Stiell et al., 2012). The average decrease of 3.4 mm observed may seem modest but can be clinically significant, potentially reducing the efficacy of CPR and the likelihood of patient survival (Babbs & Kern, 2002).

These findings are consistent with previous studies that have demonstrated decreased compression depth on compliant surfaces due to mattress compression (Baubin et al., 2015; Sugerman et al., 2009). The surface’s compliance absorbs part of the force applied during compressions, resulting in less effective chest compression depth.

Although this study was conducted in a clinical setting, the findings have significant implications for lay responders performing CPR in out-of-hospital environments. In many cases, cardiac arrests occur at home, where the patient may be lying on a bed, couch, or other soft surfaces. Lay responders may need to recognize that CPR on these compliant surfaces can reduce compression effectiveness.

To mitigate this, lay responders should move the patient to a firm surface when possible and safe before initiating CPR. If moving the patient is not feasible, they should be aware of the need to push harder to compensate for the soft surface. First aid education should emphasize the importance of surface firmness in CPR effectiveness and guide how to address this issue in various settings.

The results underscore the importance of addressing surface compliance during in-hospital cardiac arrests. While using backboards has been recommended to mitigate mattress compression, their effectiveness is variable, and placement can delay CPR initiation (Hellevuo et al., 2014; Shin et al., 2014). Alternative strategies, such as integrating CPR feedback devices for mattresses or mechanical compression devices, may offer solutions (Couper et al., 2016; Ong et al., 2010).

Furthermore, the increased exertion required on a mattress may contribute to rescuer fatigue, potentially compromising CPR quality over time. Regular switching of providers and ensuring adequate staff availability during resuscitation efforts may help maintain high-quality compressions (AHA, 2020).

This study has several limitations. First, using a manikin model may not fully replicate human chest compliance, although it allows for controlled comparisons between conditions. Second, the study was conducted with participants who were young and physically fit nursing and health science students, which may limit the generalizability to older or less physically fit providers. Third, the study did not assess the use of adjuncts such as backboards or CPR feedback devices, which could influence the outcomes.

Further research should explore interventions to mitigate the effects of surface compliance, including backboards’ efficacy, mattress-deflation strategies, and advanced feedback technologies. Studies involving actual resuscitation events and diverse provider populations would enhance the external validity of the findings.