Comparison of the quality of chest compressions on a dressed versus an undressed manikin: A controlled, randomised, cross-over simulation study

Survival following out-of-hospital cardiac arrest (OHCA) increases two- or three-fold if bystanders perform cardiopulmonary resuscitation (CPR) [1‐7]. However, the likelihood of bystanders performing CPR varies from as low as 15% to 52% [8‐10]. Bystanders may be reluctant to perform CPR for reasons as diverse as lack of confidence, unfamiliarity with resuscitation guidelines, or even fear of harming the victim [11]. Expecting them to unclothe a patient's chest may also increase reluctance. As such, this study was undertaken to examine if unclothing the thorax has any measurable benefit in terms of how well chest compressions are performed. If not, it would seem prudent to recommend not initially unclothing the victim's chest, especially if this approach also mitigates a potential barrier to bystanders performing CPR [2, 11].

The 2005 CPR guidelines emphasise the prime importance of chest compressions [1, 2], and that survival decreases if compressions are not initiated promptly [12, 13]. The effectiveness of those chest compressions also affects the outcome [14]. Performance by both bystanders and experienced professionals in administering compressions (whether measured by chest compression depth, adequacy of rate, correct hand positioning, or complete release) has been shown to be suboptimal [10, 15‐17]. We therefore wished to determine the quality of compressions by novices and professionals; whether layers of clothes were associated with the poorer quality compressions, as well as the average time delay associated with unclothing the thorax.

It is currently unclear whether the chest should be unclothed or not, prior to initiating chest compressions. For examples, guidelines from 1966 onwards have typically depicted chest compressions performed on a bare chest. However, undressing the chest is not described in more recent guidelines. As such, there may be confusion as to whether valuable time should be expended in undressing the chest. The aim of this study was to examine if the quality of chest compressions was impaired if performed on a dressed manikin compared to an undressed manikin.

Fifty-seven participants were included: 32 inexperienced laypeople and 25 experienced firefighters (Table 1). Two participants from the inexperienced group were excluded because they misunderstood instructions. Seven firefighters were excluded because they misunderstood instructions; the manikin malfunctioned, or because they were called away on duty. Therefore, on occasion, daily tasks prevented full compliance with the study protocol (Figure 1).

For the inexperienced group, there was no significant difference in compression depth between the unclothed manikin (mean maximum compression depth of 40 mm (95% CI 36;43)) and the clothed manikin (mean maximum compression depth of 40 mm (95% CI 37;44)) (p = 0.57) (Figure 2). For the experienced group, there was a mean increased maximum compression depth of 3 mm on a dressed manikin: 48 mm on a dressed manikin (95% CI 45;51), compared to 45 mm (95% CI 42;48) on an undressed manikin (p = 0.039). However, this difference (3 mm) is below the defined limit for clinical relevance (5 mm).

There was no statistically significant difference for either group regarding mean compression rate (per min). In the layperson group, the mean compression rates were 85 (95% CI 80;90) and 87 (95% CI 81;92) on an unclothed and clothed manikin, respectively (p = 0.31). The firefighters performed CPR with mean compression rates of 123 (95% CI 116;131) and 124 (95% CI 119;129) on an unclothed and clothed manikin, respectively (p = 0.75) (Figure 3).

Neither group showed any significant difference regarding the average percentage of correct hand positioning, the likelihood of complete release (≤ 10 mm), correct compression depth (range 40-50 mm), or the percentage of completely correct compressions (in all aspects) (Table 2 and Table 3) when performance was compared between an undressed versus dressed manikin.

Although not statistically significant we observed within both groups an interesting trend towards an improved performance regarding the percentage of compressions within the recommended depth (range 40-50 mm) on a dressed chest compared to undressed. For laypeople, performance improved from 25% to 34% (Table 2), and firefighters improved from 38% to 49% (Table 3), when giving compressions on a dressed chest compared to undressed.

The average pause in chest compressions (to allow ventilation) before and after the second cycle of chest compressions did not differ significantly for either the inexperienced or experienced group. For laypeople, the pause was approximately 13 seconds (p = 0.57) with both a clothed and unclothed chest, while for the firefighters it was approximately 9 seconds (p = 0.49).

Regarding the quality of chest compressions, both compression depth and compression rate were higher in the experienced group than in the inexperienced group (compression depth: p = 0.007 and p = 0.041 with and without clothes, compression rate p < 0.0001 for both).

In the supplementary study, the average time for laypeople to undress the person's chest and place the hands in the centre of the chest was 23 seconds (N = 15, 95% CI: 19;27).

This study is, to our knowledge, the first to investigate if the presence of clothes on the chest influences the quality of chest compressions. While the sample size was small, we found no significant differences in the quality of chest compressions between the dressed and undressed manikin in either experienced or inexperienced responders. Furthermore, even if inexperienced responders are not deterred by the presumed need to undress the thorax, we showed that this was associated with a delay in the initiation of chest compressions of over 20 seconds. Given that each minute of delay is associated with 7-10% decreased survival, time spent undressing a patient may be clinically relevant [1, 2]. We also showed that there was no significant difference in terms of hand placement in the dressed versus undressed scenario. In other words, we observed that for a standard resuscitation manikin it was not necessary to undress the chest for the purpose of "landmarking". In short, there was no apparent benefit gained by undressing the thorax, and there may be a detriment.

Current guidelines do not clearly state whether the victim should be initially undressed before chest compressions are started [1, 2]. However, the illustrations in the 2000 and 2005 guidelines [1, 2, 19, 20] depict a naked chest. For this reason, both laypeople and experienced practitioners might assume that taking the time to undress the patient's chest before starting compressions is essential. Our study indicates that this might not be the case. As such, our study suggests that the guidelines could be more explicit about this issue. Furthermore, the alternative for professionals might be to leave the clothing intact, but to find an alternative way to gain access for defibrillator pads (for rhythm analysis and possible future defibrillation). While, objects in upper extremity pockets would typically obstruct the lateral chest rather than sternum, rescuers may have no option but to occasionally unclothe the thorax. Our study emphasises that this should be done as quickly as possible, in order to minimise any delay in the initiation of chest compressions.

This study has limitations. For example, randomisation of the firefighters was suboptimal. Work requirements meant that randomisation had to be performed on a day-to-day basis and was interrupted by professional duties (such as call-outs and temporary cover for colleagues). This situation made it impossible to adhere strictly to the planned randomisation in all cases and resulted in an unequal distribution between clothed and unclothed manikin trials. As these factors were arbitrary and uncontrollable by the researchers, we believe they did not introduce any systematic bias. In addition, our analysis measured the effect on average performance by groups and therefore it is possible that individual performance may be affected by the presence or absence of clothes.

By including both novices and professionals, our results offer insights for both experienced and inexperienced responders. By contrasting these two groups, our results show, that with four hours of instruction, laypeople can be taught to perform reasonable effective chest compressions although less deep and slower than experienced first responders.

However, several authors have emphasised that work is also needed to decrease the reluctance of laypersons to perform bystander CPR [8‐11]. Notably, recent guidelines now recommend starting chest compressions before rescue breaths [1, 2]. One advantage of this focus on chest compressions is that bystanders may be more willing to initiate BLS due to reduced fear of infection [21, 22].

While speculative is it also plausible that not needing to immediately remove a stranger's clothes could further reduce reluctance to perform CPR due to reduced embarrassment. Regardless, our hope is that this small study might encourage simpler and clearer BLS guidelines, promote bystander BLS, and, optimise the chance of survival following cardiac arrest.

Overall, the quality of chest compressions was unchanged by the presence of clothes on the manikin chest; both when chest compressions were performed by inexperienced laypeople and by trained and experienced responders.