Using smartphone app-based real-time instruction in resuscitation is thought to be beneficial, because mobile phones are often close at hand and might reduce fear of making mistakes during CPR. As our results illustrate, smartphone guidance shows mixed benefits.
For detection and treatment of persons with suspected cardiac arrest an easy to follow algorithm was developed for medical laypersons. This algorithm involves check of consciousness, check for breathing, call for help and start of chest compressions and was taught in our study. During the simulated scenario most pupils adhered to this algorithm, regardless of whether the app was used or not. While check of consciousness was done correctly by most pupils, check for airway obstructions and assessment of normal breathing were a higher challenge. Even pupils, who received detailed instruction by the app, had difficulties performing this task. In a study done by Choa, participants, who were shown videos using animated motion capture technique on a smartphone app, performed better airway management (head tilt-chin lift manoeuvre and checking for breathing) in comparison to participants receiving audio-guidance only .
High quality chest compression is essential for survival . A chest compression rate of 100–120 compressions per minute was shown to be the optimal frequency of thoracic compression [37, 38]. Instructions issued by the app lead to a significantly higher amount of chest compressions within the recommended pace. This might be accountable to the metronome, similar to findings in a study by Paal .
High quality CPR further includes a chest compression depth of 5–6 cm . In our study, pupils using the app achieved significantly more often the recommended compression depth. The results regarding improved chest compression rate and depth are in concordance with a study by Merchant et al, who tested the benefit of CPR-instructions by voicemail using a flip-design cell telephone . Concordantly, a study done by Choa et al. showed better chest compression quality when using an app showing video clips .
Alongside a deep chest compression, a total release of compression is also necessary. In our study no differences between pupils with and without app use were seen. This is probably due to the fact, that the app did not address release of chest compression. Also, no significant differences were seen regarding hand position on the chest.
To achieve adequate chest compression depth and rate, it is advisable to kneel directly beside the victim and to press with both arms stretched. While app guidance led to a significantly better body position, no significant differences regarding correct arm posture was detectable. Nearly all pupils used correct body and arm positioning, probably because it was demonstrated in the CPR training six weeks in advance. Correct body and arm position can be learnt best with hands-on-training. Hence, smartphone guidance in real-time should be considered as an additional tool to support traditional hands-on CPR training, because important psychomotor skills can be better taught in direct training with manikins .
In cardiac arrest it is essential to start resuscitation as soon as possible [8, 29]. Numerous studies could show a benefit for early start of chest compressions by bystanders [40, 41]. Hence, it is of paramount importance that real-time guidance by smartphones does not lead to a substantial time delay. Yet, in our study pupils, who examined the manikin for cardiac arrest with support by the smartphone app, took longer time to start and complete check for breathing, more time to call for help and more time until first chest compression. This prolonged time until first compression was also found in other studies evaluating real-time guidance through mobile phones or smartphones [26, 33, 39]. In studies comparing app or video-demonstrated instructions with audio-only instructions (as in telephone-CPR), time until first chest compression was found to be shorter with app-/ video-based instructions [42, 43].
When scrutinising these findings, several aspects have to be considered. All pupils in our study received a CPR training six weeks ahead of this examination. Different results may be found with laypersons, whose training was years ago or who had no previous training. Medical laypersons without CPR training are often overwhelmed by the situation and are afraid of doing something wrong and might prefer doing nothing at all . Hence, smartphone guidance may prompt them to assess consciousness and breathing. Additionally, it helps bystanders with limited CPR knowledge to remember all steps. Furthermore, in our study the time delay ascribable to the app accounts for approximately one minute. This is a relatively small loss of time compared to a situation, in which no bystander CPR is initiated and first chest compression is done by ambulance crew. Hence, in an app leading to a higher amount of high quality bystander CPR, one could argue, that a loss of time of approximately one minute might be acceptable. Additionally, pupils using the app tended to have fewer and shorter pauses during chest compressions. In situations, in which the ambulance takes 10 minutes or longer to reach the emergency site, the initial time delay might be mitigated by a shorter overall hands-off-time.
This study is a simulation study with manikins, thus, generalisability to real-life scenarios is limited. Resuscitation was performed with one-person hands-only CPR, which might be different in real-life scenarios. This study was done with pupils. Because of their young age this reduces the transferability to other bystanders. Pupils in mandatory group were slightly older than pupils in the other groups, which could lead to a greater body strength resulting in deeper chest compressions . However, heights and weights differences in pupils of 14–15 years are not as pronounced as in younger years .
Randomisation into the three groups was done on school level to reduce communication between different study groups. However, it bears the risk of bias by different educational strategies of different schools. We tried to diminish this bias by providing every pupil with a standardised CPR-training.
The timespan between training and examination was six weeks. Other results may have been observed after a different time interval. Pupils in the mandatory group, were trained how to operate the app. Outside study environment people often download apps without familiarizing with it . Thus, they might not know how to operate the app in case of witnessing cardiac arrest and are expected to have longer time delays before starting CPR.
During simulation the duration of chest compressions was stopped after two minutes to allow standardisation, similar to other studies[26, 47]. In real emergencies, CPR by bystanders is often required for a longer time-interval. A longer timespan might pronounce or mitigate the differences in quality of chest compressions.
To allow qualified recommendation regarding smartphone app- based real-time guidance for medical laypersons in resuscitation, studies evaluating the benefits and drawbacks in real cardiac arrests are needed. The future goal is to analyse impact on return of spontaneous circulation and quality of life.