a b s t r a c t

Background: Paediatric out-of-hospital cardiac arrest (OHCA) is the reason for an emergency call in approxi- mately 8/100,000 person-years. Improvement of OHCA resuscitation needs a quality Chain of survival and a rapid start of resuscitation.

The aim of this study was to compare the efficacy of two resuscitation techniques provided on a mannequin, the two-fingers technique (TFT) and the two-thumbs encircling hand technique (TTHT), explained by a trained emergency call responder on the phone in a population of non-health professionals.

Methods: We conducted a randomised crossover study in the simulation lab of a University Hospital. The partic- ipants included in the study were non-health professional volunteers of legal age. The participants were assigned (1:1 ratio) to two groups: group A: TFT then TTHT, group B: TTHT then TFT. Scenario and techniques were discov- ered during the evaluation.

Results: Thirty-five volunteers were randomised before the sessions and 33 ultimately came to the simulation lab. We found a better median QCPR global score during TTHT sessions than during TFT sessions (74 vs. 59, P = 0.046). Linear mixed models showed that the TTHT method was the only variable associated with a better QCPR global score [model 1: ? = 14.3; 95% confidence interval (CI), 2.4-26.2; model 2: ? = 14.5; 95% CI,

2.5-26.6].

Conclusion: Our study showed the superiority of TTHT for infant CPR performed by non-health professionals when an emergency call responder advised them over the phone. It seemed to be the best technique for a solo rescuer regardless of previous training.

(C) 2022

1. Introduction

The main factors to improve the chance of survival among victims of out-of-hospital cardiac arrest (OHCA) are the chain of survival quality and a rapid start of resuscitation. Survival of paediatric patients after a cardiac arrest occurring outside or inside the hospital are respec- tively 6% and 27% [1-3], emphasising the importance of early

* Corresponding author at: University Hospital of Bordeaux, Pellegrin Hospital, Pole of Emergency, Place Amelie Raba-Leon. 33076, Bordeaux Cedex, France.

E-mail address: [email protected] (C. Gil-Jardine).

cardiopulmonary resuscitation (CPR). In fact, paediatric OHCA repre- sents around 8/100,000 person-year emergency calls [1,2].

Nevertheless, the large majority of OHCAs are diagnosed during the call, and only half receive proper and early CPR [1,4]. This could multiply the chances of survival by two or four [5] but CPR quality is frequently poor. As soon as possible, emergency call responders (ECRs) should help CA witnesses to begin the best possible CPR. Providing good advice to improve CPR is one of the main difficulties faced by emergency re- sponders. Indeed, instructions given by ECR can clearly improve the rate and Quality of CPR and also shorten the delay to first compression, thereby increasing the survival rate [6-16].

https://doi.org/10.1016/j.ajem.2022.09.012

0735-6757/(C) 2022

Previous adult studies have shown that simplified instructions pro- vided over the phone during CPR improve the depth of chest compres- sions without modifying frequency [17,18]. Thus, ECRs have a major CPR assistance role during the phone call. Most previous studies only assessed CPR guided by ECRs for adults, and no study has evaluated CPR in newborns.

Resuscitation guidelines for children <1 year of age recommend be- ginning CPR as early as possible with five breaths and then starting chest compressions [19]. Two techniques are currently proposed for chest compressions depending on the number of rescuers (Fig. 1): i) the two-fingers technique (TFT) for one rescuer, and ii) the two-thumbs encircling hands technique (TTHT) for two or more rescuers. In 2015, the European Resuscitation Council (ERC) defined some other parame- ters, such as a 15:2 compression/ventilation ratio, 100-120 compres- sions per minute to a depth of 4 cm, followed by full thoracic relaxation between compressions and trying to limit any interruptions of CPR [19].

Some studies have compared TFT and TTHT, including only care- givers. TTHT was superior in almost all CPR parameters, such as fre- quency range, depth, and blood pressure provided by chest compressions [20-27]. Strength of the fingers was also measured, and TTHT was more effective than all combinations of two fingers [28]. In- deed, the release rate seemed to be lower for TTHT than for TFT [20]. Based on these findings, some authors have recommended TTHT even if there is only one rescuer [20,21,25]. Moreover, TTHT does not result in more fatigue, according to the perceptions of rescuers [24,25].

Based on the ERC guidelines, one of the main limitations of TTHT is the duration of interrupted CPR while alternating ventilations and com- pressions [21,25] and an increased time-to-efficacy [22-29].

Thus, the aim of the study was to compare the efficacy of TFT and

TTHT in performing CPR on a mannequin as explained by trained ECRs over the phone to a population of non-health professionals.

1. Methods
   1. Study design and setting

We conducted a randomised crossover study in the simulation lab of a University Hospital. Four sessions were performed. Randomization was conducted using random.org website [30]. Participants were assigned (1:1 ratio) to two groups: group A: TFT then TTHT; group B: TTHT then TFT. The scenario and technique applied were discovered

during the evaluation. All sessions were performed individually, with- out any other participants.

• 1. Participants

Participants included in the study were non-health professional vol- unteers of legal age recruited from social network. Thus, nurses, para- medics, doctors, and other caregivers were not included.

• 1. Protocol

All sessions were performed in the Simulation Lab of our University Hospital, Centre d’Enseignement des Soins d’Urgence (CESU33). All ses- sions lasted 2 min with 5 min break between. A dedicated room with a one-way glass and a microphone were used to perform the simulations. A simulation mannequin, Resusci Baby QCPR (Laerdal, Stavanger, Norway) (RBQCPR) linked to a SimPAD plus with Skill reporter (Laerdal) (SPPSR) was placed in the room. The supervisors were two emergency physicians trained in pre-hospital care and telephone calls. The same trainers were used for all simulations. All participants were blinded to the scenario. Supervisors were not blinded from the study question but were not involved in study protocol.

The first trainer was placed behind the one-way glass to record data displayed by the SimPAD plus with a chronometer that delayed the call for the first chest compression. He was only asked to monitor the test subject. The second trainer managed the telephone. He was in the Sim Lab but did not see the simulation scene. He gave advice about the re- suscitation technique according to the randomised group. Both trainers were emergency physicians with experience in emergency call re- sponse. There was no communication between the two trainers.

The first approach after taking the call was previously written and standardized (Supplement 1) but the rest of the call was not standard- ized and was managed as usual in emergency call center. TFT consists of chest compressions using the tip of the index and middle fingers on the lower half of the thorax. For TTHT, the rescuer encircles the thorax in his hands and then places both thumbs one above the other on the lower half of the thorax (Fig. 1). During sim sessions participants were only asked to perform chest compressions, no insufflation was attended.

Then, depending on participants’ questions, the ECR accompanied the resuscitation to obtain the best external cardiac massage as possible, as in a typical medical phone call. After a short break, the simulation was restarted with the other technique.

Fig. 1. Cardiopulmonary resuscitation techniques for infants. a) The two-thumbs encircling hands technique (TTHT), and b) the two-fingers technique.

• 1. Primary outcome

The primary outcome was chest Compression quality measured after 2 min of CPR. It was assessed using the QCPR score automatically com-

Table 1

Volunteer characteristics.

All

n = 33

Group A

TFT then TTHT

Group B

TTHT then TFT

puted by the SPPSR for chest compressions. This algorithm was con- Sex
structed by members of the American Heart Association to assess CPR Female N (%)		18 (54.5)	8	(47)	10	(63)
quality from 0% to 100%. A 100% score was given when CPR strictly fol- Age	Med [IQR]	36 [33-53]	49	[33-53]	35.5	[33-54]
low the actual guidelines for resuscitation. More details about software Height	Med [IQR]	170 [165-176]	171	[164-181]	170	[167-172]
scoring could be found on manufacturer’s website (http://cdn.laerdal. Weight	Med [IQR]	70 [62-86]	75	[64-90]	65	[60-76]
BMI	Med [IQR]	23.7 [21.5-27.8]	24.8	[22.6-28.1]	22.3	[20.7-25.6]
com/downloads/f3943/Att_2_to_00021778.pdf). The global chest com- First Aid Training
pression score was a combination of i) depth of compressions, ii) com-	Yes n(%)	9 (27.3)	6	35	3	19

pression frequency, iii) compression release, iv) number of compressions per cycle, and v) hand position. Any deviation from the reference reduced the score. We did not record ventilation data, so we set the SPPSR in the “chest compression only” mode.

• 1. Data collected

Participant biometric data, such as age, sex, height, and weight of all participants, were recorded. We also asked them whether they had any previous first aid training.

We also collected information about CPR quality to compare these

data to ERC 2015 guidelines. Thus, we assessed mean compression fre- quency, mean depth of the compressions, delay from call to CPR start, and mean No-flow time for the 2-min session. Supervisors made notes of the participants’ finger positions, any changes in the hand or position. Participants were asked to provide verbal comments at the end of both sessions.

• 1. Statistical analysis

We hypothesised that a difference of 10 in the QCPR global score be- tween TTHT and TFT would be required to determine the best tech- nique. This difference was defined by a committee composed of physicians trained in paediatric CPR training. We fixed a standard devi- ation of 20, a power of 80%, and an alpha risk of 5%. Thus, the sample size for the paired data was 34 [31]. The statistical analysis was performed using R (Version 3.5.1 “Feather Spray”; R Project for Statistical Comput- ing, Vienna, Austria). The primary outcome was assessed by the Wilcoxon signed-rank test for paired data. Other outcome variables and population characteristics between groups were compared using the Wilcoxon signed-rank test for continuous variables or Fisher’s test for categorical variables.

We conducted a complementary analysis using a linear mixed model (R packages mgcv [32-35] and effsize) with participant as a ran- dom effect. The outcome variable was the global score and the main ex- position of the CPR method performed. We then constructed two models that included age, sex, body mass index, and previous training.

• 1. Ethics

This study was approved by the Ethics Committee of Bordeaux Uni- versity Hospital. All participants gave written informed consent. Once the simulation was completed, the participants were debriefed, and they were free to ask questions of an emergency physician and receive an introduction to first aid techniques.

1. Results

Thirty-five volunteers were randomised before the sessions and 33 (17 in group A and 16 in group B; age, 25-75 years; median, 36 years) ultimately came to the simulation lab. Their characteristics are pre- sented in Table 1. Nine of the participants (27%) had already been trained in first aid, but only 2 within the past five years.

Table 2 and Fig. 2 show the main results of the study. We found a better median QCPR global score during TTHT sessions than during

TFT: Two-Fingers Technique

TTHT: Two-Thumbs Encircling Hands Technique Med: median

IQR: Interquartile Range

TFT sessions (74 vs. 59, P = 0.046) (Table 2 and Fig. 2). Fig. 3 presents the global QCPR scores for all participants by group. TTHT was more ef- ficient than TFT for almost all of the bystanders (Fig. 3). Time spent in the proper position for chest compressions was also better during TTHT (91 vs. 73, P = 0.015). Chest compressions release was more effec- tive with TFT (72 vs. 51, P = 0.002). No differences were found between the two session types for any of the other CPR parameters measured by the SPPSR, such as chest compression rate, rate of correct chest com- pressions, chest compression depth, length of no flow, and time to first chest compression. (See Table 3.)

Volunteers committed more errors during TFT (19 vs. 1), as noticed by the observer. A large majority of participants in both groups preferred TTHT and described this technique to be less tiring and less painful (94%).

1. Discussion

The results of the study support the hypothesis that TTHT may be more effective than TFT for infant CA when explained by a trained ECR over the phone and provided by non-health professionals. The results of this study support the hypothesis that TTHT may be easier to provide. This is the first study to assess the efficacy of the two CPR techniques recommended for infant CPR in a population of non-caregivers. The de- sign chosen for the study enhanced the results, as each bystander per- formed both types of CPR. A large majority of participants had better results during the TTHT session (Fig. 2). These results obtained in an un- trained population are very important in the context of OHCA. In fact, the proportion of the population trained in CPR is low (around 20%) [36-38], suggesting that TTHT should be used for all new CPR, whether

the rescuer is alone or not.

Although we find a better overall performance of the QCPR score for the TTHT, the lack of release that we found there must require our atten- tion in the transmission of oral instructions. It could be surprising to find a better efficacy on the global score, but the reason is probably that “wrong” releases in the TTHT group were much closer to the guidelines threshold than in TFT group. In fact, chest compression release is a bi- nary variable when used alone but it is not a non-binary variable when applied to compute the global score [39].

This is also one of the first studies using RBQCPR and SPPSR associ- ated with an observer evaluation to assess the efficacy of CPR. SPPSR im- proved objectivity, as the QCPR score was automatically computed. The design and objective measurement that we used reduced measurement bias and enhanced the superiority of TTHT.

One of the main limitations of the study was the absence of insuffla- tion before starting CPR as recommended by the ERC [19]. In fact, one of the leading causes of infant CA is hypoxemia [40]. For that concern, the international guidelines advocate beginning with insufflations [19,41]. However, bystander witnesses are occasionally embarrassed by insuf- flations, and the ERC also considered it better to perform only chest compressions when a rescuer is alone. It could be interesting to assess

Table 2

Comparison of Cardiac resuscitation data according to chest compression technique: median [IQR].

	All		TFT		TTHT		P
QCPR Global score (%)	71	[32-90]	59	[22-85]	74	[55-90]	0.046
Compression score (%)	73	[32-90]	65	[22-86]	74	[55-90]	0.058
Chest compressions per min	108	[99-119]	108	[101-119]	108	[98-116]	NS
Rate of correct chest compression (%)	51	[25-74]	51	[25-73]	51	[25-74]	NS
Number of chest compressions	208	[187-230]	208	[194-231]	204	[186-228]	NS
Mean depth of chest compression (mm)	43	[40-43]	42	[41-43]	43	[40-43]	NS
Rate of correct chest compression depth (%)	100	[98-100]	100	[98-100]	100	[99-100]	NS
Chest compression release (%)	73	[30-98]	83	[58-99]	42	[12-95]	0.002
No flow (s)	1	[0-1]	1	[0-1]	0	[0-1]	NS
Correct position for chest compression (%)	100	[86-100]	98	[38-100]	100	[99-100]	0.015
Time to first chest compression (s)	36	[35-40]	37	[35-40]	36	[35-40]	NS

Linear mixed models, computed for the complementary analysis, showed that the TTHT method performed was the only variable associated with a better QCPR global score (model 1: ? = 14.3; 95% CI, 2.4-26.2; model 2: ? = 14.5; 95% CI, 2.5-26.6).

the impact of adding five insufflations before starting CPR on the effi- cacy of both techniques, but this is not likely to change the results.

As a first approach among non-heath professional’s, we decided to perform short sessions of 2 min CPR. Results found in our study could be different if length of session was longer. Fatigability induced by each technique should be investigated in further studies.

Selection of participant using social network potentially introduced a bubble effect. However, supervisors didn’t know them, and measure- ments were performed by RBQCPR. Thus, bias introduced by this re- cruitment method should be minimal.

Standardized telephone answers used by the same ECR limited dif- ferences between information provided to bystanders at the beginning of CPR. Specific advice based on rescuer questions was given during chest compressions to assist with CPR, which should have reduced in- formation bias.

However, we cannot exclude that these findings about paediatric CPR, observed in a sim environment could be different in real-life condi- tions. Yet, some studies suggested that results obtained during simula- tion could have a good correlation with real-life [42]. In fact, an observational study with video based comparison did not find much dif- ferences between TTHT and TFT [43].

Moreover, during simulations participants did not have access to au- tomated defibrillator and of course this can change efficacy of resuscita- tion but for newborn infants, CA mostly happens at home with parents without immediate access to defibrillator.

Bystanders mostly preferred the TTHT technique. This may be the consequence of less pain and fatigue experienced during CPR. Moreover, as suggested by Rodriguez et al. [44], this result emphasises the point

Fig. 2. Boxplot comparing the effects of the two-thumbs encircling hand technique (TTHT) and the two-fingers technique (TFT) on the QCPR global score.

that if the explanation is easier, it leads to the best results. This study was conducted on a 6-year-old mannequin that provided two types of information for the two groups: 1) “PUSH HARD” and 2) “PUSH TWO INCHES”. The “PUSH HARD” group showed better chest compression depth results. We found that the technique preferred by participants with the younger mannequin was also the one that gave the best effi- cacy and quality.

We also found that TTHT seemed easier for the ECR to explain. Thus, the fewer numbers of errors in the TTHT group were likely due to the easier understanding and set up of this technique. This is also supported by Fig. 3. In fact, no improvement was found whatever the order of re- suscitation technic. Experience of people in doing paediatric CPR seemed to be not modified by the order defined by randomization.

The results from this study support those of previous studies per-

formed in a caregiver population [20-29], suggesting the superiority of TTHT for infant CPR. Although previously advisable only for two or more rescuers, we think that TTHT should be considered when only

Fig. 3. Bland-Altman plot (a) and scatter plot (b) computed to compare the effects of TTHT and TFT on the QCPR global score.

Table 3

Multivariate analysis performed with a linear mixed model to assess the effect of CPR technique on QCPR global score.

? 95% CI

Model 1: age, sex, body mass index, previous training, order

TTHT vs. TFT 14.3 [2.4-26.2]

Model 2: age, sex, body mass index, previous training

TTHT vs. TFT 14.5 [2.5-26.6]

one rescuer is available, and for all CPR in <1-year-old children, regard- less of whether the rescuer is trained.

1. Conclusions

This study supports the superiority of TTHT for infant CPR performed by non-health professionals when an ECR provides advice during the call. It seemed to be the best technique for a solo rescuer regardless of previous training. An algorithm detailing the exact scripting for the in- terrogation of the call by ECRs to assist with bystander CPR should be further clarified to improve and standardize the emergency call re- sponse for infant CA.

Contributor’s statement

(1) substantial contributions to conception or design of the work, or the acquisition, analysis, or interpretation of data for the work (all au- thors); and (2) drafting of the work (CGJ, ML and ET) or revising it crit- ically for important intellectual content (all authors); and (3) final approval of the version to be published (all authors); and (4) agreement to be accountable for all aspects of the work by ensuring that questions related to the accuracy or integrity of any part of the work are appropri- ately investigated and resolved (all authors).

Ethical approval

The protocol was approved by the French data protection authority and the regional ethics committee under the number GP-CE-2019-02. All participants gave informed consent.

Transparency declaration

The lead authors (ET, ML and CGJ) affirm that the manuscript is an honest, accurate, and transparent account of the study being reported; no important aspects of the study have been omitted; and any discrep- ancies from the study as planned have been explained.

The English in this document has been checked by at least two pro- fessional editors, both native speakers of English. For a certificate, please see: http://www.textcheck.com/certificate/ePa7cy

Declaration of Competing Interest

All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corre- sponding author) and declare: no financial relationships with any orga- nization that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.

The authors declare no conflicts of interest with respect to this article.

Acknowledgements

We thank people whose ongoing participation made this study possible. We are grateful to the participating families. CGJ, ET and ML had full access to all the data in the study and take responsibility for the integrity

of the data and the accuracy of the data analysis.

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi. org/10.1016/j.ajem.2022.09.012.

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