Are two or four hands needed for elderly female bystanders to achieve the required chest compression depth during dispatcher-assisted CPR: a randomized controlled trial

We performed a randomized controlled trial comparing bystander CC quality using Andrew’s manoeuvre (four-hands CC) versus standard HO-CPR (two-hands CC) during simulated DA-CPR in a population aged 50 or older.

The Regional Ethics Committee approved the study (Protocol No. BC-MF-188/2011), and all participants provided written informed consent.

The setting was two classes in the Department of Disaster Medicine of the Lithuanian University of Health Sciences (LUHS).

The sample size was calculated based on the data of our previous research [12], which identified a 6.4 mm (52.9+/−6.8 vs. 46.6+/−8.0 mm) increase in CC depth using Andrew’s manoeuvre. To detect a similar change, at an error of 5 % and a power of 80 %, we estimated that a minimal sample size of at least 20 participants in each group was required.

Lay-people aged 50 or older were recruited from August to November 2013. We posted an invitation letter with an online Google registration form and shared it using Facebook.

The inclusion criteria were: (1) male or female participants aged 50 or older, with or without previous CPR training; (2) participants must score 3 or less on the validated Clinical Frailty Scale (the least frail group of elderly) as assigned by the investigators after interviewing the participants [14]. Exclusion criteria were: (1) musculoskeletal condition precluding the ability to kneel down and perform CC, including status after joint replacement; (2) cardiovascular condition precluding the ability to exert a moderate effort, including previous MI; (3) inability to go up the stairs to the fourth floor where the study was performed; and (4) arterial blood pressure >180/110 mmHg, heart rate <50 and >120 min prior to testing.

We screened the participants for the inclusion and exclusion criteria. Next, we divided the participants in pairs based on their preferences (whom they wanted to work with in a pair) and/or arrival time (males and females separately) and assigned them to a control or intervention group in a randomized fashion. Pairs were randomized employing a randomization list created with Research Randomizer (www.​randomization.​com) and allocated to either control or intervention group. The pair assignments were concealed in opaque envelopes. After randomization, one member of each pair chose one of the 2 opaque envelopes with the letter A or B. Participants were aware that a pair member who received A would start CPR first during testing, but were unaware of the allocation to the intervention and control groups until the end of the test.

After the registration and randomization procedures, the participants were informed that they would perform DA-CPR in pairs and would be prompted to switch between each other at regular intervals. A flow chart of the testing is presented in Fig. 1. Testing was performed in two identical classrooms, with two investigators present in each room. The participants were informed that during the testing, they would only be able to communicate with the medical dispatcher over the telephone and the investigators would not answer their questions. Two certified emergency medical dispatchers from Kaunas EMS who were trained to provide the standard and four-hands CC instructions, received the phone calls from the investigators in their emergency dispatch center located 5 km away from the study setting. On the basis of the randomization results, the investigator informed the EMS dispatcher to read out the standard text (control group) or standard plus CC instructions with Andrew’s manoeuvre (intervention group). Next, the instructor placed an iPhone 4 with the loudspeaker turned on next to the head of the manikin and invited the participants into the classroom. The instructor prompted the dispatcher (by saying “Start”) to begin the simulation and the dispatcher read the standard MPDS ProQA® software (v12.1, 2010 release) text aloud: “Listen carefully, and I’ll tell you how to do resuscitation. Place the heel of your hand on the breastbone in the centre of his chest, right between the nipples. Place your other hand on top of that hand. Push down firmly 5 cm with only the heel of your lower hand touching the chest. Now, listen carefully. Pump the chest hard and fast, at least twice per second. Let the chest come up all of the way between pumps. We’re going to do this until help can take over. Count out loud so that I can count with you. One, two, three, four….”.

The dispatcher asked the participant to switch every 2 min according to MPDS ProQA® protocol. The test lasted for 8 min. (4 cycles of 2 min) and was stopped by the dispatcher. CCs were performed on a resuscitation manikin placed on the floor. Each participant had to complete two CC cycles of 2 min (4 min in total).

To the intervention group pairs, the dispatcher read an intervention text: “Is there anybody else next to the victim who could help you? OK, continue performing compressions. The other person should now stand behind you and place his hands on your shoulders. He should press on your shoulders as you perform compressions to make them deeper. Are the instructions clear? Let’s start: one two three four.” during testing in the middle of every 2-min CC cycle (approximately after 80 CC).

We measured the following baseline characteristics: age, gender, height (m), weight (kg), body mass index, and Clinical Frailty Scale (range 1–9) [14]. We also measured the heart rate (beats per minute), blood pressure (mm Hg), and saturation (%) before and 5 min after the CPR test. Each participant completed a brief survey before and after the CPR test to evaluate his own ability to perform CC, perceived stress and fatigue level (after test), dispatcher’s assistance and Andrew’s manoeuvre (only for intervention group). We used the Likert scale (range 1–5) in our survey.

CC quality data (rate, depth, leaning, hands-off time) were collected automatically using the Laerdal Resusci Anne Manikin PC SkillReporter™ System (Laerdal Medical, Stavanger, Norway) for each participant and every pair. We quantified the total CC number, CC with adequate depth, mean CC depth, CC rate, and leaning of every participant every 2 min. We also manually quantified the mean CC depth, CC rate, and leaning separately for two vs. four hands CC episodes for every participant in the intervention group for 1 min. The chest compression fraction (CCF), hands-off time, and average compression duty cycle was quantified for every pair for the entire 8-min test (although we were not able to assess the average CCF for every participant). The primary outcome was the mean CC depth. The appropriate depth was defined as 5–6 cm, according to the current guidelines [5].

Sixty-eight lay-rescuers were considered for participation in the study (Fig. 2). There were 49 female and 19 male participants. One male was excluded from the study due to high blood pressure. A description of all study groups is presented in Table 1. Male and female groups were comparable according to age, height, weight, and Frailty scale. There were 4 females in the control group who had previous BLS training (median time from the last training was 24 months). Other participants had no prior BLS training experience. Data obtained from 66 bystanders was used for further analysis.

Overall, the CCs in the intervention group were significantly deeper (54.2 vs. 47.8 mm) and CC number with adequate depth was higher (334 vs. 188) compared to the control group (Table 2). Statistical analysis revealed no differences between the intervention and control groups for the CC rate and leaning. There were no significant differences between the intervention and control pairs in CCF, hands-off time and average compression duty cycle (Table 3).

The female rescuers in the intervention group, in which the Andrew’s manoeuvre was employed, achieved the recommended CC depth compared to control group (51.5 vs. 44.9 mm). The CC depth of every male in both groups exceeded 50 mm and did not differ between groups.

All of the participants completed the anonymous questionnaire prior to and after testing; thus, we were unable to analyse the responses based on the group. The questions and answers (median value of Likert scale 1–5) of all 66 participants are presented in Fig. 3. Most of the participants had no prior CPR training and their ability to perform CC significantly improved after testing, 4.0(1.0) vs. 1.0(2.0) according to the Likert scale. The participants of the study stated that the stress level, median 3.0(2.0) and fatigue 2.5(1.0), were moderate. They highly rated the medical dispatcher’s instructions for their usefulness, 5.0(00), and clarity, 5.0(00). The participants of the intervention group described the instructions on Andrew's manoeuvre as very clear, 5.0(00), and useful during CPR, 5.0(0.75). They stated that Andrew’s manoeuvre appeared to help to achieve deeper CCs, 5.0(00).

The participants’ resuscitation skills were evaluated in a simulated situation; however, their abilities during actual resuscitation are unknown. The sample size of the male participants was insufficient to evaluate the effects of Andrew’s manoeuvre on males. Recruiting rescuers via the internet.

A speakerphone was used for all of the participants, which whilst necessary for this study, is not always possible during real DA-CPR. Holding a phone whilst trying to perform Andrew’s manoeuvre may not be as effective.

The test only lasted for eight minutes, and the average response time in Kaunas was 11 min.¹ Thus, the data did not demonstrate the effectiveness of the manoeuvre over realistically longer time periods.