a b s t r a c t

Purpose: To evaluate the effect of one-hand chest compression while continuously maintaining an Open airway (OCOA) on rescue breath-associated hands-off time (RAHO) during single-lay rescuer cardiopulmo- nary resuscitation (CPR).

Methods: In this study, 193 CPR/automated external defibrillator certified lay rescuers were randomly allocated into 2 groups and were tested in a standard scenario using a mannequin. In control group (group A), the participants provided standard CPR. In group B, OCOA was performed by placing the heel of the strong hand in the center of the mannequin’s chest while maintaining an open airway using the other hand.

Results: Mean RAHO was statistically significantly different between the two groups (group A: 8.38 +- 1.97 vs group B: 7.71 +- 2.43, P = .008). Only 13 (13.5%) group A and 25 (25.8%) group B providers ventilated the manikin with tidal volumes of 500 to 600 mL, while most participants caused hyperventilation. Although there were no significant differences in mean tidal volume between the groups, stomach inflation was greater in group A (b .001). Chest compressions were deeper in group A (P b .001), while chest recoil was significantly better in group B. In group B, there was a positive correlation between body mass index and compression depth (group A, P = .423; group B, P b .001).

Conclusions: In our study, OCOA resulted in shorter RAHO and less stomach inflation. Our results indicate that the airway should be maintained open during chest compressions, regardless of the technique. Larger studies are needed for the full clarification of OCOA.

(C) 2013

1. Introduction

Cardiac arrest is a major cause of death worldwide. Approximately 300000 arrested people are treated annually by medical personnel, but only one-third of patients admitted to an intensive care unit survive to hospital discharge [1]. The second link of the Chain of survival depict the integration of immediate cardiopulmonary resuscitation (CPR) as a fundamental component of resuscitation; in fact, immediate CPR can double or triple survival from out-of-hospital cardiac arrest (OHCA) [2,3].

After OHCA, the quality of lay rescuer CPR may be suboptimal, as frequent pauses for rescue breaths or Rhythm analysis occur [4]. This “hands-off” period results in interruption of chest compressions and decreases coronary and cerebral blood flow for significant periods of time. Indeed, various studies have shown that a lower total hands-off-

? Source of support: None.

?? Conflicts of interest: None.

* Corresponding author. National and Kapodistrian University of Athens, Medical School, MSc “Cardiopulmonary Resuscitation”, Hospital “Henry Dunant”, 115 26, Athens, Greece. Tel.: +30 210 4133992; fax: +30 210 6972396.

E-mail address: [email protected] (A. Chalkias).

¹ These authors contributed equally to the study.

ratio may increase venous return, coronary perfusion pressure, and the possibilities for return of spontaneous circulation [5-7]. Further- more, positive-pressure ventilation during the initial provision of CPR may be harmful as it may increase intrathoracic pressure which further decreases coronary perfusion pressure. To avoid hyperventi- lation of cardiac arrest victims and prolonged interruptions of chest compressions, passive oxygen insufflation has been recommended as an initial approach to ventilation. According to this, oxygen insufflation is applied by opening the airway with an oropharyngeal device, placing of a non-rebreather mask, and administering high flow (about 10 L/min) oxygen [8]. However, this is practically impossible in a single-lay rescuer OHCA scenario.

We assumed that rescue breath-associated hands-off time (RAHO) may be improved if the airway is maintained open throughout the CPR. Therefore, the aim of our study was to evaluate the effect of one- hand chest compression while continuously maintaining an open airway (OCOA) on RAHO during single-lay rescuer CPR.

1. Methods

From March 2012 to March 2013, all lay people who had successfully completed a European Resuscitation Council CPR/

0735-6757/$ – see front matter (C) 2013 http://dx.doi.org/10.1016/j.ajem.2013.07.030

A. Chalkias et al. / American Journal of Emergency Medicine 31 (2013) 1462–1465 1463

Automated external defibrillator course in Athens, Greece were invited to participate in the study. The study was approved by the Postgraduate (MSc) Study Program “Cardiopulmonary Resuscitation” of the Medical School of the National and Kapodistrian University of Athens, while participation was voluntary and all participants gave informed consent. Exclusion criteria were age b 18 years, any healthcare profession, and previous participation in similar courses; participants with previous experience in CPR were excluded in order to have a more homogenous sample.

The CPR/AED provider textbook was sent to all candidates at least 1 month prior to the course in order to get theoretically prepared, while the courses were organized as previously described [9]. After the end of each course, the participants were randomly allocated into 2 groups and were tested in a standard scenario requiring the use of an AED in a public place. Prior to testing, various variables were recorded. Weight was measured as the average of two determinations with the participant barefoot and in light clothes, height was measured as the average of two determinations, with the participant standing barefoot on standing position, and body mass index (BMI) was calculated as weight (kg) divided by height (m²). In addition, BMI was categorized according to the age and gender cut-off points defined by the World Health Organization in underweight (b 18.5 kg/m²), normal weight (18.5-24.9 kg/m²), and overweight/obesity (>=25 kg/m²) [10]. Also, the maximum strength of the upper body was evaluated with a hand grip dynamometer (Adjustable-handle mechanic Jamar dynamometer-FEI, Irvington, NY, USA) as the average of alternatively making two attempts with each hand with the subject standing up and resting his arm parallel to the body [11].

The manikin used in scenario was “Little Anne” (Laerdal Medical Corporation, Wappingers Falls, NY) and was connected to a computer with a special skill reporting software (Resusci Anne SkillReporter, Laerdal Medical) enabling the recording of CPR variables. The rhythm was ventricular fibrillation, while each individual was asked to perform defibrillation-2 minutes CPR-defibrillation in real time, until professional help arrived. In control group (group A), the participants provided standard CPR according to the 2010 European Resuscitation Council Guidelines for Resuscitation [12], while in group B, the providers performed one-hand chest compressions by placing the heel of the strong hand (compression hand) in the center of the victim’s chest while maintaining the airway open by lifting the chin with the thump and placing the fingers on the lateral surface of the mannequin’s face (airway hand). After completing 30 compressions, the rescuers had to retract the compression hand from the chest and use it for maintaining the initial position of the head in order to use the airway hand for tilting the head and closing the nostrils. After

Table 1

The OCOA sequence

1. Place the heel of the strong hand (compression hand) in the centre of the mannequin’s chest. Keep the arm straight.
2. Open the airway with the other hand by lifting the chin with the thump and placing the fingers on the lateral surface of the face (airway hand).
3. Position yourself vertically above the mannequin’s chest and press down on the sternum 5-6 cm using the compression hand.
4. After each compression, release all the pressure on the chest without losing contact between the compression hand and the sternum; repeat at a rate of 100-

120 min^-1. Compression and release should take equal amounts of time. Maintain the airway open during chest compressions.

1. After completing 30 compressions, place the fingertips of the compression hand under the chin without changing the position of the head. Maintain the airway open with the compression hand and place the airway hand on the forehead.
2. Pinch the soft part of the nose closed, using the index finger and thumb of the airway hand.
3. Give 2 breaths within 5 seconds.
4. Maintain Chin lift using the airway hand as in Step 2 and return the compression hand without delay to the correct position on the sternum.
5. Give a further 30 chest compressions.
6. Continue with chest compressions and rescue breaths in a ratio of 30:2.

Table 2

Demographic data of the participants

	Group A (n = 96)	Group B (n = 97)	P
Age	31.83 +- 7.384	31.19 +- 6.117	.624
Gender (male)	44	42	.723
BMI	24.30 +- 3.66	23.97 +- 3.48	.521
Handgrip strength Activity	33.93 +- 9.050	33.15 +- 9.741	.566
None	5	3	.402
Low	18	16
Moderate	53	58
High	17	20
Smoking (yes)	34	40	.406
Education Primary	1	0	.655
High	13	15
College	50	53
MSc/PhD	32	29

giving two rescue breaths as recommended [12], chin lift was maintained with the airway hand, while one-hand chest compres- sions were resumed by the compression hand (Table 1). Each participant performed one cycle of CPR (2 minutes). Duty cycle was defined as the ratio of compression depth to relaxation, while the researchers did not interfere during the assessment.

Statistical analysis

Data are expressed as mean +- 1 SD for continuous variables and as median and range for ordinal parameters. Categorical variables are expressed as frequency and percentage. Comparisons of categorical variables were performed with Pearson’s chi squared test. Comparisons of continuous normally distributed variables were performed using student’s unpaired t test and for non parametric variables Mann- Whitney U test was used. The Kolmogorov-Smirnov test was used to assess the normality of the distributions. Correlations between variables were performed using Pearson’s, Spearman’s or Phi coefficient, as appropriate. Differences were considered to be statistically significant, when P b .05. Statistical analyses were performed with the SPSS statistical software version 20.0 (IBM SPSS Statistics; SPSS Inc, Chicago, IL).

1. Results

Of the 250 invited providers, 193 (77.2%) accepted the invitation and were included in the study. Between the two groups, there were no differences in demographics or handgrip strength (P = .566) (Table 2). During rescue breaths, only 13 (13.5%) group A and 25 (25.8%) group B providers ventilated the manikin with tidal volumes of 500- 600 mL, while most participants caused hyperventilation. Although there were no significant differences in mean tidal volume between the groups, stomach inflation was greater in group A. Of note, the time needed to give two breaths exceeded the recommended limit of

Table 3

Cardiopulmonary resuscitation parameters of the study

Total rescue breaths in 2 min	10.85 +- 2.103	11.25 +- 2.359	.152
Mean minute volume ventilation	4.68 +- 1.319	4.41 +- 1.466	.175
Mean tidal volume	0.86 +- 0.278	0.87 +- 0.883	.065
Mean ventilation rate	5.55 +- 1.094	5.81 +- 1.176	.107
Stomach inflation (%)	33.88 +- 22.131	16.56 +- 17.280	b.001
Completed cycles	1.06 +- 0.163	1.10 +- 0.198	.126
Hands-off time (s)	8.38 +- 1.97	7.71 +- 2.43	.008
Total compressions in 2 min	179 +- 25.131	183 +- 29.119	.218
Compression depth (mm)	36.43 +- 2.729	28.16 +- 2.556	b.001
Compression rate	144.38 +- 22.257	143.97 +- 22.070	.899
Leaning (%)	12.05 +- 21.153	3.91 +- 9.167	.003
Duty cycle (%)	45.86 +- 2.748	46 +- 4.719	.122

Group A (n = 96) Group B (n = 97) P

1464 A. Chalkias et al. / American Journal of Emergency Medicine 31 (2013) 1462–1465

Fig. 1. Rescue breath-associated hands-off time during one-hand chest compression cardiopulmonary resuscitation. Upper green line: recommended tidal volume 500 to 600 mL; lower green line: recommended compression depth 5 to 6 cm; red color: chest compressions; blue color: rescue breaths. ?t1 = Releasing the compression hand from the chest until placing the lips around the mouth; ?t2 = first rescue breath (first blow until fall of the chest); ?t3 = second rescue breath (second blow until fall of the chest); ?t4 = end of the second breath until placing the compression hand on the chest; RAHO = ?t1+?t2+?t3+?t4.

5 seconds in both groups. However, mean RAHO was statistically significantly shorter in group B (group A: 8.38 +- 1.97 vs group B: 7.71 +- 2.43, P = .008) (Table 3, Fig. 1).

There was a positive correlation between handgrip strength and compression depth in both groups (group A, P = .004; group B, P b

.001), while BMI was positively correlated with compression depth only in group B (group A, P = .423; group B, P b .001) (Fig. 2). In addition, although participants in group A provided deeper compres- sions than those in group B (P b .001), chest recoil was significantly better in group B. Nevertheless, we found no difference in duty cycle between the two groups (Table 3).

1. Discussion

In our study, OCOA resulted in significantly shorter RAHO with the most possible explanation being the execution speed of certain steps (Table 1). Although it was not possible to measure each step independently, the gain in time seemed to result from steps 1, 5, and 8. In step 1, group B participants had only to place their strong hand in the center of the chest in contrast to group A providers who had to place the heel of one hand in the victim’s chest, place the other hand on top of the first hand, and interlock the fingers before they start chest compressions. In step 5, rescue breaths were administered faster as the participants did not have to open the airway after the end of the compression phase. Also, additional time was gained in step 8 in a similar manner to step 1. It has to be mentioned that group B participants had no other experience in CPR before attending the CPR/ AED course and were not trained in OCOA prior to the evaluation. Therefore, OCOA-associated RAHO could be further decreased by optimizing the technique of OCOA. In addition, as current recom- mendations give increased emphasis on the importance of minimally interrupted high quality chest compressions and decreased hands-off time, it would be of interest to assess OCOA-associated RAHO in experienced lay rescuers or healthcare providers.

We found that the time needed to give two breaths exceeded the recommended limit of 5 seconds [12]. This was a relatively expected finding as lay rescuers not only perform Rescue breathing slower than trained professional personnel [13], but also, lay people performing single-rescuer CPR take an average of 16 seconds for providing the

recommended breaths [14,15]. Also, the prolongation of the time needed for rescue breaths may have significantly decreased the number of chest compressions delivered per minute, increasing thus hands-off time in both groups.

Of note, although there were no significant differences in mean tidal volume between the groups, stomach inflation was greater in group A. Stallinger et al reported that during mouth-to-mouth ventilation, only large (~ 1000 mL) tidal volumes are able to maintain both oxygenation and adequate carbon dioxide elimination [16]. However, when the airway is unprotected, a tidal volume of 1 L produces significant gastric distension with hemodynamic and respiratory adverse effects [17-21]. Taking into account our results, as well as that the optimization of ventilation and hemodynamics during CPR results in increased return of spontaneous circulation rates and decreased severity of Post-cardiac arrest syndrome [8,20-26], we conclude that the airway should be maintained open throughout the CPR, regardless of the technique or the number of rescuers. In two-lay rescuer CPR, OCOA may be performed by the compressor when

Fig. 2. The association between compression depth and BMI in group B. BMI = Body mass index.

A. Chalkias et al. / American Journal of Emergency Medicine 31 (2013) 1462–1465 1465

the second rescuer prepares the AED or during rescuer changing due to fatigue.

In addition, we found that although BMI and handgrip strength were not different between the two groups, compression depth was greater in group A. This suggests that OCOA is characterized by less compression force than standard CPR which is quite reasonable if we take into account the difference in power generated from both hands in contrast to one hand. However, it is noteworthy that the compression depth was not consistent with current recommenda- tions in both groups and most providers compressed the chest at a depth of less than 5 cm. This could be explained by the high compression rate in both groups which is associated with lower compression depth; avoiding excessive compression rates may lead to more compressions of sufficient depth during OCOA [27,28]. Further- more, our results support those of Geddes et al. who reported that most laypersons do not exert enough force for effective CPR [29]. Also, this finding could be explained in part by the poor cardiorespiratory fitness which usually characterizes the overweight or obese in- dividuals. This may be of major importance, especially if we consider that fatigue is one problem to perform CPR and OCOA could make more fatigue when CPR duration gets prolonged. The devastating effects of fatigue could be minimized if rescuers switch about every 2 minutes to prevent a decrease in Compression quality or with the intermittent use of standard CPR when fatigue increases during OCOA. However, OCOA-associated fatigue cannot be determined accurately as OCOA was applied and evaluated for the first time and its technique has not been optimized yet. In either case, as the duration of optimal CPR depends on the rescuers’ individual work capacity [30], increased emphasis should be given on compression force during the training of unfit lay people.

This study has several limitations. First, it was limited to a single

training center and generalizations to all lay providers cannot be assumed. Second, as OCOA was applied and evaluated for the first time, its technique has not been optimized yet. Third, the participants in group B were not trained in OCOA prior to the evaluation and technique-associated bias cannot be excluded. Another important limitation was the issue of fatigue of CPR. Finally, it was impossible for the participants to achieve the recommended compression depth, as the mannequin’s spring can be compressed up to 4 to 5 cm.

1. Conclusions

In our study, OCOA resulted in shorter RAHO and less stomach inflation. Our results indicate that the airway should be maintained open during chest compressions, regardless of the technique. Larger studies are needed for the full clarification of OCOA.

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