Article, Cardiology

The effect of inclined step stool on the quality of chest compression during in-hospital cardiopulmonary resuscitation

a b s t r a c t

Purpose: A step stool is an ordinary device to improve the quality of chest compression during in-hospital cardiopulmonary resuscitation (CPR). We investigated the effect of an inclined step stool on the quality of CC during CPR on a hospital bed.

Methods: We conducted a randomized crossover study of simulation using a manikin. Two different methods of CC were performed and compared: CC using a flat stool and CC using an inclined (20?) stool. Each session of CC was performed for 2 minutes using a metronome at a rate of 110 beats per minute. The primary outcome was the Depth of CC. The adequate CC rate, Duty cycle, Rate of incomplete recoil, and the angle between the arm of the participants and the bed were also measured.

Results: The median value of the mean depth of CC was 50.5 mm (45.0-57.0 mm) in the flat stool group and 54.5 mm (47.0-58.3 mm) in the inclined stool group (P = .014). The adequate CC rate was significantly higher in the inclined stool group (84.2% [37.6%-99.1%] vs 57.0% [15.2%-95.0%]; P = .016). The duty cycle and the rate of incomplete recoil were comparable between the 2 groups. The angles between the arm of the participants and the bed were more vertical in the inclined stool group (84.0? +- 5.2? vs 81.0? +- 4.8?; P = .014).

Conclusion: Using an inclined stool resulted in an improvement in the depth of CC and the adequate CC rate without increasing the rate of incomplete chest recoil.

(C) 2014

Introduction

Adequate chest compression is essential for ensuring high Quality of cardiopulmonary resuscitation (CPR) [1]. The quality of CC during In-hospital CPR is not optimal, even when a trained health care provider performs CPR [2]. Chest compression during CPR in a hospital is affected by the positional relationship between the victim and the rescuer because CC is usually performed on a medical bed, which is different from an out-of-hospital CPR performed on the floor. However, the American Heart Association (AHA) guidelines and European Resuscitation Council (ERC) guidelines do not provide any details about the rescuer’s position and posture during in-hospital CPR except for the use of a backboard [3,4].

In the position with the rescuer kneeling beside the victim’s chest, the rescuer can apply a greater compression force by positioning his/ her shoulders directly above the victim’s chest. Perkins et al [5]

? Funding Sources/Disclosures: The authors have no relevant financial information or potential conflicts of interest to disclose.

* Corresponding author. Tel.: +82 62 220 6809; fax: +82 62 228 7417.

E-mail address: [email protected] (B.K. Lee).

reported that the CC force was the greatest when the rescuer was kneeling on the floor rather than standing beside the bed, and the bed height had a reverse association with the CC force. The standing position beside a bed can barely result in the optimal posture for providing CC due to the height of the bed. Several studies have evaluated the effect of bed height on the quality of CC and the optimal bed height needed to maintain adequate CC [5-9]. Cho et al [7] reported that a bed height of 20 cm above the rescuer’s knee prevented adequate CC, and Lewinsohn et al [8] reported that a bed height of the rescuer’s midthigh induced the highest intrathoracic pressure during CC.

A step stool is used during in-hospital CPR to overcome the effect of bed height because fixed height beds are widely used in hospitals. A step stool helps position the rescuer’s shoulders directly above the victim’s chest. Lee et al [10] demonstrated that the use of a step stool resulted in an improvement in the quality of the CC, and Edelson et al

[11] reported that a step stool helped the rescuers less than or equal to

167 cm in height in increasing their compression depth. We hypothesized that the use of an inclined step stool could result in a better posture for providing adequate CC rather than that by the use of a flat step stool. The aim of this study was to investigate the effect of an inclined step stool on the CC performance.

http://dx.doi.org/10.1016/j.ajem.2014.04.008

0735-6757/(C) 2014

Methods

Study design

This was a randomized crossover trial. Two different methods of CC were performed: CC using a flat-type (0?) step stool or CC using an inclined-type (20?) of step stool. We made a step stool, which had an angle adjustable roof from 0? to 30? at every 5? (Fig. 1). This study was approved by the Institutional Review Board of Chonnam National University Hospital.

Study subjects and protocol

Twenty-two emergency medical technicians who had received the basic life support (BLS) certification for health care providers from the AHA within the last 2 years participated in the study. Written informed consent was obtained from all of the participants.

The participants were randomly divided into 2 groups, and the 2 methods of CC were performed in each group in a different order. Each participant performed 2 sessions of CC. A sufficient break of more than 2 hours was permitted between 2 sessions. Each session of CC was performed for 2 minutes using a metronome at a rate of 110 beats per minute without ventilation. The participants were not allowed to identify their CC quality. A height adjustable bed and a standard mattress were used. We adjusted the bed height at a level of 10 cm above the knee (midpoint of the patella) of each participant during both sessions. Before and after each CC session, the heart rate and end- tidal CO2 (ETCO2) were measured to investigate the degree of fatigue. After completion of both sessions, the fatigability during both sessions was assessed using the 10-point Visual analogue scale (VAS).

Data collection

The data for demographics (age, sex, weight, height, the last BLS certification date, and experience of performing CC) of all the participants were obtained. The VAS for fatigability after each CC session was also obtained. The mean number of CC, mean CC depth, adequate CC rate, duty cycle, and incomplete recoil rate, were measured by using the

Laerdal PC SkillReporting System (Laerdal Medical, Stavanger, Norway) and Resusci Anne (Laerdal Medical). The lateral view of CC was recorded for measuring the angle between the arm of the participants and the bed at the time of delivering the deepest CC. The heart rate was measured by using PureSAT pulse oximetry (Nonin Medical Inc, Plymouth, MA), and the ETCO2 was measured by using a CapnoFlex LF nasal CO2 sampling cannula (GE Medical Systems, Milwaukee, WI) and a Dash 5000 monitor (GE Medical Systems).

Data analysis

According to the preliminary data, the mean difference in the mean depth of CC between the flat step stool group and the inclined step stool group was 2.89 +- 4.46 cm. We calculated that a minimum sample size of 21 would be needed for a 0.05 type I error with 80% power.

The categorical variables were expressed as numbers (%). The continuous variables were expressed as means +- SD or medians (interquartile range), as a result of the normality test. The paired comparison of continuous variables was performed with the paired t test or Wilcoxon Signed Rank Test, as appropriate. Multivariate linear regression was used to identify any interactions between variables. The effect of the use of step stool during CC over time was assessed using repeated-measures analysis of variance (RM-ANOVA) with the mean depth of CC (25-30, 55-60, 85-90, and 115-120 seconds) set as the response variable. Post hoc analysis between the 2 groups at each time point (25-30, 55-60, 85-90, and 115-120 seconds) was performed using the paired t test with Bonferroni correction. Data were analyzed using the PASW/SPSS version 18.0 for Windows (IBM, Chicago, IL). A P b .05 was considered significant.

Results

All of the 22 participants (17 were males and 5 were females) were included in the analysis. The median age of the participants was 23.5 years (22.0-25.0 years). The mean weight and height were 66.4 +- 9.2 kg and 172.6 +- 5.5 cm, respectively. The median body mass index (BMI) was 22.1 (19.9-23.8). The median time interval from the last

Fig. 1. Flat step stool and inclined step stool. A, Front of the flat step stool. B, Back of the flat step stool. C, Front of the inclined (20?) step stool. D, Back of the inclined (20?) step stool.

Table 1

Comparison of CC quality and angle between the arm of the participants and the bed

Flat step stool

Inclined step stool

P

CC rate, min-1

110 (109-110)

110 (109-110)

.304

Mean depth, mm

50.5 (45.0-57.0)

54.5 (47.0-58.3)

.014

Adequate compression, %

57.0 (15.2-95.0)

84.2 (37.6-99.1)

.016

Duty cycle, %

46.5 +- 1.2

46.3 +- 0.8

.877

Incomplete recoil, %

1.6 (0.0-23.5)

0.5 (0.0-8.7)

.723

Angle between the arm of the

81.0 +- 4.8

84.0 +- 5.2

.014

participants and the bed

BLS certification was 6.5 months (2.0-7.0 months). The median number of occasions of performing CC was 2 (0-2).

The CC rate between the 2 groups was not different. The mean CC depth and adequate CC rate were significantly improved in the inclined step stool group compared with the flat step stool group (Table 1). However, the duty cycle and incomplete recoil rate were not different between the 2 groups. The angle between the arm of the participants and the bed was more likely to be 90? (P = .014) (Table 1). multivariate regression analysis found no significant interaction between the rescuer’s demographics and CC depth. The relationship between change in CC depth, height, and change in duty cycle is shown in Fig. 2.

The differences in heart rate and ETCO2 before and after the CC sessions were not different between the 2 groups (Table 2). However, the subjective score for fatigability was significantly lower in the inclined step stool group (P b .001) (Table 2). The depth of CC was significantly decreased with the lapse of time during CC in both groups (P b .001) (Fig. 3). However, RM-ANOVA showed no interaction between time and 2 groups (P = .058) (Fig. 3).

Discussion

The use of an inclined step stool (20?) helped position the participant’s shoulder more vertically over the manikin’s chest and improved the quality of CC without inhibiting the chest recoil. The depth of CC was decreased with the lapse of time. However, the use of

an inclined step stool helped maintain deeper depth of CC compared with the use of a flat-type step stool within 2 minutes of CC.

Chi et al [6] reported that the bed height (floor, 37 and 63 cm height) did not affect the CC force. However, it is clear that a bed height above the midthigh declines the quality of CC. Cho et al [7] reported that a bed height of 20 cm above the knee decreased the CC depth. Perkins et al [5] found that the CC force declined with increasing bed height, and Lewinsohn et al [8] demonstrated that when the manikin’s chest was in line with the midthigh height of the rescuer, maximal intrathoracic pressure was achieved, compared with that with the xiphisternum and anterior superior iliac spine height. The rescuers usually have difficulty in performing CC on a fixed height bed. Using a step stool during CPR in a hospital is a simple method to improve the CC performance. In the study investigating the effect of backboard and a foam mattress on the quality of CC, a step stool was also used to achieve a better position for performing CC [12]. The impact of the use of a step stool on CC depth has been proven [10,11]. The study, which demonstrated the effect of using a step stool on the quality of CC, showed that the use of a step stool helped maintain the bed height below the midthigh of rescuer and the angle between the rescuer’s arm, and the floor was more vertical [10]. Ultimately, the use of the step stool resulted in an increase in the depth of CC [10,11]. In the present study, using an inclined step stool helped make the angle more vertical as recommended by the AHA guidelines and resulted in an improvement in the depth of CC. This provides a theoretical advantage because the CPR provider can apply a greater compression force by positioning his/her shoulders directly above the victim’s chest. The significant difference in the angle between the 2 groups in the present study is one of the possible explanations for the improvement in CC depth.

A deeper CC depth is associated with increased coronary perfusion

pressure, higher success of defibrillation, increased cardiac output, and finally, improved clinical outcomes [13-16]. Edelson et al [14] reported that a 5 mm increase in CC depth was associated with an approximately 2-fold increase in the odds of defibrillation success, and Kramer-Johansen et al [15] reported that an increased CC depth was associated with increased chance of hospital admission with restoration of spontaneous circulation in an out-of-hospital cardiac

Fig. 2. The relationship between change in compression depth, change in duty cycle, and height. Cubic smoothing spline demonstrates insignificant association between compression depth change (A), duty cycle change (B), and height (compression depth change and height, R2 = 0.061; duty cycle change and height, R2 = 0.121). Each circle represents the change in compression depth or change in duty cycle for one participant.

Table 2

Comparison of fatigability after CC using the 2 methods

Flat step stool Inclined step stool P

Difference in the heart rate, min-1

42.0 +- 19.2

41.3 +- 15.5

.859

Difference in ETCO2, mm Hg

3.5 (1.8-6.0)

3.5 (2.0-7.3)

.147

VAS score for fatigue

8 (7-8)

5 (3-6)

b.001

arrest setting (5% increase per 1 mm). A study by Edelson et al [11,14], which analyzed the effect of using a step stool, demonstrated that the use of a step stool resulted in an increase in the CC depth from a mean of 46 +- 13 mm to 50 +- 11 mm, which means a 20% increase in the chances of being admitted alive according to their previous study. Using an inclined step stool in the present study resulted in an increase in the CC depth from a median value of 50.5 mm (45.0-57.0 mm) to 54.5 mm (47.0-58.3 mm) compared with that using a flat- type step stool, and this result was similar to that in the previous study. Edelson et al [11] also reported that the step stool helped a rescuer with short stature (less than 167 cm) to improve the depth of

CC. However, the rescuer’s height was not associated with change in compression depth in the present study because the bed height was adjusted to a level of 10 cm above the knee of each participant to minimize the confounding effect of height.

One of the expected adverse events of performing CC using a step stool is incomplete chest recoil. Incomplete chest recoil should be avoided because it is associated with decreased coronary perfusion pressure, cardiac index, and cerebral perfusion pressure [17]. Duty cycle is also associated with Myocardial blood flow and cerebral blood flow [18,19]. A shorter (30%) duty cycle provides superior Myocardial and cerebral perfusion than a longer (60%) duty cycle [18,19]. The AHA recommends a duty cycle of 50% under consideration of feasibility of practice [3]. Edelson et al [11] reported that CC performed using a step stool resulted in higher incomplete recoil fraction than CC performed without using a step stool. They also reported that the taller rescuer performed the higher fraction of incomplete chest recoil [11]. However, in the present study, the incomplete recoil rate was comparable between the 2 groups, and the participant’s stature was not associated with a change in duty cycle. The lower BMI of participants in the present study compared with the result of the study by Edelson et al [11] might not affect the change in duty cycle. The duty cycle in both groups in the present study indicated that the duty cycle was adequately maintained below 50%.

Fig. 3. The depth of CC with the lapse of time (30, 60, 90, and 120 seconds). The depth of CC decreased over time in both groups (P b .001). The change in CC depth over time was not different between the 2 groups (P = .058). The depth of CC at each time point (30, 60, 90, and 120 seconds) was significantly different. ?b .0125 (Bonferroni corrected P value).

The CC depth decreases within 2 minutes after starting CC due to rescuer fatigue [20,21]. Hightower et al [20] demonstrated a drastic drop in compression adequacy from 93% of CC during the first minute to 67% of CC during the second minute. Sugerman et al [21] demonstrated that the CC depth started to decline between 90 to 120 seconds after starting CC during actual in-hospital CPR. Therefore, AHA and ERC recommend switching chest compressors every 2 minutes [3,4]. The CC depth also decreased gradually over time in the present study. However, the increase in the CC depth in the inclined step stool group was maintained over time. The participants also experienced more fatigue during CC performed using a flat step stool. The CC depth at around 2 minutes after starting CC in the inclined- type step stool group was comparable with that at around 1 minute after starting CC in the flat-type step stool group. Chest compression performed using an inclined-type step stool could complement the decrease in CC depth over time with the use of a flat-type step stool. This study has several limitations. First, this was a simulation study, and therefore, our results might be different from those in human subjects. Furthermore, we adjusted the bed height by 10 cm above the knee. However, adjusting the bed height according to the height of each rescuer is not practical, and height adjustable beds are rarely used in hospitals. Second, the inclined step stool not only helps the rescuer lean forward on the bed, but it also lifts the rescuers to a slight extent. To minimize the lifting effect, the bed height was adjusted similarly by 10 cm above the knee during each session of

CC. This method could not identify the effect of height on the CC

depth. Third, it was impossible to blind the participants with respect to the method of CC performed–a flat step stool or an inclined step stool.

Conclusions

The use of an inclined step stool resulted in an increase in the CC depth without increasing the rate of incomplete chest recoil or duty cycle compared with the use of a flat step stool when performing CC on a bed. The CC depth decreased over time. However, using an inclined step stool helped maintain deeper CC depth than using a flat step stool with the lapse of time within 2 minutes. A further clinical trial is needed to confirm the effect of an inclined step stool on CC quality on a bed.

References

  1. Travers AH, Rea TD, Bobrow BJ, et al. Part 4: CPR overview: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122:S676-84.
  2. Abella BS, Alvarado JP, Myklebust H, et al. Quality of cardiopulmonary resuscitation during in-hospital cardiac arrest. JAMA 2005;293:305-10.
  3. Berg RA, Hemphill R, Abella BS, et al. Part 5: adult basic life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122:S685-705.
  4. Koster RW, Baubin MA, Bossaert LL, et al. European Resuscitation Council Guidelines for Resuscitation 2010 Section 2. Adult basic life support and use of automated external defibrillators. Resuscitation 2010;81:1277-92.
  5. Perkins GD, Benny R, Giles S, et al. Do different mattresses affect the quality of cardiopulmonary resuscitation? Intensive Care Med 2003;29:2330-5.
  6. Chi CH, Tsou JY, Su FC. Effects of rescuer position on the kinematics of cardiopulmonary resuscitation (CPR) and the force of delivered compressions. Resuscitation 2008;76:69-75.
  7. Cho J, Oh JH, Park YS, et al. Effects of bed height on the performance of chest compressions. Emerg Med J 2009;26:807-10.
  8. Lewinsohn A, Sherren PB, Wijayatilake DS. The effects of bed height and time on the Quality of chest compressions delivered during cardiopulmonary resuscita- tion: a randomised crossover simulation study. Emerg Med J 2012;29:660-3.
  9. Perkins GD, Smith CM, Augre C, et al. Effects of a backboard, bed height, and operator position on compression depth during simulated resuscitation. Intensive Care Med 2006;32:1632-5.
  10. Lee DH, Kim CW, Kim SE, et al. Use of step stool during resuscitation improved the quality of chest compression in simulated resuscitation. Emerg Med Australas 2012;24:369-73.
  11. Edelson DP, Call SL, Yuen TC, et al. The impact of a step stool on cardiopulmonary resuscitation: a cross-over Mannequin study. Resuscitation 2012;83:874-8.
  12. Andersen LO, Isbye DL, Rasmussen LS. Increasing compression depth during manikin CPR using a simple backboard. Acta Anaesthesiol Scand 2007;51:747-50.
  13. Babbs CF, Voorhees WD, Fitzgerald KR, et al. Relationship of blood pressure and flow during CPR to chest compression amplitude: evidence for an effective compression threshold. Ann Emerg Med 1983;12:527-32.
  14. Edelson DP, Abella BS, Kramer-Johansen J, et al. Effects of compression depth and pre-shock pauses predict defibrillation failure during cardiac arrest. Resuscitation 2006;71:137-45.
  15. Kramer-Johansen J, Myklebust H, Wik L, et al. Quality of out-of-hospital cardiopulmonary resuscitation with real time automated feedback: a prospective interventional study. Resuscitation 2006;71:283-92.
  16. Ornato JP, Levine RL, Young DS, et al. The effect of applied chest compression force on systemic arterial pressure and end-tidal carbon dioxide concentration during CPR in human beings. Ann Emerg Med 1989;18:732-7.
  17. Yannopoulos D, McKnite S, Aufderheide TP, et al. Effects of incomplete chest wall decompression during cardiopulmonary resuscitation on coronary and cerebral perfusion pressures in a porcine model of cardiac arrest. Resuscitation 2005;64:363-72.
  18. Dean JM, Koehler RC, Schleien CL, et al. Improved blood flow during prolonged cardiopulmonary resuscitation with 30% duty cycle in infant pigs. Circulation 1991;84:896-904.
  19. Shaffner DH, Schleien CL, Koehler RC, et al. Effect of vest cardiopulmonary resuscitation on cerebral and coronary perfusion in an infant porcine model. Crit Care Med 1994;22:1817-26.
  20. Hightower D, Thomas SH, Stone CK, et al. Decay in quality of closed-chest compressions over time. Ann Emerg Med 1995;26:300-3.
  21. Sugerman NT, Edelson DP, Leary M, et al. Rescuer fatigue during actual in-hospital cardiopulmonary resuscitation with audiovisual feedback: a prospective multi- center study. Resuscitation 2009;80:981-4.

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