Article, Resuscitation

Usefulness of the compression-adjusted ventilation for adequate ventilation rate during cardiopulmonary resuscitation

a b s t r a c t

Background: To perform high-quality cardiopulmonary resuscitation (CPR), high-quality chest compression and ventilation support should be performed. However, many providers still have not maintained an adequate ventilation rate but hyperventilated during CPR. Thus, this study was conducted to verify that the compression-adjusted ventilation (CAV) would be a more accurate ventilation method compared with the conventional ventilation (CV).

Methods: Volunteer medical students and emergency medical services personnel were recruited. They were randomly divided into either the CV group or the CAV group. In the CV group, participants performed ventilation with estimation of the rate of 8 to 10 per minute (1 ventilation/6-8 seconds). In the CAV group, the ventilation rate was adjusted in line with the compression rate (compression:ventilation, 12:1). In each group, 2-rescuer adult CPR was performed on a manikin, which was intubated with an endotracheal tube, during a period of 8 minutes. The compression rate and the ventilation rate were recorded during CPR. Results: Data on 56 medical students and 41 emergency medical services personnel were analyzed. No significant difference was observed in compression rate (P =.817); however, median (interquartile range) ventilation rate differed significantly between the CV and CAV groups (8.79 [2.19] per minute vs 9.25 [1.07] per minute, P = .016). In addition, compared with the CV group, adequacy of ventilation rate was better in the CAV group (47.9% vs 85.7%, P b .001).

Conclusion: In comparison with the CV, the CAV is a more accurate method for maintenance of an adequate ventilation rate.

(C) 2014

Introduction

High-quality cardiopulmonary resuscitation (CPR) is very impor- tant in resuscitation of the cardiac arrest patient. To perform high- quality CPR, high-quality chest compression and ventilation support should be performed; and adequate Ventilation volume and rate are needed to provide high-quality ventilation support. To maintain an adequate ventilation rate, several types of visual and/or auditory equipment were used in some studies, and significant effects were reported [1-4]. However, equipment for maintenance of an adequate ventilation rate was not usually kept in the actual CPR situation, except in the simulation. Therefore, many providers were educated in maintenance of an adequate ventilation rate by counting seconds (6-8 seconds). However, in recent studies of prehospital and inhospital CPR quality, many providers still had not maintained an adequate ventilation rate but hyperventilated [5-8].

* Corresponding author. Department of Emergency Medicine, Chungnam National University School of Medicine, 282 Munhwa-ro Jung-gu, Daejeon, South Korea. Tel.: +82 42 280 8081; fax: +82 42 280 8082.

E-mail address: [email protected] (S. Ryu).

Thus, we considered the compression-adjusted ventilation (CAV) as an alternative method for maintenance of an adequate ventilation rate and conducted this study to verify that the CAV would be a more accurate ventilation method in comparison with the conventional ventilation (CV).

Materials and methods

Study subjects

The study protocol was reviewed and approved by the institu- tional review board of the study institution (IRB no. 2012-03-009). From March to May 2012, we recruited second-grade medical students and emergency medical services (EMS) personnel who agreed to participate in this study.

Study protocol

In the medical students group, participants were given a 1-hour lecture and 1-hour practice training on chest compression and ventilation methods according to the international CPR guidelines

http://dx.doi.org/10.1016/j.ajem.2014.05.015

0735-6757/(C) 2014

914 Y.-C. Cho et al. / American Journal of Emergency Medicine 32 (2014) 913916

by advanced cardiovascular life support instructors. Then, CPR test was performed 1 hour after education. In the EMS personnel group, participants were recruited by researcher’s visit to the fire station and tested without any additional education, except for instructions on the ventilation method.

Participants were randomly divided into either the CV group or the CAV group according to the ventilation method. Randomization was performed using Microsoft Excel (version 2010; Microsoft, Co, Redmond, Washington). Then, 2 participants made up a team. Each team performed 2-rescuer adult CPR on a manikin (Resusci Anne Skill Reporter; Laerdal, Stavanger, Norway) during a period of 8 minutes. An endotracheal tube was kept on the manikin to simulate a cardiac arrest model in which an advanced airway had been applied. The participants’ roles were changed every 2 minutes during testing. In the CV group, participants performed ventilation support with the rate by estimating 8 to 10 per minute (1 ventilation/6-8 seconds). In the CAV group, the ventilation rate was adjusted in line with the compression rate (compression:ventilation, 12:1). To adjust the ventilation rate, participants who performed ventilation support counted the number of compressions to 12 repeatedly. Each team did not have knowledge of ventilation support methods used by other teams and could not use any tool for counting time. The compression rate and the ventilation rate were measured during CPR, and the results obtained from each participant were recorded separately. Adequacy of the ventilation rate was divided into 3 groups: hypoventilation, less than 8 per minute; adequate ventila- tion, 8 to 10 per minute; hyperventilation, greater than 10 per minute. No modification or additional education was provided during CPR, and in the CV group, we calculated the ventilation rate from the compression rate (compression rate/12) for comparison of the measured ventilation rate and the calculated ventilation rate (assuming that CPR was performed using the CAV method).

Data analysis

We were planning a study of independent 2 groups. From the pilot study, the proportion of adequate ventilation was 0.464 in the CV group and 0.862 in the CAV group. From that result, the calculated sample size for each group was 28 to reject the null hypothesis that the proportion of adequate ventilation for 2 groups was equal (? error of .05; ? error of .1). We used an uncorrected ?2 statistics to evaluate this null hypothesis. From the calculated sample size, we decided to recruit 100 volunteers.

Categorical variables are presented as percentages and compared using ?2 test. Continuous variables are presented as median (inter- quartile range [IQR]), and between-group comparisons were made using the nonparametric Mann-Whitney U test. All tests used a 2-tailed

Table 1

Basic characteristics of participants in each group

Group P

CV (n = 48) CAV (n = 49)

Age, median (IQR), y 30.0 (25.0-35.0)

29.0 (25.0-34.0)

.94

Male, n (%) 35 (72.9)

33 (67.3)

.55

Compression rate, median 115.75 (15.75)

114.06 (15.28)

.82

Ventilation rate, median (IQR), 8.79 (2.19)

9.25 (1.07)

.02

Range (minimum, 11.27 (4.75, 16.02)

5.25 (8.00, 13.25)

(IQR), per minute

per minute maximum)

Ventilation adequacy, n (%) b.001

Hypoventilation 14 (29.2) 0 (0.0)

Adequate 23 (47.9) 42 (85.7)

Hyperventilation 11 (22.9) 7 (14.3)

From subgroup analysis, adequacy of ventilation rate was also better in the CAV group (medical student: 48.1% vs 86.2% [P = .001], EMS personnel: 47.6% vs 85.0% [P = .025]) (Table 2). In addition, in the medical student group, a significant difference in ventilation rate was observed between the CV and CAV groups (P = .001) (Table 2). In comparison of the measured ventilation rate and the calculated ventilation rate in the CV group, significant differences were observed in the ventilation rate (median [IQR]: measured 8.79 [2.19] per minute vs calculated 9.65 [1.31] per minute, P = .004) and the ventilation adequacy (measured 47.9% vs calculated 54.2%, P = .024)

(Table 3, Fig.).

Discussion

Hyperventilation increases intrathoracic pressure and leads to reduced venous return to the right heart and Elevated intracranial pressure [5]. The reduced cerebral and coronary perfusion pressures ultimately lead to a decrease in survival rate [5,9]. On the other hand, hypoventilation or passive oxygen insufflation did not decrease but sometimes improved the survival rate [10-12]. However, there was an opposite result in that hypoventilation decreased the carotid flow [13]. Thus, based on the current Level of evidence, the authors thought that the ventilation support should be performed according to the guideline.

Table 2

Subgroup analysis

Group P

CV (n = 48) CAV (n = 49)

A total of 100 volunteers participated; however, data from 3

Hypoventilation

10 (37.0)

0 (0.0)

Adequate

13 (48.2)

25 (86.2)

Hyperventilation

4 (14.8)

4 (13.8)

EMS personnel (n = 41)

(IQR), per minute ventilation rate, median

(IQR), per minute

? of .05 for statistical significance, and analyses were performed using

IBM SPSS statistics (version 19.0; IBM, Co, Armonk, New York).

Medical student (n = 56) Age, median (IQR), y

25.0 (5.0)

26.0 (4.0)

.570

Male, n (%)

19 (70.4)

17 (58.6)

.359

3. Results

Compression rate, median

118.25 (15.25)

116.25 (18.25)

.838

8.25 (1.75) 9.50 (1.00) .001

participants were missed due to instrument error. Thus, the data used in this study were collected from 56 medical students and 41 EMS personnel. There were 68 males (70.1%), and median age of volunteers (IQR) was 29.0 (10.0) years. No significant differences in

Ventilation adequacy, n (%) .001

there was no significant difference in compression rate (P = .817). However, median (IQR) of ventilation rate was 8.79 (2.19) per minute

(IQR), per minute Ventilation rate, median

(IQR), per minute

sex and age were observed between the CV and CAV groups (Table 1).

Age, median (IQR), y

36.0 (9.5)

36.0 (14.0)

.917

Median (IQR) of compression rate was 115.75 (15.75) per minute

Male, n (%)

16 (76.2)

16 (80.0)

.768

in the CV group and 114.06 (15.28) per minute in the CAV group, and

Compression rate, median

113.50 (25.40)

112.73 (11.66)

.835

9.09 (1.90) 8.97 (1.12) .754

in the CV group and 9.25 (1.07) per minute in the CAV group, with significant difference (P = .016). In addition, compared with the CV group, adequacy of ventilation rate was better in the CAV group (47.9% vs 85.7%, P b .001) (Table 1).

Ventilation adequacy, n (%) .025

Hypoventilation

4 (19.1)

0 (0.0)

Adequate

10 (47.6)

17 (85.0)

Hyperventilation

7 (33.3)

3 (15.0)

Y.-C. Cho et al. / American Journal of Emergency Medicine 32 (2014) 913916 915

Table 3

Comparison of the measured ventilation rate and the calculated ventilation rate in the CV group

Measured Calculated P

For application of the CAV, the compression rate should be maintained within the adequate rate. In recent studies on CPR quality, the compression rate was improved in comparison with past studies and usually distributed within 90 to 120 per minute [14,15]. Although

Ventilation rate, median (IQR), per minute

8.79 (2.19) 9.65 (1.31) .004

compression rates of less than 90 per minute or greater than 150 per minute were observed, those were uncommon cases. If the CAV was

Range (minimum, maximum) 11.27 (4.75, 16.02) 4.02 (7.73, 11.75) Ventilation adequacy, n (%) .024

Hypoventilation

14 (29.2)

4 (8.3)

Adequate

23 (47.9)

26 (54.2)

Hyperventilation

11 (22.9)

18 (37.5)

Several studies for prevention of hyperventilation and mainte- nance of an adequate ventilation rate during CPR have been conducted. Such studies usually used audio-visual feedback equip- ment to control the compression rate and ventilation rate [1-4]. However, in an actual CPR situation, ventilation rate greater than 20 per minute was frequently observed, and the ratio of hyperventilation was approximately 60% of CPR [5-7]. In addition, 1 research study reported that even professional medical providers who were educated on the recent international guideline performed hyperventilation during inhospital CPR situations [8]. Like this, despite many efforts, adequate ventilation was not supported in real situations.

For this reason, we considered the CAV as an alternative method for maintenance of an adequate ventilation rate without use of assistant equipment. As a result, the adequacy of ventilation rate was higher in the CAV group than in the CV group (47.9% vs 85.7%, P b .001). Median of the ventilation rate differed significantly between the 2 groups. However, median of both groups was in the range of adequate ventilation rate. Therefore, the result was interpreted as being clinically meaningless. However, the range and IQR of the ventilation rate in the CAV group were narrower than in the CV group (range, 11.27 vs 5.25; IQR, 2.19 vs 1.07). In addition, in the CV group, the range and IQR of the calculated ventilation rate were narrower than the measured ventila- tion rate IQR (range, calculated 4.02 vs measured 11.27; IQR, calculated 1.31 vs measured 2.19). In addition, the adequacy of the calculated ventilation rate was better than the measured ventilation rate (47.9% vs 54.2%, P b .024). These results showed that the CAV was a good method for maintenance of an adequate ventilation rate without use of assistant equipment during CPR.

The current method (CV group) has been already used for many years. However, it was usually not applied in actual situations. Compared with the current method, CAV has an advantage in that the rescuer supporting ventilation is only required to know 1 number, 12. However, the rescuer who performs the CV is required to know 3 numbers, 6, 8, and 10.

applied to those studies, the ventilation rate would be distributed from 6 to 13 per minute. Therefore, the CAV may decrease severe hypoventilation and hyperventilation greater than 20 per minute. Hence, the CAV might be a better method than the CV for providing ventilation support.

Limitation

There were some limitations of our study. First, among the study subjects, medical students who did not experience an actual CPR situation and were unskilled in comparison with EMS personnel were included. However, the objective of our study was to verify that the CAV could improve the adequacy of ventilation rate without use of additional equipment. Therefore, inexperienced and less educated second-grade medical students were enrolled to verify the educa- tional effectiveness of the CAV and compared with EMS personnel who had already been educated and experienced performance of CPR. Second, our study was not a real CPR situation but a simulation using a manikin, which might lead to a decrease in hyperventilation compared with a real CPR situation. Like other simulation studies, it might be caused by a decrease in participants’ emotional stress [1,2,4]. Third, CPR duration was 8 minutes, which might be shorter than the actual situation. Longer CPR duration could increase participants’ fatigue and could change the Compression quality and rate. However, this was not reflected in our study. Finally, it was not determined whether participants who were educated on the CAV could apply the CAV in an actual situation and perform the CAV again after a lapse of time. Thus, conduct of further studies will be needed to recommend the CAV in an actual situation.

Conclusion

Results of our study show that, in comparison with the CV, the CAV is a more accurate method for maintenance of an adequate ventilation rate. Therefore, the CAV can be applied in CPR. However, conduct of further studies will be needed to evaluate the usefulness of the CAV in actual CPR situation.

Fig. Box plot of the ventilation rate. Measured, measured ventilation rate; calculated, ventilation rate calculated from compression rate (compression rate/12).

916 Y.-C. Cho et al. / American Journal of Emergency Medicine 32 (2014) 913916

References

  1. Kern KB, Stickney RE, Gallison L, Smith RE. Metronome improves compression and ventilation rates during CPR on a manikin in a randomized trial. Resuscitation 2010;81(2):206-10.
  2. Oh JH, Lee SJ, Kim SE, Lee KJ, Choe JW, Kim CW. Effects of audio tone guidance on performance of CPR in simulated cardiac arrest with an advanced airway. Resuscitation 2008;79(2):273-7.
  3. Thayne RC, Thomas DC, Neville JD, Van Dellen A. Use of an impedance threshold device improves Short-term outcomes following out-of-hospital cardiac arrest. Resuscitation 2005;67(1):103-8.
  4. Milander MM, Hiscok PS, Sanders AB, Kern KB, Berg RA, Ewy GA. Chest compression and ventilation rates during cardiopulmonary resuscitation: the effects of audible tone guidance. Acad Emerg Med 1995;2(8):708-13.
  5. Aufderheide TP, Sigurdsson G, Pirrallo RG, Yannopoulos D, McKnite S, Briesen C, et al. Hyperventilation-induced hypotension during cardiopulmonary resuscitation. Circulation 2004;109(16):1960-5.
  6. Abella BS, Alvarado JP, Myklebust H, Edelson DP, Barry A, Nicholas O, et al. Quality of cardiopulmonary resuscitation during in-hospital cardiac arrest. JAMA 2005;293(3):305-10.
  7. O’Neill JF, Deakin CD. Do we hyperventilate cardiac arrest patients? Resuscitation 2007;73(1):82-5.
  8. Maertens VL, De Smedt LEG, Lemoyne S, Huybrechts SAM, Wouters K, Kalmar AF, et al. Patients with cardiac arrest are ventilated two times faster than guidelines recommend: an observational prehospital study using tracheal pressure measurement. Resuscitation 2013;84(7):921-6.
  9. Yannopoulos D, McKnite S, Aufderheide TP, Sigurdsson G, Pirrallo RG, Benditt D, 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(3):363-72.
  10. Hayes MM, Ewy GA, Anavy ND, Hilwig RW, Sanders AB, Berg RA, et al. Continuous passive oxygen insufflation results in a similar outcome to positive pressure ventilation in a swine model of out-of-hospital ventricular fibrillation. Resusci- tation 2007;74(2):357-65.
  11. Bobrow BJ, Ewy GA, Clark L, Chikani V, Berg RA, Sanders AB, et al. Passive oxygen insufflation is superior to bag-valve-mask ventilation for witnessed ventricular fibrillation out-of-hospital cardiac arrest. Ann Emerg Med 2009;54(5):656-662.e1.
  12. Yannopoulos D, Tang W, Roussos C, Aufderheide TP, Idris AH, Lurie KG, et al. Reducing ventilation frequency during cardiopulmonary resuscitation in a porcine model of cardiac arrest. Respir Care 2005;50(5):628-35.
  13. Lurie KG, Yannopoulos D, McKnite SH, Herman ML, Idris AH, Nadkarni VM, et al. Comparison of a 10-breaths-per-minute versus a 2-breaths-per-minute strategy during cardiopulmonary resuscitation in a porcine model of cardiac arrest. Respir Care 2008;53(7):862-70.
  14. Olasveengen TM, Wik L, Kramer-Johansen J, Sunde K, Pytte M, Steen PA. Is CPR quality improving? A retrospective study of out-of-hospital cardiac arrest. Resuscitation 2007;75(2):260-6.
  15. Abella BS, Sandbo N, Vassilatos P, Alvarado JP, O’Hearn N, Wigder HN, et al. chest compression rates during cardiopulmonary resuscitation are suboptimal: a prospective study during in-hospital cardiac arrest. Circulation 2005;111 (4):428-34.

Leave a Reply

Your email address will not be published. Required fields are marked *