- Email: [email protected]
Evaluation of a prototype CPR assist-tool
Evaluation of a prototype CPR assist-tool Ernest A. Lado, Jr., D.D.S., and Thomas B Fast, D.D.S., M.S.D., Gainesville, Fla.
A CPR provider is often called upon to expend considerable physical energy to deliver external cardiac compressions. This research evaluates and compares the performance of recently certified basic rescuers on a mannequin using the standard method of CPR. and the performance with an adjunctive CPR assist-tool. Use of the tool significantly increased the overall quality of individual performances by reducing the frequency of inadequate compressions and increasing the time of acceptable performance. Other common errors were not significantly affected. (ORAL SURG. ORAL MED. ORAL PATHOL. 625280-283,
1986)
A pproximately 3,400 Americans suffer heart attacks each day. Many of these victims have sudden cardiac arrest and/or ventricular fibrillation.’ Of the sudden cardiac deaths, most (60% to 70%) occur prior to hospitalization,’ thus justifying the emphasis on CPR training of health professionals and the public alike. It is virtually impossible to guarantee strict compliance with the standards set by the American Heart Association and the American Red Cross. Therefore, all practical methods for improving quality and duration of life-sustaining CPR performance should be investigated. Recently, the overall effectiveness of CPR has been challenged, especially when it is required for periods longer than 12 minutes3 This ineffectiveness may be due to a lack of adequate perfusion of vital organs that results from inadequate or improper chest compressions. Many cardiac arrests also occur at remote sites far removed from hospitals and/or advanced life support units. Thus, it is reasonable to assumethat resuscitation support lasting 20 minutes or more might be necessary. The purpose of this study was to evaluate the efficacy of a prototype CPR assist-tool (Fig. 1) in increasing length and improving performance quality of external cardiac compressions (ECC) by comparing its use with the traditional “hands-only” method. REVIEW OF LITERATURE
The criteria for successful one-person CPR, established by the American Heart Association, requires
This study was supported by Biomedical Research Grant, College of Dentistry, University of Florida. 280
(for the average adult) that the sternum be depressed 1% to 2 inches, at a rate of 80 compressions per minute interspersed with two mouth-to-mouth ventilations after each series of 15 compressions.2This prescribed depth of compression translates to between 80 and 120 pounds of pressure, depending upon the morphology of the victim and chest compliance.4 It should be noted that all certified CPR providers must meet the criteria for certification, although there is no specific minimum time of demonstrated performance. Because considerable physical energy is required by CPR rescuers, excessive stress to the provider’s own cardiovascular system is possible and some rescuers have had heart attacks while providing CPR.5 Automatic mechanical cardiac compressors help to overcome the problem of fatigue; however, these implements are relatively expensive, cumbersome, and impractical for use in dental offices, medical offices, and other public facilities.6 In addition, the sophistication of these devices requires specific operator training or licensure; therefore, they are not widely used. METHOD
Twenty healthy young adults (fifteen women and five men) recently certified as basic CPR rescuers by the American Heart Association participated in this study. Half of the subjects started with the tool and half started by hand. Each subject was asked to provide one-person ECC at four separate sessions spaced 1 week apart, alternating between the “hands-only” method and the “tool-assisted” method. Each session lasted 20 minutes or until the subject felt unable to continue becauseof fatigue or discomfort.
Volume 62 Number 3
Prototype CPR assist-tool
281
1. A, The CPR assist-tool is constructed of a hard plastic capable of withstanding many times the force required for adequate compressionsof the chest. The working end is covered with a pliable rubber cushion to absorb forces applied to the sternum. The handles are notched, and two stops allow the tool to be easily held. B, Performance summary with respect to time. Note increase in overall performance with the assist-tool. Fig.
The tests were conducted on a standard training mannequin (Recording Resusci Anne). Each performance was recorded and later analyzed independently by two AHA-certified
instructors
for errors as
defined by the AHA’s Manual for Instructors of Basic Cardiac Life-Support, The test subjects were instructed to provide compressionsas recommended by the American Heart Association, and brief instructions were given in accordance with the manufacturer’s recommendations regarding use of the assist-tool.
In order not to bias their performance, the subjects were not advised as to the expected findings of this study. Once set up, the subjects were left alone to perform on their own. The same mannequin was used for all trials and was regularly calibrated to ensure its reliability as a mechanical test standard.* The compression pres*Mechanical calibration accomplished with the device “lnstron Universal Testing Facility” produced by Instron. Inc., of Danton, Mass.
282
hdo and Fast
Table
I. Group performance and derived t values
Oral Surg. September, 1986
Common
Inadequate
Excessive compressions
Thrusting compressions
Bouncing
lnaccurafe hand position
Toral minutes
Acceptable minutes
29 12.4
0.3 4.1
3.6 4.1
18.5 11.2
12.0 9.7
2.5
0.2 0.3 0.18 0.55 0.12 1.46
1.4 3.6 2.16 3.96 0.89 2,44*x
23.3 9.1 -4.80 7.20
19.1 9.2 -7.60 6.72
Rate
compressions
Hand Mean SD
11.6 il.2
6.1 6.3
0.5 1.1
2.4 4.2
Tool Mean SD Mean of difference SD SE
18.1 10.3 - 1.15 5.83 I .30
2.1 2.8 4.02 4.66
0.88
3.86*
5.1 16.8 -4.56 15.84 3.54 1.29
3.2 5.3 -0.76 2.92 0.65 1.11
i
1.04
errors
inaccurate hand relax
11.2
0.39 1.27 0.28 1.37
1.6 I
1.50
2.98’
5.0-l*
*I > 2.539 = P < .Ol **t>1.729=P<.05
sure required at the minimum acceptable pressure gradient on the recording tape was 82 pounds (1% inch displacement) and the maximum was 109 pounds (2 inch displacement). These pressure parameters remained constant throughout the study. A record was kept of each subject’s weight, height, arm length,* and torso length.7 Each test subject completed a subjective evaluation questionnaire at the end of the last session. Statistical
analysis
Errors associatedwith chest compressionsand the performance times were submitted for statistical analysis. A one-sided paired t test was performed to test the null hypothesis (Ho) that there is no difference between the hand and tool methods. RESULTS An aggregate total of 1,600 minutes of rescue effort was requested of the twenty providers (800 minutes of the standard hands-only method and 800 minutes using the assist-tool). Fig. 2 illustrates the length of performances with or without the assisttool. Note that the subjects were able to perform for a longer period with the tool, and at a higher quality of performance. Analysis of group performances (Table I) shows that the rate of compressions remained constant between groups, whereas there was almost a threefold decrease in inadequate compressions with the *Arm length measured from the heel of the hand to the acromion of the scapula. tTorso length measured from the floor to the acromion of the scapula {with the subject in an erect kneeling posture).
assist-tool. These values are statistically significant at a one-tail value of P < .Ol. Although there appears to be an increased tendency to overcompress with the tool, the t value is not large enough to rule out chance, even at P < .05. The increase in excessive compressions was due mainly to one volunteer who avercompressed on every compression while using the assist-tool. Other common errors tended to remain constant, although the duration of performances increased by about one third with the use of the assist-tool, as did time of acceptable performance. Both of these findings were significant at P-c .01. Analysis of the subject’s body build, size, and dimensions indicates that the assist-tool not only helps light-weight persons to deliver stronger compressions but also improves the performance of most persons. An analysis of the subjective evaluation questionnaire showed that sixteen of twenty volunteers thought the CPR assist-tool permitted compressions for a longer period than the hands-only method and with less physical discomfort (i.e., wrist pain, arm soreness,backache). Fourteen of the twenty thought they made fewer procedural errors when using the tools. Curiously, two of the persons who thought they did better by hand actually did better with the tool (according to the instructor’s interpretation of the tapes). DISCUSSION
Prompt and effective treatment can save some victims of cardiac arrest. Unfortunately, the physical ability of many rescuers is limited. Therefore, an investigation of adjunctive CPR devices is justifiable, Laboratory evaluation of the CPR assist-tool used in
Volume Number
Prototype CPR assist-tool
62 3
this study is subject to conjecture when applied to actual use; however, such devices should be tested prior to being used on a victim of cardiac arrest. The results of our study indicate that the tool could, in fact, improve a rescuer’s performance. Inadequate compression of the chest was the most frequent error of recently trained CPR providers. The assist-tool enabled most of the subjects to compressthe chest more effectively and for a longer period of time. The tool is believed to derive its effectiveness from its design. Correct cardiac compression requires that only the heel of one hand be in contact with the victim’s sternum. The fingers must be kept elevated and not allowed to contact the victim’s chest. This maneuver requires a conscious effort and results in a physical posture that is awkward and uncomfortable. If the rescuer’s arm line is held vertical, as specified by the AHA, the hand-heel requirement can be complied with only if the wrist is hyperextended. Many rescuers hnd this position difficult to maintain without discomfort. Another source of discomfort is that correct compression specifies that the arms must be held rigidly in a V configuration. This position requires more muscular energy than if the arms are held parallel to each other. Imagine doing push-ups with one hand on the other, and the required effort becomes obvious! A concern raised about the assist-tool is loss of a “sense of feel” when landmarking and while compressing. Since the only officially recommended procedure for landmarking is the “two-finger” method, the assist-tool can be positioned as easily as the heel of a hand. Second, the 1% to 2 inches of chest compressionis not measured by the heel of the hand;
283
rather, it is a distance that must be continuously estimated by watching the chest during a rescue. In fact, on occasion, this “loss of feel” may prove to be advantageous since rib fractures do occur and the tool may provide some insulation from the actual breaking or grating sensations. This is significant in that one’s tendency to compressadequately could be hindered by the psychological repulsivenessof such a situation. One could hypothesize a myriad of objections or problems associated with the assist-tools, but that is not the purpose of this study. It should be evident that, with proper training in the use of such tools, the overall performance of CPR could be improved. REFERENCES I. Levy RT, Moskowtiz 2. 3.
4.
5.
6.
J: Cardiovascular research: decades 01 progress a decade of promise. Science 217: I21 - 129. 1982. Standards and guideline for cardiopulmonary (CPR) and emergency cardiac care (ECC). JAMA 244: 453-509, 1980. Eisenbcrg MS, Hallstrom HP, Compass MK. Borgncr L, Short F. Pierce J: Treatment of ventricular fibrillation. JAMA 251: 1723.1726. 1984. Vallis CJ, MacKewie I. Lucas BG: The force necessary for external cardiac compression. Practitioner 223: 268-270, 1979. Lonergan JH, Youngberg JZ, Kaplan JA: Cardiopulmonary resuscitation: physical stress on the rescuer. Crit Care Med 9: 793.795, I98 I. Taylor GJ, Rubin R, Tucker M, Greene HL, Rudikoff MT, Weisfeldt ML: External cardiac compression: a randomized comparison of mechanical and manual techniques. JAMA 240: 644-h46. 197X.
Keprinr
rrqurs
Dr. Ernest Department College of University P. 0. Box Gainesville,
Is to.
A. Lado, Jr. of Oral Medicine Dentistry of Florida J-414 JHMHC FL 326 IO
A CPR provider is often called upon to expend considerable physical energy to deliver external cardiac compressions. This research evaluates and compares the performance of recently certified basic rescuers on a mannequin using the standard method of CPR. and the performance with an adjunctive CPR assist-tool. Use of the tool significantly increased the overall quality of individual performances by reducing the frequency of inadequate compressions and increasing the time of acceptable performance. Other common errors were not significantly affected. (ORAL SURG. ORAL MED. ORAL PATHOL. 625280-283,
1986)
A pproximately 3,400 Americans suffer heart attacks each day. Many of these victims have sudden cardiac arrest and/or ventricular fibrillation.’ Of the sudden cardiac deaths, most (60% to 70%) occur prior to hospitalization,’ thus justifying the emphasis on CPR training of health professionals and the public alike. It is virtually impossible to guarantee strict compliance with the standards set by the American Heart Association and the American Red Cross. Therefore, all practical methods for improving quality and duration of life-sustaining CPR performance should be investigated. Recently, the overall effectiveness of CPR has been challenged, especially when it is required for periods longer than 12 minutes3 This ineffectiveness may be due to a lack of adequate perfusion of vital organs that results from inadequate or improper chest compressions. Many cardiac arrests also occur at remote sites far removed from hospitals and/or advanced life support units. Thus, it is reasonable to assumethat resuscitation support lasting 20 minutes or more might be necessary. The purpose of this study was to evaluate the efficacy of a prototype CPR assist-tool (Fig. 1) in increasing length and improving performance quality of external cardiac compressions (ECC) by comparing its use with the traditional “hands-only” method. REVIEW OF LITERATURE
The criteria for successful one-person CPR, established by the American Heart Association, requires
This study was supported by Biomedical Research Grant, College of Dentistry, University of Florida. 280
(for the average adult) that the sternum be depressed 1% to 2 inches, at a rate of 80 compressions per minute interspersed with two mouth-to-mouth ventilations after each series of 15 compressions.2This prescribed depth of compression translates to between 80 and 120 pounds of pressure, depending upon the morphology of the victim and chest compliance.4 It should be noted that all certified CPR providers must meet the criteria for certification, although there is no specific minimum time of demonstrated performance. Because considerable physical energy is required by CPR rescuers, excessive stress to the provider’s own cardiovascular system is possible and some rescuers have had heart attacks while providing CPR.5 Automatic mechanical cardiac compressors help to overcome the problem of fatigue; however, these implements are relatively expensive, cumbersome, and impractical for use in dental offices, medical offices, and other public facilities.6 In addition, the sophistication of these devices requires specific operator training or licensure; therefore, they are not widely used. METHOD
Twenty healthy young adults (fifteen women and five men) recently certified as basic CPR rescuers by the American Heart Association participated in this study. Half of the subjects started with the tool and half started by hand. Each subject was asked to provide one-person ECC at four separate sessions spaced 1 week apart, alternating between the “hands-only” method and the “tool-assisted” method. Each session lasted 20 minutes or until the subject felt unable to continue becauseof fatigue or discomfort.
Volume 62 Number 3
Prototype CPR assist-tool
281
1. A, The CPR assist-tool is constructed of a hard plastic capable of withstanding many times the force required for adequate compressionsof the chest. The working end is covered with a pliable rubber cushion to absorb forces applied to the sternum. The handles are notched, and two stops allow the tool to be easily held. B, Performance summary with respect to time. Note increase in overall performance with the assist-tool. Fig.
The tests were conducted on a standard training mannequin (Recording Resusci Anne). Each performance was recorded and later analyzed independently by two AHA-certified
instructors
for errors as
defined by the AHA’s Manual for Instructors of Basic Cardiac Life-Support, The test subjects were instructed to provide compressionsas recommended by the American Heart Association, and brief instructions were given in accordance with the manufacturer’s recommendations regarding use of the assist-tool.
In order not to bias their performance, the subjects were not advised as to the expected findings of this study. Once set up, the subjects were left alone to perform on their own. The same mannequin was used for all trials and was regularly calibrated to ensure its reliability as a mechanical test standard.* The compression pres*Mechanical calibration accomplished with the device “lnstron Universal Testing Facility” produced by Instron. Inc., of Danton, Mass.
282
hdo and Fast
Table
I. Group performance and derived t values
Oral Surg. September, 1986
Common
Inadequate
Excessive compressions
Thrusting compressions
Bouncing
lnaccurafe hand position
Toral minutes
Acceptable minutes
29 12.4
0.3 4.1
3.6 4.1
18.5 11.2
12.0 9.7
2.5
0.2 0.3 0.18 0.55 0.12 1.46
1.4 3.6 2.16 3.96 0.89 2,44*x
23.3 9.1 -4.80 7.20
19.1 9.2 -7.60 6.72
Rate
compressions
Hand Mean SD
11.6 il.2
6.1 6.3
0.5 1.1
2.4 4.2
Tool Mean SD Mean of difference SD SE
18.1 10.3 - 1.15 5.83 I .30
2.1 2.8 4.02 4.66
0.88
3.86*
5.1 16.8 -4.56 15.84 3.54 1.29
3.2 5.3 -0.76 2.92 0.65 1.11
i
1.04
errors
inaccurate hand relax
11.2
0.39 1.27 0.28 1.37
1.6 I
1.50
2.98’
5.0-l*
*I > 2.539 = P < .Ol **t>1.729=P<.05
sure required at the minimum acceptable pressure gradient on the recording tape was 82 pounds (1% inch displacement) and the maximum was 109 pounds (2 inch displacement). These pressure parameters remained constant throughout the study. A record was kept of each subject’s weight, height, arm length,* and torso length.7 Each test subject completed a subjective evaluation questionnaire at the end of the last session. Statistical
analysis
Errors associatedwith chest compressionsand the performance times were submitted for statistical analysis. A one-sided paired t test was performed to test the null hypothesis (Ho) that there is no difference between the hand and tool methods. RESULTS An aggregate total of 1,600 minutes of rescue effort was requested of the twenty providers (800 minutes of the standard hands-only method and 800 minutes using the assist-tool). Fig. 2 illustrates the length of performances with or without the assisttool. Note that the subjects were able to perform for a longer period with the tool, and at a higher quality of performance. Analysis of group performances (Table I) shows that the rate of compressions remained constant between groups, whereas there was almost a threefold decrease in inadequate compressions with the *Arm length measured from the heel of the hand to the acromion of the scapula. tTorso length measured from the floor to the acromion of the scapula {with the subject in an erect kneeling posture).
assist-tool. These values are statistically significant at a one-tail value of P < .Ol. Although there appears to be an increased tendency to overcompress with the tool, the t value is not large enough to rule out chance, even at P < .05. The increase in excessive compressions was due mainly to one volunteer who avercompressed on every compression while using the assist-tool. Other common errors tended to remain constant, although the duration of performances increased by about one third with the use of the assist-tool, as did time of acceptable performance. Both of these findings were significant at P-c .01. Analysis of the subject’s body build, size, and dimensions indicates that the assist-tool not only helps light-weight persons to deliver stronger compressions but also improves the performance of most persons. An analysis of the subjective evaluation questionnaire showed that sixteen of twenty volunteers thought the CPR assist-tool permitted compressions for a longer period than the hands-only method and with less physical discomfort (i.e., wrist pain, arm soreness,backache). Fourteen of the twenty thought they made fewer procedural errors when using the tools. Curiously, two of the persons who thought they did better by hand actually did better with the tool (according to the instructor’s interpretation of the tapes). DISCUSSION
Prompt and effective treatment can save some victims of cardiac arrest. Unfortunately, the physical ability of many rescuers is limited. Therefore, an investigation of adjunctive CPR devices is justifiable, Laboratory evaluation of the CPR assist-tool used in
Volume Number
Prototype CPR assist-tool
62 3
this study is subject to conjecture when applied to actual use; however, such devices should be tested prior to being used on a victim of cardiac arrest. The results of our study indicate that the tool could, in fact, improve a rescuer’s performance. Inadequate compression of the chest was the most frequent error of recently trained CPR providers. The assist-tool enabled most of the subjects to compressthe chest more effectively and for a longer period of time. The tool is believed to derive its effectiveness from its design. Correct cardiac compression requires that only the heel of one hand be in contact with the victim’s sternum. The fingers must be kept elevated and not allowed to contact the victim’s chest. This maneuver requires a conscious effort and results in a physical posture that is awkward and uncomfortable. If the rescuer’s arm line is held vertical, as specified by the AHA, the hand-heel requirement can be complied with only if the wrist is hyperextended. Many rescuers hnd this position difficult to maintain without discomfort. Another source of discomfort is that correct compression specifies that the arms must be held rigidly in a V configuration. This position requires more muscular energy than if the arms are held parallel to each other. Imagine doing push-ups with one hand on the other, and the required effort becomes obvious! A concern raised about the assist-tool is loss of a “sense of feel” when landmarking and while compressing. Since the only officially recommended procedure for landmarking is the “two-finger” method, the assist-tool can be positioned as easily as the heel of a hand. Second, the 1% to 2 inches of chest compressionis not measured by the heel of the hand;
283
rather, it is a distance that must be continuously estimated by watching the chest during a rescue. In fact, on occasion, this “loss of feel” may prove to be advantageous since rib fractures do occur and the tool may provide some insulation from the actual breaking or grating sensations. This is significant in that one’s tendency to compressadequately could be hindered by the psychological repulsivenessof such a situation. One could hypothesize a myriad of objections or problems associated with the assist-tools, but that is not the purpose of this study. It should be evident that, with proper training in the use of such tools, the overall performance of CPR could be improved. REFERENCES I. Levy RT, Moskowtiz 2. 3.
4.
5.
6.
J: Cardiovascular research: decades 01 progress a decade of promise. Science 217: I21 - 129. 1982. Standards and guideline for cardiopulmonary (CPR) and emergency cardiac care (ECC). JAMA 244: 453-509, 1980. Eisenbcrg MS, Hallstrom HP, Compass MK. Borgncr L, Short F. Pierce J: Treatment of ventricular fibrillation. JAMA 251: 1723.1726. 1984. Vallis CJ, MacKewie I. Lucas BG: The force necessary for external cardiac compression. Practitioner 223: 268-270, 1979. Lonergan JH, Youngberg JZ, Kaplan JA: Cardiopulmonary resuscitation: physical stress on the rescuer. Crit Care Med 9: 793.795, I98 I. Taylor GJ, Rubin R, Tucker M, Greene HL, Rudikoff MT, Weisfeldt ML: External cardiac compression: a randomized comparison of mechanical and manual techniques. JAMA 240: 644-h46. 197X.
Keprinr
rrqurs
Dr. Ernest Department College of University P. 0. Box Gainesville,
Is to.
A. Lado, Jr. of Oral Medicine Dentistry of Florida J-414 JHMHC FL 326 IO