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Do clinical examination gloves provide adequate electrical insulation for safe hands-on defibrillation? I: Resistive properties of nitrile gloves
Resuscitation 84 (2013) 895–899
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Clinical paper
Do clinical examination gloves provide adequate electrical insulation for safe hands-on defibrillation? I: Resistive properties of nitrile gloves夽 Charles D. Deakin a,∗ , Victoria Lee-Shrewsbury b , Kitwani Hogg b , Graham W. Petley c a b c
Department of Anaesthetics, University Hospital Southampton, Tremona Road, Southampton SO16 6YD, United Kingdom University Hospital Southampton, Tremona Road, Southampton SO16 6YD, United Kingdom Department of Medical Physics, University Hospital Southampton, Tremona Road, Southampton SO16 6YD, United Kingdom
a r t i c l e
i n f o
Article history: Received 22 December 2012 Received in revised form 13 February 2013 Accepted 2 March 2013 Keywords: Defibrillation Safety External chest compression Glove Current Voltage
a b s t r a c t Introduction: Uninterrupted chest compressions are a key factor in determining resuscitation success. Interruptions to chest compression are often associated with defibrillation, particularly the need to stand clear from the patient during defibrillation. It has been suggested that clinical examination gloves may provide adequate electrical resistance to enable safe hands-on defibrillation in order to minimise interruptions. We therefore examined whether commonly used nitrile clinical examination gloves provide adequate resistance to current flow to enable safe hands-on defibrillation. Methods: Clinical examination gloves (Kimberly Clark KC300 Sterling nitrile) worn by members of hospital cardiac arrest teams were collected immediately following termination of resuscitation. To determine the level of protection afforded by visually intact gloves, electrical resistance across the glove was measured by applying a DC voltage across the glove and measuring subsequent resistance. Results: Forty new unused gloves (control) were compared with 28 clinical (non-CPR) gloves and 128 clinical (CPR) gloves. One glove in each group had a visible tear and was excluded from analysis. Control gloves had a minimum resistance of 120 k (median 190 k) compared with 60 k in clinical gloves (both CPR (median 140 k) and non-CPR groups (median 160 k)). Discussion: Nitrile clinical examination gloves do not provide adequate electrical insulation for the rescuer to safely undertake ‘hands-on’ defibrillation and when exposed to the physical forces of external chest compression, even greater resistive degradation occurs. Further work is required to identify gloves suitable for safe use for ‘hands-on’ defibrillation. © 2013 Elsevier Ireland Ltd. All rights reserved.
1. Introduction The quality of external chest compression during a resuscitation attempt is crucial to successful defibrillation, admission to hospital alive and survival to hospital discharge. Four factors indicate the quality of external chest compression; adequate compression rate, adequate depth of compression, complete chest recoil and a high compression fraction (percentage of time during which chest compression is being delivered). Chest compression fraction is a key determinant of subsequent survival in patients with a shockable rhythm1 and current resuscitation guidelines therefore emphasise the need to minimise interruptions to chest compressions during CPR.2
夽 A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2013.03.011. ∗ Corresponding author. E-mail address: [email protected] (C.D. Deakin). 0300-9572/$ – see front matter © 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.resuscitation.2013.03.011
Interruptions to chest compressions are surprisingly common and when they do occur, are often of considerable duration. Studies have demonstrated typical no-flow times of 24–63%.3–6 Common reasons for interruption to CPR include the need to secure the airway and subsequently ventilate the patient, assessing the rhythm or performing a pulse check, and the need to defibrillate.7 Interruptions relating to defibrillation occur as the rescuer stands clear for the rhythm check and then subsequent shock delivery. The associated pre-shock pause closely relates to the success of the ensuing defibrillation, with pauses longer than 10 s adversely impacting on defibrillation success.8 Interruptions to CPR in order to defibrillate are aimed at ensuring the safety of rescuers and avoiding an inadvertent shock from the electrical discharge of the defibrillator; typically as much as 3000 V for biphasic defibrillators and 5000 V for older monophasic defibrillators.9 When used for clinical purposes, accidental electrical contact during defibrillation generally results in no more than the sensation of a shock or mild burns which nevertheless would be unacceptable to rescuers.10 However, with a current of approximately 20 mA being required to trigger a sensory stimulus, the safe
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C.D. Deakin et al. / Resuscitation 84 (2013) 895–899
Fig. 1. Apparatus used to measure electrical resistance across the gloves.
threshold of 1 mA set by international safety standards is clearly being exceeded by a considerable margin. Being able to safely perform hands-on defibrillation would make a significant contribution to minimising no-flow time and potentially contribute to improvements in survival. Several studies have brought us closer to understanding whether this is ever likely to be a safe option. Examination of leakage current during simulated defibrillation11 led to the suggestion that “chest compressions may be safely continued through defibrillation provided self-adhesive pad electrodes are used and gloves are worn”12 and more recently, animal studies have concluded that hands-on defibrillation can be safely performed but acknowledged that further clinical studies are needed before implementation into daily practice,13 although this has been disputed.14–16 More recently, 8.5% of paramedics wearing nitrile gloves undertaking intentional hands-on defibrillation reported the sensation of an electric shock,17 suggesting that recommendations regarding the safety of hands-on defibrillation are premature. We have previously reviewed aspects of electrical safety during defibrillation and discussed the use of clinical gloves to provide an electrical barrier.9 Suggestions that clinical examination gloves provide adequate electrical resistance to safely isolate the rescuer from harmful voltages have three assumptions; that the gloves are intact, that the material from which the gloves are manufactured provides adequate resistance to current flow and that the material is able to withstand voltages of appropriate magnitude. All three requirements must be met for the rescuer to be safely isolated from the defibrillator. Even when used for relatively delicate surgical procedures, surgical gloves, which tend to be of better quality than non-sterile examination gloves, are regularly damaged and no longer provide a barrier to fluids.18 Clinical examination gloves are generally thinner and are only designed to provide a physical barrier to blood and secretions. They have been shown to be poor at providing a barrier to fluids when used for critical care procedures,19 and when subject to friction,20 but their suitability to act as an electrical barrier is unknown. A variety of methods may be used to determine electrical integrity of the glove, the simplest being visual inspection.
However, whilst gross tears may be evident visually, the glove may be compromised in more subtle ways that are either difficult to identify or invisible to the naked eye. Measurement of electrical resistance across the glove allows detection of these more subtle defects and allows an estimation of its ability to act as an electrically resistive barrier to defibrillation current. We therefore examined the ability of commonly used clinical examination gloves to meet two of these three assumptions; namely whether the material from which the gloves are manufactured provides adequate resistance to current flow and whether gloves remain intact having endured the physical rigours of cardiopulmonary resuscitation. 2. Methods Clinical examination gloves worn by members of hospital cardiac arrest teams were collected immediately following termination of the resuscitation care. Gloves were labelled according to whether they had been used to perform external chest compressions during the resuscitation attempt (the clinical (CPR) group) or worn by a member of the team not actively carrying out chest compressions (the clinical (non-CPR) group). Fresh, in-date, unused gloves were obtained from the same glove batch numbers (the control group). Medical examination gloves used in this study were Kimberly Clark KC300 Sterling nitrile examination gloves; the type normally used in the large, acute teaching Hospital in which the investigation was conducted. Gloves were initially inspected visually for the presence of a gross breach of electrical insulation such as a tear. To determine the level of protection afforded by the remaining (visually intact) gloves, electrical resistance across the glove was measured. Accordingly, gloves were filled with 0.9% saline and suspended in a 0.9% saline-filled water bath to ensure good electrical contact with both sides of the glove. A copper electrode was placed into the saline within the glove and the saline in the water bath (Fig. 1). An analogue multimeter (AVOMeter, Model 8 Mk 5, AVO International Ltd., Dover, UK), was then connected to both electrodes. Using the device
C.D. Deakin et al. / Resuscitation 84 (2013) 895–899 Table 1 Electrical resistance measured across control gloves and those used clinically during resuscitation attempts.
N Range Median
897
Unused (control) gloves
Clinical – No CPR
Clinical – CPR
group) compared to the control group (P < 0.001). A wide range of resistance values were demonstrated in all three groups of gloves, with a lower limit of 120 k in control gloves and 60–120 k in gloves used clinically.
40 120–225 k 190 k
27 60–250 k 160 k
126 60–240 k 140 k
4. Discussion
the resistance was measured by applying a D.C. voltage across the electrodes of 12.5 V. Data were analysed using ANOVA, with statistical significance being taken as P < 0.05. 3. Results A total of 40 new, unused gloves were tested for electrical resistance. Results were compared with 28 clinical (non-CPR) gloves worn by members of the resuscitation team but not used to perform external chest compressions and 128 clinical (CPR) gloves worn by members of the resuscitation team used to perform external chest compressions. Visual inspection revealed three gloves with visible tears (one new unused glove, one from the clinical (CPR) group, and one from the clinical (non-CPR) group). These three gloves were excluded from further analysis. Results of the resistance measurements are shown in Table 1. Fig. 2 shows box and whisker plots demonstrating the wide variation in resistance between gloves within each group. Median electrical resistance decreased 15.8% in the clinical (non-CPR) group) compared to the control group and 26.3% in the clinical (CPR)
This study demonstrates that the electrical resistance of standard nitrile gloves, a common glove type used for clinical procedures, reduces when worn and reduces still further when used to perform chest compressions. Additionally, some gloves may have macroscopic tears even when new, rendering them completely permeable to electrical current. Whilst a gross tear clearly compromises electrical insulation and therefore increases risk to the rescuer, the more subtle impact of a reduction of resistance is less obvious, but clearly impacts on electrical insulation. Safety standards recommend a current flow limited to no more than 1 mA.21 From a theoretical standpoint, a resistance of 5 M or more is required to restrict current to this level for a defibrillator with maximum allowable output of 5000 V, contrasting with the minimum 60–120 k documented in this study. In a clinical situation, the resistance limiting the current in the rescuer will be scenario specific, but the resistances observed in this trial do not provide the margins of safety normally expected from personal protective equipment (PPE). The tests performed in this study examine the worst case scenario; the majority of the glove area in contact with the conductor. In a clinical scenario, only a fraction of this area is likely to be in contact, which would result in a higher resistance. Nonetheless, it
Fig. 2. Box and whisker plot showing the distribution of resistance in the three groups of gloves (P < 0.001). The horizontal bar in the centre of the box represents the median value. The ends of the whisker are set at 1.5× interquartile range (IQR) above the third quartile (Q3) and 1.5× IQR below the first quartile (Q1). The minimum and maximum outliers are shown.
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may be expected that currents flowing could considerably exceed allowable current levels and therefore these gloves do not afford sufficient protection. Gloves appear to degrade in both the CPR and non-CPR groups. This suggests that material stresses due to donning a glove make the material more permeable to electrical current; a phenomenon amplified by the additional mechanical forces the glove is subjected to during delivery of chest compressions. The reason for this reduction warrants further investigation, but is likely to relate to material degradation invisible to the naked eye such as the development of microscopic holes and ingress of conductive moisture. Several recent studies have suggested that wearing clinical examination gloves may provide sufficient electrical insulation to allow ‘hands-on’ defibrillation. This study calls into doubt assertions that gloves provide insulation against electrical leakage current flowing through rescuers during defibrillation and that “chest compressions may be safely continued through defibrillation provided that . . . gloves are worn”.12 Recent animal work also concluding that ‘hands-on’ defibrillation could be safely performed based on the absence of shocks to the rescuer when wearing polyethylene gloves22 is also called into question by this study. Glove integrity can be measured using several techniques. The water leak test and pneumatic tests (British Standard (BS) EN4551:2000) are standard tests for macroscopic glove integrity.23 Several studies have however demonstrated that these tests have insufficient sensitivity to detect small glove perforations, detecting only 60% of holes created by a large calibre needle.24 We therefore chose to use a standard electrical test (BS EN 60903:2003) to assess glove integrity which has greater sensitivity to microscopic perforations, that will allow current flow, but not necessarily water or air.25 Several studies have verified the use of this test relationship between leaky holes and electrical conductivity.26,27 The AVOMeter used to measure resistance applied a D.C. voltage of 12.5 V which is significantly less than voltages applied by a defibrillator which may be as high as 5000 V. However, the low voltage was utilised in order to examine the gloves for an existing degradation of insulation. Application of a much higher voltage may lead to current flowing through existing holes but may also create new ones through arching across weaknesses in the glove. This will be investigated in a future study. Although this study solely looked at nitrile gloves, there are a number of other materials used for clinical examination gloves. Nitrile is a synthetic rubber copolymer of acrylonitrile and butadiene that, although has inferior strength and flexibility compared to natural rubber, provides excellent abrasion and puncture resistance and good tear resistance. It is one of the most common clinical examination gloves used in hospitals. Latex gloves are manufactured from natural rubber, which is a complex emulsion of proteins, alkaloids, sugars, oils and tannins. Latex is an extremely elastic and flexible material with excellent abrasion, tear and puncture resistance, but because of cost and the increasing incidence of latex allergy, use of latex containing products is declining. Vinyl is a soft, flexible synthetic low-cost polymer with good abrasion and puncture resistance but has poor tear resistance so is used less often for clinical gloves. Rego et al. found that using test methods as defined by the American Society of Testing and Materials, failure rates of vinyl, latex and nitrile gloves after stimulated use and shear stress failed 12–61%, 0–4% and 1–3% respectively in each group.28 Although we only tested commonly used nitrile gloves, these studies would suggest that gloves made of other materials may experience higher failures than those documented by us using nitrile gloves. Korniewicz et al. conducted a study using 5510 medical gloves consisting of nitrile, latex and vinyl gloves and demonstrated failure rates of 1.3%, 2.2% and 8.2% respectively,29 suggesting that nitrile gloves are best for use in hospital environments, due to the low failure rate.
None of these gloves are intended to provide any degree of protection from electrical current, and their coincidental ability to do so should not be assumed to give adequate safety for ‘handson’ defibrillation. Gloves intended to protect from high voltage must conform to BS EN60903, and when used repeatedly, must be periodically re-tested to guard against performance loss through degradation of the latex rubber from which they are constructed. The International Commission on Non-Ionizing Radiation Protection has defined a safe current limit of <1 mA.21 Although this is specifically in the context of exposure of the public, there are no specific safety standards regarding safe limits for leakage currents to rescuers during external defibrillation. We therefore consider that this threshold is appropriate to apply to clinical use during defibrillation. In this study, even the highest resistance values measured in intact gloves were less than 5% of the required resistance, demonstrating that even intact vinyl gloves are unable to safely protect the rescuer from currents above this safe threshold. In summary, this study demonstrates that unused nitrile clinical examination gloves do not provide adequate electrical insulation for the rescuer to safely undertake ‘hands-on’ defibrillation. Additionally, this study shows that the clinical use of gloves reduces their electrical resistance further and when exposed to the physical forces of external chest compression, even greater resistive degradation occurs. Further work is required to identify gloves suitable for safe use for ‘hands-on’ defibrillation. Conflict of interest statement No author has any conflict of interest with the contents of this study. Acknowledgement The authors are grateful to David Johnson, Steve Clitheroe and Brad Olden for their assistance with developing the measurement apparatus. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/ j.resuscitation.2013.03.011. References 1. Christenson J, Andrusiek D, Everson-Stewart S, et al. Chest compression fraction determines survival in patients with out-of-hospital ventricular fibrillation. Circulation 2009;120:1241–7. 2. 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. 3. Abella BS, Alvarado JP, Myklebust H, et al. Quality of cardiopulmonary resuscitation during in-hospital cardiac arrest. J Am Med Assoc 2005;293:305–10. 4. Wik L, Kramer-Johansen J, Myklebust H, et al. Quality of cardiopulmonary resuscitation during out-of-hospital cardiac arrest. J Am Med Assoc 2005;293:299–304. 5. Valenzuela TD, Kern KB, Clark LL, et al. Interruptions of chest compressions during emergency medical systems resuscitation. Circulation 2005;112:1259–65. 6. van Alem AP, Sanou BT, Koster RW. Interruption of cardiopulmonary resuscitation with the use of the automated external defibrillator in out-of-hospital cardiac arrest. Ann Emerg Med 2003;42:449–57. 7. Sayre MR, Koster RW, Botha M, et al. Part 5: adult basic life support: 2010 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations. Circulation 2010;122:S298–324. 8. 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. 9. Petley GW, Cotton AM, Deakin CD. Hands-on defibrillation: theoretical and practical aspects of patient and rescuer safety. Resuscitation 2012;83:551–6. 10. Montauk L. Lethal defibrillator mishap. Ann Emerg Med 1997;29:825.
C.D. Deakin et al. / Resuscitation 84 (2013) 895–899 11. Lloyd MS, Heeke B, Walter PF, Langberg JJ. Hands-on defibrillation: an analysis of electrical current flow through rescuers in direct contact with patients during biphasic external defibrillation. Circulation 2008;117:2510–4. 12. Kerber RE. “I’m clear, you’re clear, everybody’s clear”: a tradition no longer necessary for defibrillation? Circulation 2008;117:2435–6. 13. Neumann T, Gruenewald M, Lauenstein C, Drews T, Iden T, Meybohm P. Handson defibrillation has the potential to improve the quality of cardiopulmonary resuscitation and is safe for rescuers—a preclinical study. J Am Heart Assoc 2012;1, http://dx.doi.org/10.1161/JAHA.112.001313. 14. Sullivan JL. Letter by Sullivan regarding article, “Hands-on defibrillation: an analysis of electrical current flow through rescuers in direct contact with patients during biphasic external defibrillation”. Circulation 2008;118:e712 [author reply e3]. 15. Sullivan JL, Chapman FW. Will medical examination gloves protect rescuers from defibrillation voltages during hands-on defibrillation? Resuscitation 2012;83:1467–72. 16. Deakin CD. Clinical examination gloves – fit only for their intended purpose. Resuscitation 2012;83:1421–2. 17. Johnson TA, Meersman J, Youngquist ST. Performing hands-on defibrillation in out of hospital cardiac arrest can result in the subjective perception of current to providers. Circulation 2012:7 [ReSS Abstract, Los Angeles, October 2012. Abstract #107]. 18. Feng T, Yohannan J, Gupta A, Hyndman ME, Allaf M. Microperforations of surgical gloves in urology: minimally invasive versus open surgeries. Can J Urol 2011;18:5615–8.
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19. Hansen KN, Korniewicz DM, Hexter DA, Kornilow JR, Kelen GD. Loss of glove integrity during emergency department procedures. Ann Emerg Med 1998;31:65–72. 20. Phalen RN, Wong WK. Integrity of disposable nitrile exam gloves exposed to simulated movement. J Occup Environ Hyg 2011;8:289–99. 21. International Commission on Non-Ionizing Radiation Protection. Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz). Health Phys 2010;99:818–36. 22. Neumann T, Gruenewald M, Lauenstein C, et al. Hands-on defibrillation has the potential to improve CPR quality and is safe for rescuers: a preclinical study. Circulation 2011;124:A247. 23. Medical gloves for single use. Requirements and testing for freedom from holes; 2000. Report No.: ISBN: 0580366979. 24. Sohn RL, Murray MT, Franko A, Hwang PK, Dulchavsky SA, Grimm MJ. Detection of surgical glove integrity. Am Surg 2000;66:302–6. 25. Live working. Gloves of insulating material; 2004. Report No.: ISBN: 0580434516. 26. Morgan DJ, Adams D. Permeability studies on protective gloves used in dental practice. Br Dent J 1989;166:11–3. 27. Escoe R. Electrical permeability of vinyl gloves. N Y State Dent J 1995;61: 36–7. 28. Rego A, Roley L. In-use barrier integrity of gloves: latex and nitrile superior to vinyl. Am J Infect Control 1999;27:405–10. 29. Korniewicz DM, Garzon L, Seltzer J, Feinleib M. Failure rates in nonlatex surgical gloves. Am J Infect Control 2004;32:268–73.
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Clinical paper
Do clinical examination gloves provide adequate electrical insulation for safe hands-on defibrillation? I: Resistive properties of nitrile gloves夽 Charles D. Deakin a,∗ , Victoria Lee-Shrewsbury b , Kitwani Hogg b , Graham W. Petley c a b c
Department of Anaesthetics, University Hospital Southampton, Tremona Road, Southampton SO16 6YD, United Kingdom University Hospital Southampton, Tremona Road, Southampton SO16 6YD, United Kingdom Department of Medical Physics, University Hospital Southampton, Tremona Road, Southampton SO16 6YD, United Kingdom
a r t i c l e
i n f o
Article history: Received 22 December 2012 Received in revised form 13 February 2013 Accepted 2 March 2013 Keywords: Defibrillation Safety External chest compression Glove Current Voltage
a b s t r a c t Introduction: Uninterrupted chest compressions are a key factor in determining resuscitation success. Interruptions to chest compression are often associated with defibrillation, particularly the need to stand clear from the patient during defibrillation. It has been suggested that clinical examination gloves may provide adequate electrical resistance to enable safe hands-on defibrillation in order to minimise interruptions. We therefore examined whether commonly used nitrile clinical examination gloves provide adequate resistance to current flow to enable safe hands-on defibrillation. Methods: Clinical examination gloves (Kimberly Clark KC300 Sterling nitrile) worn by members of hospital cardiac arrest teams were collected immediately following termination of resuscitation. To determine the level of protection afforded by visually intact gloves, electrical resistance across the glove was measured by applying a DC voltage across the glove and measuring subsequent resistance. Results: Forty new unused gloves (control) were compared with 28 clinical (non-CPR) gloves and 128 clinical (CPR) gloves. One glove in each group had a visible tear and was excluded from analysis. Control gloves had a minimum resistance of 120 k (median 190 k) compared with 60 k in clinical gloves (both CPR (median 140 k) and non-CPR groups (median 160 k)). Discussion: Nitrile clinical examination gloves do not provide adequate electrical insulation for the rescuer to safely undertake ‘hands-on’ defibrillation and when exposed to the physical forces of external chest compression, even greater resistive degradation occurs. Further work is required to identify gloves suitable for safe use for ‘hands-on’ defibrillation. © 2013 Elsevier Ireland Ltd. All rights reserved.
1. Introduction The quality of external chest compression during a resuscitation attempt is crucial to successful defibrillation, admission to hospital alive and survival to hospital discharge. Four factors indicate the quality of external chest compression; adequate compression rate, adequate depth of compression, complete chest recoil and a high compression fraction (percentage of time during which chest compression is being delivered). Chest compression fraction is a key determinant of subsequent survival in patients with a shockable rhythm1 and current resuscitation guidelines therefore emphasise the need to minimise interruptions to chest compressions during CPR.2
夽 A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2013.03.011. ∗ Corresponding author. E-mail address: [email protected] (C.D. Deakin). 0300-9572/$ – see front matter © 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.resuscitation.2013.03.011
Interruptions to chest compressions are surprisingly common and when they do occur, are often of considerable duration. Studies have demonstrated typical no-flow times of 24–63%.3–6 Common reasons for interruption to CPR include the need to secure the airway and subsequently ventilate the patient, assessing the rhythm or performing a pulse check, and the need to defibrillate.7 Interruptions relating to defibrillation occur as the rescuer stands clear for the rhythm check and then subsequent shock delivery. The associated pre-shock pause closely relates to the success of the ensuing defibrillation, with pauses longer than 10 s adversely impacting on defibrillation success.8 Interruptions to CPR in order to defibrillate are aimed at ensuring the safety of rescuers and avoiding an inadvertent shock from the electrical discharge of the defibrillator; typically as much as 3000 V for biphasic defibrillators and 5000 V for older monophasic defibrillators.9 When used for clinical purposes, accidental electrical contact during defibrillation generally results in no more than the sensation of a shock or mild burns which nevertheless would be unacceptable to rescuers.10 However, with a current of approximately 20 mA being required to trigger a sensory stimulus, the safe
896
C.D. Deakin et al. / Resuscitation 84 (2013) 895–899
Fig. 1. Apparatus used to measure electrical resistance across the gloves.
threshold of 1 mA set by international safety standards is clearly being exceeded by a considerable margin. Being able to safely perform hands-on defibrillation would make a significant contribution to minimising no-flow time and potentially contribute to improvements in survival. Several studies have brought us closer to understanding whether this is ever likely to be a safe option. Examination of leakage current during simulated defibrillation11 led to the suggestion that “chest compressions may be safely continued through defibrillation provided self-adhesive pad electrodes are used and gloves are worn”12 and more recently, animal studies have concluded that hands-on defibrillation can be safely performed but acknowledged that further clinical studies are needed before implementation into daily practice,13 although this has been disputed.14–16 More recently, 8.5% of paramedics wearing nitrile gloves undertaking intentional hands-on defibrillation reported the sensation of an electric shock,17 suggesting that recommendations regarding the safety of hands-on defibrillation are premature. We have previously reviewed aspects of electrical safety during defibrillation and discussed the use of clinical gloves to provide an electrical barrier.9 Suggestions that clinical examination gloves provide adequate electrical resistance to safely isolate the rescuer from harmful voltages have three assumptions; that the gloves are intact, that the material from which the gloves are manufactured provides adequate resistance to current flow and that the material is able to withstand voltages of appropriate magnitude. All three requirements must be met for the rescuer to be safely isolated from the defibrillator. Even when used for relatively delicate surgical procedures, surgical gloves, which tend to be of better quality than non-sterile examination gloves, are regularly damaged and no longer provide a barrier to fluids.18 Clinical examination gloves are generally thinner and are only designed to provide a physical barrier to blood and secretions. They have been shown to be poor at providing a barrier to fluids when used for critical care procedures,19 and when subject to friction,20 but their suitability to act as an electrical barrier is unknown. A variety of methods may be used to determine electrical integrity of the glove, the simplest being visual inspection.
However, whilst gross tears may be evident visually, the glove may be compromised in more subtle ways that are either difficult to identify or invisible to the naked eye. Measurement of electrical resistance across the glove allows detection of these more subtle defects and allows an estimation of its ability to act as an electrically resistive barrier to defibrillation current. We therefore examined the ability of commonly used clinical examination gloves to meet two of these three assumptions; namely whether the material from which the gloves are manufactured provides adequate resistance to current flow and whether gloves remain intact having endured the physical rigours of cardiopulmonary resuscitation. 2. Methods Clinical examination gloves worn by members of hospital cardiac arrest teams were collected immediately following termination of the resuscitation care. Gloves were labelled according to whether they had been used to perform external chest compressions during the resuscitation attempt (the clinical (CPR) group) or worn by a member of the team not actively carrying out chest compressions (the clinical (non-CPR) group). Fresh, in-date, unused gloves were obtained from the same glove batch numbers (the control group). Medical examination gloves used in this study were Kimberly Clark KC300 Sterling nitrile examination gloves; the type normally used in the large, acute teaching Hospital in which the investigation was conducted. Gloves were initially inspected visually for the presence of a gross breach of electrical insulation such as a tear. To determine the level of protection afforded by the remaining (visually intact) gloves, electrical resistance across the glove was measured. Accordingly, gloves were filled with 0.9% saline and suspended in a 0.9% saline-filled water bath to ensure good electrical contact with both sides of the glove. A copper electrode was placed into the saline within the glove and the saline in the water bath (Fig. 1). An analogue multimeter (AVOMeter, Model 8 Mk 5, AVO International Ltd., Dover, UK), was then connected to both electrodes. Using the device
C.D. Deakin et al. / Resuscitation 84 (2013) 895–899 Table 1 Electrical resistance measured across control gloves and those used clinically during resuscitation attempts.
N Range Median
897
Unused (control) gloves
Clinical – No CPR
Clinical – CPR
group) compared to the control group (P < 0.001). A wide range of resistance values were demonstrated in all three groups of gloves, with a lower limit of 120 k in control gloves and 60–120 k in gloves used clinically.
40 120–225 k 190 k
27 60–250 k 160 k
126 60–240 k 140 k
4. Discussion
the resistance was measured by applying a D.C. voltage across the electrodes of 12.5 V. Data were analysed using ANOVA, with statistical significance being taken as P < 0.05. 3. Results A total of 40 new, unused gloves were tested for electrical resistance. Results were compared with 28 clinical (non-CPR) gloves worn by members of the resuscitation team but not used to perform external chest compressions and 128 clinical (CPR) gloves worn by members of the resuscitation team used to perform external chest compressions. Visual inspection revealed three gloves with visible tears (one new unused glove, one from the clinical (CPR) group, and one from the clinical (non-CPR) group). These three gloves were excluded from further analysis. Results of the resistance measurements are shown in Table 1. Fig. 2 shows box and whisker plots demonstrating the wide variation in resistance between gloves within each group. Median electrical resistance decreased 15.8% in the clinical (non-CPR) group) compared to the control group and 26.3% in the clinical (CPR)
This study demonstrates that the electrical resistance of standard nitrile gloves, a common glove type used for clinical procedures, reduces when worn and reduces still further when used to perform chest compressions. Additionally, some gloves may have macroscopic tears even when new, rendering them completely permeable to electrical current. Whilst a gross tear clearly compromises electrical insulation and therefore increases risk to the rescuer, the more subtle impact of a reduction of resistance is less obvious, but clearly impacts on electrical insulation. Safety standards recommend a current flow limited to no more than 1 mA.21 From a theoretical standpoint, a resistance of 5 M or more is required to restrict current to this level for a defibrillator with maximum allowable output of 5000 V, contrasting with the minimum 60–120 k documented in this study. In a clinical situation, the resistance limiting the current in the rescuer will be scenario specific, but the resistances observed in this trial do not provide the margins of safety normally expected from personal protective equipment (PPE). The tests performed in this study examine the worst case scenario; the majority of the glove area in contact with the conductor. In a clinical scenario, only a fraction of this area is likely to be in contact, which would result in a higher resistance. Nonetheless, it
Fig. 2. Box and whisker plot showing the distribution of resistance in the three groups of gloves (P < 0.001). The horizontal bar in the centre of the box represents the median value. The ends of the whisker are set at 1.5× interquartile range (IQR) above the third quartile (Q3) and 1.5× IQR below the first quartile (Q1). The minimum and maximum outliers are shown.
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may be expected that currents flowing could considerably exceed allowable current levels and therefore these gloves do not afford sufficient protection. Gloves appear to degrade in both the CPR and non-CPR groups. This suggests that material stresses due to donning a glove make the material more permeable to electrical current; a phenomenon amplified by the additional mechanical forces the glove is subjected to during delivery of chest compressions. The reason for this reduction warrants further investigation, but is likely to relate to material degradation invisible to the naked eye such as the development of microscopic holes and ingress of conductive moisture. Several recent studies have suggested that wearing clinical examination gloves may provide sufficient electrical insulation to allow ‘hands-on’ defibrillation. This study calls into doubt assertions that gloves provide insulation against electrical leakage current flowing through rescuers during defibrillation and that “chest compressions may be safely continued through defibrillation provided that . . . gloves are worn”.12 Recent animal work also concluding that ‘hands-on’ defibrillation could be safely performed based on the absence of shocks to the rescuer when wearing polyethylene gloves22 is also called into question by this study. Glove integrity can be measured using several techniques. The water leak test and pneumatic tests (British Standard (BS) EN4551:2000) are standard tests for macroscopic glove integrity.23 Several studies have however demonstrated that these tests have insufficient sensitivity to detect small glove perforations, detecting only 60% of holes created by a large calibre needle.24 We therefore chose to use a standard electrical test (BS EN 60903:2003) to assess glove integrity which has greater sensitivity to microscopic perforations, that will allow current flow, but not necessarily water or air.25 Several studies have verified the use of this test relationship between leaky holes and electrical conductivity.26,27 The AVOMeter used to measure resistance applied a D.C. voltage of 12.5 V which is significantly less than voltages applied by a defibrillator which may be as high as 5000 V. However, the low voltage was utilised in order to examine the gloves for an existing degradation of insulation. Application of a much higher voltage may lead to current flowing through existing holes but may also create new ones through arching across weaknesses in the glove. This will be investigated in a future study. Although this study solely looked at nitrile gloves, there are a number of other materials used for clinical examination gloves. Nitrile is a synthetic rubber copolymer of acrylonitrile and butadiene that, although has inferior strength and flexibility compared to natural rubber, provides excellent abrasion and puncture resistance and good tear resistance. It is one of the most common clinical examination gloves used in hospitals. Latex gloves are manufactured from natural rubber, which is a complex emulsion of proteins, alkaloids, sugars, oils and tannins. Latex is an extremely elastic and flexible material with excellent abrasion, tear and puncture resistance, but because of cost and the increasing incidence of latex allergy, use of latex containing products is declining. Vinyl is a soft, flexible synthetic low-cost polymer with good abrasion and puncture resistance but has poor tear resistance so is used less often for clinical gloves. Rego et al. found that using test methods as defined by the American Society of Testing and Materials, failure rates of vinyl, latex and nitrile gloves after stimulated use and shear stress failed 12–61%, 0–4% and 1–3% respectively in each group.28 Although we only tested commonly used nitrile gloves, these studies would suggest that gloves made of other materials may experience higher failures than those documented by us using nitrile gloves. Korniewicz et al. conducted a study using 5510 medical gloves consisting of nitrile, latex and vinyl gloves and demonstrated failure rates of 1.3%, 2.2% and 8.2% respectively,29 suggesting that nitrile gloves are best for use in hospital environments, due to the low failure rate.
None of these gloves are intended to provide any degree of protection from electrical current, and their coincidental ability to do so should not be assumed to give adequate safety for ‘handson’ defibrillation. Gloves intended to protect from high voltage must conform to BS EN60903, and when used repeatedly, must be periodically re-tested to guard against performance loss through degradation of the latex rubber from which they are constructed. The International Commission on Non-Ionizing Radiation Protection has defined a safe current limit of <1 mA.21 Although this is specifically in the context of exposure of the public, there are no specific safety standards regarding safe limits for leakage currents to rescuers during external defibrillation. We therefore consider that this threshold is appropriate to apply to clinical use during defibrillation. In this study, even the highest resistance values measured in intact gloves were less than 5% of the required resistance, demonstrating that even intact vinyl gloves are unable to safely protect the rescuer from currents above this safe threshold. In summary, this study demonstrates that unused nitrile clinical examination gloves do not provide adequate electrical insulation for the rescuer to safely undertake ‘hands-on’ defibrillation. Additionally, this study shows that the clinical use of gloves reduces their electrical resistance further and when exposed to the physical forces of external chest compression, even greater resistive degradation occurs. Further work is required to identify gloves suitable for safe use for ‘hands-on’ defibrillation. Conflict of interest statement No author has any conflict of interest with the contents of this study. Acknowledgement The authors are grateful to David Johnson, Steve Clitheroe and Brad Olden for their assistance with developing the measurement apparatus. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/ j.resuscitation.2013.03.011. References 1. Christenson J, Andrusiek D, Everson-Stewart S, et al. Chest compression fraction determines survival in patients with out-of-hospital ventricular fibrillation. Circulation 2009;120:1241–7. 2. 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. 3. Abella BS, Alvarado JP, Myklebust H, et al. Quality of cardiopulmonary resuscitation during in-hospital cardiac arrest. J Am Med Assoc 2005;293:305–10. 4. Wik L, Kramer-Johansen J, Myklebust H, et al. Quality of cardiopulmonary resuscitation during out-of-hospital cardiac arrest. J Am Med Assoc 2005;293:299–304. 5. Valenzuela TD, Kern KB, Clark LL, et al. Interruptions of chest compressions during emergency medical systems resuscitation. Circulation 2005;112:1259–65. 6. van Alem AP, Sanou BT, Koster RW. Interruption of cardiopulmonary resuscitation with the use of the automated external defibrillator in out-of-hospital cardiac arrest. Ann Emerg Med 2003;42:449–57. 7. Sayre MR, Koster RW, Botha M, et al. Part 5: adult basic life support: 2010 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations. Circulation 2010;122:S298–324. 8. 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. 9. Petley GW, Cotton AM, Deakin CD. Hands-on defibrillation: theoretical and practical aspects of patient and rescuer safety. Resuscitation 2012;83:551–6. 10. Montauk L. Lethal defibrillator mishap. Ann Emerg Med 1997;29:825.
C.D. Deakin et al. / Resuscitation 84 (2013) 895–899 11. Lloyd MS, Heeke B, Walter PF, Langberg JJ. Hands-on defibrillation: an analysis of electrical current flow through rescuers in direct contact with patients during biphasic external defibrillation. Circulation 2008;117:2510–4. 12. Kerber RE. “I’m clear, you’re clear, everybody’s clear”: a tradition no longer necessary for defibrillation? Circulation 2008;117:2435–6. 13. Neumann T, Gruenewald M, Lauenstein C, Drews T, Iden T, Meybohm P. Handson defibrillation has the potential to improve the quality of cardiopulmonary resuscitation and is safe for rescuers—a preclinical study. J Am Heart Assoc 2012;1, http://dx.doi.org/10.1161/JAHA.112.001313. 14. Sullivan JL. Letter by Sullivan regarding article, “Hands-on defibrillation: an analysis of electrical current flow through rescuers in direct contact with patients during biphasic external defibrillation”. Circulation 2008;118:e712 [author reply e3]. 15. Sullivan JL, Chapman FW. Will medical examination gloves protect rescuers from defibrillation voltages during hands-on defibrillation? Resuscitation 2012;83:1467–72. 16. Deakin CD. Clinical examination gloves – fit only for their intended purpose. Resuscitation 2012;83:1421–2. 17. Johnson TA, Meersman J, Youngquist ST. Performing hands-on defibrillation in out of hospital cardiac arrest can result in the subjective perception of current to providers. Circulation 2012:7 [ReSS Abstract, Los Angeles, October 2012. Abstract #107]. 18. Feng T, Yohannan J, Gupta A, Hyndman ME, Allaf M. Microperforations of surgical gloves in urology: minimally invasive versus open surgeries. Can J Urol 2011;18:5615–8.
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