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Resuscitation 83 (2012) 1467–1472
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Resuscitation
journal homepage: www.elsevier.com/locate/resuscitation
Simulation and education
Will medical examination gloves protect rescuers from defibrillation voltages
during hands-on defibrillation?夽
Joseph L. Sullivan ∗ , Fred W. Chapman
Physio-Control, Inc., Redmond, WA, United States
a r t i c l e
i n f o
Article history:
Received 2 May 2012
Received in revised form 27 June 2012
Accepted 21 July 2012
Keywords:
Defibrillation
Safety
Medical examination gloves
a b s t r a c t
Background: Continuing compressions during a defibrillation shock has been proposed as a method of
reducing pauses in cardiopulmonary resuscitation (CPR) but the safety of this procedure is unproven.
The medical examination gloves worn by rescuers play an important role in protecting the rescuer yet
the electrical characteristics of these gloves are unknown. This study examined the response of medical
examination gloves to defibrillation voltages.
Methods: Part 1 of this study measured voltage–current curves for a small sample (8) of gloves. Part
2 tested more gloves (460) to determine the voltage required to produce a specific amount of current
flow. Gloves were tested at two current levels: 0.1 mA and 10 mA. Testing included four glove materials
(chloroprene, latex, nitrile, and vinyl) in a single layer and double-gloved.
Results: All gloves tested in part 1 allowed little current to flow (<1 mA) as the voltage was increased until
breakdown occurred, at which point current flow increased precipitously. In part 2, 118 of 260 (45%)
single gloves and 93 of 120 (77%) double gloves allowed at least 0.1 mA of current flow at voltages within
the external defibrillation voltage range. Also, 6 of 80 (7.5%) single gloves and 5 of 80 (6.2%) double gloves
allowed over 10 mA.
Conclusions: Few of the gloves tested limited the current to levels proven to be safe. A lack of sensation
during hands-on defibrillation does not guarantee that a safety margin exists. As such, we encourage
rescuers to minimize rather than eliminate the pause in compressions for defibrillation.
© 2012 Elsevier Ireland Ltd. All rights reserved.
1. Introduction
Pauses in chest compressions during CPR are known to be
detrimental to survival.1 The 2005 American Heart Association
Guidelines eliminated some reasons for pauses,2 but interruptions
still occur to allow intubation,3 ventilations,4 AED analyses, charging, and defibrillation shocks.5 While shock delivery accounts for a
relatively minor fraction of the total hands-off time in most cases,
elimination of the shock pause is consistent with the overall goal
of minimizing hands-off time. In addition, pausing CPR for shock
delivery complicates the resuscitation protocol, requiring close
coordination between multiple members of the resuscitation team
to avoid inadvertent rescuer shocks while minimizing hands-off
time.
Recently, Lloyd et al. suggested that it may be possible for rescuers to continue chest compressions during a defibrillation shock.6
夽 A Spanish translated version of the summary of this article appears as Appendix
in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2012.07.031.
∗ Corresponding author at: Physio-Control, Inc., 11811 Willows Road NE, Redmond, WA 98052, United States. Tel.: +1 425 867 4405.
E-mail address: [email protected] (J.L. Sullivan).
0300-9572/$ – see front matter © 2012 Elsevier Ireland Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.resuscitation.2012.07.031
They studied the safety of “hands-on defibrillation” by simulating
chest compressions while delivering external cardioversion shocks
to patients with atrial fibrillation. No harm came to the “rescuers,”
and although the authors cautioned against extrapolation beyond
the limits of their model, they concluded that, “Uninterrupted manual chest compressions during shock delivery are feasible.”
Although defibrillator shock intensity is commonly expressed
in terms of joules, it is the voltage that determines the risk of an
unintended operator shock. For common biphasic external defibrillators, the voltage applied to the patient for the first shock ranges
from about 1300 to 1800 V.13 Maximum energy biphasic shocks can
be as high as 2700 V.7 Due to the large magnitude of these voltages
caution is wise. The best approach for providing optimal patient
care while minimizing the rescuer hazards is unclear.
A number of factors contribute to the risk of hands-on defibrillation. Two key factors are, (1) the fraction of the shock voltage
presented across the rescuer and (2) the voltage standoff capability
of the gloves. Neither of these factors is known.
The fraction of the shock voltage presented across the rescuer is
dependent on the electrical circuit formed by the patient and the
rescuer. This is illustrated in Fig. 1.
The possible current paths through a rescuer have not been well
studied but one model has been proposed that includes current flow
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Fig. 1. At least two points of contact with the patient are required for a rescuer shock. The gloves form one point of contact. The second point of contact may be through the
ground or inadvertent patient contact. High-voltage current is known to puncture dry skin, penetrate clothing, and jump across a small air gap.23,24
through the rescuer’s chest.17 In this model the gloves can serve as
a barrier to current flow through the rescuer and may provide an
important safety mechanism.
In general, medical examination gloves are designed as a barrier to bodily fluids, not electricity, and manufacturers typically
do not provide electrical specifications for their gloves. One study
using the AC (alternating current) voltage from an electrocautery
device found latex and neoprene glove breakdown voltages as low
as 2000 V,8 but it is unclear how these results relate to handson defibrillation. Little other information is available that would
allow the safety of hands-on defibrillation to be assessed. A recent
review paper by Petley et al. suggested, “Further work needs to be
carried out to determine the necessary electrical and mechanical
properties required of an insulator suitable to be used to protect
rescuers.”9
The purpose of this study was to compare the DC (direct current)
electrical characteristics of common medical examination gloves
with the output voltages of biphasic defibrillators.
2. Methods
2.1. Part 1
Part one of this study examined the shape of the voltage–current
curve for several types of gloves by applying a range of DC voltages
to each glove and recording the current flow at each level. The goal
of this part of the study was to determine if the current flow in
these gloves typically exhibits a “breakdown” characteristic and, if
so, to determine the voltage level at which it occurs.
A dielectric analyzer (Vitrek 944i, San Diego, CA) was used to
apply the voltage to the gloves and monitor current flow. The voltage across the glove was manually increased and allowed to dwell
at each level long enough for the current to stabilize. Current values
were recorded at 100 V, 200 V, 500 V, and 500 V increments thereafter until the current exceeded the device maximum (20 mA) or
until a breakdown occurred. At breakdown the dielectric analyzer
rapidly removes the voltage to prevent excessive current flow and,
rather than reporting the actual current flow, simply reports that
a breakdown was detected. All measurements in this part of the
study were made by inserting a roughly palm-sized metal electrode
into the glove, placing the unstretched glove on a metal sheet, and
applying the voltage between the electrode and the sheet. Minimal
compressive force (<0.5 pounds) was applied for each measurement.
Gloves made of four commonly used polymers were tested:
• latex (Safe-Touch powder-free latex examination gloves,
Dynarex Corporation, Orangeburg, NY; and Ambidex Powder
free cleanroom latex gloves, Ambidex Corporation, Thailand),
• nitrile (Esteem Stretchy Nitrile power-free nitrile exam gloves,
CardinalHealth, McGaw Park, IL; and Safe-Touch power-free
nitrile examination gloves, Dynarex Corporation, Orangeburg,
NY),
• chloroprene (NeoPro powder-free chloroprene examination
gloves, Microflex Corporation, Reno, NV), and
• vinyl (Safe-Touch powder-free vinyl examination gloves,
Dynarex Corporation, Orangeburg, NY; and Disposable vinyl
gloves powdered, Magid Corporation, China).
Part 1 of the study tested two gloves of each polymer.
2.2. Part 2
Part 2 measured the voltage necessary to produce a specific
amount of current flow in each glove. This was done by programming the dielectric analyzer to increase the voltage until a pre-set
current limit was reached. The voltage required to produce that
current level was then recorded. If the desired current flow was
not achieved before reaching the maximum output voltage of the
dielectric analyzer (5000 V), then 5000 V was recorded.
The tests in Part 2 were performed using one of two current
limits. The first current limit was 0.1 mA. This is the maximum
direct current (DC) allowed to flow incidentally through an operator from a medical device with no faults as established by the
widely recognized standards agency, the International Electrotechnical Commission (IEC).10 A current flow less than this amount is
J.L. Sullivan, F.W. Chapman / Resuscitation 83 (2012) 1467–1472
1469
Current Flow (mA)
Breakdown Voltage
Nitrile
Nitrile
Chloroprene
Chloroprene
Vinyl
Vinyl
Latex
Latex
1mA
0
500
1000
1500
2000
2500
3000
3500
4000
Applied Voltage (Volts)
Fig. 2. Measured current flow (mA) through the gloves tested in Part 1 as a function of applied voltage. The 1 mA line represents the approximate threshold of perception.
The current flow at breakdown is represented here at about 10 mA for the purpose of illustration.
generally considered to be safe. For this study the voltage required
to produce this amount of current flow is referred to as the “leakage
voltage.”
The second current limit was set at 10 mA. This is more current
than is allowed by any regulatory standards of which we are aware
and is also above the threshold of perception (about 1 mA).11 This
current limit was also chosen because Part 1 of our study showed
that 10 mA is above the knee of the curve for all glove types. In other
words, it represents a complete electrical breakdown of the glove
material.
While Part 1 measurements were all made on single gloves,
the measurements in Part 2 were made on both single and double
gloves. The double-glove measurements were made by placing the
electrode on top of the glove (rather than inside the glove) so that
current flowed through two layers of material to reach the metal
sheet.
The testing in Part 2 involved all four polymers listed in Part
1. Each polymer was tested at both current limits in single and
double-layer configurations, giving a total of 16 polymer–currentlayer combinations. At least 20 measurements were made of each
combination, resulting in a total of 460 measurements in Part 2 of
our study.
3. Results
3.1. Part 1
All gloves exhibited a highly nonlinear “hockey-stick” shaped
voltage–current relationship that is characteristic of an electrical breakdown (Fig. 2). The current flow for every glove stayed
below about 1 mA until breakdown, at which point current flow
abruptly jumped up and the dielectric analyzer removed the voltage. The breakdown voltage varied greatly among gloves, ranging
from 2500 V to 4000 V.
3.2. Part 2
Some single gloves (32/80 = 40% chloroprene, 2/60 = 3% latex,
42/60 = 70% nitrile, and 42/60 = 70% vinyl) of each polymer showed
either a leakage voltage or a breakdown voltage (or both) within
the output voltage range of biphasic defibrillators (Fig. 3). The
leakage voltage of most double gloves (18/20 = 90% chloroprene,
35/40 = 87% nitrile, 40/40 = 100% vinyl gloves, and 0/20 = 0% latex)
also fell within this range. The breakdown voltage for all (20
each) double latex, double nitrile, and double vinyl gloves tested
increased to a level higher than the highest biphasic defibrillator
output voltage.
4. Discussion
The main findings of this study are that current flow through
medical examination gloves is highly non-linear with respect to
voltage, and that the current flow is very inconsistent among glove
types and between samples of a single glove type. This makes the
risks of hands-on defibrillation difficult to predict (Fig. 4).
This study was the first to measure voltage–current curves for
medical examination gloves. These data are relevant because they
illustrate the difficulty of assessing the safety of hands-on defibrillation. During this procedure the rescuer may be relying partially or
completely on the gloves to avoid an electrical shock. In our study
the current flow for the gloves tested in Part 1 stayed low – below
the threshold of perception – until an arc developed and the current precipitously increased. Importantly, this demonstrates that
rescuers should not construe the absence of sensation as an indication of a safety margin. It is likely that hands-on defibrillation with
medical examination gloves will produce no sensation at all unless
the gloves completely break down, at which time the current will
be limited by factors other than the gloves. In our study the current
was limited by the dielectric analyzer but current flow through a
rescuer could be far higher.
Part 2 of this study measured leakage and breakdown voltages.
One strategy for ensuring the safety of hands-on defibrillation is
to use only gloves that are guaranteed to have a leakage voltage
greater than the defibrillator shock voltage. With biphasic defibrillators this appears to be possible with double latex gloves. None
of the double latex gloves exceeded the leakage voltage threshold
at less than 5000 V, giving these sample gloves at least a twoto-one voltage margin over most biphasic defibrillation voltages.
All other polymers showed a distribution of leakage voltages that
either straddles or is lower than some of biphasic shock voltages,
even with gloves doubled up.
However, the risk to the operator from leakage current is probably small, even in the worst case, one in which a current path
includes the heart. The 0.1 mA leakage current limit set by the IEC
was selected to ensure that 1–3 s of current flow would induce
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Fig. 3. Histograms of leakage (hatched bars) and breakdown (clear bars) voltages for single and double gloves. Median values are given for each group. For reference, biphasic
defibrillation shock voltages are shown. Monophasic shock voltages are much higher, ranging up to 5000 V.
VF in less than 5% of the population.12 Defibrillation shocks are
much shorter, typically less than 20 ms.13 In order for a defibrillation pulse to induce fibrillation the shock must be timed to hit
the vulnerable period of the cardiac cycle. VF may be triggered in
people with heart disease if they receive a well-timed low-energy
internal defibrillation shock (≤0.2 J)14 or pacing pulse (0.5 V)15 ; but
for healthy adults it is estimated that, even if the defibrillation
pulse is appropriately timed, as much as 500 mA of current flow is
required to induce VF.16 Petley et al. propose a limit of 1 mA through
a rescuer9 , and Hoke et al. assert that, “currents up to 200 mA should
be regarded as safe.”17 If this is true, then any voltage less than the
glove breakdown voltage would not present a hazard. By this standard, the double nitrile, double vinyl, and double latex gloves tested
in our study appear safe.
Although the risk from leakage current is debatable, the potential harm from a glove breakdown is another matter. Hoke et al.
report that healthy non-rescuers have suffered serious injuries
from accidental or erroneous defibrillator shocks.17 All of these
people apparently placed the defibrillator paddles directly on their
chest, head, or other body part, delivered a shock, and suffered
burns, arrhythmias, or death. This situation is somewhat different
from a rescuer shock from hands-on defibrillation because during
resuscitation the main current path is believed to be through the
patient, with a smaller, secondary path through the rescuer. There
are no data available that allow the amount of current on any of the
possible secondary paths to be quantified.
Hoke et al. report that, although minor injuries are not rare, the
medical literature contains no examples of a “life-threatening condition or long-term disability” suffered by a rescuer delivering an
external defibrillation shock to a patient.17 This is a remarkable
record considering that there are approximately 60,000 VF cardiac arrests in the United States annually.18 It should be pointed
out, though, that these rescuers were trained to stand clear during a shock. It is not known how many of those rescuers may have
been injured had they been trained to continue compressions during defibrillation. Even a relatively small glove failure rate could
translate into a large number of rescuer shocks.
It is also possible that a rescuer could be harmed in other ways
than immediate induction of VF. There are reports of arrhythmias, conduction disturbances, elevated cardiac enzymes, coronary
J.L. Sullivan, F.W. Chapman / Resuscitation 83 (2012) 1467–1472
High
Voltage
Applied Voltage >
Glove Breakdown
Voltage
Dangerous
Glove Breakdown Voltage
Glove Breakdown Voltage
> Applied Voltage > Glove
Leakage Voltage
Safety
Uncertain
Glove Leakage Voltage
Glove Leakage Voltage
> Applied Voltage
Known
Safe
Low
Voltage
Fig. 4. The safety of hands-on defibrillation depends on the voltage applied to the
gloves, the glove leakage voltage, and the glove breakdown voltage.
occlusive thrombosis, and myocardial infarction due to coronary
spasm as a result of an electrical shock from either an AC power
line or a lightning strike.19 Unfortunately, the level and duration of
current flow is not known in any of those cases so it is impossible
to say whether an accidental defibrillation shock can cause any of
those effects.
Besides shocks from AC power lines, lightning, and external
defibrillators, there is one report in the literature of a nitrile-gloved
rescuer suffering permanent nerve damage as a result of a shock
from an implanted defibrillator.20 This report is of particular concern because internal defibrillator voltages are much lower than
external defibrillator voltages. The defibrillator, a Medtronic Concerto C174AWK, outputs a maximum peak voltage of 800 V21 –
lower than even the first shock voltage of most common external defibrillators.13 The risk of rescuer injury would be even more
of a concern when treating patients with subcutaneous defibrillators which likely possess a higher output voltage and may utilize
electrodes closer to the surface.
There is also a chance that gloves may contain a pinhole or
small tear. Although gloves may be punctured by the wearer, some
authors have suggested that as many as 15% of gloves may be
manufactured with defects.8 We did not notice any defects in the
hundreds of gloves that we tested, but our experiment was set up to
examine the properties of glove materials, not to look for pinholes.
While it is clear that hazards exist for rescuers performing
compressions during defibrillation, the potential patient benefit
appears to be small. It should be possible for well trained rescuers
to charge the defibrillator while performing chest compressions,
take their hands off, shock, and resume compressions with a total
interruption of perhaps four seconds.22 If a shock is delivered every
2 min CPR period, then these four second interruptions would only
add 3.3% to the total hands-off time.
Our results indicate a need for further study of the other key
factor not addressed in this study: the voltage to which the rescuer is exposed. Had we found that glove leakage and breakdown
1471
voltages were consistently higher than the shock voltages, then we
could have concluded that hands-on defibrillation is safe. Because
we instead found that many gloves allow current flow and some
break down completely when faced with defibrillation voltages, the
safety of this situation is much less clear. Without additional information about the voltages presented to rescuers in resuscitation
scenarios, continuing compressions during defibrillation cannot be
advised.
5. Limitations
This study was limited primarily because it characterized only
one factor relating to the safety of hands-on defibrillation: the
electrical characteristics of medical examination gloves. The other
factor – the fraction of the shock voltage presented to the rescuer –
is equally important. Currently, there are no data available on that
factor.
In order for current to flow through a rescuer there must be
a current path. This study is not predicated on a particular current
path but merely postulates that one or more paths may exist. In the
interests of safety, we believe this assumption is prudent unless it
is proven otherwise.
For the sake of simplicity the gloves in our study were not compressed as they would be during chest compressions nor were they
stretched as they would be when worn by a person. These factors
would likely reduce the leakage and breakdown voltages for the
gloves, increasing the risk to the wearer.
We applied voltages to these gloves relatively slowly compared
to the rise time of a defibrillation shock. It is not known whether
the rate of voltage application influences the leakage or breakdown
voltages.
6. Conclusions
Few of the gloves tested limited the current to levels proven to
be safe. A lack of sensation during hands-on defibrillation does not
guarantee that a safety margin exists. As such, we encourage rescuers to minimize rather than eliminate the pause in compressions
for defibrillation.
Conflict of interest statement
The authors are both employees of Physio-Control, Inc., a manufacturer of external defibrillators.
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