Original Article
Removal of the stylet from the tracheal tube: effect of lubrication
A. M. Taylor,1 O. R. Hung,2 K. Kwofie,2 C. R. Hung,3 D. R. Hung3 and A. Guzzo4
1 Anaesthesia trainee, 2 Anaesthesia Consultant, 3 Anaesthesia Assistant, Department of Anaesthesia, DalhousieUniversity, Halifax, Canada4 Anaesthesia Consultant, Department of Anaesthesia, McGill University, Montreal, Canada
SummaryWe compared the work needed to retract a non-lubricated and a lubricated stylet from a tracheal tube over 24 h. Stylets
were lubricated with sterile water, silicone fluid, lidocaine spray, lidocaine gel, MedPro� lubricating gel or Lacri-Lube�.
The mean (SD) work in joules needed to retract the stylet by 5 cm from the tracheal tube was recorded immediately
(time 0), at 5 and 30 min and at 1, 3 and 24 h. At time 0 lubrication with sterile water (0.53 (0.09); p = 0.001), silicone
fluid (0.43 (0.10); p < 0.001), lidocaine gel (0.60 (0.15); p = 0.01) and MedPro gel (0.57 (0.07); p = 0.005), were better
than no lubrication (0.94 (0.28)). Where a tracheal tube is pre-loaded with a stylet for use at an indeterminate time,
silicone fluid was the best choice of lubricant as it performed consistently well up to 24 h. At 24 h only silicone fluid
(0.49 (0.01)) outperformed no lubrication (0.77 (0.24); p = 0.04).................................................................................................................................................................
Correspondence to: Orlando R. Hung
Email: [email protected]
Accepted: 9 April 2012
Anaesthesia personnel frequently participate in airway
emergencies throughout the hospital utilising pre-
prepared emergency equipment. Such equipment often
includes tracheal tubes with pre-loaded stylets. The
stylet provides stiffness to the tracheal tube to facilitate
tracheal intubation. In an emergency, difficulty in
withdrawing the stylet from the tracheal tube may be
detrimental to the patient. In particular, tracheal tube
dislodgement or inability to remove the stylet at this
critical time can result in morbidity or mortality
secondary to inadequate oxygenation. Furthermore,
difficulty in the removal of the stylet has led to reports
of trauma to the upper airway of the patient [1], as well
as equipment failure [2, 3]. These problems are just as
relevant in the non-emergency situation.
Lubrication of the stylet is commonly used to
decrease friction between the tracheal tube and the
stylet, facilitating removal of the stylet following the
placement of the tracheal tube into the glottic opening.
There are many types of lubricants commonly used to
lubricate the stylet. There is, however, no information in
the literature comparing the effectiveness of these
lubricants, or their effect over time when tracheal tubes
are pre-loaded with stylets.
The aim of this study was to compare the work
required to remove stylets from non-lubricated and
lubricated tracheal tubes, using a number of commonly
available lubricants, and to determine the effect of
lubrication over time.
MethodsThis was a quality assurance study approved by our
institution. For this experiment, a new stylet (Satin-
Slip�; Mallinckrodt Inc., St. Louis, USA) and a new size
Anaesthesia 2012 doi:10.1111/j.1365-2044.2012.07192.x
Anaesthesia ª 2012 The Association of Anaesthetists of Great Britain and Ireland 1
7.0 mm internal diameter (ID) tracheal tube (Interme-
diate Hi-Lo� Tracheal Tube; Mallinckrodt Inc.,
St. Louis, USA) were used for each test, so that a total
of 210 stylets and 210 tracheal tubes were used. A
standard 15-mm connector was inserted maximally into
the proximal end of each tracheal tube.
Six commonly available lubricating agents were
studied: sterile water (water); silicone fluid (Endoscopic
Instrument Lubricant, ACMI, Norwalk, USA); lidocaine
spray (Xylocaine� Endotracheal Spray; ASTRA, Missis-
sauga, Canada); lidocaine gel (Xylocaine Jelly; ASTRA,
Mississauga, Canada), MedPro� gel, a water-based
lubricant (AMG MedPro Lubricating Gel; AMG Medical
Inc., Montreal, Canada); and Lacri-Lube� (Ophthalmic
Ointment, Allergen Ltd., Buckinghamshire, UK). All
lubricants, stylets and tracheal tubes were kept at a room
temperature of 22 �C during the experiments.
The test sequence was randomised using a computer
random number generator (Excel, Microsoft Corpora-
tion, Redmond, WA, USA). Except for the non-
lubricated group (control), each stylet was lubricated
with one of the test lubricants before placing it in the
tracheal tube. The differing nature of the lubricating
agents meant that they could not be applied in a
standardised manner. For lubrication with water, 3 ml
sterile water was instilled into the tracheal tube using a
syringe and the excess water was allowed to drain off.
The stylet was then inserted and retracted into the
tracheal tube three times, as is commonly done in
clinical practice, to allow distribution of the water on to
the stylet. For lubrication with lidocaine spray, the
lidocaine spray was dispensed three times into the
tracheal tube, and then the stylet was inserted and
retracted three times to again allow adequate distribu-
tion. For the silicone, lidocaine gel, MedPro gel and
Lacri-Lube groups, a 5-cm length of the respective
lubricant was applied onto the stylet. The lubricant was
then spread evenly over the stylet before inserting and
retracting it into the tracheal tube three times.
Following the application of the lubricant, the stylet
was introduced into the tracheal tube until the distal tip
of the stylet was at the proximal edge of the bevel of the
tracheal tube. A 7.0-mm ID tracheal tube was used, as
this is commonly one of the smaller tracheal tubes used
in adults. The tracheal tube loaded with the stylet was
then bent to 90� using a protractor at 7 cm from the
distal tip (measured using a ruler), which correlates with
the set-up of the TrachlightTM lightwand stylet com-
monly used in our institution [4]. These parameters were
easily reproducible, and a 90� angle was also considered
to be the maximum angle practitioners would consider
bending the tracheal tube before insertion.
The stylet was then withdrawn at a constant velocity
for a distance of 5 cm, and the amount of work required
to do so was recorded. The absence of acceleration
allowed for a simple work analysis (work = force · dis-
tance). A commercial device capable of measuring this
was not available and therefore an in-house designed
device was used (Fig. 1). It comprised a hanging mass
scale (CE Digital Hanging Scale, Model PF-905D25;
Orix Enterprise, Taichung, Taiwan), calibrated in new-
tons, fixed to the moving portion of a syringe infusion
pump (Harvard Apparatus Syringe Infusion Pump 22,
St. Laurent, Quebec, Canada). A ruler was fixed to the
stationary portion of the syringe pump, and a needle
attached to the mobile portion of the syringe pump was
used to measure the distance of the stylet withdrawal.
The tracheal tube was attached to the fixed portion of
the syringe pump with two vices via the 15-mm
connector, and the stylet was secured to the moving
hanging mass scale. During the removal of the stylet, the
instantaneous force in newtons was manually recorded
every millimetre interval until the stylet was withdrawn
from the tracheal tube by 5 cm. The peak withdrawal
force had been reached in all cases by 5 cm of stylet
withdrawal. Each experiment was video recorded to
ensure accurate data collection.
The force was determined immediately after the
tracheal tube was loaded with the stylet (time 0), at 5
Figure 1 Device used to measure the force in newtonsrequired to retract the stylet from the tracheal tube.
Anaesthesia 2012 Taylor et al. | Lubrication and stylet removal from tracheal tube
2 Anaesthesia ª 2012 The Association of Anaesthetists of Great Britain and Ireland
and 30 min, and 1, 3 and 24 h. Each experiment was
repeated five times for each lubricant and the control at
each time point, giving a total of 210 experiments. The
work in joules required to withdraw the stylet by 5 cm
was determined by the area under the curve of the
force:distance plot. Data were analysed using ANOVA
with repeated measures and post hoc Tukey’s test for
multiple comparisons (SPSS Inc., Chicago, USA), with
p < 0.05 indicating statistical significance.
ResultsFigure 2 summarises the work required to remove the
stylet from the tracheal tube for the control and the
lubricant groups up to 24 h, and compares the results
both within and between the groups. Lubrication with
silicone gave the best results overall (Fig. 2). At times 0,
30 min, 1, 3 and 24 h, significantly less work was
required to retract the stylet compared with the control
(p < 0.001, p = 0.004, p < 0.001, p = 0.04, p = 0.04,
respectively). It behaved more consistently at each time
point, and over the 24 h, with less variability both within
and between time points compared to the control.
Silicone also significantly outperformed lidocaine spray
at 30 min, 1, 3 and 24 h (p < 0.001, p < 0.001,
p = 0.008, p = 0.001, respectively), and lidocaine gel at
30 min, 1 and 24 h (p = 0.001, p < 0.001, p < 0.001,
respectively).
The control showed no statistically significant
difference in work needed to retract the stylet over
time. It behaved inconsistently with more variability
both within and between most time points compared to
other groups (Fig. 2).
At time 0, there was no difference between the
water, silicone, lidocaine gel and MedPro gel groups, and
they all outperformed the control (p = 0.001, p < 0.001,
p = 0.01, p = 0.005, respectively). There was, however,
no difference between lubrication with lidocaine spray
and Lacri-Lube compared to the control at time 0.
Lubrication with water and lidocaine gel required
significantly more work to retract the stylet at 24 h
compared to time 0 (p = 0.028, p = 0.007, respectively).
DiscussionEasy and atraumatic removal of a stylet from a tracheal
tube is vital to ensure that the airway of a patient is
quickly secured in both emergency and routine tracheal
intubations. Lubrication of the stylet facilitates this
objective. In assessing the force required to remove
different bougies from different tracheal tubes, a recent
paper found that some tracheal tube and bougie
combinations are very difficult to separate without
excessive force where lubrication is not used [5]. We
have demonstrated that for removal of stylets from
tracheal tubes, some lubricants perform better than
others compared to no lubrication, and that over time
some lubricants lose their lubricating properties.
Overall, at time 0, less work was required to retract
the stylet from a tracheal tube in the water, silicone,
lidocaine gel and MedPro gel groups, compared with the
control. Over 24 h, however, only silicone performed
better than the control at all points in time, apart from at
5 min. Although it is not clear why silicone did not
outperform the control at this time point, we speculate
that it is possibly the result of a small sample size
together with a large variability in the control.
The water and lidocaine gel groups needed signif-
icantly more work to retract the stylet at 24 h, when
compared to time 0. We postulate that for water, this
may have been due to evaporation, while for lidocaine
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0Immediate
Wor
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)
5 min 30 min 1 h 3 h 24 h
Figure 2 Data are mean (SD) work in joules required toretract the stylet 5 cm from the tracheal tube with andwithout lubrication at 0, 5, 30 min and 1, 3 and 24 h.Each group has been slightly separated at each timepoint to improve clarity. Control (no lubrication) (ÆÆdÆÆ),water (ÆÆsÆÆ), silicone (ÆÆ.ÆÆ), lidocaine spray (ÆÆnÆÆ),lidocaine gel (ÆÆhÆÆ), MedPro gel (ÆÆmÆÆ) and Lacri-Lube(ÆÆnÆÆ). Lubrication with water, silicone, lidocaine gel andMedPro gel was significantly better than no lubricationat time 0 (p < 0.05). At 24 h, only silicone performedbetter than no lubrication (p < 0.05).
Taylor et al. | Lubrication and stylet removal from tracheal tube Anaesthesia 2012
Anaesthesia ª 2012 The Association of Anaesthetists of Great Britain and Ireland 3
gel, it may have been due to a solidification of the
lidocaine gel in the tracheal tube as the lubricant dried.
Some of the results showed large variability in the
amount of work required to retract the stylet. It is
possible that the amount of lubricant used to lubricate
the stylets was inadequate or inconsistent, or that the
precision of the measuring device was less than
expected. We were unable to apply the different
lubricants to the stylets in a standardised manner due
to their differing physical properties. To minimise
inconsistencies, the same investigator (ORH) applied
the lubricants and prepared the stylets. The measuring
device used in this study was not validated. It was
designed in-house as there was no similar, validated,
commercial device available to us.
It is possible that inadequate study power contributed
to the variability seen in the results in some groups. We are
unaware of any previously reported similar investigations
and, therefore, were unable to anticipate both the work
required to withdraw the stylet and any differences
between or within the groups, making a prospective power
analysis not possible. Given the significance of our results
we did not perform a retrospective power analysis.
The safety profile of the various lubricants is a
potential factor that may affect the choice of lubricant,
and whether tracheal tubes should be pre-loaded with
lubricated stylets. This was not assessed in this study, but
there is some evidence in the literature that various
lubricants may have a detrimental effect on the tracheal
tube and the stylet. Silicone fluid has not been tested for
use as described in our experiment. However, silicone
fluid has been used clinically for many decades for
flexible bronchoscopy, as well as many other fibreoptic
instruments. Lidocaine-based products have been asso-
ciated with postoperative sore throat, as well as damage
to the tracheal tube cuff [6, 7]. There are reports of
various water-based gels causing blockages in tracheal
tubes, both at the time of initial application, and also
after time when the gel has dried [8–10].
Our data suggest that where tracheal tubes are being
pre-loaded with stylets for use at an indeterminate time,
silicone fluid is the best choice of lubricant as it performs
consistently well over time up to 24 h. Where a stylet-
loaded tracheal tube is being used immediately, lubri-
cation with sterile water, silicone fluid, lidocaine gel or
MedPro gel is better than no lubrication.
AcknowledgementsWe thank Colleen O’Connell, Research Associate, for
her help with the statistics.
Competing interestsNo external funding and no competing interests
declared.
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