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: hungorla@dal.ca

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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