Russo et al. BMC Anesthesiology 2012, 12:18
http://www.biomedcentral.com/1471-2253/12/18
RESEARCH ARTICLE
Open Access
Randomized comparison of the i-gel™, the LMA
Supreme™, and the Laryngeal Tube Suction-D
using clinical and fibreoptic assessments in
elective patients
Sebastian G Russo1*, Stephan Cremer1, Tamara Galli1,2, Christoph Eich1,3, Anselm Bräuer1, Thomas A Crozier1,
Martin Bauer1 and Micha Strack4
Abstract
Background: The i-gel™, LMA-Supreme (LMA-S) and Laryngeal Tube Suction-D (LTS-D) are single-use supraglottic
airway devices with an inbuilt drainage channel. We compared them with regard to their position in situ as well as
to clinical performance data during elective surgery.
Methods: Prospective, randomized, comparative study of three groups of 40 elective surgical patients each. Speed
of insertion and success rates, leak pressures (LP) at different cuff pressures, dynamic airway compliance, and signs
of postoperative airway morbidity were recorded. Fibreoptic evaluation was used to determine the devices’ position
in situ.
Results: Leak pressures were similar (i-gel™ 25.9, LMA-S 27.1, LTS-D 24.0 cmH2O; the latter two at 60 cmH2O cuff
pressure) as were insertion times (i-gel™ 10, LMA-S 11, LTS-D 14 sec). LP of the LMA-S was higher than that of the
LTS-D at lower cuff pressures (p <0.05). Insertion success rates differed significantly: i-gel™ 95%, LMA-S 95%, LTS-D
70% (p <0.05). The fibreoptically assessed position was more frequently suboptimal with the LTS-D but this was not
associated with impaired ventilation. Dynamic airway compliance was highest with the i-gel™ and lowest with the
LTS-D (p <0.05). Airway morbidity was more pronounced with the LTS-D (p <0.01).
Conclusion: All devices were suitable for ventilating the patients’ lungs during elective surgery.
Trial registration: German Clinical Trial Register DRKS00000760
Keywords: Laryngeal mask airway, Leak pressure, Laryngeal Tube
Background
Since the introduction of the classic laryngeal mask
airway the field of supraglottic airway devices (SGA)
has experienced a remarkable evolution and SGA are
now routinely used in clinical anaesthesia. Newer
SGA have an inbuilt drainage channel to facilitate the
efflux of gastric fluid and gas and allow the insertion
of a gastric tube.
* Correspondence: s.russo@medizin.uni-goettingen.de
1
Department of Anaesthesiology, Emergency and Intensive Care Medicine,
University Medical Centre Göttingen, Robert-Koch-Straße 40, Göttingen
37083, Germany
Full list of author information is available at the end of the article
Many SGA are available in single-use versions [1,2].
The i-gel™ (Intersurgical Ltd.), the LMA-Supreme™
(LMA-S; The Laryngeal Mask Company Ltd), and the
Laryngeal Tube Suction - D (LTS-D, VBM Medical
GmbH) are disposable SGA with inbuilt drainage
channel. The i-gel™ has a non-inflatable, gel-filled cuff
[3] while the LMA-S is a disposable, pre-curved
modification of the older LMA-ProSeal™ [4]. The
LTS-D is the disposable version of the double-cuffed
laryngeal tube [5].
These three SGA have previously been evaluated alone
or in pair-wise comparisons but differing study designs
make it difficult to compare the results [2,6-8]. To the
best of our knowledge, no previous study has compared
© 2012 Russo et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
Russo et al. BMC Anesthesiology 2012, 12:18
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the three devices in a single study setting. We therefore
compared the three SGA in a, randomized, prospective
clinical study with a detailed evaluation of their performance. We evaluated the leak pressures (LP) at different
cuff volumes and cuff pressures, the speed of insertion,
the insertion success rates, the fibreoptically determined
positions, dynamic airway compliance and signs of airway morbidity.
Methods
With the approval of our institutional ethics committee
and after having obtained written informed consent,
patients were recruited for this prospective, randomized
clinical study (German Clinical Trial Register number
DRKS00000760). Inclusion criteria were: age >18 years
and scheduled elective surgical intervention in the supine position with predicted anaesthesia duration between 60 and 180 minutes. Exclusion criteria were: BMI
>35 kg/m2, ASA status III or higher, known risk of aspiration, known or predicted difficult airway. The patients
were assigned to their groups with a computergenerated randomisation list (www.randomizer.org). The
sealed envelope method was used for blinding.
Leak pressure (LP) was the primary endpoint. Secondary endpoints were speed of insertion, insertion success
rates, fibreoptically assessed in situ position, dynamic
airway compliance and signs of airway morbidity.
Anaesthesia
The patients were premedicated with midazolam
(7.5 mg p.o.) thirty minutes prior to anaesthesia induction. Anaesthesia was induced with sufentanil (0.30.5 μg/kg) and propofol (1.5-2.5 mg/kg) and maintained
during the measurement period with a propofol infusion
(5-8 mg/kg/h) and repeated injections of sufentanil when
necessary. No muscle relaxants or opioids other than
sufentanil were given.
Airway management and ventilation
Two senior anaesthesia registrars (SC and TG) skilled in
placing SGA performed all cases. Although the recommended insertion techniques of the three SGA are quite
similar the investigators were required to perform a
minimum of 15 insertions with all three devices before
starting patient recruitment, particularly because they
had previous experience with reusable laryngeal mask
type devices (classical laryngeal mask airway and PLMA)
but not i-gel™ and LMA-S. Depth of anaesthesia was
assessed by performing a jaw thrust manoeuvre [9,10].
The size of the device was determined according to the
manufacturers’ weight-based recommendations.
If two attempts to insert the initially randomized SGA
failed, the study protocol prescribed a change to one of
the other two devices selected randomly (coin toss). If
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two attempts with the second SGA device were also unsuccessful the trachea was intubated.
Failed insertion of the SGA was defined as the inability
to position the device within 60 seconds, an air leak
through the drainage channel during positive pressure
ventilation despite corrective manoeuvres (e.g. deeper
insertion or up-and-down-manoeuvre) [11], inability to
introduce a suction catheter (12Ch for the i-gel™, 16Ch
for the LMA-S and LTS-D) beyond the tip of the device,
inability to establish successful ventilation with a stable
end-expiratory CO2 signal with a targeted expiratory
tidal volume of 7 ml/kg because of leakage or airway
obstruction.
The time required for successful insertion was defined
as the time from placing the SGA in the front of the
patient’s mouth to its placement in the correct position.
A non-blinded observer who was not involved in the
study recorded the time needed for insertion.
After successful insertion, the cuff of the LMA-S was
inflated to a pressure of 60 cmH2O. The cuff of the
LTS-D was initially inflated with the volume indicated
on the syringe provided by the manufacturer for emergency use. The cuff pressure was measured at this inflation volume and air was then withdrawn until cuff
pressure was also 60 cmH2O.
Ventilation was pressure-controlled (PCV) with a positive end-expiratory pressure (PEEP) of 3 cmH2O, a respiratory rate between 14 and 16 and an inspiratory to
expiratory ratio of 1:1.5. It was adapted to give an endtidal CO2 of 35-40 mmHg.
Leak pressure was determined as a function of cuff
pressure for the SGA with inflatable cuffs (LMA-S and
the LTS-D). Cuff pressure was measured with a manometer (VBM Medical GmbH, Sulz, Germany; range from
0 to 110 cmH2O) that was connected to the SGA
through a three-way stopcock with an attached syringe.
Air was injected until the pre-determined cuff pressure
was obtained and the required inflation volume was
recorded. Cuff pressures started at 0 cmH20 (completely
deflated and equilibrated to ambient pressure) and were
increased in 10 cmH20 increments to 60 cmH20. It was
further increased in the LTD-S in two 20 cmH20 increments to a maximum of 100 cmH2O. The pressure limit
of the anaesthesia circuit was set to 35 cmH2O and airway pressure was increased steadily with a continuous
flow of oxygen (3 l/min). Leakage was defined as air escape audible with a stethoscope placed on the larynx,
and leak pressure was defined as the airway pressure at
which leakage was first detected [12]. After these measurements the cuff was inflated to 60 cmH2O and kept
at that pressure for the remainder of the study duration.
Airway pressures (PAW) and tidal volumes (Vt) were
recorded and averaged over one minute after insertion, as
well as after equilibration of ventilator settings. Dynamic
Russo et al. BMC Anesthesiology 2012, 12:18
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airway compliance (Cdyn) was calculated using the formula
Cdyn ¼ Vt =ðPAWmax PEEPÞ . The LP defined the maximum inspiratory airway pressure setting.
Fibreoptic evaluation
Fibreoptic (FO) evaluation of the SGA’s position was
performed after successful insertion and determination
of the airway pressures and tidal volumes. The position
was assessed using a previously described four points
score (1 = only vocal cords seen; 2 = cords and/or
arytenoids seen; 3 = only epiglottis seen; 4 = other (e.g.
cuff, pharynx, etc)) [13].
If an unexpected reduction in tidal volume occurred
during stable anaesthesia and unchanged ventilator settings, the airway was assessed with the fibrescope for dislocation of the device or obstruction due to glottic
narrowing or laryngospasm. Glottic narrowing was differentiated from laryngospasm by a partial closure of the
vocal cords that was not reversed by deepening anaesthesia or by the administration of a neuromuscular blocker.
Airway morbidity
All devices were evaluated for traces of blood on the
mask bowl (LMA-S, i-gel™) or the airway apertures and
cuff (LTS-D). The patients were questioned about sore
throat, discomfort during swallowing and hoarseness at
one hour and at 24 hours after anaesthesia. These complaints were classified as none, mild, or severe.
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Statistical analysis
Published data on leak pressures were used to estimate
the necessary sample size. Assuming a mean LP of
24 cmH2O for the i-gel™ [3,14], 26 cmH2O for the
LMA-S [6,7,15], and 28 cmH2O for the LTS-D [8,16]
and an assumed standard deviation of 5 cmH2O for all
devices, a total sample size of 83 was calculated to detect
differences with 90% power and a significance level of
0.05 [17]. To allow for potential dropouts, a sample size
of 40 patients per group was chosen.
The data were documented in an Excel™ spreadsheet
and analyzed using SPSS Statistics™ software (IBM SPSS
Inc., Chicago, IL, USA). Depending on the level of measurement of the dependent variables, ANOVA, rank variance analysis (Kruskall-Wallis), or multinomial logistic
regressions and chi-square tests were used.
Results
One hundred and thirty-four patients on the surgical list
were identified as possible participants. Of these, 14 were
not eligible due to exclusion criteria. The remaining 120
patients fulfilled all criteria, and after having given written
informed consent were recruited to participate in the
study. They were randomly allocated to receive one of the
three SGA. Three patients were excluded from further
analysis because of protocol violation (wrong sized device;
one LMA-S, two i-gel; Figure 1). The results of 117
patients, 78 female and 39 male, were analyzed. The
groups did not differ with regard to duration of
Figure 1 Flow chart of the study, showing the subdivision into groups corresponding to each supraglottic airway device. 1st or 2nd
success = insertion success rate for the first or the second insertion attempt. i-gel™; LMA-S = LMA-Supreme™; LTS-D = Laryngeal Tube Suction-D;
TT = tracheal tube.
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anaesthesia (120 ± 48 minutes, p = 0.63). For further biometric data see Table 1.
Leak pressure for the intention-to-treat patients
There was no significant difference in LP between the
three devices (cuff pressure = 60 cmH20 for LMA-S and
LTS-D): i-gel™ 25.9 ± 5.6; LMA-S 27.1 ± 5.2; LTS-D
24.0 ± 3.9 (p = 0.184; see also Figure 2).
In both the LMA-S and the LTS-D, LP increased with
increasing cuff pressure. Leak pressure was significantly
higher for the LMA-S at lower cuff pressures (p <0.05,
Figure 2). In the LTS-D, LP increased only insignificantly
at cuff pressures above 60 cmH20 (Figure 2).
Injected air volumes of 24 ± 5 ml and 58 ± 15 ml were
required to generate a cuff pressure of 60 cmH2O in a
size four LMA-S and LTS-D, respectively. Generating
cuff pressures of 80 and 100 cmH2O in the LTS-D group
required inflation volumes of 67 ± 13 and 76 ± 6 ml, respectively. When the size four LTS-D was inflated with
80 ml of air as indicated on the colour-coded syringe
intended for emergency use, the cuff pressure markedly exceeded the manometer scale’s maximum of
110 cmH2O in all cases.
Success rates and insertion times
The overall insertion success rate was significantly lower
for the LTS-D than for the other two SGA (Chi-square,
p = 0.014; Figure 1). Insertion times did not differ significantly (i-gel™ 10 ± 5 sec; LMA-S 11 ± 9 sec; LTS-D 14 ±
10 sec; p = 0.173).
Three patients in the LTS-D group did not complete
the entire study protocol due to complications during
insertion. Despite absent response to a forced jaw thrust
one patient developed severe laryngospasm immediately
after insertion and required muscle relaxation and endotracheal intubation. One patient suffered a clinically relevant aspiration of gastric contents necessitating
postoperative admission to the intensive care unit, and
one had a suspected regurgitation of gastric contents.
These were graded as insertion failures (see also
Figure 1).
Figure 3 shows the success rates of the alternative
SGA that had to be used when insertion of the initially
randomized SGA failed. Analysing the primary endpoints it made no difference whether a SGA had been
Table 1 Biometric data of the intent-to-treat groups
BMI
Height (cm)
Age (yrs)
Male / Female (n)
i-gel™
25.9 ± 4.5
172 ± 11
48 ± 17
16 / 24
LMS-S
26.8 ± 4.3
172 ± 10
50 ± 17
13 / 27
LTS-D
25.8 ± 3.5
168 ± 10
51 ± 16
10 / 30
= 0.508
= 0.168
= 0.641
= 0.272
p-value
LMA-S = LMA-Supreme™; LTS-D = Laryngeal Tube Suction-D.
Figure 2 Leak pressure (LP) versus cuff pressure shown for the
i-gel™, the LMA-Supreme™ and the Laryngeal Tube Suction-D.
LP is given in cmH20. The grey circle represents the i-gel™, white
circles represent the LMA-S, black circles represent the LTS-D.
inserted as the primary or as the backup device. Adding
randomised and alternative devices gave a total number
of insertions of 45 i-gel™ (38 randomised + 7 alternative),
44 LMA-S (39 + 5), and 41 LTS-D (40 + 1) (Figure 3).
Airway pressures and Cdyn are shown in Table 2.
Fibreoptic assessment
All successfully inserted SGAs were assessed by
fibrescope. The vocal cords and epiglottis were visible in
all patients with an i-gel™ or a LMA-S, which corresponds to grade 2. In 40 of the 42 patients with an i-gel™
(95%), the epiglottis was not on the intended epiglottis
rest as described in the user’s manual but was caught in
the bowl of the mask (Figure 4A). In one of 42 patients
with an LMA-S, the epiglottis was folded down. Airway
obstruction was not observed in any of these patients.
Glottic narrowing that was not due to laryngeal distortion or laryngospasm was seen in three of the 42
patients (7%) with an LMA-S (see also Figure 4B).
The concept and construction of the LTS-D is different from that of the i-gel™ and the LMA-S, which makes
it difficult to apply the fibreoptic scoring system.
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Figure 3 Flow chart indicating the number of failures and the supraglottic airway device used as the secondary device, including the
corresponding success rates. 1st or 2nd success = insertion success rate for the first or the second insertion attempt. i-gel™; LMA-S = LMASupreme™; LTS-D = Laryngeal Tube Suction-D; TT = tracheal tube. Below the horizontal line is the summary for each device (intention-to-treat plus
rescue device).
However, in 21 of 29 patients (72%) we were able to
visualise laryngeal structures through one of the LTS-D’s
ventilatory openings to varying degrees (grades 1 to 3).
In eight of the 29 (28%) patients, no laryngeal structures
were visible but we were able to ventilate the patients’
lungs nonetheless.
with blood on the device described a slight sore throat
one hour after surgery. Two patients with a bloodstained LMA-S complained of a slight sore throat and
dysphagia, and one complained of hoarseness one hour
after surgery. All but one of the patients with a bloodstained LTS-D complained of airway morbidity.
Airway morbidity
Discussion
In this study we compared three different SGA, i-gel™,
LMA-S, and LTS-D in surgical patients with regard to
leak pressure, insertion success rate and adverse effects.
The overall incidence of airway morbidity for the
intention-to-treat groups was low. No statistical intergroup difference was seen regarding hoarseness. There
was significantly more sore throat and dysphagia associated with the LTS-D than with the other two devices
(Table 3). No difference was found between the latter.
Traces of blood were found more often on the LTS-D
(see also Table 4). One of the five patients with an i-gel™
Table 2 Airway pressure and airway compliance
dPAW [cmH20]
Cdyn [ml/cmH20]
i-gel™
11.2 ± 2.8
49.9 ± 12.7
LMS-S
12.0 ± 0.5
43.4 ± 11.4
LTS-D
13.2 ± 4.3*
38.0 ± 13.4*
dPAW = delta pressure airway (=PAWpeak - PEEP), Cdyn = dynamic airway
compliance. LMA-S = LMA-Supreme™; LTS-D = Laryngeal Tube Suction-D.
* p <0.05.
Leak pressure and cuff pressure
Leak pressures did not differ between the devices when
the inflatable devices had a cuff pressure of 60 cmH2O.
The LP determined for the i-gel™ and the LMA-S are
similar to those described previously [3,6,7], but we
found a LP for the LTS-D, which is at the lower end of
the range of 25 to 33 cmH2O described in other studies
[8,16]. This might be because we measured LP at a cuff
pressure at 60 cmH2O as recommended by the manufacturer for elective patients [18] and not at the presumably
higher pressures used in other studies. The mean inflation volume required for a cuff pressure of 60 cmH2O
was 57.9 ml, which is markedly less than that used in
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Figure 4 Examples of fibrescopic images. A) i-gel™, note that the epiglottis does not rest on the epiglottis rest outside the mask bowl; B)
LMA-Supreme™, note the narrowing of the vocal cords; C and D) Example of awkward position in situ of the Laryngeal Tube Suction-D,
ventilation was possible in both examples. 1 = glottic inlet, 2 = arytenoids.
other studies, so that even though the actual cuff pressures in these studies were not reported, one can conclude they were higher than 60 cmH2O [2,16]. For
emergency situations the manufacturer, of course, prefers a fail-safe pragmatic approach and provides a
colour-coded 80 ml syringe that produces cuff pressures
of more than 110 cmH2O.
Three patients were excluded from analysis because
size selection of the device was not according to the prescribed weight-based guideline, even though it would
have been correct according to the gender-based guideline [19]. A recalculation of LP and success rates using
the data of these three patients showed that their exclusion did not affect the results, which were essentially the
same as those presented in the results section (LP: i-gel™
25.7 ± 5.7 cmH20; LMA-S 26.5 ± 5.1 cmH20; LTS-D
25.7 ± 3.9 cmH20, p = 0.667; insertion success rate:
p = 0.002).
LP correlated positively with cuff pressure, which confirms recently published data for the LMA-S [20]. This
is clinically relevant, since there is less postoperative airway morbidity at lower cuff pressures [21], and the incidence and severity of sore throat is markedly reduced at
cuff pressures below 40 cmH2O [22]. This may be due
Table 3 Incidence of airway morbidity
sore throat
hoarseness
dysphagia
% of patients with none /mild /severe
% of patients with none / mild / severe
% of patients with none / mild / severe
1h
1d
1h
1d
1h
1d
i-gel™
72 / 14 / 14
88 / 6 / 6
86 / 14 / 0
97 / 3 / 0
83 / 14/ 3
100 / 0 / 0
LMA-S
84 / 16 / 0
95 / 5 / 0
92 / 5 / 3
98 / 2 / 0
95 / 2.5 / 2.5
95 / 5 / 0
LTS-D
29 / 50 / 21
79 / 17 / 4
82 / 11 / 7
93 / 7 / 0
54 / 32 / 14
82 / 14 / 4
p <0.001
p <0.005
p = 0.75
p = 0.64
p <0.001
p <0.005
LMA-S = LMA-Supreme™; LTS-D = Laryngeal Tube Suction-D. 1h = one hour after surgery; 1d = one day after surgery.
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Table 4 Blood on the devices of the intention-to-treat group
all insertions
i-gel™
successful insertions
blood inside
blood outside
blood inside
blood outside
8% (n = 3)
13% (n = 5)
8% (3 of 36)
14% (5 of 36)
failures without blood
2 of 2 (100%)
LMS-S
8% (n = 3)
13% (n = 5)
3% (1 of 37)
8% (3 of 37)
0 of 2 (0%)
LTS-D
20% (n = 8)
37.5% (n = 15)
14% (4 of 28)
35% (10 of 28)
7 of 12 (58%)
= 0.132
= 0.006
= 0.216
= 0.01
p-value
LMA-S = LMA-Supreme™; LTS-D = Laryngeal Tube Suction-D.
to a lower mucosal pressure as discussed below. The decrease in LP was more pronounced with the LTS-D, so
that the LMA-S had higher leak pressures at cuff pressures below 50 cmH20 (Figure 2).
Leak pressure of an SGA depends on a tight contact of
the cuff with the surrounding tissues [23]. If the radial
pressure of the cuff on the mucosa is above the mucosal
perfusion pressure it will obviously cause tissue ischemia, which can contribute to airway morbidity. This radial pressure is a non-linear function of cuff pressure
and depends also on the elasticity and dimensions of the
cuff and the compliance of the surrounding tissue. It
probably cannot be calculated directly from cuff pressure
but must be determined empirically. However, UlrichPur et al. concluded that increasing cuff volumes are directly transferred to increasing mucosal pressures [24]
and one study with the modified cuffed oropharyngeal
airway in patients did demonstrate a significant, direct
correlation between cuff pressure and mucosal pressure
[25].
Studies have shown that mucosal perfusion remains
normal as long as the maximum mucosal pressure is
lower than 32 cmH2O, but that perfusion is slightly
reduced at mean pressures of 34 cmH2O with a pressure
range of 4 to 65 [25]. A recent study of the i-gel™ and
the LMA-S with a cuff pressure of 60 cmH2O in surgical
patients found that maximal mucosal pressures were
lower than 38 cmH2O and that there was no difference
between the two devices [26]. Other laryngeal mask airways and laryngeal tubes have been studied in cadavers
with conflicting results [24,27,28], however, the recorded
mucosal pressures were generally below the ischemia
threshold.
Success rates
The success rates with the i-gel™ and the LMA-S are
similar to published data [3,7]. The insertion success rate
with the LTS-D in this study was significantly lower than
for the other two devices but still lay within the range of
published data [2,16,29-32]. Schalk et al. [32] had high
success rates with the LTS II and LTS-D, while Kette
et al. [33] and Heuer at al. [34] described successful ventilation in only 75-80% of the cases. There may be methodological reasons for the low insertion success rates in
our study. First of all, we limited the number of insertion
attempts to two and set somewhat higher criteria for a
successful insertion, i.e. absence of any air leak at sufficient tidal volumes in addition to simply being able to
ventilate. Another possible factor might be that the two
investigators had less experience inserting the LTS-D
than they had with devices similar to the i-gel™ and the
LMA-S (classical laryngeal mask airway and PLMA). On
the other hand, it is claimed that the laryngeal tube is
easy to insert, even for persons with little experience
[32]. A third factor might have been inadequate anaesthesia. None of our patients responded to the forced jaw
thrust, generally considered a reliable sign that anaesthesia is deep enough to insert an LMA [9,10], and several
studies have shown that a similar depth of anaesthesia
was required for laryngeal tube and laryngeal mask airway insertion [35-37]. One study even found that insertion conditions were better for the laryngeal tube at the
same depth of anaesthesia [35]. On the other hand, there
is data showing that laryngeal tube insertion requires a
deeper level of anaesthesia [38], and in view of the fact
that some of our patients responded to the insertion
attempts, the level of anaesthesia might have been
insufficient.
Airway position, compliance and morbidity
The employed scoring system gave identical ratings for
the position of the i-gel™ and the LMA-S. There was no
airway obstruction, even when the epiglottis was kinked
or otherwise not in the correct position.
The lower scores for the LTS-D confirm previous findings. Bortone et al. compared the laryngeal tube with a
classic LMA in children and found that no laryngeal
structures were identifiable in six of eleven children [39].
Kim et al. demonstrated that the view of the laryngeal
structures during the fibreoptic assessments of the LTSII depended significantly on the position of the head [40].
Mihai et al. were able to visualize the glottis only in 51%
of the cases with the LTS-II [30]. In our study, ventilation
was possible even though the correct position of the device could not be confirmed (e.g. Figure 4C and D).
Dynamic airway compliance was lowest for the LTS-D.
This is in accordance with the data of Gaitini et al. who
reported that a significantly higher peak airway pressure
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was required to achieve comparable tidal volumes [41]
and with those of Cook et al., who reported that ventilation efficacy was higher with the PLMA than with the
LTS [42]. Based on the results of our fibreoptic evaluations, one could postulate that the lower airway compliance may be partially caused by pharyngeal tissue
(epiglottis, pharyngeal wall) obstructing the airway
openings.
We observed a glottic narrowing not attributable to
insufficient anaesthesia in 7% of the patients with an
LMA-S. This is in accordance with previous results that
described an incidence of approximately 10% [7]. Neither in this, nor in our previous study [7] did glottic narrowing necessitate removal of the LMA-S. However,
glottic narrowing is an unintended clinical occurrence
not fully understood as the anatomical position of the
LMA-S appears to be correct and, importantly, the condition cannot be reversed by deepening the anaesthesia
or by administering muscle relaxants. It is our experience that the only option to facilitate glottic opening is
to remove and to reinsert the device.
The greater incidence of blood on the devices was significant for the LTS-D and could possibly also be so for
the i-gel™. The latter result would confirm that of
Eschertzhuber et al. [26]. Although our study was neither designed nor powered to detect a relationship between blood on the devices and airway morbidity, it
appears that there might be an association between mucosal injury and airway morbidity with the LTS-D.
Limitations
The observer who measured the insertion times was not
blinded to the type of SGA being used. The investigators
inserting the devices had less experience with the LTS-D
than with devices similar to the other two. The cuff of
the LTS-D but not that of the LMA-S was briefly
(<60 seconds) inflated to 100 cmH2O for inflation volume and LP measurements. The study was not powered
to draw conclusions on small differences in airway
morbidity.
Conclusions
All devices were found to be suitable for ventilating the
patients’ lungs during elective surgery. Leak pressures
did not differ, but airway morbidity was more pronounced with the LTS-D.
Competing interests
This study was funded by departmental resources only. The corresponding
author declares that he had sole and complete control over collection of
data, data analysis, interpretation of the results and content of the
manuscript. He was not influenced by any company.
Authors’ contributions
SGR designed and conducted the study, analyzed the data, and wrote the
manuscript. SC conducted the study, analyzed the data, and drafted the
Page 8 of 9
manuscript. TG conducted the study. CE, AB and MB helped designing the
study and writing the manuscript. TAC drafted the manuscript. MS analyzed
the data and helped to write the manuscript. All authors read and approved
the final manuscript.
Acknowledgements
Thanks to Professor Arnd Timmermann, MD, D.E.A.A, MME (Department of
Anaesthesiology, Intensive Care Medicine and Pain Therapy, DRK Kliniken
Westend, Berlin, Germany) for his logistical support provided during the
initial study period.
Author details
1
Department of Anaesthesiology, Emergency and Intensive Care Medicine,
University Medical Centre Göttingen, Robert-Koch-Straße 40, Göttingen
37083, Germany. 2Current affiliation: Department of Anaesthesia and
Emergency Care, University Hospital San Giovanni Battista di Torino, Turin,
Italy. 3Current affiliation: Department of Anaesthesia, Paediatric Intensive Care
and Emergency Medicine, Children’s Hospital Auf der Bult, Hannover,
Germany. 4Georg-Elias-Müller Institute for Psychology, Georg-August
University, Göttingen, Germany.
Received: 7 December 2011 Accepted: 28 July 2012
Published: 7 August 2012
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doi:10.1186/1471-2253-12-18
Cite this article as: Russo et al.: Randomized comparison of the i-gel™,
the LMA Supreme™, and the Laryngeal Tube Suction-D using clinical
and fibreoptic assessments in elective patients. BMC Anesthesiology 2012
12:18.
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