Full text of DOI:10.1007/BF03016840

604
CARDIOTHORACIC ANESTHESIA, RESPIRATION AND AIRWAY
Routine use of the intubating laryngeal mask air-
way results in increased upper airway morbidity
[L’utilisation courante du masque laryngé d’intubation augmente la morbidité
des voies aériennes supérieures]
Shinichi Kihara,* Yuuichi Yaguchi,* Joseph Brimacombe,† Seiji Watanabe,* Noriko Taguchi*
Purpose: The classic laryngeal mask airway (LMA) has a soft, sili-
cone tube and the intubating laryngeal mask airway (ILM) has a
rigid, silicone-coated steel tube. We compare postoperative
pharyngolaryngeal morbidity in patients randomised to receive
either device.
morbidité pharyngo-laryngée postopératoire chez des patientes qui
ont accepté de recevoir, au hasard, l’un ou l’autre masque.
Méthode : Soixante-cinq femmes (d’état physique ASA I ou II, de 18
à 80 ans) devant subir une anesthésie régionale balancée pendant
une laparotomie gynécologique, censée durer une ou deux heures, ont
été réparties au hasard pour une intubation avec le ML ou le MLI. La
pression à l’intérieur du ballonnet a été maintenue à 60 cm H2O. La
morbidité pharyngo-laryngienne postopératoire (mal de gorge, diffi-
culté d’avaler, irritation de la bouche, douleur au cou/à la mâchoire,
enrouement) a été évaluée à deux, 24 et 48 h par des expérimenta-
teurs impartiaux.
Methods: Sixty-five female patients (ASA physical status class I or
II, aged 18–80 yr) undergoing balanced regional anesthesia for
gynecological laparotomy expected to last one to two hours were
randomly assigned for airway management with the LMA or ILM.
Intracuff pressure was maintained at 60 cm H O. Postoperative
2
pharyngolaryngeal morbidity (sore throat, difficulty swallowing, sore
mouth, sore neck/jaw, hoarseness) was assessed at two, 24 and 48
hr by blinded investigators.
Résultats : Le nombre d’essais nécessaires pour insérer le masque et
la durée de l’anesthésie ont été similaires dans les deux groupes. Le
mal de gorge a été plus fréquent avec le MLI à deux heures (44 vs 15
%, P = 0,01), à 24 h (59 vs 21 %, P = 0,008) et à 48 h (34 vs 3
%, P = 0,005). L’irritation de la bouche a été plus fréquente aussi
avec le MLI à deux heures (16 vs 0 %, P = 0,02) et à 24 h (12 vs 0
%, P = 0,04), mais non à 48 h (6 vs 3 %). La difficulté d’avaler se
retrouve plus souvent avec le MLI à deux heures (25 vs 0 %, P =
0,04), mais non à 24 h (31 vs 3 %) ni à 48 h (12 vs 9 %). L’incidence
de douleur au cou/à la mâchoire n’a pas présenté de différence inter-
groupe (MLI, 3–12 %; ML, 0–3 %), ni l’enrouement (MLI, 12–31 %;
ML, 16–18 %). Il n’y a pas eu de corrélation entre la morbidité
pharyngo-laryngienne postopératoire et la durée de l’anesthésie.
Results: The number of insertion attempts and duration of anes-
thesia was similar between groups. Sore throat was more common
for the ILM at two hours (44 vs 15%, P=0.01), 24 hr (59 vs 21%,
P=0.008) and 48 hr (34 vs 3%, P=0.005). Sore mouth was more
common for the ILM at two hours (16 vs 0%, P=0.02) and 24 hr
(12 vs 0%, P=0.04), but not at 48 hr (6 vs 3%). Difficulty swal-
lowing was more common for the ILM at two hours (25 vs 0%,
P=0.04), but not at 24 hr (31 vs 3%) and 48 hr (12 vs 9%). There
were no differences in the incidence of sore jaw/neck (ILM,
3–12%; LMA, 0–3%) and hoarseness (ILM, 12–31%; LMA,
16–18%). There was no correlation between postoperative
pharyngolaryngeal morbidity and duration of anesthesia.
Conclusion : La morbidité pharyngo-laryngienne est plus élevée avec
le MLI qu’avec le ML à la suite d’une anesthésie qui dure une ou deux
heures.
Conclusion: Pharyngolaryngeal morbidity is more common with
the ILM than the LMA following anesthesia lasting one to two
hours.
H E intubating laryngeal mask (ILM) is a
new airway device designed to have better
intubation characteristics than the classic
Objectif : Le masque laryngé traditionnel (ML) possède un tube de
silicone mou tandis que le masque laryngé d’intubation (MLI) com-
porte un tube de métal rigide enrobé de silicone. Nous comparons la
1
T
laryngeal mask airway (LMA). The prima-
From the Department of Anaesthesia, Pain Clinic, and Clinical Toxicology,* Mito Saiseikai General Hospital, Ibaraki, Japan; and the
University of Queensland, Department of Anaesthesia and Intensive Care,† Cairns Base Hospital, Cairns, Australia.
Address correspondence to: Prof. J. Brimacombe, University of Queensland, Department of Anaesthesia and Intensive Care, Cairns Base
Hospital, The Esplanade, Cairns 4870, Australia. Phone: 61 7 40 506960; Fax: 61 7 40 311628; E-mail: jbrimacombe@austarnet.com.au
Support was received solely from institutional and/or departmental resources.
Accepted for publication November 9, 2000.
Revision accepted March 11, 2001.

Kihara et al.: I L M A N D UPPER AIRWAY MORBIDITY
605
ry role of the ILM is as an airway intubator, but it has
a potential role as an alternative to the LMA in rou-
tine anesthesia practice since placement is conceptual-
ly easier and does not require insertion of the fingers
in the patient’s mouth.2 Unlike the LMA, which has a
soft silicone tube, the ILM has a rigid silicone coated
steel tube. In a recent study, Keller and Brimacombe3
found that the ILM exerted greater pressures against
the pharyngeal mucosa than the LMA and suggested
that the ILM was unsuitable for routine anesthesia
practice. In the following randomised, double- blind
study, we compare postoperative pharyngolaryngeal
morbidity with the LMA and ILM.
recorded (maximum three allowed). The ILM/LMA
cuff was inflated with air to an intracuff pressure of 60
cm H2O and the cuff volume noted. The intracuff pres-
sure was maintained at approximately 60 cm H2O
throughout the surgery by intermittent withdrawal of
air. Intracuff pressure was measured using an arterial
pressure transducer attached to the pilot balloon.6
Oropharyngeal leak pressure and fiberoptic position
were measured before the start of surgery.
Oropharyngeal leak pressure was measured by closing
the expiratory valve of the circle system at a fixed gas
flow of 3 L·min– 1 and noting the airway pressure at
which the dial on a calibrated aneroid manometer
reached equilibrium.7 The fibreoptic view was scored as
follows: 4 (only vocal cords visible), 3 (vocal cords plus
posterior epiglottis visible), 2 (vocal cords plus anterior
epiglottis visible), and 1 (vocal cords not seen).8
Patients were allowed to spontaneously ventilate during
surgery. Oropharyngeal suctioning was avoided. Thirty
minutes before the end of the surgery, morphine 50
µg·kg–1 with 7 mL of 0.5% bupivacaine was given
epidurally. The ILM/LMA were removed when the
patient was able to open her mouth on command. Any
blood detected on the ILM/LMA was noted.
Postoperative analgesia was with buprenorphine 0.2 mg
with 7 mL of saline given epidurally as a top-up by
investigators blinded to the type of device used. Oxygen
was given via a Hudson-type face mask at 2–4 L·min–1
until patients were discharged to the ward.
Intraoperative data was collected by unblinded
observers. Patients were unaware of the device used.
Postoperative pharyngolaryngeal morbidity was
assessed at two, 24 and 48 hr by investigators blinded
to the devices inserted. Sore throat, sore mouth, sore
neck/jaw, difficulty swallowing and hoarseness were
graded using a 4-point scale. Sore throat was graded as:
0=no sore throat (nil); 1=less severe than with a cold
(mild); 2=similar to that noted with a cold (moderate);
3=more severe than with a cold (severe). Sore mouth
and sore neck/jaw was graded as: 0=nil; 1=mild;
2=moderate; 3=severe. Swallowing difficulty was grad-
ed as: 0=no difficulty (nil); 1=discomfort at swallowing
(mild); 2=pain at swallowing (moderate), 3=severe pain
at swallowing (severe). Hoarseness was graded as: 0=no
hoarseness (nil); 1=noted by a patient (mild); 2=obvi-
ous to observer (moderate); 3=aphonia (severe).
Methods
Sixty-five female patients (ASA physical status class I
or II, aged 18–80 yr) scheduled to undergo balanced
regional anesthesia for gynecological laparotomy
expected to last one to two hours were randomly
assigned (by opening a sealed envelope) for airway
management with either the ILM or LMA. Patients
were excluded if they had oropharyngeal/cervical
pathology, or had jaw, neck, mouth or upper respira-
tory tract symptoms in the previous ten days.
Institutional Ethical Committee approval and written
informed consent was obtained. Airway management
was by anesthesiologists with experience of greater
than 300 uses with each device. All ILM and LMAs
used in the study were sterilised by steam autoclaving
and had passed the pre-use check tests.
Premedication was with diazepam 5 mg and roxati-
dine (H2-blocker) 75 mg po 1.5 hr preinduction. An
epidural catheter was inserted at the L2/L3 interspace
and 3 mL of 1.5% lidocaine with 1:200.000 epineph-
rine given as a test dose. Patients were placed in the
supine position with the head-neck on a pillow 7 cm in
height. A standard anesthesia protocol was followed
and routine monitoring applied. Patients were induced
with lidocaine 0.5 mg·kg– 1, fentanyl 2 µg·kg–1 and
propofol 2.5 mg·kg–1. Maintenance was with oxygen
33% and sevoflurane 1–3% in nitrous oxide.
Humidification was with a bacterial filter placed
between the anesthesia breathing system and the airway
device. Fresh gas flow was 3 L·min– 1.The patient was
face mask ventilated for one minute before ILM/LMA
insertion. Face mask ventilation was graded as: easy
(Guedel airway not required); moderate (Guedel air-
way required), difficult (Guedel airway plus jaw thrust
required) and failed (failure to ventilate, alternative
technique required). The ILM/LMA (size 4 only) was
inserted and fixed using the manufacturer’s recom-
mended techniques.4,5 A water based jelly was used for
lubrication. The number of insertion attempts were
Sample size was to detect a 20% difference in sore
throat based on data from previous studies reporting a
15% incidence of sore throat with the LMA9 and a
50% incidence10 with the ILM for a type I error of
0.05 and a power of 0.8. Descriptive data were tested
using a two-tailed independent t test. Categorical data
were tested using a Chi-square test. The Mann-

606
CANADIAN JOURNAL OF ANESTHESIA
TABLE Incidence of postoperative pharyngolaryngeal morbidity for the intubating laryngeal mask airway (ILM) and the classic laryngeal
mask airway (LMA). Data are numbers and percentage.
ILM
3
LMA
3
P
Severity score
1
2
T(%)
1
2
T(%)
n
32
0
1
33
0
1
Sore throat
2 hr
24 hr
48 hr
9
14
8
5
4
3
14 (44)
19 (59)
11 (34)
4
5
1
1
1
0
5 (15)
7 (21)
1 (3)
0.01
0.008
0.005
0
0
Hoarseness
2 hr
24 hr
48 hr
7
8
3
2
2
1
0
0
0
9 (28)
10 (31)
4 (12)
2
3
0
4
3
2
0
0
0
6 (18)
6 (18)
2 (6)
NS
NS
NS
Sore mouth
Sore jaw/neck
2 hr
24 hr
48 hr
5
4
2
0
0
0
0
0
0
5 (16)
4 (12)
2 (6)
0
0
1
0
0
0
0
0
0
0 (0)
0 (0)
1 (3)
0.02
0.04
NS
2 hr
24 hr
48 hr
4
0
1
0
0
0
0
0
0
4 (12)
0 (0)
1 (3)
0
1
0
0
0
0
0
0
0
0 (0)
1 (3)
0 (0)
NS
NS
NS
Swallowing
difficulty
2 hr
24 hr
48 hr
2
7
3
6
3
1
0
0
0
8 (25)
10 (31)
4 (12)
0
1
3
0
0
0
0
0
0
0 (0)
1 (3)
3 (9)
0.04
NS
NS
Severity score: 1=mild; 2=moderate; 3=severe; T (%) = total (percentage).
Whitney U-test was used for the ordinal data. The
Spearman’s rank correlation was used to test correla-
tions between the duration of anesthesia and the
severity of the upper airway complications. Unless
mouth was more common for the ILM at two and 24
hr, but not at 48 hr. Difficulty swallowing was more
common for the ILM at two hours, but not at 24 and
48 hr. There was no difference in the incidence of sore
jaw/neck and hoarseness between groups. There was
no correlation between postoperative pharyngolaryn-
geal morbidity and 1) duration of anesthesia; 2) mask
ventilation score or 3) those patients who had two or
more airway devices inserted - i.e., a Guedel airway
plus the randomised device or more than one attempt
with the randomized device. There were no significant
differences in airway morbidity among anesthesiolo-
gists. Severe airway morbidity was only documented
in one patient and this improved within 48 hr.
otherwise noted, data is presented as mean
SD.
Significance was taken as P <0.05.
Results
There were no demographic differences between
groups. Five anesthesiologists participated in the study
and each conducted 3–40 cases. The mean SD for
age, height and weight for the ILM/LMA group was
40 15 yr; 44 13 yr, 158 7 cm; 157 7 cm and
60 12 kg; 57 11 kg respectively. There were equal
number of smokers in each group (ILM, n=23; LMA,
n=26). The duration of anesthesia (ILM, 105
35
Discussion
min vs LMA, 103 59 min), mask ventilation score
(4/3/2/1 n; ILM, 27/5/0/0 vs LMA, 29/3/1/0)
the number of insertion attempts (1/2/3 n; ILM,
29/3/0 vs LMA, 32/1/0), cuff volume (ILM, 21
3 mL vs 20 3 mL) and fibreoptic score (4/3/2/1 n;
ILM, 20/0/7/5 vs LMA, 14/6/12/1) were similar
between groups. Oropharyngeal leak pressure was
Our data show that postoperative pharyngolaryngeal
morbidity is more common with the ILM than the
LMA. Although this supports the suggestion that the
ILM is less suitable for routine anesthesia practice than
the LMA,3 it should be noted that only one patient
had severe airway morbidity and it is unlikely that mild
or moderate morbidity would prevent discharge.
There are no formal studies determining the incidence
of postoperative pharyngolaryngeal morbidity with
the ILM, but Nakazawa et al.1 1found a high incidence
of pharyngeal edema when the ILM was left in situ
following its use as an airway intubator and Shung et
al.1 0 found there was a high incidence of sore throat
greater for the ILM (24 5 vs 19
5 cm H2O, P
<0.0001). Blood was detected upon removal in three
patients in the ILM group and in two patients in the
LMA group. Postoperative pharyngolaryngeal mor-
bidity data is presented in the Table. Sore throat was
more common for the ILM at two, 24 and 48 hr. Sore

Kihara et al.: I L M A N D UPPER AIRWAY MORBIDITY
607
following its use for awake intubation. The incidence
of pharyngolaryngeal morbidity for the LMA was sim-
ilar to a previous study where the LMA cuff was inflat-
ed to half the maximum recommended cuff volume.1 2
Mucosal pressures are generally higher for the ILM
compared with the LMA over the range of cuff vol-
umes and are always greater than 157 cm H2O where
the curved metal tube pressed into the posterior
oropharyngeal wall.3 This is much higher than the
perfusion pressure of the posterior pharyngeal wall
that is between 34 and 80 cm H2O.13 It is likely that
the increase in pharyngolaryngeal morbidity is related
to pharyngeal ischemic damage given that insertion
success rates and macroscopic airway trauma were
similar for both devices. However, it is possible that
the difference is related to microscopic airway trauma
during insertion. Interestingly, we found that there
was no relationship between duration of anesthesia
and airway morbidity. Like the tracheal mucosa,1 4 the
level of pressure and its duration of application prob-
ably determine the extent of pharyngeal mucosal
injury. It may be that the range of anesthesia duration
was too small to detect this effect and it is generally
considered that pressure is thought to be more impor-
tant in causing trauma than time.1 4
Our data show that the oropharyngeal leak pressure
is greater for the ILM compared with the LMA. This
confirms the findings of Keller and Brimacombe3 who
suggested that this might be related to the increased
mucosal pressure exerted by the ILM. Interestingly,
we found that oropharyngeal leak pressure was greater
even when the intracuff pressures are similar. Our data
show that fibreoptic position is similar for the ILM
and LMA. This contrasts with the findings of Keller
and Brimacombe that showed that fiberoptic position
was superior for the LMA.3 These interstudy differ-
ences may be related to different size selection strate-
gies or different skill levels with the ILM.
that the area of highest mucosal pressure for the ILM
(posterior oropharyngeal wall) does not vary with
intracuff pressure/cuff volume.3 Finally, some clinicians
might consider use of laryngeal mask devices inappro-
priate for gynecological laparotomy. However, the
uneventful use of the LMA for gynecological laparoto-
my in 644 patients has been reported.1 6 Our patients
were not considered to be at risk of aspiration.
We conclude that pharyngolaryngeal morbidity is
more common with the ILM than the LMA following
anesthesia lasting one to two hours.
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