Laryngeal mask airway

(LMA-ProSeal) malfunction causing acute airway obstruction Binu Puthur SIMON and Syed Harun HABIBULLAH

Department of Anaesthesiology, RIPAS Hospital, Brunei Darussalam

ABSTRACT

The Laryngeal Mask Airway ProSealTM (LMA-ProSealTM; Laryngeal Mask Company Limited) is a reusable

supraglottic airway device developed to enhance supraglottic airway protection and extend the benefits

of the classic LMA (Laryngeal Mask Airway) to greater number of patients. Added features include an

additional drain tube to channel fluid away from the airway and a tighter seal against the glottic open-

ing with no increase in mucosal pressure. Clinicians have extended the use of the LMA-ProSealTM inside

and outside the operating theatre including use for difficult airway management and airway rescue.

However, even these new devices have their limitations. We report an unforeseen acute airway ob-

struction caused by LMA-ProSealTM malfunction during ophthalmic surgery. The cuff of the device was

deformed with herniation to one side upon insufflation of the balloon.

Keywords: Laryngeal mask airway, malfunction, complications, LMA-ProSeal

INTRODUCTION

Laryngeal masks are used broadly for elective

and emergency airway management and are

an essential part of the American and Europe-

an difficult airway management algorithm. 1-3

Due to their wide use, noticeable complica-

tions and side effects have been reported

over the last years. The rare reports of airway

obstruction directly triggered by the laryngeal

mask are swelling of the pharyngeal soft tis-

sues caused by the leakage of irrigation fluid,

4 herniation of the laryngeal mask airway

cuff, 5-7 foreign bodies (Ascaris lumbricoides),

Case Report

Correspondence author: Binu Puthur SIMON,

Department Of Anaesthesiology RIPAS Hospital, Bandar Seri Begawan BA 1710

Brunei Darussalam E mail: binupsimon@yahoo.com

CASE REPORT

A 48-year-old man with a body mass index of

38.9 kg/m2 was scheduled for Trans Pars Pla-

na Vitrectomy and intra-ocular lens insertion

of the left eye under general anaesthesia. His

8 and intermittent obstruction related to a va-

gal nerve stimulator. 9 We report the case

where an unanticipated airway problem arose

due to a defect in a reusable Laryngeal Mask

Airway ProSealTM (LMA-ProSealTM) when it was

used for an ophthalmic procedure. Upon care-

ful investigation post procedure, the inflatable

part of the device had weakened and bal-

looned out causing deformation of the mask

resulting in loss of proper fit and seal.

Brunei Int Med J. 2012; 8 (4): 205-209

past medical history was relevant for obs–

tructive sleep apnoea, hypertension and dia-

betes mellitus.

The patient was pre-oxygenated with

100% oxygen for three minutes and general

anaesthesia was induced with 200mgs of

propofol and 75mcgs of fentanyl. Anaesthesia

was maintained with oxygen, nitrous oxide

and isoflurane. Mask ventilation was fairly

easy and intravenous atracurium (40mg) was

given for relaxation. A size 4 cuff LMA-

ProSealTM laryngeal mask airway was suc-

cessfully placed after checking of the cuff with

30ml air insufflation. The cuff was inflated

with 20ml of air. The patient was ventilated

with pressure controlled ventilation (PCV)

mode with following parameters; inspiratory

pressure of 15cm H2O, respiratory rate of 12

per minute and an inspiratory: expiratory

(I:E) ratio of 1:1. An I:E ratio of 1:1 was pre-

ferred to achieve a higher tidal volume at a

lower pre-set inspiratory pressure (normal

ratio is 1:2). The patient could generate

around 550mls of tidal volume with the above

settings. As a precautionary measure, a size

12 nasogastric tube was introduced through

the drain tube of the laryngeal mask airway

(LMA). His end tidal CO2 was 35-40mm of Hg

(Normal range 35 to 45mm of Hg).

Thirty minutes into the surgery a

gradual decrease in tidal volume (350ml) and

a rise in the end tidal CO2 were noted. An ad-

ditional dose of atracurium (40mg) and fenta-

nyl (75mcgs) were given on the assumption

that the effect of the initial dose was wearing

off, but there was no improvement. Then the

ventilator mode was changed to volume con-

trol with the following setting; tidal volume of

500ml and respiratory rate of 12/minute.

SIMON and HABIBULAH. Brunei Int Med J. 2012; 8 (4): 206

After this adjustment, the peak airway pres-

sure went up to 29-30cm of H2O and the

mean airway pressure was around 17cm of

H2O. The end tidal CO2 was maintained at 48

to 50mm of Hg. We managed to continue with

this strategy for another 40 minutes.

Approximately 10 to 15 minutes be-

fore completion of surgery, breathing at-

tempts by the patient were noted and we at-

tempted to manage the patient on spontane-

ous ventilation mode with manual assistance.

It was noticed that at this point there was

hardly any end tidal CO2 trace and the reser-

voir bag did not show any movement. The

patient seemed to be experiencing acute air-

way obstruction during spontaneous attempts

of breathing. The patient was paralysed with a

10mg dose of atracurium. Volume control

mode was reinstated with the same settings

as before. The patient was then satisfactorily

ventilated until the surgical procedure was

completed.

An intravenous dose of neostigmine

and atropine were then administered to re-

verse the residual effect of the muscle relax-

ants. When breathing attempts commenced,

the patient appeared to be further exhibit air-

way obstruction. At this point the LMA-

ProSealTM was removed and a Guedel airway

(size 4) was inserted. The patient was venti-

lated with a face mask until a good respirato-

ry effort was observed. Further recovery was

uneventful. The LMA-ProSealTM was later ex-

amined and it was noted that the cuff was

deformed with herniation to one side (Figure

1). A faulty LMA with herniation after insuffla-

tions, together with formation of a fold on the

cuff was suspected as the cause of the airway

problem we had encountered in this case.

DISCUSSION

Cases of herniation have been reported with

the Classic LMA™ airway. There was a case

where the plastic layers between the inflated

cuffs of a disposable LMATM had separated and

resulted in a herniation 10 and, another case

where the classic reusable LMA had herniated,

probably as a result of material fatigue follow-

ing repeated sterilisation. 7

In this case, we suspected herniation

(deformation) of the LMA occurred intra-

operatively causing leakage around the LMA-

ProSeal TM. A fold formed on the cuff facing

the laryngeal inlet (Figure 1 b). The defor-

mation led to loss of proper seal causing the

subsequent events.

Though we were successful in venti-

lating the patient using the volume control

mode, the peak airway pressures were high

(30cm of H2O) despite administering a repeat

dose of muscle relaxant. Initially we were

able to get the same tidal volume at a setting

of 15 cm H2O with pressure control mode.

With intermittent positive pressure

ventilation (IPPV) and adjustment to volume

control we succeeded in ventilating the pa-

tient adequately. Since a constant flow of gas

is delivered in the volume control mode, more

tidal volume was achieved with the same air-

way pressure, unlike the decelerating flow

noticed in pressure control mode. Moreover

an airway obstruction at laryngeal inlet could

generate an auto positive end expiratory

pressure (PEEP). This intrinsic PEEP together

with long inspiratory time places the patient

on a less compliant (over distended) part of

the volume pressure curve.

When the patient started breathing

spontaneously the obstruction became more

severe causing inadequate ventilation. The

reasons for almost complete airway obstruc-

tion once spontaneous breathing commenced

could be due to the deformed cuff displacing

the LMA inlet away from the glottis. This ef-

fect possibly got worse with the negative

pressure caused by spontaneous inspiratory

SIMON and HABIBULAH. Brunei Int Med J. 2012; 8 (4): 207

a b

Figures 1: a) Inflated ProSeal TM showing

herniation of the right side (arrow) and b)

View from the other side showing the

herniation resulting in deformation and

loss of seal contour.

efforts. In this particular case, LMA-ProSealTM

was preferred over the endotracheal tube to

obtain smooth recovery and avoid the stress

of extubation occurring after posterior cham-

ber eye surgery. 11 LMA-ProSealTM was used

as we could take extra precautionary

measures against aspiration and gastric dis-

tension (like insertion of an orogastric tube).

Additionally, LMA ProSeal has proven to have

better seal at higher ventilating pressures. 12

There have been case reports of her-

niation of the classic reusable type LMA, pos-

sibly as a result of overuse, over inflation or

repeated sterilisation. 13 Repeated uses of

LMA™ airways beyond 40 uses increases the

probability of device malfunctions. 15 In this

particular case we were unable to determine

how often the LMA-ProSealTM had been sub-

jected to repeated use. As a standard practice

we utilise a cuff volume of 20-30 ml for LMA-

ProSealTM size 3 in accordance with manufac-

turer recommendations and, our sterilisation

complies with manufacturer instructions.

Since the head was draped and cov-

ered for our case, we did not have access to

the airway such that, in the worst case sce-

nario of total airway obstruction we would

have been left with no choice but to stop the

surgery and replace the faulty LMA with an

oral endotracheal tube.

Cuff herniation of the LMA-Classic

may not be apparent if the cuff is inflated

with volume less than the recommended

maximal volume (e.g., 30 ml for size 4) and

may only become apparent when inflated with

a volume of air 50% greater (45 ml). 15 This

practice is now recommended by the manu-

facturer. We recommend this practice to be

followed in LMA–Pro SealTM prior to insertion.

In conclusion, when a ventilation

problem is encountered with a reusable

LMA™, particularly if this had experienced

repeated sterilisation, a herniated cuff should

be considered, even if initial testing was in-

conspicuous. 7 Removal of the malfunctioning

LMA™ and inspection of the cuff should be

considered to rule out this potentially deleteri-

ous technical problem.

SIMON and HABIBULAH. Brunei Int Med J. 2012; 8 (4): 208

AKNOWLEDGEMENT: We would like to acknow-

ledge our colleagues, Dr Salil G NAIR, Dr Anand H

KULKARNI and Dr Hj Zulaidi HJ ABDUL LATIF for

their help with the management of this patient.

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SIMON and HABIBULAH. Brunei Int Med J. 2012; 8 (4): 209

Brunei Darussalam Brunei Darussalam Brunei Darussalam Brunei Darussalam ———— Healthcare in PicturesHealthcare in PicturesHealthcare in PicturesHealthcare in Pictures

Hj Ahmed Yunos Bin Hassan (Dresser) doing his daily round with his team in the

surgical ward of the Brunei General Hospital.

(Picture courtesy of Dayangku Dr Siti Nur’Ashikin Bte Pengiran Tengah).