RANDOMIZED CROSS-OVER COMPARISON OF AMBULARYNGEAL MASK AIRWAY WITH CLASSIC LARYNGEALMASK AIRWAY DURING ANAESTHESIA WITH CONTROLLED
VENTILATION.
.

I Shariffuddin MBChB; C Y Wang MBChB, FRCA
Department of Anaesthesia, University Malaya Medical Centre, Malaysia.
Introduction
There is a potential risk with prion disease such as variant CreutzfeldtJakob disease associated with the use of reusable airway equipment.
This has led to an increase in disposable airway equipment in themarket including laryngeal mask. The aim of this study was to compare
the performances of Classic Laryngeal mask airway (Classic LMA) andsingle use ambu LMA during controlled anaesthesia . The primary
outcome measured was oropharyngeal leak pressure(OLP) and thesecondary outcome measures include insertion time and success rate,
manipulations required to achieve a patent airway, grade of fibre optic
laryngoscopy and the quality of ventilation during anaesthesia.

Material and methods
With institutional approval and patient consent, 40 patients werestudied using a randomised cross- over design. Following standardised
induction of general anaesthesia with fentanyl, propofol and muscle
relaxant, the patients had ambu LMA and classic LMA inserted by asingle anaesthetist.
An independent observer assessed the insertion times and number ofattempts. Patients were ventilated with oxygen-air mixture with tidal
volumes of 7 ml/kg and rate of 12 -15 /min. The OLP was measured
with cuff pressures adjusted to 60 cmH2O. Devices were inspected fortraces of blood after removal.
Statistical analysis: The paired test were used to compare OLP, leakfraction, leak volume and peak airway pressure. Chi-squared test wasused to compare the number of attempts at insertion and incidence oftrauma with each device. Wilcoxon rank test was used to compare
insertion time.

Results and Discussion
In this study, we have shown that Ambu LMA has a greater mean
OLP as compared to the Classic LMA [Table 2].
The leak fractions and leak volumes with the Ambu LMA wassignificantly less than classic LMA (p<0.05; p<0.05 respectively).
Despite these differences, there were no difference in gas exchange interm of SpO2 and ETCO2. Insertion time was similar between theclassic LMA and the ambu LMA. [Table 3]
Although the number of insertion attempts were significantly less thanthe classic LMA (p<0.05), there was 1 failure of insertion with theambu LMA and none in the classic LMA .The classic LMA required
less manipulations to achieve a patent airway during induction (p<0.05)[Table 3]. However during maintenance of anaesthesia the quality ofventilations were similar in both groups. The incidence of trauma andgrade of fibre-optic view and mean PAP were similar in both groups

Summary
The ambu LMA was as effective as the classic LMA as a supra glottic
airway device during anaesthesia with controlled ventilation. It also
provides better seal pressure

VariableGroup Ambu/Classic

Male:Female

14:26

Age (years)

35.78 + 10.34

Weight (kg)56.23 + 10.57

Height (cm)159.55 + 7.80

Table 2. Oropharyngeal leak, anatomic position and mucosal injury.
Data are mean + SD or n ;*P Value < 0.05
Variables

Ambu

ClassicP Value

19.18+ 7.54

15.28+ 5.24

*p=0.004

3/15/18/3

3/18/11/7

P=0.801

6/13

P=0.461

Oropharyngeal
leak pressure
testing (OLP):Pressure(cm H2O)
Anatomic
position:

Airway tube
(4/3/2/1)

Mucosal Injury
Y/N

4/15

Table 3. Ease of insertion and positive pressure ventilation
Data are mean + SD or n ;*P Value < 0.05
Variables

Ambu LMAClassic LMA

P- Value

Insertion time (s)27.738 +7.95

27.972 +10.45

P=0.764

Number of attempts(1/2/failed)

39/0/1

35/5/0*P=0.045

Peak airway
pressure (cmH2O)

14.95 + 3.12

14.61 + 2.45

P=0.394

Leak volume (ml)15.93 + 41.75

36.59 + 68.19*P=0.054

Leak Fraction (%)

3.690 + 9.120

9.295 + 16.774*P=0.041

99.0 + 0.9

99.1 + 1.2

10/29

9/30

Ease of insertion:

Positive pressure
ventilation:

Acknowledgements
We would like to thank the Ambu LMA Malaysia for providing the Ambu LMA. I would also wish to acknowledge thekind support of sisters and staff nurses of the Day Care Surgery, UMMC.

Classic LMA

Table 1. Demographic data Data are mean + sd or nAmbu LMA

SpO2 (%)
Leaks detectable(Y/N):Mouth

Fig .1

P=0.792