Performance of the Size 5 Laryngeal Mask Airway in Males and Females

Summary.

We compare the functional performance (ease of insertion, oropharyngeal leak pressure and anatomic position) of the size 5 LMA in males and females over a range of cuff volumes. We also determine 1) if age, height, weight and body mass index predict functional performance and 2) the relationship between oropharyngeal leak pressure (OLP) and anatomic position (judged by fibreoptic scoring). One hundred male and one hundred female paralysed, anaesthetised patients were studied. The number of insertion attempts and time to placement were recorded. OLP and fibreoptic score (FOS) were measured during inflation of the cuff from 0 - 40 ml in 10 ml increments. There were no failed insertions. Insertion times were similar for males and females. There were no differences in OLP or FOS between males and females at any cuff volume. For males, OLP increased from 0 to 10 ml and 10 to 20 ml (p < 0.001), but was unchanged from 20 to 30 and 30 to 40 ml. For females, OLP increased from 0 to 10 ml, 10 to 20 ml (p < 0.001) and decreased from 20 to 30 ml (p = 0.02), but was unchanged from 30 to 40 ml. For males, FOS increased from 0 to 10 ml (p = 0.02) and 10 to 20 ml (p < 0.001), but was unchanged from 20 to 30 and 30 to 40 ml. For females, FOS increased from 0 to 10 ml (p = 0.02), 10 to 20 ml (p < 0.001), decreased from 20 to 30 ml (p = 0.001), but was unchanged from 30 to 40 ml. There was a significant positive correlation with height and OLP in males and females at higher cuff volumes, but no correlation with any other variable. There was no correlation between OLP and FOS at any cuff volume for males, but there was a correlation at 0 (p = 0.03) and 10 ml (p = 0.01) for females. We conclude that ease of insertion, efficacy of seal and anatomic position for the size 5 LMA is similar in males and females. Age, weight and body mass index do not predict performance, but efficacy of seal improves with increasing patient height. Fibreoptically determined anatomic position is a poor predictor of efficacy of seal. The shape of the pharynx may be different between tall and short adults.

Key words:

Equipment: laryngeal mask airway - Size selection - Anatomy: pharynx

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