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Re-evaluation of appropriate size of the laryngeal mask airway

Asai T, Murao K, Yukawa H, Shingu K

British journal of anaesthesia, 1999

Abstract

We have assessed 32 males and 31 females in a randomized, crossover study to see if there was any difference in the correct positioning of the laryngeal mask, optimal ventilation (defined as no gas leak around the mask at an airway pressure of 18 cm H2O) and cuff visibility between sizes 4 and 5 masks in males and sizes 3 and 4 in females. The position of the mask in relation to the glottis was assessed using a fibreoptic bronchoscope. There was no significant difference in correct positioning between the two sizes in either sex. Gas leak was significantly less frequent for a larger than a smaller mask (P < 0.01 for both sexes), whereas the cuff was more often seen in the mouth with larger masks (P < 0.02 for males and P < 0.01 for females). Therefore, larger masks (size 4 in females and size 5 in males) provided a better seal than smaller sizes without worsening the relative position of the mask to the glottis; however, the larger mask came up within the mouth more often, which could interfere with tonsillectomy and could increase the risk of sore throat or lingual nerve damage.

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Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design.

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