The incidence of incorrect device position ( 18 % vs. 21 % ) , failed ventilation ( 10 % vs. 9 % ) , leak pressure ( 24.8 vs. 25.2 cmH2O , p = 0.63 ) , failed lube-tube test ( 16.3 % vs. 17.6 % ) and glottic narrowing ( 19.3 % vs. 14.1 % , p = 0.35 ) was similar in both groups ( control vs. study , resp . )