A 4 year old girl was admitted for correction of PDA under the general anesthesia. A 4.5mm ID cuffed orotracheal Rusch tube was inserted and the Jackson-Rees system was used for maintenance of anesthesia with enflurane-nitrous oxide-oxygen. During surgery a mild increase in airway resistance was noticed and tachycardia was seen but all other vital signs were within normal limits. In the recovery room, she exhibited signs of complete airway oibstruction, and so the endotracheal tube was extubated. The obstruction was due to a dried mucous crust attached to the bevel of the endotracheal tube.