To avoid leaks while manually bagging a patient with a laryngeal mask airway (lma) in place, you should:

To avoid supraglottis airway leaks during bagging with an LMA, ensure that 15-mm connector is properly sealed and the cushion does not leak. During insertion of the LMA the head of the patient should be slightly tilted forward at the neck in a position known as sniffing position for a good pharyngeal seal.

substitution is the answer in this case