You should expect difficulty in placing a supraglottic airway in patients with:

Supraglottic airway helps patients with difficult airways. It can be a better alternative if tracheal intubation or facemask ventiation are both difficult. Supraglottic airway device, moreover, serves as a passageway for ventilation, oxygenation and administration of anesthetic gases. Limited mouth opening, restricted head and neck movement, and cricoid (ring-shaped cartilage of the larynx) pressure are several situation where insertion of supraglottic airway is difficult. It is also more difficult to place supraglotic airway in children than adult. In addition, it is also vital to consider the condition of the lungs and trachea before insertion. It is also best to set high precautionary measures in insertion of supraglottic airway because even in healthy individuals with healthy airways, there is a 10% of the cases that it failed.