We conducted a single-centre , prospective parallel-group , ` open label ' randomised controlled trial in subjects with OOHCA ( aged greater than or equal to 12 years of age ; weighing greater than or equal to 30 kg ) were allocated to either the i-gel supraglottic airway ( IG-SGA ) or the Portex Soft Seal Laryngeal Mask ( PSS-LM ) within a large Australian ambulance service .