A randomised comparison between Cobra PLA and classic laryngeal mask airway and laryngeal tube during mechanical ventilation for general anaesthesia

Abstract

The aim of this study was to compare ventilation parameters during mechanical ventilation using Laryngeal Mask Airway (LMA), Laryngeal Tube (LT), and Peri-Laryngeal Airway Cobra (PLA). In a prospective, randomised controlled trial, 90 patients undergoing general anaesthesia for elective surgery were divided into three subgroups. The settings of controlled ventilation were: oxygen 50%, air 50%, sevoflurane 1.5-2.0%, TV 7 mL kg(-1), RR 10 breath min(-1), inspiratory/expiratory ratio 1:2 and FGF 3 L min(-1). The number of attempts, time taken to insert the device, airway pressure (peak airway pressure, plateau airway pressure), air leak (inspiratory and expiratory volume difference), and dynamic compliance were measured. The timepoints for collecting data were after successful insertion of the device, and after ten, 20, 30 and 50 mins of ventilation. The presence of visible blood traces, patients' assessment of their throat soreness, dysphonia and dysphagia were noted postoperatively. The success rates at first insertion were 90% and 80% and 90%, while time for insertion was 5 sec and 21.94 sec and 5.24 sec in the Cobra PLA, LMA and LT groups respectively. Ventilation pressures during procedure were highest in the LT group, where compliance was lowest compared to the Cobra PLA and LMA groups. The air leak was similar in all the groups. 30% vs. 40% vs. 10% of devices had positive blood traces; 20% vs. 40% vs. 30% of patients suffered from a sore throat; and 30% vs. 30% and 30% of patients suffered from dysphagia in the Cobra PLA, LMA and LT groups respectively. The differences were small, but Cobra PLA seemed to be slightly superior in terms of the measured parameters.