Role Of Laryngeal Mask Airway In Simulated Difficult Airway

Objective: Compare the role of laryngeal mask airway(LMA) in difficult airway scenarios simulated by three different ways and evaluate whether the difficult airway is simulated successfully.Methods: One hundred adult patients undergoing elective surgical procedures requiring general anesthesia were randomly assigned into four groups. After anesthesia induction, the LMA was inserted with the neck in neutral position(normal control group, group A)、rotation(simulate spasmodic torticollis or scar contracture in lateral neck,group B)、flexion(simulate head and neck flexion caused by scar contracture in anterior neck,group C)、and manual in-line stabilization(head and neck were fixed in neutral position caused by scar contracture in anterior neck 、 cervical spondylopathy or cervical injury,group D), respectively.Inflating the cuff to an intracuff pressure of 60 cm H2 O, then fixed the LMA if successful ventilation was obtained. Then the cuff volume(V60) and oropharyngeal leak pressure(OLP60) at the 60cmH2 O intracuff pressure were tested. In order to decrease cuff pressure related complications,we deflated the cuff gradually to a minimal cuff volume(Vm),and its corresponding intracuff pressure(ICPm) and oropharyngeal leak pressure(OLPm) were recorded. Before surgery,we also used a fiberoptic bronchoscope(FOB) to assess LMA position.When finishing the whole study, the following were compared : insertion time, success rate of LMA insertion, FOB grade, peak airway pressure, pharyngeal complications and any other adverse reaction.Results: All the patients had get efficient ventilation except three failed insertion cases in group C and one exchanged to endotracheal intubation during surgery for gastric dilation in group B. There were no significant difference among the four groups in demographic character, FOB grade, Vm, V60, OLPm, incidence of adverse reaction. The ICPm in group C was higher than that in group A and D, and when compared with other three groups, the group C had longer insertion time、lower success rate and higher peak airway pressure. However, in group B and D, the only significant difference was that the insertion time were higher than that in group A.Conclusion: The LMA can provide efficient ventilation in those scenarios,but only the difficult airway simulated by neck flexion had get obvious difference. There still need some efforts to estimate the efficacy of difficult airway simulated by head rotation and manual in-line stabilization of the head.