oa Southern African Journal of Anaesthesia and Analgesia - A clinical comparison of disposable airway devices : original research
Background : The re-usable Classic laryngeal mask airway (LMA®) is widely used. There are concerns regarding the transmission of pathogens. Disposable airway devices provide a cost-effective alternative. We performed a side by side clinical comparison of these devices applicable to the South African context.
Methods : Adult ASA 1-3 patients (30 - 100 kg) presenting for elective peripheral surgery in Tygerberg Academic Hospital were randomised to receive the gold standard Classic LMA®, or one of four disposable devices. They all received a standardised anaesthetic with propofol, fentanyl and isoflurane in 40% O2 / N2O. Insertion technique, mask sizes and maximum cuff volumes were per manufacturer's instructions. The cuff was inflated to achieve an adequate airway seal (no audible leak at an airway pressure of 20cm H2O), or to the maximum recommended volume. Cuff and airway pressures were measured continuously. A protocol was followed for repeated or failed attempts. 115 of the proposed 130 patients were recruited. Categorical data was analysed using Chi squared tests, and one-way ANOVA was performed on parametric data. An alpha level of 0.05 was accepted.
Results : The patients were of comparable age, weight, ASA grade and airway grading. There were no statistical differences in the number of times the airway device size had to be changed (p = 0.627), ease of insertion (p = 0.357) or insertion attempts (p = 0.909). Only the Cobra PLA was graded as "Grade 4 : impossible to establish an airway" in 10% of cases, and the insertion time with this device was prolonged (p = 0.018). The Cobra PLA predictably differed from the other groups in cuff volumes (p = 0.001). Cuff pressures were significantly higher in the Ambu and LMA Unique (p = 0.001). Maximum airway pressure attainable after 5 minutes was significantly higher in the Ambu (p = 0.036). Airway trauma as graded by visible blood on the device was low, and similar between groups (p = 0.237). Secretions were negligible in 67.8% patients and there was no difference in the amount of suctioning required (p = 0.094). Patient comfort was exceptional and comparable, achieving similar visual analogue scores for sore throat (p = 0.742), dysphagia (p = 0.760) and hoarseness (p = 0.258). No complications were noted.
Conclusions : We found no difference in routine clinical practice between the Classic LMA®, LMA Unique, Portex Soft Seal, Ambu and Cobra PLA in terms of ease of insertion, number of attempts, size changes, patient comfort or airway trauma. The Ambu device allowed an airway seal at higher pressures. The Cobra devices had a prolonged average insertion time. The Cobra devices were the only ones found impossible to achieve a satisfactory airway after 3 attempts in 10% of cases, although this did not reach statistical significance.
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