Objective and hypothesis:
(1) To examine the vocal symptoms and acoustic changes perceived in the short period immediately after laryngeal mask airway, and (2) to compare these findings in patients using laryngeal mask airway and endotracheal tube.
Materials and methods:
A total of 27 patients were enrolled. They were evaluated pre-operatively and then at 2 and 24 hours post-operatively. Patients were divided into two subgroups, laryngeal mask airway and endotracheal tube. Patients were asked about the presence or absence of the following: hoarseness, vocal fatigue, loss of voice, throat-clearing sensation, globus pharyngeus and throat pain. Patients then underwent acoustic analysis of their voice, measuring the average fundamental frequency, relative average perturbation, shimmer, noise to harmony ratio, voice turbulence index, habitual pitch and maximum phonation time.
In the laryngeal mask airway group, there was an increase in the incidence of all vocal symptoms two hours post-operatively, except for globus pharyngeus. The increase was statistically significant for vocal fatigue, loss of voice and throat pain. All the symptoms had reverted back to a normal baseline level by 24 hours. There was a decrease in the maximum phonation time and habitual pitch, with an increase in all the perturbation parameters, two hours post-operatively. At 24 hours, an increase was still present for shimmer, noise to harmony ratio and voice turbulence index. The maximum phonation time and habitual pitch reverted back to normal values.
In the endotracheal tube group, there was a significant increase two hours post-operatively in the incidence of hoarseness, loss of voice and throat pain. At 24 hours, all the symptoms reverted to baseline, except for vocal fatigue and throat pain. Two hours post-operatively, there was a significant decrease in maximum phonation time and an increase in all other parameters (however, the latter was significant only for relative average perturbation and noise to harmony ratio). At 24 hours, there was a significant increase in the maximum phonation time and a persistent (but statistically insignificant) increase in the average fundamental frequency, habitual pitch, noise to harmony ratio and voice turbulence index.
At two hours, there was more loss of voice and vocal fatigue in the laryngeal mask airway group, compared with the endotracheal tube group. At 24 hours, these symptoms were comparable in both groups. Comparing changes in acoustic parameters to baseline values in both groups, there were no statistically significant changes.
Shortly after reversal of anaesthesia, laryngeal symptoms following laryngeal mask airway are no less significant than those experienced following endotracheal tube anaesthesia. Both methods can be regarded as nontraumatic, in view of the lack of significant vocal symptoms and acoustic changes 24 hours after anaesthesia.