Voice recovery time following short-term intubation
Pearson, Michael Glen
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Many patients undergo endotracheal intubation, a procedure in which a tube is placed into the trachea via the oral cavity. This procedure is performed to assist patients' respiration while their muscles are paralyzed due to anaesthesia. The placement of the tube has been cited in the literature as one possible cause of postintubation changes in phonation. Even though there have been studies of laryngeal damage and estimations of how long it takes a patient's voice to return to normal, the time course of these changes has not been objectively investigated in terms of recovery. The purpose of this study was to determine objectively whether phonation returned to normal within previous researchers' estimated time frame of up to 72 hours. Baseline electroglottographic (EGG) and acoustic vocal measures were taken before ten subjects' surgeries, and posttest ECJG and acoustic measures were taken following surgery and at 24 hour intervals up to 72 hours. Identical protocols were followed with ten subjects who did not have surgeries to insure that differences were caused by intubation and not normal daily changes in their voices. To take ECJG fundamental frequency (fg) measurements, two electrodes were placed anterior to each subject's thyroid laminae. Simultaneous audio recording of all samples were made to obtain acoustic measurements of the second and third formants, jitter, shimmer, and noise-to-harmonic ratio (NHR). Samples of five prolonged vowels and a short reading passage were obtained in a pretest and four consecutive post-test conditions. The EGG and audio recordings were analyzed using a Kay Elemetrics Computerized Speech Lab (CSL) system. Average fundamental frequencies of all samples were computed using ECJG data. The second and third formants, jitter, shimmer, and NHR were determined using the CSL program for acoustic analysis of audio samples. Means comparisons of data revealed no main effect for group and no two way factorial effects statistically. However, descriptive results indicated some consistent patterns of changes between non-intubated and intubated groups. Even so, the results were not uniform across vowels, variables, and tests. Therefore, further research is warranted.