Selected acoustic characteristics of voices before intubation and after extubation

Effects of endotracheal intubation on acoustic characteristics of voices were investigated for 8 male and 8 female subjects using a miniature neck accelerometer and computerized analysis methods. Variables extracted from sustained vowels were (1) spectral slopes of the average waveforms, (2) harmonics-to-noise ratios (H/N), (3) coefficients of variation for amplitude (CVA), (4) coefficients of variation for fundamental frequency (CVF), (5) amplitude perturbation (shimmer), and (6) fundamental frequency perturbation (jitter). Fundamental frequency (Fo) distributional statistics (mean Fo, Fo standard deviation, and Fo mid-90% range) were also obtained from oral readings. Results for the sustained vowel samples showed that after extubation, (1) spectral slopes were less steep, and (2) both shimmer and jitter were greater than before intubation. Results for the passage reading revealed that the mean Fo was lower and the Fo standard deviation and mid-90% range were smaller after the extubation than before intubation. It was concluded that even short-term endotracheal intubation affects acoustic characteristics of voice and that selected measures of waveform characteristics are sensitive enough to reveal such effects.