Evaluation of Laryngeal Morbidity After Orotracheal Intubation by Vocal Analysis and Laryngostroboscopy

Acoustic analysis aims at studying the acoustic emission of the pneumo-phono-articulatory system, i.e. the vocal signal. Currently, digital technology instruments enable the processing and analysis of the verbal signal quickly and reliably, also offering graphical products and numerical data. Among the various existing software products for the study of the vocal signal, PRAAT is available.

In practice, the vocal parameters are acquired in a non-invasive way with a microphone. At the same time, these analysis systems can be integrated by other methods, such as laryngostroboscopy. This method is one of the most widely used techniques for laryngeal clinical evaluation. This is a non-invasive endoscopic practice performed by means of a flexible fibroscope, which, through a pulsed light source, allows visualization of the chordal movement.

At first, a study will be carried out on healthy volunteers, comparable for their demographic characteristics to the second population to be included. In this way the investigators will test the instrument used for the voice analysis, in order to set the reference values for the general population. In a second step, the investigators will evaluate the incidence of post-intubation laryngeal complications, considering as a pathological all values above 95% percentile compared to healthy individuals.

During the first phase, healthy volunteers will undergo voice analysis in two different days. Subsequently, the patients included in the study population will be undergo during the preoperative, intraoperative and postoperative to a combined evaluation between Anesthesiologists and ENTs for data collection.

The data to be recorded, both for the healthy volunteers as well as for patients, will include personal data, anamnestic, working exposure and specific risk factors such as smoking, alcohol, irritants, a previous diagnosis of GERD, frequent inflammation of upper respiratory tract (VADS); moreover, only for patients, the pre-, intra and post-surgery anesthesia evaluation parameters will be collected.

During the pre-surgery visit, patients will receive an otorhinolaryngeal evaluation by laryngostroboscopy and the vocal analysis.

Any lesions due to endotracheal intubation will be standardized according to Mendels et al.'s modified classification, in grade I (lesion of the vocal cords in terms of vibratory changes, which can be observed in the epithelium, lamina propria or arytenoid cartilages ) and grade II (vocal cords movement disorders in terms of paralysis, arytenoid dislocation or incomplete glottal closure).

The vocal analysis will consist, instead, in asking the patient to voice through a microphone (Sennheiser E 835 S) placed at about 15 cm from the mouth, a certain vowel (ie "a") and recording it using PRAAT software (version 6.0. 29 64bit). The PRAAT is a multi-platform application developed since 1992, constantly updated and made available free of charge by Paul Boersma and David Wenink of the Phonetics Laboratory of the University of Amsterdam. It provides numerical data with the possibility of objective evaluations of the vocal characteristics. The system provides information on the fundamental frequency (F0), glottal impulses, microperturbations or causal variations of the fundamental period (Jitter) and of the amplitude (Shimmer) and also the relationship between the periodic and aperiodic signal (NHR).

F0 is the frequency of vocal cord vibrations during phonation, it is calculated in Hz and it differs from man to woman with a difference of about 1.5 times higher in women.

Jitter is a parameter related to the microperturbation of the fundamental period and in particular the Jitter % represents the percentage ratio between the absolute average of the differences between the consecutive fundamental periods and the average fundamental period. The parameters relating to changes in the fundamental period increase in the presence of an irregular glottal vibration.

The Shimmer identifies the microperturbations of the signal amplitude, therefore the Shimmer % expresses the average relative perturbation of the amplitude period; the values increase in case of organic or functional vocal pathology, as a consequence of the inability of the chordal oscillator to maintain a regular vibration.

NHR (noise-to-harmonics ratio) expresses the relationship between the disharmonic component (noise) and the harmonic component, it constitutes a global evaluation of the presence of noise in the analyzed signal due to the simultaneous variation of frequency and amplitude, of turbulent noise, of sub-harmonic components and sound interruptions; its increase is related to the subjective perception of dysphonia.

Then, after a forced inhalation, the sound emitted until exhaustion will represent the maximum phonatory time (MPT), ie the longest time during which a patient can sustain the phonation of a vowel sound and it is calculated in seconds (s). These measurements will be performed three consecutive times; for the F0 variation, Jitter %, Shimmer % and NHR will be kept the avarage value while for the MPT the best recording will be kept.

Finally, the investigators will submit to the subject a self-assessment questionnaire on the quality of the voice (Voice Handicap Index or VHI 10). This assessment is necessary to estimate the psychological and social impact of the severity of dysphonia according to the subject with regard to his normal daily activity. In this case, it will help the investigators to exclude patients with pre-existing dysphonic problems. It will not be used after surgery, since it is not indicative of short term variations. The anaesthesiological evaluation will consist of a normal pre-surgery visit with particular regard to demographic and anamnestic parameters and difficulties associated with respiratory tract, which will be indicated in the appropriate form.

During surgery patients will be monitored and the respiratory tract will be handled as the usual standard of care, collecting all necessary data for subsequent evaluations. 24-48 hours after surgery, the patient, still hospitalized, will undergo an otorhinolaryngeal re-evaluation by means of vocal analysis and laryngostroboscopy.

In case of laryngeal morbidity (i.e edema, granulomas, mucosal damage, cordial paralysis and/or alterations in the voice characteristics) the patient will be advised to undergo an otorhinolaryngology visit.

The pilot study will enroll patients who must undergo general and/or urology surgery of an elective type.