Objective and Perceptual Characteristics of the Voice After Endotracheal Intubation in Head and Neck Surgery

The Voice Handicap Index (VHI) is one of the most frequently used self-assessment scales for voice disorders. The Croatian version was adapted and validated by Bonetti and Bonetti (2013), while Benšić et al. (2024) confirmed normative values for the Croatian language. The scale consists of 30 items divided into three subscales:

• Functional, emotional and physical component. Each item is rated on a 5-point Likert scale (0 = Never, 1 = Almost Never, 2 = Sometimes, 3 = Almost Always, 4 = Always), giving a total score from 0 to 120, with higher scores indicating greater perceived voice handicap. Participants will complete the VHI questionnaire at Baseline (within 7 days before surgery with endotracheal intubation) and at postoperative follow-up time points (Day 1, Week 2, and Week 4).

The primary VHI outcome is the change in total score before and after surgery.

Units of Measure:

• Total score range: 0-120

Method of Administration:

• Self-administered paper

The perceptual voice assessment (GRBAS) will be conducted by two speech-language pathologists with several years of clinical experience. Each parameter-Grade, Roughness, Breathiness, Asthenia, and Strain-will be scored on a 4-point scale (0 = Normal, 1 = Slight, 2 = Moderate, 3 = Severe). The average of the two evaluators' scores will be taken, and in the case of significant discrepancies, a third evaluator will be consulted to reach consensus.

Voice samples will be recorded at baseline and post-intervention at 4 time points total. The primary GRBAS outcome will be the change in the 'Grade' score; secondary analyses will include changes in R, B, A, and S.

Units of Measure:

• Ordinal scores (0-3) for each parameter

Videostroboscopy uses an endoscope containing a built-in video camera and a stroboscope, which records phonation while the vocal cords are being filmed. The recording captures the frequency of vocal cord vibrations during voice production and provides an apparently slow-motion view of these vibrations. In the stroboscopic video, the movements of the vocal cords are slowed down enough to precisely follow their motion. This technique allows detailed observation of the amplitude and symmetry of vibrations, as well as the phase of vocal cord closure during voice production. It facilitates diagnosis of numerous physical problems with the vocal cords, including paresis resulting from injury to the recurrent laryngeal nerve. Evaluations will be performed pre- and post-intervention using a standardized protocol. 2 experienced phoniatrists will independently review the recordings to identify possible pathology in vocal fold motion or structural damage. No formal scoring system will be applied.

Objective voice evaluation will be performed using selected acoustic and aerodynamic measures. Voice assessment involves recording sustained phonation of the vowel /a/ in a sound-treated room using a calibrated digital recording system. The recordings will be acquired with a high-quality microphone positioned at a fixed distance of 30 cm from the participant's mouth, placed at a 45° angle. The sound signal will be analyzed using the LingWAVES SLP Suite Pro VPR software (WEVOSYS medical technology GmbH, Germany). This software converts the analog voice signal to digital form and processes it to extract relevant voice parameters.

Parameters to be evaluated:

• Fundamental frequency (F0) in Hz.

Physiological reference values:

• Fundamental frequency: Female: ~206 Hz, Male: ~120 Hz,

Objective voice evaluation will be performed using selected acoustic and aerodynamic measures. Voice assessment involves recording sustained phonation of the vowel /a/ in a sound-treated room using a calibrated digital recording system. The recordings will be acquired with a high-quality microphone positioned at a fixed distance of 30 cm from the participant's mouth, placed at a 45° angle.

The sound signal will be analyzed using the LingWAVES SLP Suite Pro VPR software (WEVOSYS medical technology GmbH, Germany). This software converts the analog voice signal to digital form and processes it to extract relevant voice parameters.

Parameters to be evaluated:

• Intensity (in dB)

Physiological reference values:

• Intensity: Female: 68-74 dB, Male: 68-76 dB

Objective voice evaluation will be performed using selected acoustic and aerodynamic measures. Voice assessment involves recording sustained phonation of the vowel /a/ in a sound-treated room using a calibrated digital recording system. The recordings will be acquired with a high-quality microphone positioned at a fixed distance of 30 cm from the participant's mouth, placed at a 45° angle.

The sound signal will be analyzed using the LingWAVES SLP Suite Pro VPR software (WEVOSYS medical technology GmbH, Germany). This software converts the analog voice signal to digital form and processes it to extract relevant voice parameters.

Parameters to be evaluated:

• Jitter (%)

Physiological reference values:

• Jitter: 0-0.5%

Objective voice evaluation will be performed using selected acoustic and aerodynamic measures. Voice assessment involves recording sustained phonation of the vowel /a/ in a sound-treated room using a calibrated digital recording system. The recordings will be acquired with a high-quality microphone positioned at a fixed distance of 30 cm from the participant's mouth, placed at a 45° angle.

The sound signal will be analyzed using the LingWAVES SLP Suite Pro VPR software (WEVOSYS medical technology GmbH, Germany). This software converts the analog voice signal to digital form and processes it to extract relevant voice parameters.

Parameters to be evaluated:

• Shimmer (%)

Physiological reference values:

• Shimmer: 0-5%

Objective voice evaluation will be performed using selected acoustic and aerodynamic measures. Voice assessment involves recording sustained phonation of the vowel /a/ in a sound-treated room using a calibrated digital recording system. The recordings will be acquired with a high-quality microphone positioned at a fixed distance of 30 cm from the participant's mouth, placed at a 45° angle.

The sound signal will be analyzed using the LingWAVES SLP Suite Pro VPR software (WEVOSYS medical technology GmbH, Germany). This software converts the analog voice signal to digital form and processes it to extract relevant voice parameters.

Parameters to be evaluated:

• Maximum phonation time (MPT, in seconds)

Physiological reference values:

• Maximum phonation time: Female: 15-25 sec, Male: 25-35 sec