Autonomic Dysfunction in Functional Dysphonia

Heart rate variability (HRV, in ms) is an autonomic index measuring the variation of the interval between consecutive heartbeats and is vagally regulated (PSA) (Thayer et al., 2009; Pizzoli et al., 2021; Singh Solorzano et al., 2022). It measures direct Vagus nerve activation potential on a cardiac level (Thayer & Lane, 2000; Sars, 2022). High HRV is associated with high vagal tone, whereas low HRV indicates ANS dysregulation with low vagal tone and SA prominence (Idrobo-Ávila et al., 2022). HRV will be determined at rest with electrocardiography using Kubios HRV analysis software (Tarvainen et al., 2002; 2014; Niskanen et al., 2004). Ag/AgCl surface electrodes will be positioned on the participant's chest in a modified lead II configuration.

The DSI is an objective multiparametric indices that quantifies voice quality (Wuyts et al., 2000)

The pre-ejection period is the time between the onset of depolarization of the left ventricle and the opening of the aortic valves and will be calculated as a cardiovascular index of SA (Lozano et al., 2007)

Respiration rate (in bpm) will be determined via thoracic impedance (De Geus et al., 1995). For each respiratory cycle, the total cycle time between the start of inspiration and the end of expiration will be extrapolated to a per-minute respiration rate

Skin conductance level (in µS) will measure the tonic electrodermal activity and reflects increased SA (Dawson et al., 2017).

The Neuroception of Psychological Safety Scale (NPSS; Morton et al., 2022) is a psychometrically valid measure determining psychological, relational and physiological safety. It consists of 29 items subdivided into 3 subscales: compassion (e.g. I felt caring), social engagement (e.g. I felt accepted by others) and body sensations (e.g. My body felt relaxed).

The Depression Anxiety and Stress Scale 21 (DASS-21; Lovibond PF & Lovibond SH, 1995; Dutch Version: De Beurs et al., 2001) is a validated 21-item checklist covering 3 subscales measuring the emotional states of depression (e.g. I felt that I had nothing to look forward to), anxiety (e.g. I felt scared with any good reason) and stress (e.g. I found myself getting agitated).

The Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5; Weathers et al., 2013; Dutch version: Boeschoten et al., 2014; De Beurs et al., 2020) is a validated 20-item checklist that assesses the DSM-5 symptoms of PTSD. It exists of 4 clusters: re-experiencing (e.g. Repeated, disturbing dreams of the stressful experience), avoidance (e.g. Avoiding memories, thoughts, or feelings related to the stressful experience), numbing (e.g. Loss of interest in activities that you used to enjoy), and arousal factors (e.g. Irritable behavior, angry outbursts, or acting aggressively).

The short version of the Self Regulation Questionnaire (Brown & Miller, 1999; Carey et al., 2004; Neal & Carey, 2005) is a 31-item self-report measure of the ability to self-regulate one's behavior (e.g. Once I have a goal, I can usually plan how to reach it, I have a lot of willpower).

The Pittsburgh Sleep Quality Index (Dutch Version: Buysse et al., 1989) is a validated 19-item index assessing overall sleep quality. It consists of 7 subscales: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication and daytime dysfunction.

A flexible strobovideolaryngoscopy will be performed by an experienced otorhinolaryngologist to visualize the laryngeal function and (supra)glottic activity. The video samples will be evaluated randomly and blindly by a specialized otorhinolaryngologists and SLP to assure interrater reliability; 15% of the samples will be randomly repeated to assess intrarater reliability. The Voice-Vibratory Assessment with Laryngeal Imaging (VALI) rating form (Poburka et al., 2017) will be used for these evaluations.

An instrumental voice assessment will be performed by an experienced SLP, different from the therapist. Acoustic measures will be obtained by the Computerized Speech Lab (KayPENTAX, Montvale, NY) and the software program Praat (Boersma & Weenink, 2013). A Shure SM-48 and an AKG Lyra microphone will be used. Two objective multiparametric indices will quantify voice quality: the DSI (Wuyts et al., 2000) and the AVQI (Maryn et al., 2010).

An auditory-perceptual (subjective) voice evaluation will be performed using the Consensus Auditory Perceptual Evaluation of Voice (Kempster et al., 2009). Speech samples (sustained vowel and continuous speech) will be evaluated randomly and blindly by 2 experienced SLPs to assure interrater reliability; 15% of the samples will be randomly repeated to assess intrarater reliability.

The Voice Handicap Index (Jacobson et al., 1997; Dutch version: De Bodt et al., 2000), the Vocal Tract Discomfort Scale (Mathieson et al., 2009; Dutch version: Luyten et al., 2016) and the Vocal Fatigue Index (Nanjundeswaran et al., 2015) will be administered to evaluate the psychosocial impact, vocal tract discomfort and vocal fatigue associated with dysphonia.