Institutional review board approval was obtained from the Human Research Ethics Board at the University of Alberta (Pro00076731).
All new patients referred for possible PVFM to a tertiary care laryngology practice between January 1st, 2018 to February 1st, 2020 were approached for participation in the study. Routine history, physical examination, and flexible in-office laryngoscopy was performed in all patients. Patients were excluded from the study if they had known refractory PVFM or were undergoing active SLP therapy. Additional exclusion criteria included patients in acute airway distress or those with untreated laryngeal, airway or lung pathologies. Patients with otherwise normal laryngoscopy underwent provocation maneuvers to elicit inspiratory adduction, but the absence of positive findings did not exclude the diagnosis of PVFM, which is in keeping with the current literature .
After topicalization of the nasal cavity with 1% lidocaine and 0.05% otrivin 50:50 mixture, surgeon-performed visual biofeedback was administered with continuous laryngoscopy performed using a distal-chip flexible rhinolaryngoscope. The following intervention was provided: explanation of normal laryngeal anatomy and breathing physiology, performance of laryngeal release exercises (e.g. rapid nasal breathing, pursed-lip breathing, etc.) [10, 13, 14]. Patients visualized their larynx throughout and were encouraged to palpate their anterior neck to recognize laryngeal tension, posture, and breathe control during laryngeal release exercises. Follow-up at 3 months and one-year was offered to all patients. Telephone follow-up was performed with patients who could not attend in-clinic follow-up due to geographic distance or patient-specific factors.
Baseline basic demographic information was collected including age, sex, and comorbidities. Specific information such as concurrent diagnosis of asthma, psychiatric illnesses, and smoking status were collected. Specific triggers for PVFM or laryngospasm episodes were also recorded, including exercise, acid reflux, upper respiratory tract infections, and environmental exposures.
Primary outcome measure
The primary outcome measure was Dyspnea Index score pre- and 3 months post-intervention. The Dyspnea Index Score is a validated tool to measure subjective dyspnea symptom burden and has been previously validated by PVFM patients . It is simple to administer, provides a measure of overall symptom severity, and can be used to monitor treatment progress . The questionnaire was administered to patients in person at each the initial visit and at each follow-up.
Secondary outcome measures
Our secondary outcome was change in patient reported use of inhaled bronchodilators and corticosteroids pre- and 3 months post-intervention. At baseline and follow-up, we recorded the patients’ reported weekly use of these medications in the preceding one-month time period.
Sample size calculation
A previous study determined that a change in Dyspnea Index of 8 is considered the minimally clinically important difference (MCID) . Using a power of 0.8 and alpha-error of 0.05, at least 16 patients with pre- and post-intervention data would be needed.
Statistical analysis was carried out using SPSS (Statistical Package for the Social Sciences, Version 25, IBM Corp, Chicago, USA). Basic descriptive and frequency statistics were performed for patient demographics, comorbidities, and presenting symptoms. Paired sample t-test was used to compare pre- and post-intervention Dyspnea Index scores.
Wilcoxon signed-rank test to compare the differences in bronchodilator and corticosteroid use pre- and post-intervention at both are considered non-parametric, discrete data.