Adjustments of non-invasive ventilation and mechanically assisted cough by combining ultrasound imaging of the larynx with transnasal fibre-optic laryngoscopy: a protocol for an experimental study

Introduction Application of non-invasive positive airway pressure may provoke laryngeal responses that obstruct the airways, especially in patients with disturbed laryngeal control. To control and adjust for this, transnasal fibreoptic laryngoscopy (TFL) is used to visualise laryngeal movements during therapeutic interventions. Being an invasive procedure, this may be unpleasant for patients. The aim of this study is to evaluate if ultrasound (US) imaging of the larynx may be used as an alternative less invasive diagnostic tool for evaluating the upper airway responses to non-invasive ventilation (NIV) and mechanical insufflation-exsufflation (MI-E). Methods and analysis This protocol presents an experimental cross-sectional study of a novel method to study laryngeal responses in adult healthy volunteers (n=30). The participants will be assessed with simultaneous TFL and laryngeal US imaging (anterior and lateral approaches) during NIV and MI-E therapy. Additionally, airflow and pressure signals will be registered during the procedures. The primary outcome is whether laryngeal US is a feasible method to study laryngeal responses and, if so, to compare the laryngeal responses visualised with TFL and US. The participants' perception of the examinations will be recorded. Secondary outcomes include airflow curve shapes and calculated ventilation volumes during the interventions. Ethics and dissemination The study has been approved by The Regional Committee for Medical Research Ethics in Norway, and registered in ClinicalTrials.gov. Results will be disseminated through peer-reviewed journals, presentation of scientific abstracts at international medical conventions and oral presentations in relevant medical conventions.