BOTOX for vocal cord dysfunction in severe asthma

INTERVENTION: Botulinium Toxin 3 units (1.5 units to each thyro‐arytenoid muscle = 0.1ml total volume) will be injected into the thyroarytenoid muscle (vocal cord) localised by using Electromyography. Percutaneous transcricothyroid injection is the method of injection to be used. Treatment will occur on one occasion only for the purpose of this study. CONDITION: Severe asthma Vocal cord Dysfunction PRIMARY OUTCOME: Asthma Control Test (ACT) Pre‐bronchodilator FEV1 Primary outcome measure for first hypothesis is RATIO (vocal cord diameter:tracheal diameter) using 320‐slice CT scan of the larynx, adjusted for baseline SECONDARY OUTCOME: Asthma Control Questionnaire Changes in BORG score Changes in FEV1 Daily Symptom scores and Peak Flow reading Voice related Quality of Life score (VRQoL) INCLUSION CRITERIA: Asthma confirmed by airway reversibility (FEV1 >12% and 200mls) OR airway hyperreponsiveness; Subjects with clinical features of severe refractory asthma; Subjects with well documented requirement for regular treatment with high dose ICS; Subjects with well documented requirement for controller medication in addition to high dose ICS; Evidence of optimal medication use; Sub‐optimally controlled asthma, as indicated by ACT score <15; Post‐bronchodilator FEV1 >40% predicted; VCD demonstrated by 320‐slice CT larynx (RATIO below LLN during either inspiration or expiration;