Inspiratory muscle strength training on exercise induced laryngeal obstruction, a qualitative assessment of effect

Purpose: Exercise Induced Inspiratory Symptoms (EIIS) are often confused with symptoms of exercise induced asthma. In most patients EIIS is related to exercise induced laryngeal obstruction (EILO), for which there is a lack of evidence based treatment options. Inspiratory muscle training (IMT) is widely used among athletes and positive effects have been reported in EILO. We aimed to test this within an explorative study design using objective outcome measures. Methods: Continuous laryngoscopy exercise (CLE) testing was used to visualize laryngeal response patterns before and after six weeks of supervised IMT in patients consecutively referred to our clinic for EIIS. Results: Fifty-two patients were included, with two main outcome categories: (i) deterioration (ii) improvement. Those who deteriorated clearly had a primary supraglottic adduction with large aryepiglottic folds that increasingly and seemingly passively collapsed inwards during the inspiratory respiratory phase in parallel to increasing ventilatory volumes as the load of exercise increased. IMT apparently tended to exaggerate this characteristic. Those who improved with IMT had a more generalized and thus potentially more muscular laryngeal adduction, with a stronger involvement of the complete larynx, including also the vocal cords. After IMT these patients kept their larynx more open and they endured a higher exercise load before inward collapse occurred. Conclusion: IMT can improve symptom control in EILO; however, it can also precipitate worsening of the obstruction and increase the symptoms. Uncritical use of IMT in EILO will therefore be counterproductive in a considerable proportion of patients.