Inhaled Menthol for Dyspnea Relief During Cycle Exercise in COPD: A Randomized Trial.

BACKGROUND

Menthol inhalation (MI) lowers dyspnea ratings during loaded breathing in COPD and cycle exercise in healthy adults. Proposed mechanisms include stimulation of cold receptors in the upper airways, modulating perception of breathing-related effort and airflow.

RESEARCH QUESTION: Does MI also alleviate exertional dyspnea in COPD?

STUDY DESIGN AND

METHODS

Twenty patients with COPD (60% male; mean age ± SD, 68 ± 6 years; FEV1, 47% ± 17% predicted) completed 2 constant-load cycle exercise tests (73% ± 7% peak power output) to exhaustion with menthol or placebo (strawberry flavoring) added to the breathing circuit in counterbalanced order and on separate days. Ventilatory and neuromuscular parameters were measured continuously. Dyspnea intensity was serially assessed using the 0 to 10 category ratio Borg scale, and dyspnea unpleasantness and related sensory qualities were assessed using the Multidimensional Dyspnea Profile at end exercise. Participants were asked in which test their inspiratory airflow felt easier.

RESULTS

Serial dyspnea intensity ratings were lower with menthol vs placebo (estimate [Δ/10% peak time]: -0.09; 95% CI, -0.15 to -0.02; P = .01), whereas ratings of dyspnea unpleasantness, air hunger, and mental breathing effort were lower at end exercise (all P < .05). Menthol-related improvements in dyspnea intensity at symptom limitation of the shorter test vs equivalent time on the other were correlated with higher endurance time (r = -0.73, P < .001). There were no differences in ventilatory and neuromuscular parameters (P > .05). Exercise endurance time was unaffected by menthol (Δ 0.3 ± 1.6 minutes with menthol vs placebo; P = .50). A total of 85% reported easier inspiratory airflow with menthol.

INTERPRETATION: MI may be useful for management of exertional dyspnea in selected patients with COPD. Future work should investigate if MI can improve outcomes of exercise rehabilitation programs.

CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT05785026; URL: www.

CLINICALTRIALS: gov.