Vaporized Cannabis Has Lack of Effect on Airway Function in COPD

Vapor, smoke
Vapor, smoke
When compared with a placebo control cannabis, cannabis had no effect on breathlessness intensity ratings during exercise at isotime or on exercise endurance time.

The use of a single-dose inhalation of vaporized cannabis had no effect on exertional breathlessness, exercise endurance time (EET), and airway function in adults with advanced chronic obstructive pulmonary disease (COPD), according to the results of a single-center, randomized, double-blind, crossover trial.

The CAN BREATHE in COPD study ( Identifier: NCT03060993) was conducted at the McConnell Centre for Innovative Medicine of the McGill University Health Centre in Montreal, Quebec, Canada. Results of the study were published in the Annals of the American Thoracic Society.

Investigators sought to test the hypothesis that inhaled vaporized cannabis would improve EET and alleviate exertional breathlessness by the enhancement of static and dynamic airway function in COPD. A total of 16 adults 40 years or older with advanced COPD (defined as mean forced expiratory volume in 1 second, 36%±11% predicted) were recruited from the Montreal Chest Institute.

All participants received 35 mg of cannabis (18.2% delta-9-tetrahydrocannabinol; <0.99% cannabidiol) or 35 mg of a placebo control cannabis (CTRL) administered via an inhaled vaporizer. The acute effect of each treatment on physiologic and perceptual responses during cardiopulmonary cycle EET, spirometry and impulse oscillometry at rest, and cognitive function, psychoactivity, and mood were evaluated.

The primary outcome was the posttreatment difference in breathlessness intensity ratings during exercise at isotime, which was defined as the highest-equivalent 2-minute interval of exercise completed by a participant during each of the constant-load cardiopulmonary cycle exercise tests (CPETs). The coprimary outcome was posttreatment difference in EET, which was defined as the duration of loaded pedaling during constant-load CPET.

When compared with CTRL, the use of cannabis had no effect on breathlessness intensity ratings during exercise at isotime (cannabis, 2.7±1.2 Borg units vs CTRL, 2.6±1.3 Borg units) or on EET (cannabis, 3.8±1.9 min vs CTRL, 4.2±1.9 min). Cardiac, metabolic, gas exchange, ventilator, breathing patterns and/or operating lung volume parameters at rest and during exercise were also unaffected. In addition, cannabis did not have an effect on spirometry and impulse oscillometry-derived pulmonary function test parameters at rest as well as cognitive function, mood, and psychoactivity.

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The investigators noted that this randomized, controlled study is the first to demonstrate that 35 mg of inhaled vaporized cannabis “had no clinically meaningful positive or negative effect on exercise endurance, exertional breathlessness, and airway function in symptomatic adults with advanced COPD receiving dual or triple inhalation therapy for the management of their underlying pulmonary pathophysiology.”


Abdallah SJ, Smith BM, Ware MA, et al. Effect of vaporized cannabis on exertional breathlessness and exercise endurance in advanced COPD: a randomized controlled trial [published online June 27, 2018]. Ann Am Thorac Soc. doi:10.1513/AnnalsATS.201803-198OC