A study titled "Does smoking marijuana increase the risk of chronic obstructive pulmonary disease?" and published in the Canadian Medical Association Journal,(read the abstract here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2665954/), concluded that marijuana smoking by itself probably does not lead to COPD.
More recently, a 2012 study published in The Journal of the American Medical Association found that people who suffered from asthma and smoked marijuana on a moderate basis actually increased their lung function, without suffering the lung damage associated with tobacco cigarettes (https://jamanetwork.com/journals/jama/fullarticle/1104848)
Cannabis is a powerful anti-inflammatory and one of the main ways it treats respiratory symptoms is by discouraging inflammation; thereby opening the passages of the respiratory system. This, in turn, decreases coughing and shortness of breath. Seek out flowers or oils that have been lab-tested by a reputable 3rd party lab for microbial/pesticide contaminants and residual solvents. You may also want to consider a vaporizer device that has adjustable heat controls which may provide a more comfortable vaping experience for you.