I have asthma, and Pulmonary Fibrosis. I can't use any nebulizer or inhalers because I react to the propellant. I have found a few things that help me manage the tightness.
My incentive Spirometer (voldyne 4000). Several times throughout the day for a few minutes.
Constricted muscles can really limit our ability to take a breath, and with a chronic condition we tend to adjust to that constriction.
Chest opening stretches are really helpful!! Massaging the upper chest, neck, shoulders and upper back is also really helpful!! I use an essential oil called Larch, mixed with a little carrier oil, which is soothing to the muscles, but that's just a bonus.
Warmest regards!