COPD is a progressive (i.e. gets worse with time), chronic, inflammatory lung disease obstructing air-flow to the lungs, mainly caused by breathing pollutants.
To help understand what is going on with COPD, first please see brief description of how the lungs work:
COPD damage reduces the natural elasticity of the alveoli (air sacs) and bronchial tubes. Elasticity is required to force out air/carbon dioxide for exhalation. As a consequence, unexpelled air is trapped in the lungs, which makes it difficult for the air sacs to deflate and bring in new air

Image: www.lung.net/copd
COPD describes several progressive lung diseases characterized by shortness of breath. Includes:
• CHRONIC bronchitis. The constant irritation/inflammation of the MUCUS MEMBRANE LINING (epithelium) of the bronchial airways (bronchi/bronchioles, which carry air to and from the alveoli of the lungs), causes it to swell and produce mucus, which narrows the airways, making it harder to breathe; a cough ensues to try and clear the mucus.
FYI - Mucus membranes also line the sinuses, GI and urinary tracts
• Emphysema. Breakdown of the elastin of lung connective tissues weakens/damages the thin walls and fibers of the alveoli (air sacs) at the end of the smallest bronchial airways (bronchioles); the alveoli walls eventually break down, producing less, but larger air spaces instead of many small ones, and so reducing the surface area available for gas exchange;
• Non-reversible asthma
• Some forms of bronchietasis
COPD is the THIRD leading cause of death in the U.S. affecting ~30 million Americans. Of those, >50% are unaware they have it
COPD progression causes loss of lung function. Can increase risk for:
• Respiratory infections. E.g. flu, colds, pneumonia - making it even more difficult to breathe
• Lung cancer
• Pulmonary hypertension. High blood pressure in arteries delivering blood to lung
• Heart disease. Reason not well understood
A breathing test, called spirometry, measures the amount of air blown out of the lungs in how long. This simple test can detect COPD ahead of symptoms
• Increased breathlessness - especially during activities
• Chronic / Ongoing cough (trying to clear produced sputum/mucus) - especially first thing in the morning
• Frequent repiratory infections
• Wheezing
• Blueness of lips or fingernail beds (cyanosis) - due to lower oxygen availability
• Chest tightness
Most COPD is caused by inhalation of pollutants. Including:
• Smoking (LEADING CAUSE IN U.S.) and second-hand smoke - ~90% of those with COPD have a history of smoking;
• Chemicals, fumes, dust in occupational environments - especially those who have had long term exposure
• In the developing world, breathing cooking fuel or poorly vented heating fumes
Being over 40 years old and male. Although most COPD deaths are women
Genetics. ~1% of those with COPD have a deficiency of liver-produced, lung-protective alpha-1 antitrypsin protein (AAt), which is the most commonly known genetic risk for emphysema - with the result that white blood cells (WBCs) are able to harm the lungs
>90% of bronchial infections are caused by a virus
Albert, RH (1 December 2010). "Diagnosis and treatment of acute bronchitis.".American family physician(11): 1345-50. PubMed
Alternative medicines administered via a nebulizer
The fastest way to increase magnesium presence in your body is to apply magnesium chloride oil (MCO) transdermally:
Transdermal Magnesium Chloride
The best way to increase body's vitamin D levels is to take a sunbath:
Taking a Sunbath for Vitamin D
Especially Omega-3:

Keep well hydrated - drink enough water; also breathing water vapor helps loosen mucus and makes breathing easier
Ensure sufficient dietary/supplementary antioxidants - to counter inflammation by reducing free radicals
Herbs to soothe and lubricate mucus membranes - include slippery elm, marshmallow, licorice, mullein
Consume zinc-rich foods - especially pumpkin seeds
Nebulizing moistens mucus membranes
Proteolytic enzymes - E.g. bromain, papain and serrapeptase all reduce inflammation, but serrapeptase especially helps break down excessive mucus