Disorders of the Respiratory System: Asthma, COPD, Pneumonia and More

When breathing becomes work

Most of the time, you don't notice breathing. For people with a respiratory disorder, it can take real effort. Every disorder in this lesson can be understood with ideas you already know: airway width (how easily air flows), alveolar surface area and thickness (how fast gases diffuse), and the elastic recoil of the lungs.

Asthma

In asthma, the lining of the bronchi and bronchioles is chronically inflamed and over-sensitive. When a person meets a trigger, an asthma attack can happen:

• the smooth muscle around the airways contracts (bronchoconstriction),
• the lining swells, and
• extra, thick mucus is produced.

The airways narrow, especially during exhalation, causing wheezing, coughing, chest tightness and shortness of breath.

Common triggers: colds and flu; allergens such as pollen, dust mites, mould and pet dander; cold, dry air (a real issue in Canadian winters); exercise; smoke (including wildfire smoke) and air pollution; strong scents.

Treatment:

• A reliever inhaler contains a fast-acting bronchodilator that relaxes airway smooth muscle within minutes.
• A controller inhaler (usually a low-dose inhaled corticosteroid) reduces airway inflammation over time, preventing attacks. It must be used regularly, even when the person feels well.
• A spacer helps more medicine reach the lungs. An asthma action plan from a doctor tells the person what to do in each situation.

Emergency: if a reliever doesn't help, if the person can't speak in full sentences, or if their lips or fingernails look blue or grey, call 9-1-1.

COPD: emphysema and chronic bronchitis

Chronic obstructive pulmonary disease (COPD) is a long-term, mostly irreversible blockage of airflow. Smoking is the main cause; long-term exposure to dust, chemical fumes and smoke from burning wood or other fuels indoors also contributes.

• Emphysema: the thin walls between alveoli are destroyed, so many small sacs become fewer, larger ones. This reduces surface area for gas exchange and destroys the elastic fibres that make the lungs recoil. Air gets trapped, exhaling becomes hard work, and blood oxygen falls.
• Chronic bronchitis: long-term inflammation of the bronchi, with too much mucus and damaged cilia, so mucus can't be cleared. The result is a daily, productive cough and frequent infections.

Treatment can't reverse the damage but can help: quitting smoking (the single most important step; it slows further loss of lung function), bronchodilators, pulmonary rehabilitation (exercise training and breathing techniques), vaccines against flu and pneumonia, and oxygen therapy in severe cases.

Spirometry: measuring obstruction

A patient takes the deepest possible breath and blows out as hard and fast as possible into a spirometer.

• FVC (forced vital capacity): the total volume blown out.
• FEV₁: the volume blown out in the first second.

In healthy adults, most of the air comes out in the first second: FEV₁/FVC is usually above 0.70 (often about 0.75 to 0.85). In obstructive diseases (asthma, COPD), narrowed airways slow the air, so FEV₁ falls more than FVC and the ratio drops below 0.70. In asthma, the ratio usually improves after a bronchodilator, because the narrowing is reversible; in COPD it improves little.

Pneumonia, lung cancer and cystic fibrosis

Pneumonia is an infection of the lungs by bacteria, viruses or (less often) fungi. Alveoli become inflamed and fill with fluid and pus, so the barrier is thicker and less surface is available: oxygen diffusion falls. Symptoms include cough, fever, chest pain and shortness of breath. Bacterial pneumonia is treated with antibiotics; vaccines (for example, against pneumococcus, flu and COVID-19) lower the risk.

Lung cancer is uncontrolled growth of cells in the lungs. In Canada, it causes more cancer deaths than any other type. Smoking causes most cases. According to Health Canada, radon gas is the leading cause of lung cancer in people who have never smoked. Radon seeps from the ground into basements, and its level can be measured with an inexpensive long-term test kit; high levels can be fixed. Second-hand smoke and some workplace exposures (such as asbestos) also raise the risk.

Cystic fibrosis (CF) is an inherited disorder caused by changes in the CFTR gene, which controls the movement of chloride ions (and so water) into mucus. The mucus becomes thick and sticky, clogging the airways (causing repeated infections) and the pancreatic ducts (so digestive enzymes can't reach the intestine). The CF gene was identified in 1989 by a team led by Lap-Chee Tsui at the Hospital for Sick Children in Toronto, working with John Riordan and with Francis Collins in the United States. Ontario now screens newborns for CF. Treatments include airway-clearance therapy, enzyme capsules with meals and, more recently, medicines called CFTR modulators that help the faulty protein work better. (You'll see how CF is inherited in the Genetic Processes unit.)

Protecting your lungs

• Don't smoke or vape. Vaping delivers nicotine, which is highly addictive, plus other chemicals into the airways; Health Canada warns that vaping has health risks and that its long-term effects are not yet fully known.
• Check the Air Quality Health Index (AQHI) on hot, smoggy days and during wildfire smoke; people with asthma may need to limit time outdoors.
• Test your home for radon and make sure CO alarms work.
• Stay up to date with vaccines; wash hands to reduce respiratory infections.
• Exercise regularly: it doesn't enlarge your lungs much, but it makes your breathing muscles and circulation more efficient.