It is generally characterized by inflamed and easily collapsible airways, obstruction to airflow, problems exhaling, and frequent medical clinic visits and hospitalizations.

[2] Asthma is an obstructive lung disease where the bronchial tubes (airways) are extra sensitive (hyperresponsive).

[3] Asthma causes recurring episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or in the early morning.

Spirometry, a measurement of lung function, can provide an assessment of the severity, reversibility, and variability of airflow limitation, and help confirm the diagnosis of asthma.

[3] Bronchiectasis refers to the abnormal, irreversible dilatation of the bronchi caused by destructive and inflammatory changes in the airway walls.

[7] In COPD, there is an increase in airway resistance, shown by a decrease in the forced expiratory volume in 1 second (FEV1) measured by spirometry.

In severe cases that are difficult to control, chronic treatment with oral corticosteroids may be necessary, although this is fraught with significant side effects.

[9] Pulmonary rehabilitation programmes involve intensive exercise training combined with education and are effective in improving shortness of breath.

[10] Alpha 1-antitrypsin deficiency is a fairly rare genetic condition that results in COPD (particularly emphysema) due to a lack of the antitrypsin protein which protects the fragile alveolar walls from protease enzymes released by inflammatory processes.