Registered Nurses' Association of Ontario

What is Asthma?

  • Asthma is the most common chronic respiratory disease in Canada.
  • Asthma is defined as “an inflammatory disorder of the airways characterized by paroxysmal or persistent symptoms such as dyspnea, chest tightness, wheezing, sputum production and cough, associated with variable airflow limitation and airway hyper-responsiveness to endogenous or exogenous stimuli” ).
  • Although the exact cause of asthma has not been well established (National Institutes of Health, asthma is generally thought to develop as a result of a gene–environment interaction. Factors that are believed to be involved in the development of asthma include genetics (i.e., having a family history of asthma or a personal or family history of atopy), exposure to tobacco smoke (e.g., children whose mothers smoked while pregnant are more likely to develop asthma), exposure to outdoor air pollution, and occupational exposures.
  • The underlying pathophysiology of asthma is the interaction of airway inflammation, airway hyper-responsiveness, and airway narrowing
  • Hyper-responsiveness refers to the tendency of airway smooth muscle to contract more intensely in response to a given stimulus or trigger than a person without asthma. For a list of common triggers, please see Point of Care Resources.
  • Airway narrowing is a result of airway inflammation, airway smooth muscle contraction (bronchospasm) and excess mucus. 
  • Airway inflammation and airway hyper-responsiveness are directly related. The greater the degree of airway inflammation, the more hyper-responsive the person’s airway will be; thus, the degree of hyper-responsiveness changes with the level of airway inflammation under
  • This figure under Point of Care Resources provides illustrations of both normal/controlled asthma airways and uncontrolled asthma airways.

Chronic Disease
Adult Asthma Care Guidelines for Nurses: Promoting Control of Asthma
Background Information