Asthma is a chronic respiratory condition causing a combination of variable respiratory symptoms which may include but are not limited to wheezing, shortness of breath, cough and excessive variation in lung function (National Asthma Council Australia 2019).
People with asthma have hypersensitivity to ‘triggers’ (external stimuli) that may set off symptoms. Triggers commonly include cigarette smoke, pollen, exercise and dust mites (National Asthma Council 2017).
People may experience flare-ups when symptoms start or worsen. These require treatment and may become serious medical events (National Asthma Council Australia 2019).
Some individuals may only experience symptoms when exposed to a trigger, but others may experience symptoms all of the time (CDC 2016).
Asthma is considered a spectrum of conditions with several recognised phenotypes that vary in severity (National Asthma Council 2019; Severe Asthma Toolkit 2019).
It is estimated to affect 1 in 10 adults and 1 in 9 children in Australia, causing about 400 deaths annually. Over 2.7 million Australians have asthma, including children and adults (Asthma Australia 2018).
Although it cannot be cured, if managed properly, those with asthma should be able to enjoy unhindered lives (National Asthma Council 2019).
Definition of Asthma
Asthma is clinically defined by the presence of both:
Excessive variation in lung function (more variation and at a greater magnitude than a healthy person would experience) and varying respiratory symptoms; and
Chronic inflammation, airway hyperresponsiveness and intermittent narrowing of the airways.
(National Asthma Council 2019; Global Initiative for Asthma 2019)
What Happens to the Body in a Person Diagnosed With Asthma?
The underlying mechanism of asthma is usually a chronic inflammation of the airways, which is exacerbated by triggers (Global Initiative for Asthma 2019).
Airway Hyperresponsiveness describes the predisposition for the airways to respond to triggers in an exaggerated and reactive way. It involves an increased sensitivity to triggers as well as an excessive constriction of the airways when exposed to them (Chapman & Irvin 2015).
When exposed to triggers, the airways undergo physical changes that result in intermittent airway narrowing. These are:
Bronchoconstriction: The smooth muscle in the wall of the airways contracts, becoming tighter and narrower. This muscle contracts more easily and strongly in people with asthma.
Inflammation and swelling of the airway walls, reducing space.
Excessive mucus production, which blocks the inside of the airways.
(Severe Asthma Toolkit 2019; CDC 2017; National Asthma Council 2019)
There is no single reliable test to diagnose asthma. Diagnosis is based on the individual’s history, physical examination, considering other diagnoses and noting variable airflow limitation. Spirometry is the recommended method for confirming the diagnosis, assessing severity and monitoring asthma (National Asthma Council 2019).
A combination of genetic and environmental factors is thought to be the cause of asthma (Mayo Clinic 2018).
Risk factors for developing asthma may include:
Having another atopic condition such as hay fever or eczema;
Smoking or second-hand smoking;
Being born prematurely;
Having bronchitis as a child;
Being born at a low weight (under 2 kg);
Exposure to exhaust fumes or pollution; and
Exposure to certain chemicals.
(Mayo Clinic 2018; Healthdirect 2018)
Asthma triggers vary from person-to-person. They may include:
Sulphites and preservatives in foods and beverages; and
Gastroesophageal reflux disease;
(Mayo Clinic 2018, National Asthma Council 2019)
Symptoms vary from person-to-person. They may be constant or only occur during flare-ups (Mayo Clinic 2018). They may include:
Shortness of breath;
Chest tightness or pain;
Wheezing or whistling when exhaling;
Coughing or wheezing attacks that are exacerbated by respiratory infections; and
Difficulty sleeping due to the above symptoms.
(Mayo Clinic 2018)
Airflow obstruction is usually reversible but some people with asthma may experience airway remodelling - irreversible structural changes to the airways wherein the walls become thicker and the airways become narrower (Severe Asthma Toolkit 2019).
Remodelling is generally thought to be associated with repeated airway tissue destruction and subsequent repair caused by chronic inflammation, but this may not always be the case (Fehrenbach, Wagner & Wegmann 2017).
Airway remodelling is thought to be associated with progressive lung function decline, and furthermore, has been present in cases of fatal asthma (Fehrenbach, Wagner & Wegmann 2017; Malmström et al. 2017).