Asthma



Last Review Date: March 6, 2017


What is it?

Asthma is a chronic (long term) inflammatory lung disease characterised by wheeze, shortness of breath, cough or chest tightness that varies over time and excessive variation in lung function compared to normal people (i.e. The amount and rate of air that can be exhaled). Australia has a high prevalence of asthma, up to 1 in 6 children and 1 in 10 adults are affected. Asthma is a condition that cannot be cured, but it can be controlled and most people who have it can lead active and relatively normal lives.

With asthma, the walls of the muscular tubes that carry air throughout the lungs, transporting it to and from smaller airway branches (bronchi) are inflamed and swollen which narrows the airway and makes it more difficult to breathe, resulting in wheezing, breathlessness, chest tightness or coughing. The airway narrowing in asthma responds to medications that dilate the airway (bronchodilators) and reduce inflammation in the airway (corticosteroids). These medications are predominantly given as inhalers (relievers and preventers) but corticosteroid tablets may be required for an asthma attack or flare up.

Asthma affects people to different extents. Some people will only use inhalers once a month if they are exercising. Others may need to attend hospital regularly and when they have severe attacks they may be put onto a ventilator.

The exact cause of asthma is unknown, it is a complicated mix of genetics, the environment and other factors. The triggers for asthma attacks will be slightly different for each person. Many people with asthma are allergic to particular substances which are called allergens. Asthma attacks can be triggered in these people if they come into contact with these substances. The airways over-react to allergens in the air such as pollen, pollution, mould, dust mites, animals, particles and fumes. Asthma attacks may also be caused by stress, strong emotional response (laughing, crying, and anger), exercise, and cold air. Medicines such as beta-blockers, aspirin and ibuprofen can trigger attacks. Sulphites found in wine and dried fruit and respiratory infections like the common cold can cause episodes of asthma in some people.

Other lung diseases and conditions can have symptoms similar to asthma. Sometimes other lung disease can occur at the same time as asthma and this may make the asthma attacks worse. Conditions such as GORD (gastro-oesophageal reflux disease, also called acid reflux) can trigger or make asthma attacks worse in some people. There is also significant overlap with asthma and Chronic Obstructive Pulmonary Disease (COPD).


Lung Function tests and imaging studies

These are the primary tests used to diagnose, assess, and monitor asthma.

Asthma diagnosis

  • There is no gold standard test for asthma and the diagnosis is based on a detailed medical history and physical examination, focusing on the chest and airways
  • Spirometry for patients 5 years old or older to demonstrate airway narrowing that can be overcome with an inhaler. This test measures the amount and rate of air exhaled as a patient blows out through a tube.
  • Additional testing as required to help rule out other diagnoses. This may include “challenges” that provoke the airways to constrict, such as exercise, cold air, methacholine or histamine, and a chest x-ray.

Asthma assessment and monitoring

  • Peak expiratory flow (PEF) determination - measures the ability to push air out of the lungs or how fast air can be exhaled. This test uses a small device called a Peak Flow meter and can be performed by the patient at home to monitor lung function.
  • Spirometry - to evaluate lung function
  • Pulse oximetry - measures oxygen in the blood by placing a small plastic device over the end of a finger. This may be used in hospital for an emergency to see if enough oxygen is getting around the body.
  • Chest x-ray - to look for signs of infections or other lung diseases such as a collapsed lung.

For other lung function tests see, Johns Hopkins Medicine: Pulmonary Function Tests.

Laboratory Tests
Laboratory testing is used to help rule out conditions that cause symptoms similar to asthma, to identify patient allergies, and to help identify and evaluate complications of asthma. During severe asthma attacks, testing may be used to look for problems with oxygen levels, the body's acidity and signs of infection. Tests include:

  • Allergy testing – blood tests (e.g. IgE) that are specific for the allergen(s) suspected to be causing symptoms, such as dust mites, mould, pets and pollens.
  • FBC (Full blood count) – to look for signs of infection or the level of eosinophils (blood cells involved in a type of allergic reaction which may be raised in asthma)
  • Blood gases – an arterial blood sample is collected to look at acidity, oxygen, and carbon dioxide. Blood gases may be used in severe asthma attacks

Other tests that may be occasionally ordered, mainly to rule out other lung diseases:

For additional laboratory testing that is sometimes performed, see Lung Diseases.


Treatment

The goals with asthma treatment are to:

  • Achieve and maintain good asthma control:
    • Minimise daytime symptoms (less than 3 days per week)
    • Minimise need for reliever medications (less than 3 days per week)
    • No nightime and symptoms on awakening
    • Maintain normal activities of daily living (school, sport & work) without limitation
  • Manage asthma flare-ups when they occur and reduce emergency department visits and hospitalisations
  • Optimise lung function
  • Identify, treat and resolve, where possible, conditions or lifestyle factors (e.g. smoking) that make asthma worse and, complications associated with asthma or medication side effects
  • Educate patients and family about the condition and its treatment, enabling self-management

Prevention of asthma attacks is achieved through a combination of avoiding substances that trigger episodes, having good asthma control, and recognising and addressing the early signs of an impending attack. For more on this, visit National Asthma Council Australia.

Asthma treatment is tailored to the individual and depends upon the severity. Both long-term and short-term controls must be addressed. Even people with mild intermittent asthma may occasionally have severe asthma attacks.

People should work with their doctor to learn about their own or their child's asthma. Doctors can help patients keep a close eye on their asthma and ensure they get the best medicine to treat their asthma over time. They should develop a treatment plan that guides their day-to-day asthma control, guides their actions when an asthma attack occurs, and helps them determine when they should seek medical attention. Doctors will take into account the entire clinical picture and all of the drugs that they are taking when determining the best course of treatment.


Related pages

On this site
Tests: Allergy testing, blood gases, full blood count 
Conditions: Lung diseases, allergies, cystic fibrosis, osteoporosis

Elsewhere on the web
healthdirect Australia: Asthma
National Asthma Council Australia

Asthma UK
Centers for Disease Control and Prevention: Asthma and Allergies
National Heart Lung and Blood Institute: What is Asthma?
American Academy of Allergy Asthma and Immunology: Asthma overview
American Academy of Allergy Asthma and Immunology: Childhood Asthma