Asthma

Types

Introduction

Risk Factors

Pathophysiology & Causes

Air pollution indoors and outdoors: some research shows that people who live near major highways and other polluted places are more likely to get asthma. Also, kids who grow up in a home with mould or dust may be more likely to get asthma.

Work-related asthma (occupational asthma): People who work in certain types of jobs can get asthma from things they work with. For example:

Laboratory workers can get asthma from lab animals: rats, mice, guinea-pigs

Spray painters can get asthma from isocyanates

Grain handlers can get asthma from grain dust

Crab processors can get asthma from crab dust

Even in patients with no prior history of asthma, viral respiratory infection is occasionally associated with increased airway reactivity for several weeks to months after resolution of the infection. 

Symptoms

• Recurrent wheezing
• Coughing
• Trouble breathing
• Chest tightness
• Symptoms that occur or worsen at night
• Symptoms that are triggered by cold air, exercise or exposure to allergens

In a young child, additional signs and symptoms may indicate asthma. They may include:

• Breathing that is louder than normal or faster than normal. Newborns typically take 30 to 60 breaths a minute. Toddlers typically take 20 to 40 breaths a minute.
• Frequent coughing or coughing that worsens after active play.
• Coughing, clear mucus and a runny nose caused by hay fever

Physical Examination

• An examination of your nose, throat and upper airways (upper respiratory tract)
• Listening to the sounds your lungs make with a stethoscope as you breathe.
  • Wheezing — high-pitched whistling sounds when you breathe out — is one of the main signs of asthma
• Examining your skin for signs of allergic conditions such as eczema and hives, which are often associated with asthma

Differential

• Other lung disease such as chronic obstructive pulmonary disease (COPD)
• Airway tumors
• Airway obstruction
• Bronchitis
• Lung infection (pneumonia)
• Blood clot in the lung (pulmonary embolism)
• Congestive heart failure
• Vocal cord dysfunction
• Viral lower respiratory tract infection

Diagnosis

1. Unclear diagnosis of asthma in a patient with acute shortness of breath warrants the need for pulmonary function tests (PFTs) before and after inhaled bronchodilators.  Pulmonary function testing is a noninvasic measure of how well you breathe.  It reveals two measurements:

• FEV1 à Forced expiratory volume at 1 second:  The maximum amount of air you can exhale in 1 second
• FVC à Forced vital capacity:  The maximum amount of air you inhale and exhale

Asthma and reactive airway disease may be confirmed with an increase in the FEV1 of >12 %.

1. Diagnosis of asthma in a patient with a history of intermittent episodes of shortness of breath but no current symptoms warrants the need for methacholine stimulation test (histamine challenge test).  During this test, bronchoconstriction is provoked in a medical setting and then airway narrowing is quantified with spirometry.  Individuals with pre-existing bronchial hyperactivity will respond to lower doses of methacholine.  A bronchodilator can be added to assess reversibility of obstruction and may help distinguish between asthma and chronic obstructive pulmonary disease.

Treatment

• Inhaled short-acting bronchodilators (e.g., albuterol)
• Inhaled corticosteroids
• Inhaled Long-acting bronchodilator
• Oral steroids (e.g., methyl prednisone)
  • Recall, steroids usually take about 4-6 hours to be effective
• Oxygen

Mild Intermittent Symptoms in which you experience one or more of the following:

• Asthma attach < 2 times/wk
• Nocturnal awakenings < 2 times/wk
• Use of bronchodilators < 2 times/wk
• Baseline FEV1 & FEV1/FVC ratio are normal
• No limitations on daily activities
  • Treatment: 
    • Short acting inhaled bronchodilator (e.g., albuterol) as needed

Mild Persistent Symptoms in which you experience one or more of the following:

• Asthma attack > 2 times/wk – but not everyday
• Nocturnal awakenings > 2 times/month
• Normal PFTs
• Minor limitations on activities
  • Treatment: 
    • Inhaled low dose corticosteroids daily
    • Short acting inhaled bronchodilator (e.g., albuterol) as needed

Moderate Persistent Symptoms in which you experience one or more of the following:

• Daily symptoms but get relief between attacks with inhaled bronchodilators
• Nocturnal awakenings > 1 times/wk
• FEV1 60-80% of predicted value
  • Treatment:
    • Daily inhaled high dose corticosteroids (e.g., beclomethasone)
    • Long acting bronchodilator (e.g., salmeterol)
    • Short acting bronchodilator (e.g., albuterol)

Severe Persistent Symptoms in which you experience one or more of the following:

• Continuous symptoms without relief
• Nocturnal awakenings frequently (4-7 times/wk)
• FEV1 < 60% of predicted value
  • Treatment:
    • Oral corticosteroids (e.g., prednisone)
    • High dose inhaled corticosteroids (e.g., beclomethasone)
    • Long acting inhaled bronchodilators (e.g., salmeterol)
    • Short acting bronchodilator as needed (e.g., albuterol or ipratropium)

Additional Causative Treatment Options:

• Extrinsic allergies (hay fever):  Cromolyn
• Atopic disease:  Monteleukast
• Chronic obstructive pulmonary disease:  Tiotropium, Ipratropium
• High IgE levels:  Cromolyn, Omalizumab

Exercise Induced Asthma:

• Best treated with inhaled bronchodilator prior to exercise

Expected Management

• Oxygen
• Continuous oximeter
• Chest x-ray
• Arterial blood gases

Complications

• School absenteeism
• Home confinement
• Breathing difficulty
• Hospitalization
• Asphyxia
• Death
• Status asthmaticus – repeated bouts of asthma attacks without relief

Each year, asthma causes more than 18 million days of restricted activity.  One study found that children with asthma lose an extra 10 million school days each year; this problem is compounded by an estimated $1 billion in lost productivity for their working parents.