Asthma comprises a range of diseases and has a variety of heterogeneous phenotypes. The recognized factors that are associated with asthma are a genetic predisposition, specifically a personal or family history of atopy (propensity to allergy, usually seen as eczema, hay fever, and asthma).
Asthma also is associated with exposure to tobacco smoke and other inflammatory gases or particulate matter.
The overall etiology is complex and still not fully understood, especially when it comes to being able to say which children with pediatric asthma will carry on to have asthma as adults (up to 40% of children have a wheeze, only 1% of adults have asthma), but it is agreed that it is a multifactorial pathology, influenced by both genetics and environmental exposure.
Asthma is a common pathology, affecting around 15% to 20% of people in developed countries and around 2% to 4% in less developed countries. It is significantly more common in children. Up to 40% of children will have a wheeze at some point, which, if reversible by beta-2 agonists, is termed asthma, regardless of lung function tests. Asthma is associated with exposure to tobacco smoke and inhaled particulates and is thus more common in groups with these environmental exposures.
Asthma is a condition of acute, fully reversible airway inflammation, often following exposure to an environmental trigger. The pathological process begins with the inhalation of an irritant (e.g., cold air) or an allergen (e.g., pollen), which then, due to bronchial hypersensitivity, leads to airway inflammation and an increase in mucus production. This leads to a significant increase in airway resistance, which is most pronounced on expiration.
If not corrected rapidly, asthma may become more difficult to treat, as the mucus production prevents the inhaled medication from reaching the mucosa. The inflammation also becomes more edematous. This process is resolved (in theory complete resolution is required in asthma, but in practice this is not checked or tested) with beta-2 agonists (e.g., salbutamol, salmeterol, albuterol) and can be aided by muscarinic receptor antagonists (e.g., ipratropium bromide), which act to reduce the inflammation and relax the bronchial musculature, as well as reducing mucus production.
The only relevant toxicokinetics in asthma relate to its management as the absorption and systemic side effects of the beta-2 agonists must be monitored. Typically these will be removed from the body in 2 to 4 hours if salbutamol and albuterol, 18 to 24 hours if salmeterol, or 48 to 72 hours if clenbuterol, which is no longer used in the management of asthma.
The side effects of the beta-2 agonists include tachycardia, flushing, sweating, and other signs of sympathetic system overdrive. There is also the chance of iatrogenic hypokalaemia, which must be monitored.
Patients will usually give a history of a wheeze or a cough, exacerbated by allergies, exercise, and cold. There is often diurnal variation, with symptoms being worse at night. Patients may give a history of other forms of atopy, such as eczema and hay fever. There may be some mild chest pain associated with acute exacerbations.
Physical exam findings will depend on whether the patient is currently experiencing an acute exacerbation.
During an acute exacerbation, there may be a fine tremor in the hands due to salbutamol use, and a mild tachycardia. Patients will show some respiratory distress, often sitting forwards to splint open their airways. On auscultation, a bilateral, expiratory wheeze will be heard. In life-threatening asthma, the chest may be silent, as air cannot enter or leave the lungs, and there may be signs of systemic hypoxia.
Pulse oximetry can be useful in assessing the severity of an asthma attack or monitoring for deterioration. Note that pulse oximetry lag, and the physiological reserve of many patients means that a falling pO2 on pulse oximetry is a late finding, indicating a severely unwell or peri-arrest patient.
Peak flow measures also can be used to assess asthma and should always be checked against a nomogram as well as the individual patient's normal baseline function. The different severities of acute asthma attacks have an associated peak flow measurement, recorded as a certain percentage of expected peak flow.
Urea and electrolytes (kidney function) should be taken if the patient has a high dose or repeat salbutamol, as one of the side effects of salbutamol is to cause potassium to shift into the intracellular space transiently, which can induce a transient, iatrogenic hypokalaemia.
A chest x-ray is an important test, especially if patients have a history of risk of the potential foreign body or possible infection.
Spirometry is the diagnostic method of choice and will show an obstructive pattern that is partially or completely resolved by salbutamol.
Measures to take include calming the patient to get them to relax, moving outside or away from the likely source of allergen, and cooling the person. Removing clothing and washing the face and mouth to remove allergens is sometimes done, but it is not evidence-based.
Medical management includes bronchodilators like beta-2 agonists and muscarinic antagonists (salbutamol and ipratropium bromide respectively) and anti-inflammatories such as inhaled steroids (usually beclometasone but steroids via any route will be helpful).
There is no surgical input into the management of typical asthma.
Weight loss, smoking cessation, occupational change, and self-monitoring are all important in preventing disease progression and reducing the number of acute attacks.
The main differential for an acute, life-threatening asthma attack is an anaphylactic reaction. In this case, the patient may also present with orofacial swelling, a rash, and itching. The patient will partially respond to salbutamol and steroids, but intramuscular adrenaline is the lifesaving medication needed to manage these patients.
The severity of asthma is usually classified as follows:
Patients with asthma need life-long follow up for monitoring of the disease, quality of life and functional status. At each visit, compliance with medications should be emphasized.
Patient education about the disease and modifying behavior is vital. The patient should also be encouraged to change lifestyle and control the environmental trigger factors.
If the patient requires nebulized salbutamol and is not ordinarily on home nebulizers, he or she should be admitted. Anyone who has presented with severe or life-threatening asthma should usually be monitored to ensure that the disease does not return when the medication has worn off.
Issues include forgetting to remove the nebulizer mask once the nebulizer is done (thus leaving the patient on only 6L of 02/min, rather than changing them to 15 L/min via a non-rebreather mask), not assessing inhaler technique, and neglecting to stress the importance of maintenance therapy with inhaled steroids even when the patient is well.
In many countries, including the US, asthma kills one out of every 100,000 persons. The worse the lung function, the higher the mortality. In addition, mortality has also been linked to poor management and lack of medication compliance, especially in young people. Other factors that increase the risk of death include smoking and use of illicit drugs.
Asthma also results in millions of school and work days lost. In the US alone, close to 2 million asthmatics seek regular care in the emergency department, which also increases the costs of healthcare.
Even though asthma is a reversible disorder, poor lifestyle and lack of management can lead to airway remodeling that leads to chronic symptoms, which are disabling.
Many guidelines have been published for the diagnosis and management of asthma, but the most critical feature is patient education. The nurses are the last professionals to see the patient before discharge from the emergency department or the floors. Similarly, since most asthmatics are treated as outpatients, pharmacists encounter them regularly. Evidence shows that teaching patients about this disorder and the importance of compliance are critical for good outcomes. The patient should be taught about monitoring technique, inhaler use, and modifying the environment. Many evidence-based asthma plans are available for the management of asthma and should be handed out to patients. Finally, nurses also play a vital role in school-based asthma education programs that can help improve self-esteem, knowledge and self-management behaviors. (Level II)
Despite great awareness of the disease, asthma still results in high morbidity and even mortality. There are universal guidelines on managing the disorder, but patient compliance with medications remains a big problem. Hence, all healthcare workers have a responsibility in encouraging medication compliance and close follow up with the primary care physician.(Level V)