Introduction to Asthma

Asthma is a long-lasting disease that affects the airways of the lungs. These airways are the breathing tubes that bring air in and out of lungs. Its pathological characteristics include chronic airway inflammation and increased airway hyperresponsiveness. Due to certain conditions, breathing becomes difficult. Symptoms of asthma include wheezing, coughing, chest tightness and shortness of breath (dyspnea). These symptoms are associated with airflow obstruction that is variable and reversible.

Epidemiology

The prevalence rate of asthma increased in developing countries and currently its affecting 300 million people around the world and additional 100 million people will be diagnosed by 2025. Although the progression of the disease and its response to the treatment and management are influenced by genetic determinants. Environmental factor plays a major role in increasing its prevalence rate. The study also shows the potential role of microbial exposure, diet, breastfeeding, air pollution, overweight, vitamins and other supplements with side effects but still, no clear consensus has emerged.

Pathophysiology

Airway hyperreactivity (AHR) is a characteristic feature of asthma which has the tendency of contracting airways too easily and too much in response to triggers that have little or no effect in individuals with no disease. Other factors that are important includes, the narrowing of the airway, obstruction of the airway and the influence of neurogenic mechanisms.
As the disease progresses, causing the severity and chronicity of the disease, this leads to the fibrosis of the airway wall, narrowing of the airway permanently and reduced response to the bronchodilator medication. Besides, there is a strong relationship between atopy (a propensity to produce IgE) and asthma and in many individuals, there is a clear relationship between sensitization and allergen exposure. Inhalation of allergic contents into the lungs is followed by two phases. Broncho-constrictor responses with both early and late phase response. The daily based examples are house dust mites, pollen, mould spores, pets such as cats and dogs, pests such as cockroaches and fungi. Allergic mechanisms are also involved in several cases of occupational or industrial asthma.
In aspirin-sensitive asthma, symptoms follow the ingestion of salicylates. It inhibits cyclooxygenase which leads to pushing of acid metabolism through the lipoxygenase pathway. In exercise-induced asthma, hyperventilation results in water loss from the lining fluid of the pulmonary mucosa which in response, release mediator. In persistent asthma, there is a chronic and complex inflammation which is characterized by numerous inflammatory cells, the transformation and participation of airway structural cells, chemokines, and other growth factors. It results in hypertrophy of smooth muscle, hyperplasia, the thickness of the basement membrane, plugging of the mucous, and destruction of the epithelium. Examination procedure of the inflammatory cells include sputum samples which is characterized by airway eosinophilia while in some patient’s neutrophilic inflammation predominates and in others, scant inflammation is seen which is also called ‘pauci-granulocytic’ asthma.

Clinical Presentation

Typical symptoms of asthma include recurrent episodes of wheezing, cough, breathlessness. Sometimes, asthma is mistaken for a cold or chest infection that is failing to resolve even after more than 10 days. Classical precipitants include exercise, predominantly in cold weather, exposure to airborne allergens or pollution and viral upper respiratory tract infections. Nasal polyps and eczema should be inspected. Besides, in rare cases, vasculitis rash may also be present in Churg-Strauss syndrome. Patients with mild asthma are usually not present with symptoms between aggravations. While the patients with persistent asthma report their condition with ongoing shortness of breath, wheeze but variability is usually present with symptoms fluctuating the course of one day, from day to day or month to month.
Asthma usually presents during the day with symptoms and pulmonary function being worse in the early morning. Mainly when symptoms such as cough and wheeze are poorly controlled. It may also create the sleep disturbance which is also termed as ‘nocturnal asthma’. In some circumstances, the presence of asthma is triggered by several medications such as antagonists and β-adrenoceptor. Even with medicines given topically such as eyedrops that may induce bronchospasm, aspirin, and other non-steroidal anti-inflammatory drugs (NSAIDs) may induce wheezing. Some patients with asthma have a similar inflammation response in the upper respiratory tract. A careful investigation should be made as to a history of sinusitis, headache, blocked or runny nose, loss of smelling sensation. The minority of patients develop a severe form of asthma which is more common in females. Allergic triggers are less common as compared to airway neutrophilia.

Diagnosis

Asthma is diagnosed clinically and based on a characteristic history. Supportive evidence may include variable airflow obstruction by using spirometry. The measurement of FEV1 and VC identifies the ventilatory obstruction, its severity and provide the basis of bronchodilator reversibility. A peak flow meter can be used if spirometer is not available and the patient should be instructed to record reading after rising in the morning and before retiring in the evening. Its variation provides an indication of the severity of the disease. Some other useful investigations include:

1. Measurement of allergic status
2. Radiological examination
3. Assessment of airway inflammation

Management

It is a chronic condition, but effective treatment is available for most patients and it is modified according to the condition of the patient. The patient should be encouraged to take responsibility for managing their own disease. Avoidance of aggravating factors is particularly important in managing occupational asthma where reducing exposure to relevant antigens such as house dust mites, a pet animal etc. reduction of fungal and allergen exposure, eliminate pests may also be applicable in some circumstances. Medications that precipitate or aggravate asthma should also be avoided. Smoking should be ceased as it is an important aggravating factor which not only encourages sensitization but also induces resistance in the airway. Asthma in pregnancy can be managed by safety data including, steroids, oral leukotriene receptor antagonist as there is no evidence of harm to the fetus, and inhaling steroids. Ventilation should be indicated in patient with acute severe asthma when present with, coma respiratory arrest, and deterioration of arterial blood gases (ABGs).
The outcome from severe asthma is generally good. Mortality rate is low and rare but considerably occurs in young patients while many are preventable. Before discharge, patient should be stable on medication and nebulized therapy should have beendiscontinued for at least 24 hours.