Asthma is a common long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction (non-permanent narrowing of the airways, limiting the airflow) and bronchospasm (constriction of the bronchi, narrowing their lumen, Pic. 1).
Symptoms include episodes of wheezing, coughing, chest tightness, and shortness of breath. People with asthma have very sensitive airways that narrow in response to certain "triggers", leading to difficulty in breathing. The airway narrowing is caused by inflammation and swelling of the airway lining, the tightening of the airway muscles, and the production of excess mucus. This results in a reduced airflow in and out of the lungs. Depending on the person, they may become worse at night or with exercise.
Asthma is thought to be caused by a combination of genetic and environmental factors. Factors that trigger asthma are allergens found in dust, animal fur, mould, dust mites, pollen from, grass, and flower (Pic. 2). Other factors are irritants such as cigarette smoke, air pollution, chemicals or dust in the workplace, and sprays such as hairspray also trigger asthma symptoms. All these factors contribute to constriction of the airways.
The airways of the lungs called bronchi (or bronchial tubes), are tubes with muscular walls that contract when irritated. Along the lining of the Bronchi there are cells with microscopic structures called G protein coupled receptors. These G protein coupled receptors are called beta-2 adrenergic receptors and cholinergic receptors. The beta-2 adrenergic receptors respond to chemicals such as epinephrine to make the muscles relax and thus opening the airways and increasing airflow. Cholinergic receptors on the other hand respond to a chemical called acetylcholine making the muscles contract, thereby decreasing airflow.
During an Asthma attack constriction of the Bronchi are caused by abnormal sensitivity of the cholinergic receptors, which cause the muscles of the airways to contract when they should not. There are cells in the Bronchi called mast cells which are held responsible for this cellular response. These mast cells release substances such as histamine and leukotrienes, which activate the cholinergic receptors cellular response for smooth muscle contraction, mucous buildup, and white blood cell migration to certain areas. Eosinophils, a type of white blood cell is found in the airways of asthmatic people, also release substances that contribute to airway constriction.
Diagnosis is usually based on the pattern of symptoms, response to therapy over time, and spirometry (a diagnostic test of the lung function).
Asthma is classified according to the frequency of symptoms, forced expiratory volume in one second (FEV1), and peak expiratory flow rate. It may also be classified as atopic or non-atopic, where atopy refers to a predisposition toward developing a type 1 hypersensitivity reaction. This reaction is commonly referred to as allergic reaction (Pic. 3), and represents an excessive immune system response to a harmless stimulus, called the allergen. Atopic asthma therefore arises in patients predisposed to allergic reactions.
There’s no cure for asthma, however there are Albuterol inhalers for keeping asthma symptoms in a controlled state. There are several inhalers such as Albuterol, Ventolin and Proventil. Albuterol inhalers also known as a bronchodilator is a quick-relief or rescue medication used to decrease asthma symptoms.
Asthma is characterized by recurrent episodes of wheezing, shortness of breath, chest tightness, and coughing. Almost all asthmatics will have at least one and often more than one of those symptoms. Less common symptoms of asthma include prolonged exhalations, feeling as if you have to work to exhale, and feeling as if you can’t get all of your air out when you breathe out, all of which are signs of air trapping. Sputum may be produced from the lung by coughing but is often hard to bring up. During recovery from an attack, it may appear pus-like due to high levels of white blood cells called eosinophils. Symptoms are usually worse at night and in the early morning or in response to exercise or cold air. Some people with asthma rarely experience symptoms, usually in response to triggers, whereas others may have marked and persistent symptoms.
Chronic obstructive pulmonary disease (COPD)
Historically, asthma and COPD have been considered separate and unique diseases with distinct characteristics. Classically, asthma has been characterized by reversible airways obstruction and COPD by fixed, less reversible, or irreversible airways obstruction (Pic. 4). Even though asthma and COPD can be and are often appropriately separated as clinical entities, there are times when they are physiologically indistinguishable. Both diseases are characterized by airways inflammation and sometimes cannot be distinguished clinically. Thus, COPD and asthma may coexist or overlap in individual patients or within specific phenotypic (physical appearance-based) categories.
Gastro-esophageal reflux disease (GERD)
An association between symptoms of asthma and gastro-oesophageal reflux is now well-recognised, with a number of studies reporting a much higher prevalence of reflux symptoms (symptoms of GERD) in patients with asthma than in control subjects. Reflux symptoms are associated with respiratory symptoms in young adults independently of body mass index. The mechanism of these associations remains unclear.
Rhinosinusitis (RS) is a common disease in children that is sometimes overlooked. Rhinosinusitis is defined as a symptomatic inflammatory condition of mucosa of the nasal cavity and paranasal sinuses, the fluids within these sinuses, and/or the underlying bone. A separate condition of inflammation of the paranasal sinuses is called simply sinusitis, whereas the inflammation of the nasal cavity is called rhinitis. The clinical symptoms of acute rhinosinusitis in children include nasal stuffiness, coloured nasal discharge, and cough with resultant sleep disturbance. Symptoms of chronic sinusitis may include any combination of the following: nasal congestion, facial pain, headache, night-time coughing, an increase in previously minor or controlled asthma symptoms, general malaise, thick green or yellow discharge, feeling of facial 'fullness' or 'tightness' that may worsen when bending over, dizziness, aching teeth, and/or bad breath. Recent theories of sinusitis indicate that it often occurs as part of a spectrum of diseases that affect the respiratory tract and is often linked to asthma.
Atopic dermatitis (AD) or atopic eczema (Pic. 5) is a chronic relapsing inflammatory skin disease. It is clinically manifested by itching and scratching, dry skin, patchy eczema especially on flexural locations, exudation, and skin thickening and discoloration. Genetic predisposition is obvious in AD patients, who often have a personal or familial history of other allergic diseases, such as asthma and allergic rhinitis. A triad of atopic eczema, allergic rhinitis and asthma is called atopy (Pic. 6).
Obstructive sleep apnoea
Asthma and obstructive sleep apnoea (OSA) may coexist to result in an overlap syndrome where a bidirectional relationship may deleteriously affect each other. Both asthma and OSA have airway obstruction in the pathogenesis and have many diurnal and nocturnal symptoms in common.. Obstructive sleep apnoea is identified as an independent risk factor for asthma exacerbation (worsening of the condition) and OSA is reported to be more prevalent among patients with severe asthma than in moderate asthma which may be linked to the potential pathophysiologic interaction between OSA and asthma severity.
Both asthma and COPD (chronic obstructive pulmonary disease) affect mental health due to their impact on activities, sleep and social life of patients and can be resulted in anxiety and depression. Evidence have shown that individuals with asthma have twice risk of developing depressive symptoms as compared with those who do not have asthma. Although there is clear relationship between anxiety, depression and asthma, the association with asthma severity is controversial.
There are several studies that indicate both coherence between asthma and endometriosis as well as a correlation between metabolic syndrome/PCOS (polycystic ovary syndrome) and asthma. Studies of women with endometriosis show a higher prevalence of asthma than among the general population. A common inflammatory pathway has been indicated as an explanation.
Complications of asthma include acute exacerbations, remodelling of the airways, and associated conditions that interfere with the quality of life. Exacerbations occur most frequently in individuals with severe disease. They present with acute shortness of breath, wheezing and chest tightness. The narrowing of the airways leads to obstruction of air flow and eventually to hypoxia (lower oxygen concentration in blood), which can be even life threatening. Other conditions associated with airway obstruction include sleep apnoea, which causes the airways to close during the night, usually causing the patient to wake up repeatedly and severely compromising the quality of sleep. Sleep apnoea, together with other conditions associated with asthma, can negatively affect the patients´ mood, leading frequently to depression and anxiety. Furthermore, the inflammatory mediators released in asthma can have long-term effects on the airways. Subgroups of asthma patients develop airflow obstruction that is irreversible or only partially reversible and experience an accelerated rate of lung function decline. The structural changes in the airways of these patients are referred to as airway remodelling.
Reproductive changes such as impaired fertility and adverse pregnancy outcomes have been related to female asthma. It has been recently found that time to pregnancy is prolonged in asthmatic females especially in women with moderate to severe asthma and in those above 30 years of age. Despite their reproductive difficulties the asthmatics ultimately conceived just as many biological children as healthy throughout their reproductive lives. The mechanisms linking asthma to fertility still remain poorly investigated. However, recent data indicate that the nature and degree of inflammation characterizing asthma are important since non-atopic asthma, untreated asthma, and moderate to severe asthma had the largest effect on fertility, that is, increased TTP (time to pregnancy). It is therefore proposed that the asthmatic inflammation is a universal problem compared to allergy alone and is involving mucosal surfaces other than the bronchi. Accordingly, one assumption is that the same inflammation and increased number of inflammatory cells and mediators are also found in the uterus or the Fallopian tubes in asthmatic women.
Furthermore, several studies indicate correlation between asthma and gynaecological conditions linked to infertility, such as endometriosis and polycystic ovary syndrome (PCOS)/metabolic syndrome. Common features of PCOS, metabolic syndrome, and endometriosis are subfertility, systemic inflammation, and increased number of spontaneous abortions and an association to asthma could therefore, to some extent, explain the reduced fertility in asthmatics. These data substantiate the hypothesis of an association between asthma and infertility. Based on the available evidence, we know that asthma and maybe other systemic inflammatory diseases can have negative influence on fertility. The association increases with the degree and nature of the inflammation, and data suggest that the severity of asthma and the treatment level as well as the asthma phenotype can increase this tendency.
The effects of asthma on male fertility are yet to be fully explained, but it appears that asthma does not significantly decrease male fertility.
The prognosis for asthma is generally good, especially for children with mild disease. Mortality (death rate) has decreased over the last few decades due to better recognition and improvement in care. Of asthma diagnosed during childhood, half of cases will no longer carry the diagnosis after a decade. Airway remodelling is observed, but it is unknown whether these represent harmful or beneficial changes. Early treatment with corticosteroids seems to prevent or ameliorates a decline in lung function.
Although the inflammatory processes present in asthma interfere with normal function of the reproductive system, it has been found that ultimately, women with asthma have the same average number of children as unaffected ones.