(First of two parts)
Ever get the feeling of something taking one’s breath away? That’s not love; that’s probably an asthma attack.
The World Health organization estimated thag 339 million people suffered from asthma and 417,918 deaths because of asthma in 2016.
Asthma affects the respiratory system, particularly the bronchi and the bronchioles.
These airways have an inner lining called the mucosa surrounded by a smooth muscle which helps in contraction especially in the process of ventilation and breathing.
Asthma is usually triggered by a lot of things depending on the individual, but particularly common ones are smoke, dust and pollution.
When asthma is triggered, the smooth muscle in the airways constrict and the mucosal lining becomes swollen and secretes more mucous.
Normally the mucosa secretes mucous and lines the airway as a defense mechanism to trap unwanted particles and then expel them.
In an asthma attack mucous secretion is increased. This, in combination with a swollen mucosa and contraction of the smooth muscle, makes it hard to breathe.
SIGNS and SYMPTOMS of ASTHMA
The submucosa (the area containing the mucosa and the epithelium) of the airways usually contains a lot of eosinophils, which are white blood cells that carry a cargo of granules full of inflammatory mediators such as histamines, leukotrienes, prostaglandins and platelet activating factor. If these eosinophils sense an environmental trigger such as cigarette smoke, it releases these inflammatory mediators and creates a strong inflammatory reaction in the airways.
This causes the smooth muscle to spasm and constrict the airways and the mucosa to increase its mucous production. Combined, this makes it difficult to breathe. Asthma may also produce pleuritic chest pain which is pain when breathing in.
Smooth muscle contraction leads to the feelings of chest tightness, the increased mucous production lead to productive or non-productive cough, and the wheezing noise is caused by the narrowed airways causing a sort of whistling sound which is what physicians hear when listening through a stethoscope.
All of these produce dyspnea or breathing difficulties.
Occasionally in the sputum there may be curschmann spirals, which are elongated mucous casts that semi-solidified in the small bronchi, taking their shape. Not to be mistaken for some Lovecreaftian squid invading one’s lungs.
These may actually be dangerous because not only do they block exchange of air they may also block medications from getting into the site of inflammation. Charcot leyden crystals may also be found in the sputum which are needle like substances formed from the breakdown of eosinophils.
Asthma is considered an obstructive lung disease. Generally the difference between an obstructive and a restrictive lung disease is, in the simplest sense, is that in obstruction one “cannot get the air out” while in restrictive diseases one “cannot get the air in”.
Asthma and Chronic Obstructive Pulmonary Disease (COPD) may have the same symptoms, the difference is that asthma is reversible and episodic, while COPD is fixed and irreversible.
While it’s true that these changes are usually reversible, over the years through continued triggers these changes in the lung may become irreversible due to edema, scarring and fibrosis – thickening the basement membrane and permanently reducing the airway’s diameter.
Chronic asthma may be an irreversible type of severe persistent asthma and then may overlap with COPD.
IMMUNOLOGY of ASTHMA: Why do some people have asthma and some don’t?
Asthma may be divided into extrinsic or intrinsic asthma. Extrinsic asthma is basically allergic asthma, or caused by an external pathogen and is Immunoglobulin E (IgE) mediated.
Intrinsic asthma is also known as non-immune / non allergic / non atopic asthma and may be induced by exercise or stress but not by allergies.
The specific causes of asthma are ultimately unknown, it is thought to be a combination of genetic and environmental factors. People may be genetically predisposed to have immune cells more likely to trigger asthma which is more often than not activated by a trigger inducing environment.
An example of these immune cells is TH2 or T Helper cells type 2 – which is an immune cell involved in allergic reactions that is why in some cases asthma and allergies go hand in hand. TH2 cells release cytokines, like interleukin 5 (IL5) which attracts and activates Eosinophils.
Which is why some asthma medications block Interlukin 5.
Childhood asthma less than age 12 are said to be related to a stronger genetic influence. And adult onset asthma are more likely due to environmental factors.
There’s a theory called THE HYGIENE HYPOTHESIS which basically states that reduced early exposure to bacteria and viruses in the early stages of life may predispose to an increased risk of developing asthma. This may be because of altering the proportion of immune cell subtypes in the body.