So in this post, we’ll discuss about Asthma.
It is defined as “a common chronic disorder of the airways that is complex and characterized by variable and recurring symptoms, airflow obstruction, bronchial hyperresponsiveness, and an underlying inflammation. The interaction of these features of asthma determines the clinical manifestations and severity of asthma as well as the response to treatment”
Now, how a patient of asthma presents with?
- Cough (often worse at night)
- Wheeze: just listen this wheezing sound. So it is high-pitched whistling sound, usually upon exhalation
- Shortness of breath or difficulty breathing
Physical findings that suggest severe airflow obstruction in asthma include tachycardia(inceased heart rate), tachypnea (increased resp rate), , prolonged expiratory phase of respiration (decreased I:E ratio), and a seated position with use of extended arms to support the upper chest (“tripod position”) . Use of the accessory muscles of breathing (eg, sternocleidomastoid) during inspiration and a pulsus paradoxus (greater than 10 mmHg fall in systolic blood pressure during inspiration) These last two are usually found only during severe asthmatic attacks.
In this pic, this is the trachea of the patient which divides into right and left bronchus and then into bronchioles. On the left side, this is the normal airway whereas on the right side, you can see the increased smooth muscle along with increased mucus inside the airway which has caused the narrowing of the airway lumen thereby responsible for all the signs and symptoms of asthma.This is how an asthmatic airway looks like. Now lets understand with the help of this dynamic short video of the airway. When an allergen goes into the trachea, smooth muscle contracts and on continued exposure of allergen to its walls, it contracts further along with increased mucus production(which you can see in green color), further causing narrowing of the airway passage and ultimately leading to the collapse of the whole airway resulting in total airway occlusion.
Now lets discuss how and which cells are primarily involved in allergic airway inflammation: when an allergen enters into body, it initiates cascade of reactions causing activation of Th2 cells and mast cells. Th2 cells releases a family of cytokines like IL4, 5,which causes IgE production and these IgE antibodies gets attached to mast cell causing degranulation and release of mediators from mast cells that includes histamine, leukotrienes, and prostaglandins that directly contract airway smooth muscle causing bronchoconstriction.
Etiology
Factors that can contribute to asthma or airway hyperreactivity may include:
- Environmental allergens (eg, house dust mites; animal allergens, especially cat and dog
- Environmental pollutants, tobacco smoke
- Exercise
- Aspirin or nonsteroidal anti-inflammatory drug (NSAID) hypersensitivity
- Viral respiratory tract infections
DIAGNOSIS is based on:
- History
- Clinical features
- Lab investigations: The laboratory evaluation of a patient with suspected asthma is predominantly focused on pulmonary function testing. Most important of PFT’s is Spirometry —, in which a patient is asked to breathe in and breathe out through a mouthpiece. And the amount of air inhaled and exhaled is recorded. It also includes measurement of forced expiratory volume in one second (FEV ) and forced vital capacity (FVC) which is volume of air that can forcibly be blown out after full inspiration.
When the ratio of FEV1 and FVC is less than 0.7, it indicates obstructive disease like asthma
- Bronchodilator response —
Acute reversibility of airflow obstruction is tested by administering 2 to 4 puffs of a quick-acting bronchodilator (eg, albuterol), and repeating spirometry 10 to 15 minutes later.
An increase in FEV of 12 percent or more, accompanied by an absolute increase in FEV of at least 200 mL, can be attributed to bronchodilator responsiveness with 95 percent certainty of asthma.
other tests: Peak expiratory flow, exhaled nitric oxide, blood test (eosinophilia)
Now coming onto most important topic- ASTHMA MANAGEMENT. This is guided by GINA i.e Global Initiative for asthma
- Routine assessment of symptoms and lung function
- Patient education and preference
- Controlling environmental factors (trigger factors) and comorbid conditions that contribute to asthma Severity
- Pharmacologic and non pharmacological therapy
- Adjust treatment
- Review response in form of symptoms, exacerbation, side effects, patient satisfaction and lung function
Pharmacologic treatment is the mainstay of management in most patients with asthma. This is guided by the Stepwise approach given by GINA (Global initiative for asthma). There are the 5 steps which are based on frequency of asthma symptoms/ frequency of short acting beta agonist use with or without risk factors for exacerbation.
If the patient is on step1, reliever medication in the form of SABA or short acting beta agonist is the preferred option and there is no need for any controller medication. In step 2, low dose ICS i.e inhaled corticosteroid is the preferred controller choice. Other options are leukotriene receptor antagonist along with low dose theophylline.
In Steps 3-5, reliever medication can be either SABA or low dose ICS whereas LABA i.e long acting beta agonist can be used as controller choice in both step 3 and 4. In step 5, add on treatment like tiotropium, anti IgE, anti IL5 can be used as preferred controller choice and low dose oral corticosteroids can be tried.
New modalities:
For patients whose asthma is inadequately controlled on high-dose inhaled GCs and LABAs, the anti-IgE therapy omalizumab may be considered if there is objective evidence of sensitivity to a perennial allergen and if the serum IgE level is within the established target range.
Monoclonal antibodies (mepolizumab and reslizumab) against interleukin-5 (IL-5), a potent chemoattractant for eosinophils, are available for patients with eosinophilic severe asthma. They are indicated for the treatment of severe eosinophilic asthma poorly controlled with conventional therapy.
Bronchial thermoplasty is a device-based intervention available to treat severe asthma. Utilizing a special catheter introduced via a fiberoptic bronchoscope, thermal energy is applied to bronchial walls in an effort to impair bronchial smooth muscle contractility. The role of bronchial thermoplasty in managing severe asthma is still not clear.
So that was all about asthma. Please feel free to ask any question or your feedback in the comment section below.
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