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Definition:
Asthma is often defined as a chronic inflammatory disorder of the airways.
So what does that mean? Well normally, our body has an amazing filtering system for the air we breathe that starts at our nose. Our nose secretes this thick and sticky substance called mucus that traps unwanted particles like dirt, pollen, or smoke. Small hairs called cilia move in wave like motions pushing the mucus to the back of our throat where it either gets swallowed or spit out. Have you ever noticed a lot of post-nasal drip during pollen season? As irritating as it can be, that is your nose is working overtime to clear out the pollen before it reaches your lungs. This is completely normal and our body’s way of protecting us from particles that may contain bacteria or viruses that can lead illnesses.
Pathophysiology:
In asthma, the body’s inflammatory process goes into overdrive! This occurs when the immune system is exposed to something called an allergen or trigger such as pollen, pet dander, smoke, or mold. It mistakenly tags it as something bad by producing antibodies to it called IgE.
Upon reexposure to the same allergen, the body’s hyperinflammatory system remembers the allergen and causes the release of IgE antibodies that bind to and activate mast cells. Mast cells are a type of immune cell that function as the body’s first line of defense against harmful allergens preventing them from entering the body. They do this by releasing granules that contain such as histamine, prostaglandin and leukotriene. These granules sound fancy but they are just names for types of mediators of anaphylaxis. These mediators go on to cause constriction of the airway smooth muscle and increase mucous production. This process is something called the ‘early asthmatic response. This is followed 3-6 hours later by a ‘late asthmatic response’ where proinflammatory cytokine proteins recruit and activate additional immune cells such as eosinophils that contribute to continued and sustained bronchoconstriction and mucous production.
Symptoms:
These series of events lead to the symptoms of asthma including:
- Wheezing
- Breathlessness
- Chest tightness
- Coughing
In asthma, the smooth muscles around the airways tighten and shrink making them narrower leading to chest tightness. In addition, overproduction of mucous produces mucous plugs throughout the lining of the airway that can cause coughing. This makes it tough to move air through and almost causes a whistling sound as air passes through the narrow space. This is known as wheezing. The narrow and inflamed airways not only lead to decrease oxygenation but also decrease ventilation as air gets trapped inside the lungs. The increase work of breathing to get air in and out can lead to exhaustion and breathlessness as seen in patients with asthma.
Diagnosis:
In addition to the patient’s symptoms, medical history and physical exam, physicians commonly use a spirometer to diagnose asthma. A spirometer is a device used to measure the volume of air inspired and expired by the lungs. A physician will have a patient use the spirometer after administering a medication called a beta agonist. If there is an improvement in the spirometry readings after using the beta agonist, this is a good indication of asthma since it is reversible with medications, unlike COPD. Once the diagnosis is confirmed, initial asthma management depends on how often they have symptoms such as nighttime awakenings, the need for a rescue inhaler to control symptoms, activity limitations due to asthma and daytime symptoms.
