This week’s focus piece will cover asthma.
What is asthma? Asthma is essentially, a disease that inhibits the ability to get air out of the lungs. Asthma is caused by bronchial spasms. What is this? Your bronchioles are the tubes in your lungs that take air (and oxygen!) to your alveoli: where gas exchange (O2 for CO2!) occurs. In an asthma attack, these bronchioles swell, and excess mucus is produced, preventing the air from getting out. Why is that?! Well, when you inhale air, you are using the negative pressure inside your lungs (created by your diaphragm contracting!) to pull air into your lungs. However, when you are exhaling, the pressure inside your lungs equals the pressure outside (because your diaphragm is relaxed!). Therefore, you can think of inhaling as an active process, versus exhaling, a passive process. When your bronchioles swell, you can still pull air into your lungs (because the pressure difference helps!), but you can’t get it out. The pressure difference also helps your bronchioles open up a tiny bit to get air in, but as you try to breathe out, the walls of the bronchioles clamp down, and the air is stuck. This is called air trapping. Plus when your lungs and alveoli are full of CO2, it is super hard to get any air to move at all.
Here is an image that shows normal versus asthmatic bronchioles:
This pathophysiology of asthma all leads to the signs and symptoms that are visible in asthma patients. The first sign of many asthma attacks may be a tight chest. This is caused by the beginning of the air trapping. Patients may cough, creating extra pressure, and trying to push that air out of their lungs. Wheezing is also one of the main signs of an asthma attack. Wheezing is caused by the sound made as small amounts of air pass through the bronchioles.
Asthma attacks in the early stages can have low CO2 levels and low O2 levels, as a result of hyperventilation. This causes respiratory alkalosis (high pH levels, due to low levels of CO2) in the early stages. As an asthma attack progresses, patients may have some carbon dioxide retention, and as this CO2 builds up in the blood, it causes respiratory acidosis (low pH levels). Severe asthma attacks can be complex to manage.
You may also see retractions of different muscles, more commonly seen in kids. Check out this video!
Here is an image that shows the different types of retractions, and how they correspond with the severity of an asthma attack.
Asthma can have many, many different causes, such as allergies, genetics, stress, cold air, irritants in the air, and physical activity (exercise induced asthma). Approximately 30% of cases are diagnosed in childhood; the remaining 70% fall into the category of “adult onset asthma”. Within that, 30% of adult onset asthma cases are estimated to actually be allergy-induced asthma. In general, those diagnosed with childhood asthma may have more intermittent asthma (and it may actually go away in early adulthood!) versus those diagnosed with adult onset asthma are more likely to need daily control medications.
So how is asthma managed?
- Systemic steroids: ie Prednisone, oral beclamethasone, etc; most commonly used during illness. Systemic steroids are fairly strong and can be harmful to be on for long periods of time.
- Inhaled steroids: ie QVAR, Asmanex, etc; quite effective at decreasing overall inflammation in lungs.
- Long acting beta agonists + steroids: The most common asthma medications, these are a combination of medications that include a bronchodilator and a steroid. Includes medications such as Advair, Dulera, etc.
- Short acting bronchodilators: These medications are to be used during an attack, and not for ongoing maintenance of asthma. They can be used in a nebulizer, in a metered dose inhaler, and with a spacer. Albuterol is the most common.
- Other medications include:
- Epinephrine: Used in prehospital settings in severe asthma attacks, those not relieved with short acting bronchodilators via nebulizer. Epinephrine is extremely effective at inducing relief of bronchospasm. Generally the high blood pressure and high pulse rate (hypertension and tachycardia) induced by the anxiety and hypoxia of a severe attack is actually relieved by the administration of epinephrine
- Magnesium Sulfate: Very effective at inducing bronchial smooth muscle relaxation in severe attacks. This medication can be given either via nebulizer or via IV
There have also been many studies on other ways to manage asthma, and positive correlations have been found between low LDL levels in children, adequate vitamin D levels, and regular physical activity.
How do you know when to call 911 or go to the Emergency Department when you or your child are having an asthma attack?? You should always follow the asthma action plan given to you by your doctor.