Asthma 101. Knowing The Basics.

Published by Dr Gigi on October 12, 2018

Introduction

Asthma is a chronic disease of the lungs, characterized by inflammation, swelling and narrowing of the airways with excessive mucus production that makes it difficult to breathe.

First, let’s look at how air gets to the lungs. When you breathe, air enters through the airways; nose, pharynx, larynx, bronchus, bronchioles and alveoli, to get to the lungs where gases (oxygen, carbon dioxide) are exchanged.

The longitudinal structure of the airways consists of 4 layers from top to bottom: the mucosa (the inner lining of the airway), basement membrane (supports the mucosa), smooth muscle, connective tissue (supporting layer).

Individuals with asthma have recurrent, episodic inflammation of the airways, resulting in swollen airways that are sensitive to foreign substances. If you have asthma, the smooth muscles in your lungs have exaggerated responses to signals from the stretch and irritant receptors domicile in your airways. Also, certain cells in the airways (e.g mast cell, eosinophils) produce substances that mediate the pathologic cascade of asthma. The smooth muscle surrounding the airways narrows the diameter of the airways when it contracts. The combined effect of smooth muscle contraction and airway inflammation greatly narrows the airway producing the clinical symptoms observed in asthma attacks.

Cause

The exact cause of asthma is unknown, however it is believed that your genes and interaction with the environment may make you likely to develop asthma.

Asthma Triggers

Asthma triggers vary among individuals with asthma, what may trigger asthma in one may not in another. Here are several known triggers capable of eliciting an asthma attack.

• Environmental pollutants e.g tobacco smoke,
• Airborne substances: pollen, cockroach waste, mold spores, dust mites
• Animal droppings
• Cold, dry air
• Viral respiratory tract infection
• Irritants such as perfumes, sprays, paint fumes
• Stress and strong emotions
• Physical exercise (exercise induced asthma)
• Aspirin (aspirin induced asthma)
• Gastro-esophageal reflux disease (a condition where acid in the stomach moves up into the throat, irritating the airways)
• Preservatives and chemicals added in some beverages and processed foods such as canned fruits and vegetables.

Who Is At Risk Of Asthma?

Asthma often starts in childhood, however everyone is at risk of asthma. If your child wheezes often, or has recurrent respiratory infections, eczema, food or animal allergies, they may be at risk for asthma.  If you or your spouse has asthma your children may be likely to develop asthma too.

Risk Factors for Asthma Include

• Having a sibling or a parent with asthma. These individuals are 3-6 times more likely to develop asthma than someone who does not have a parent or sibling with asthma
• Having other forms of allergic conditions, such as : allergic rhinitis (hay fever), atopic dermatitis (eczema)
• Having severe or recurrent respiratory infections as a child
• Environmental and occupational exposures such as, exhaust fumes, exposure to secondhand smoke, insecticides, pesticides, paint fumes, chemicals used in manufacturing. Individuals that live in urban areas at a higher risk of  asthma due to industrialization
• Being a smoker. Cigarettes produce smoke that irritate the airways. individuals whose mothers smoked during pregnancy are at a high risk of asthma

Signs and Symptoms

The frequency and severity of asthma varies between individuals. Symptoms can be minor or severe enough to interfere with an individual’s daily activities.  Note however that, you may have any of these symptoms without necessarily having asthma.

• Wheezing
• Coughing. Cough is often experienced at night or early in the morning. Night time cough may interrupt your sleep and make you tired the rest of the day
• Chest pain and tightness
• Shortness of breath

Types of Asthma

• Intermittent Asthma -this means you experience shortness of breath for a maximum of once a week and symptoms wake you up one or 2 nights a month.
• Mild Persistent Asthma -this means you experience shortness of breath, two or more days a week and symptoms wake you up about three to four nights a month.
• Moderate Persistent Asthma – this means you experience shortness of breath every day and symptoms wake you up one or more nights a week.
• Severe Persistent Asthma – this means you experience shortness of breath everyday and wake up every night due to asthma symptoms.

Asthma Diagnosis

History: Your doctor will ask about your symptoms, your family history of asthma, if you have any allergies, if you smoke or are exposure to environmental and occupational pollutants.

Additionally, your doctor may prescribe some medicines for asthma for a trial course. If your symptoms improve after the trial medicine, it may be an indication that you have asthma.

Breathing tests: Your doctor may perform any of the lung function tests

• Peak flow meter: It is a portable device that measures lung function. It is important that you have this device handy as it accurately detects your asthma symptoms, even before they start and helps you prevent an attack. Peak flow meter measures how fast you are able to exhale forcefully after maximum inhalation of air. This air expelled is known as peak expiratory flow (PEF).  Your PEF value tells you if your asthma  symptoms are under control or deteriorating. Remember to record your PEF in your asthma diary. PEF should be measured daily, in the morning before taking your asthma medications.
• Spirometry: Spirometer measures the  amount of air you can inhale, exhale and how fast you are able to blow air out of your lungs. If the test shows that your lung function is reduced, your doctor may give you a medicine (a bronchodilator) to inhale, this is supposed to open your airways. If your lung function improves after inhaling the medicine, it may be an indication that you have asthma.

   Steps In Using a Peak Expiratory Flow Meter

• While standing straight, make sure the indicator is at the base of the numbered scale
• Breathe in deeply as much as you can, place the meter between your teeth and close your lips around the mouthpiece. Your tongue should not block the hole in the mouthpiece
• In a single breath, exhale as hard and as fast as you can. Note the PEF value
• Repeat at least two more times
• In your asthma diary, record the highest of the three values
• Always use the same peak flow meter

   Interpreting Peak Expiratory Flow 

• Green zone. PEF of 80-100% of normal, means you are in the clear and your asthma may be under control.
• Yellow zone. PEF of 50-80% of normal, signals caution.
• Red zone. PEF less than 50% of normal, signals a medical emergency. It is an indication that your airways are narrowing and you need to visit your doctor.

If your values are below 80% of your personal best, you will need to check your asthma action plan and plan a visit to your doctor if necessary. It is important to note that PEF values depend on, if you are male or female, how old your are and your height.

Treatment For Asthma

Although asthma can not be cured, it can be controlled. The frequency and severity of asthma symptoms vary between individuals. This means that you and your doctor will have to come up with a personalized treatment plan that includes instructions on how to take your medications, ways to avoid your triggers and an asthma action plan.

The most effective way to control asthma and keep the frequency of your symptoms to a minimum, is to identify your specific triggers and to avoid them. Sometimes, you may not be able to avoid them, for example, patients with exercise induced asthma may want to keep exercising to stay healthy. In this case, you are advised to take your medication as prescribed.

Your doctor may prescribe medications to be taken by mouth or by inhalation or a combination of both. Asthma medicines are generally divided into 2 categories: quick relief and long term control medicines.

Asthma Medicine Delivery Devices

Inhalers  and nebulizers are two asthma medicine delivery devices that get the medications directly into your lungs.

Inhalers: One out of 3 individuals with asthma do not use their inhalers correctly. (1) It is important to learn to use it correctly to ensure you are getting adequate amount of the medicine. Your doctor or nurse can teach the proper way to use the inhaler. Knowing the proper inhaler techniques and compliance with your medications will help bring your asthma symptoms under control. (2)

• Metered dose inhaler.

  This is a handheld device that delivers a measured amount of aerosolized medicine into the lungs. It consist of an aerosol canister inserted into a plastic mouthpiece. Oftentimes, holding chambers or spacers may be used as a reservoir in order to reduce the speed at which the aerosolized medicine enters the mouth, so most of the medication gets to your lungs instead of your mouth. MDI with spacers are helpful in children and adults who have difficulty using the regular MDI. Spacers are recommended for people using corticosteroids, this is to prevent oral yeast infections that may result from getting corticosteroids in the mouth. Every MDI has a certain number of puffs contained in each canister. Even though the medication in the canister may be finished, it may continue to work but may not dispense any medication. So it is important you keep this in mind and promptly refill your medication to ensure you don’t run out.

• Dry powder inhaler (DPI)

• Dry powder inhaler (DPI) is a handheld device that delivers asthma medicine in dry powder form directly to the lungs. It may be used in place of a metered dose inhaler. To use a DPI, put the mouthpiece in your mouth, inhale a small actuated amount sharply and deeply making sure the medicine gets into your lungs. Hold your breath for about 5-8 seconds. Inhaling large quantities of the medicine will make you cough uncontrollably.It is required that you inhale the appropriate amount into the lungs, as such the efficacy of DPI’s depends on the individual’s inspiratory effort. This is why DPI is only recommended in older children and adults.

  Exposure to humidity and other elements reduce the effectiveness of the device and its ability to dispense the medicine in form of dry powder. Therefore, it is recommended to store DPI medicines in a dry place (temperature 22 °C).

• Nebulizers

A Nebulizer is a portable device that delivers asthma medicine in the form of mist into the lungs. Asthma medicines dispensed through nebulizers often come in liquid form. It is useful if you need to take a large dose of an inhaled medicine and highly effective in delivering asthma medications to infants, small children and adults with difficulty using an inhaler.

Asthma Medicines

Quick Relief Asthma Medicines

Medicines in this class are fast acting and relieve asthma symptoms when they occur. They act by opening up the airways by relaxing the smooth muscles in your airways. If you have to use any of these medicines more than 2 days in any given week, it is recommended that you visit your doctor for a review of your medications with your doctor.

• Short-acting beta agonists come in inhaled form. It is the first choice among the quick relief medicines. e.g Albuterol (trade names; AccuNeb, Proair HFA, Proventil HFA, Ventolin HFA), Metaproterenol, Levalbuterol (Xopenex HFA), Pirbuterol (Maxair)
• Anticholinergics are also in inhaled form. They are not as fast acting as the short-acting beta agonist medicines. They also reduce mucus production in the airways. e.g Atrovent MDI
• Combined quick relief medicines consists of  both a short-acting beta agonist and an anticholinergic. They often come as either an inhaler or nebulizer for inhalation. e.g  Combivent Respimat

Long Term Asthma Control Medicines

In contrast to the fast acting quick relief medicines, long term control medicines mostly prevent and control asthma symptoms. If prescribed, you’ll need to take it everyday to keep your asthma under control and prevent symptoms. There are several types:

• Inhaled corticosteroids. They prevent and reduce airway inflammation and excess mucus production. They are very popular as the most effective long-term control medicines. e.g Beclomethasone dipropionate(Qvar), Budesonide (Pulmicort), Fluticasone (Flovent), Fluticasone inh powder(Arnuity Ellipta), Mometasone (Asmanex).
• Inhaled long acting beta agonists. They keep the airways open by relaxing the smooth muscles. They are almost always used in combination with an inhaled corticosteroid. e.g Foradil (formoterol), Serevent (salmeterol), Perforomist (formoterol in solution form)
• Combination inhaled medicines. They consist of both an inhaled corticosteroid and a long-acting beta agonist. e.g Budesonide/Formoterol(Symbicort), Fluticasone/Salmeterol (Advair), Mometasone/formoterol(Dulera) 
• Oral corticosteroids. These come in pill or liquid form. Your doctor may prescribe them if your asthma is difficult to control with other commonly used medicines. e.g Prednisone (Orapred, Prelone), Hydrocortisone (Cortef)
• Biologics. They are taken as shots or infusions taken every few weeks. They work by prevent airway inflammation. They are very expensive and may be prescribed when other asthma medicines fail to control your symptoms.
• Leukotriene modifiers. They come in pill or liquid form. They reduce airway inflammation and relax the smooth muscles.e.g Montelukast (Singulair).
• Cromolyn sodium. They can be inhaled. They prevent airway inflammation.
• Theophylline. It may be taken orally, in the form of a tablet, capsule, syrup or solution. It keeps the airways open by relaxing the smooth muscles.

When To See The Doctor

See your doctor immediately if

• you have recurrent episodes of difficulty breathing, shortness of breath, unusual cough or wheezing that lasts for days.
• If you have been diagnosed with asthma but feel your symptoms are getting worse
• If you feel your medications are no longer working for you or you have to use your rescue inhaler more.

Asthma symptoms change over time. It is important to visit your doctor from time to time to review your medications.

References

1. Inhaler devices in asthma and COPD – An assessment of inhaler technique and patient preferences
   Chorão, Pedro et al. Respiratory Medicine , Volume 108 , Issue 7 , 968 – 975
2. Sawsan Baddar, B. Jayakrishnan & Omar A. Al-Rawas (2014) Asthma control: importance of compliance and inhaler technique assessments, Journal of Asthma, 51:4, 429-434, DOI: 10.3109/02770903.2013.871558