Respiratory Case Study: Exercise Induced Asthma

Our Patient Mike

Mike is sitting in his athletic training suite feeling sorry for himself.  He moved from hot and humid southern Florida. He went to play soccer in the cold and dry air of the Utah mountains. He was a highly-recruited player.  All was well until he got sick with a miserable cold.  He soon recovered. Now he finds himself with a lingering dry cough. He struggles to catch his breath any time he exerts himself. This happens every day!  He also notices it has gotten worse toward the end of October, as the weather has become colder.  Every practice is a major effort for Mike; he is feeling fatigued even before getting to the field.  To make things worse, Mike feels out of shape. He also looks that way. His coach has been criticizing him for dogging it.

A few days later, Mike relays his story to JP, the headRounded proximal end that fits into the acetabulum of the hip bone. athletic trainer.  “I’m thinking my cold is coming back, or something else is wrong with me. When I’m just hanging out, like now, I feel fine. But as soon as I start to run I get winded and can’t stop coughing.  After I exercise outside, I get this tightness in my chest. It’s like I need to take a big breath, but I can’t.  I feel like my sides hurt, as if I’ve overworked my latissimus dorsiExtensor / Adductor Covers lower back; pulls arms down and back, ‘swimmer’s muscle’. muscles. 

The front of my neckNarrow region just below the head; common fracture site. hurts too.”  JP listens to Mike’s breathing sounds with his stethoscope, but hears nothing abnormal.  He reassures Mike that the lack of abnormal breathing sounds is good. Mike’s lungs sound completely healthy. This is expected for an athlete his age.  JP tells Mike to head out to soccer practice but to come back as soon as the symptoms return.  Twenty minutes later, Mike is back in the athletic training suite, audibly wheezing, coughing, and short of breath.   JP can see that Mike is using his sternocleidomastoidFlexor / Rotator From sternum and clavicle to skull behind the ear; turns and bends the head. muscle while breathing.

The team physician, Dr. McInnis, happens to be there and performs a complete physical exam.  He also does pulmonary function tests with Mike using spirometry.  He instructs Mike to take a maximal inhalation. Mike then exhale as forcefully and maximally as possible into the spirometer. This measures Mike’s forced vital capacity(FVC) – The maximum amount of air a person can forcibly exhale after a deep inhalation. (FVC).  Dr. McInnis measures the amount of air Mike can exhale in 1 second. This is also known as Mike’s forced expiratory volume in one second (FEV1).  He divides the FEV1 by the FVC. This calculates the proportion of Mike’s FVC that is exhaled in the first second.

Based on his findings, Dr. McInnis tells Mike he thinks he is experiencing exercise-induced bronchoconstriction, which is made worse by exertion. The doctor explains to Mike that his recent upper respiratory infection probably inflamed his airways. This inflammation makes them hypersensitive to cold and/or dry air.  When Mike exercises in the cold air in the morning, his sensitive airways temporarily constrict. This causes the symptoms he is experiencing.  Asthma is almost always a reversible condition.  Dr. McInnis prescribes two puffs of an inhaler, to be used 10 minutes before a bout of exercise in the cold.  The inhaler contains albuterol. This drug connects with beta-2 adrenergic receptorsReceptors that bind norepinephrine and epinephrine; divided into α (alpha) and β (beta) types with on the smooth muscle of the trachea and the bronchiThe large airways that branch from the trachea into the lungs, dividing into smaller bronchioles..  These receptorsProteins located on the surface or inside cells that bind specific molecules (e.g., neurotransmitter, also sensitive to epinephrineadrenaline): Fight-or-flight hormone from the adrenal medulla., cause relaxation of the smooth muscle and bronchodilation.

Spirometry Testing

Spirometry is performed by deeply inhaling. Then, one forcefully exhales into a spirometer. This device records the various measurements of lung function. Two measurements are crucial in the interpretation of spirometry results. The first is called the forced vital capacity (FVC). This measures lung size in liters. It represents the volume of air that can be exhaled after a deepAway from the surface of the body. inhalation. The second is the forced expiratory volume-one second (FEV1). This is a measure of how much air can be exhaled in one second following a deep inhalation. You will also see another number on the spirometry test results — the FEV1/ FVC ratio. This number represents the percent of the lung size (FVC) that can be exhaled in one second. For example, if the FEV1 is 4 and the FVC is 5, the FEV1/ FVC ratio is 4/5. That equals 80%. This means the individual can breathe out 80% of the inhaled air in the lungs in one second. 

Interpretations of spirometry results require a comparison between an individual’s measured value and the reference value. If the FVC and the FEV1 are within 80% of the reference value, the results are considered normal. The normal value for the FEV1/FVC ratio is 70% (and 65% in persons older than age 65). When compared to the reference value, a lower measured value corresponds to a more severe lung abnormality. 

Table 0	NORMAL	ABNORMAL
FVC and FEV1	Equal to or greater than 80%	Mild Moderate Severe	70-79% 60-69% less than 60%
FEV1/FVC	Equal to or greater than 70%	Mild Moderate Severe	60-69% 50-59% less than 50%

Restrictive lung diseases can cause the FVC to be abnormal. This means that the lung is restricted from filling to its normal capacity of air.  Tuberculosis causes scarring of the lung, making it lose its elasticity.  These reduce the maximum volume that can be inhaled. Chronic obstructive pulmonary disease (COPD) is an obstructive disease, as the name suggests. In this disease an incomplete exhale restricts the maximum volume able to be inhaled upon the next respirationThe process of gas exchange, including ventilation, external and internal respiration..

Asthma is an obstructive lung disease because the trachea, bronchi, and bronchiolesSmall airways branching from the bronchi that lead to alveoli; lack cartilage and control airflow wi have a smaller diameter. This limits the flow of air to the respiratory membrane, even though the lung tissue is undamaged. This is what our patient Mike is experiencing. Mike is a healthy, young, athlete. If Mike could inhale forever, his FVC would be just fine. The capacity of his lungs are not affect, the tubes delivering the air are.

Treatment of EIB

Pre-exercise medications

Doctors may prescribe a drug that you take before exercise to minimize or prevent exercise-induced bronchoconstriction.  How much time you need between taking the drug and exercising should be discussed. Drugs in this group include the following:

Short-acting ß-agonists are inhaled drugs that help cause bronchodilation of the trachea, bronchi, and bronchioles. They work similarly to how epinephrine from the adrenal medullaInner part of adrenal glands producing catecholamines (epinephrine, norepinephrine). functions in a sympathetic response. These are the most commonly used and generally most effective pre-exercise medications. Daily use of these medications is not recommended, however, because you may develop a tolerance to the drugs. 

Doctors may prescribe a long-term control drug along with a daily pre-exercise medication. This helps manage underlying chronic asthma. It also controlsVariables that remain constant to ensure a fair test. symptoms when pre-exercise treatment alone isn’t effective. Inhaled corticosteroids help suppress inflammation. You may need to use this treatment for up to four weeks before it will have maximum benefit. 

Combination inhalers contain a corticosteroid and a long-acting ß-agonist, a drug that relaxes airways. While these inhalers are prescribed for long-term control, your doctor may recommend use prior to exercise. 

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