Coughing
Mike is sitting in his athletic training suite feeling sorry for himself. He moved from Southern California to play soccer at Northern Minnesota University (NMU) as a highly recruited player. All was well until he got sick with a miserable cold. He soon recovered, but now he finds himself with a lingering dry cough and difficulty catching his breath any time he exerts himself, which is every day! He also notices it has gotten worse as the weather has become colder. To make things worse, Mike feels, and looks, like he's out of shape, so his coach has been criticizing him for dogging it. A few days later, Mike relays his story to JP, the head athletic trainer at NMU. "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." JP listens to Mike's breathing sounds with his stethoscope, but hears nothing abnormal. So he tells Mike to come back as soon as the symptoms return during soccer practice. Twenty minutes later, Mike is back in the athletic training suite, audibly wheezing, coughing, and short of breath. 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, including a forced vital capacity (FVC) and forced expiratory volume in one second (FEV1). He instructs Mike to take a maximal inhalation and then exhale as forcefully and maximally as possible into the spirometer. Based on his findings, Dr. McInnis tells Mike he thinks he is experiencing cold-induced bronchoconstriction (also called cold-induced asthma), which is made worse by exertion. The doctor explains to Mike that his recent upper respiratory infection probably inflamed his airways, making them hypersensitive and reactive to irritants, such as cold and physical exertion. When Mike exercises in the cold, autumn afternoons of Minnesota, his sensitive airways temporarily bronchoconstrict, causing the symptoms he is experiencing. Asthma is almost always a reversible condition. Dr. McInnis prescribes two puffs of an albuterol inhaler, to be used 10 minutes before a bout of exercise in the cold.
Discussion
1. Which of the following factors affect the mechanics of pulmonary ventilation? Explain.
• airway resistance
• lung compliance
• pulmonary blood flow
• alveolar surface tension
2. Under normal conditions airway resistance is highest in which segment of the conducting airway?
3. Which of these physical factors change during Mike’s cold-induced asthma? Explain
• airway resistance
• lung elasticity
• alveolar surface tension
• lung compliance
4. In order to maintain a normal air flow during inspiration while Mike is experiencing cold-induced asthma which of the following must happen?
a. decrease the pressure gradient between atmospheric and intrapulmonary pressure
b. decrease intrapulmonary pressure more than usual
c. decrease intrapleural pressure
d. increase intrapulmonary pressure
5. Dr. McInnis measured Mike's forced vital capacity (FVC). The vital capacity includes what three lung volumes?
6. Dr. McInnis wants to obtain Mike's greatest possible vital capacity measurements. Which of the following body positions should Mike assume?
a. lying on his stomach
b. lying on his back
c. standing
d. sitting on a chair
7. Mike's wheezing and shortness of breath is due to asthma, and obstructive pulmonary disease. Do the following data tend to confirm asthma? FEV1 = 55%; FVC = 65%. Explain
8. Albuterol is a selective beta-2 adrenergic agonist. The intended beta-2 adrenergic effect is ____________. The undesirable effect of beta-1 adrenergic stimulation is ____________.
9. Describe the relationship between intrapulmonary pressure, atmospheric pressure, and air flow during normal inspiration and expiration, referring to Boyle's law.
10. How does Mike's body make the necessary changes in intrapulmonary pressure to maintain normal air flow when he is experiencing cold-induced asthma?
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