Mike is sitting in his athletic training suite feeling sorry forhimself. He moved from Southern California to play soccer atNorthern Minnesota University (NMU) as a highly recruited player.All was well until he got sick with a miserable cold. He soonrecovered, but now he finds himself with a lingering dry cough anddifficulty catching his breath any time he exerts himself, which isevery day! He also notices it has gotten worse as the weather hasbecome colder. To make things worse, Mike feels, and looks, likehe's out of shape, so his coach has been criticizing him fordogging it.
A few days later, Mike relays his story to JP, the head athletictrainer at NMU. "I'm thinking my cold is coming back, or somethingelse is wrong with me. When I'm just hanging out, like now, I feelfine. But as soon as I start to run I get winded and can't stopcoughing." JP listens to Mike's breathing sounds with hisstethoscope, but hears nothing abnormal. So he tells Mike to comeback as soon as the symptoms return during soccer practice. Twentyminutes later, Mike is back in the athletic training suite, audiblywheezing, 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 expiratoryvolume in one second (FEV1). He instructs Mike to take a maximalinhalation and then exhale as forcefully and maximally as possibleinto the spirometer.
Based on his findings, Dr. McInnis tells Mike he thinks he isexperiencing cold-induced bronchoconstriction (also calledcold-induced asthma), which is made worse by exertion. The doctorexplains to Mike that his recent upper respiratory infectionprobably inflamed his airways, making them hypersensitive andreactive to irritants, such as cold and physical exertion. WhenMike exercises in the cold, autumn afternoons of Minnesota, hissensitive airways temporarily bronchoconstrict, causing thesymptoms he is experiencing. Asthma is almost always a reversiblecondition. Dr. McInnis prescribes two puffs of an albuterolinhaler, to be used 10 minutes before a bout of exercise in thecold.
Short Answer Questions
1. Describe the relationship between intrapulmonary pressure,atmospheric pressure, and air flow during normal inspiration andexpiration, referring to Boyle's law.
2. Resistance varies in Mike's conducting airways. Using yourunderstanding of respiratory anatomy, explain where in his airwaythe resistance is highest and why.
3. Several physical factors that influence the efficiency ofpulmonary ventilation are compliance, alveolar surface tension, andairway resistance. Briefly describe each factor and identify theone that is affecting Mike's efficiency of breathing.
4. What must happen to Mike's intrapulmonary pressure in order forhim to maintain normal air flow during inhalation and exhalationwhen he is having one of his asthma attacks?
5. How does Mike's body make the necessary changes inintrapulmonary pressure to maintain normal air flow when he isexperiencing cold-induced asthma?
6. When Mike is experiencing an asthmatic attack, his forced vitalcapacity (FVC) is 65%, and his FEV1 is 65%. Are these valuesnormal? Knowing how one performs FVC tests, explain these testresults in Mike's case. (Assume that Mike and the doctor haveperformed an accurate test.)
7. Albuterol is a selective beta-2 adrenergic agonist, which meansit specifically activates beta-2 adrenergic receptors on smoothmuscle in the airways. How does this improve Mike's asthma?
