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27 Nov 2019

Mike is sitting in his

athletic training suite feeling sorry for himself. He movedfrom

Southern California to play soccer at Northern MinnesotaUniversity

(NMU) as a highly recruited player. All was well until he gotsick

with a miserable cold. He soon recovered, but now he findshimself

with a lingering dry cough and difficulty catching his breathany

time he exerts himself, which is every day! He also notices ithas

gotten worse as the weather has become colder. To makethings

worse, Mike feels, and looks, like he's out of shape, so hiscoach

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 wrongwith

me. When I'm just hanging out, like now, I feel fine. But assoon

as I start to run I get winded and can't stop coughing." JPlistens

to Mike's breathing sounds with his stethoscope, but hearsnothing

abnormal. So he tells Mike to come back as soon as thesymptoms

return during soccer practice. Twenty minutes later, Mike isback

in the athletic training suite, audibly wheezing, coughing,and

short of breath. The team physician, Dr. McInnis, happens tobe

there and performs a complete physical exam. He also doespulmonary

function tests with Mike using spirometry, including a forcedvital

capacity (FVC) and forced expiratory volume in one second(FEV1).

He instructs Mike to take a maximal inhalation and then exhaleas

forcefully and maximally as possible into the spirometer. Basedon

his findings, Dr. McInnis tells Mike he thinks he isexperiencing

cold-induced bronchoconstriction (also called cold-inducedasthma),

which is made worse by exertion. The doctor explains to Mikethat

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 thecold,

autumn afternoons of Minnesota, his sensitive airwaystemporarily

bronchoconstrict, causing the symptoms he is experiencing.Asthma

is almost always a reversible condition. Dr. McInnis prescribestwo

puffs of an albuterol inhaler, to be used 10 minutes before about

of exercise in the cold.

How does Mike's body make the necessary

changes in intrapulmonary pressure to maintain normal air flowwhen

he is experiencing cold-induced asthma?

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?

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?

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.

Describe the relationship between intrapulmonary pressure,atmospheric pressure, and air flow during normal inspiration andexpiration, referring to Boyle's law.

Resistance varies in Mike's conducting airways. Using yourunderstanding of respiratory anatomy, explain where in his airwaythe resistance is highest and why.

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