Question

I Can’t Stop Coughing: A Case Study on the Respiratory System

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.

Short Answer Questions:

1) Describe the relationship between intrapulmonary pressure, atmospheric pressure, and air flow during normal inspiration and expiration, referring to Boyle’s law.

2) Resistance varies in Mike’s conducting airways. Using your understanding of respiratory anatomy, explain where in his airway the resistance is highest and why.

3) Several physical factors that influence the efficiency of pulmonary ventilation are compliance, alveolar surface tension, and airway resistance. Briefly describe each factor and identify the one that is affecting Mike’s efficiency of breathing.

4) What must happen to Mike’s intrapulmonary pressure in order for him to maintain normal air flow during inhalation and exhalation when he is having one of his asthma attacks?

5) How does Mike’s body make the necessary changes in intrapulmonary pressure to maintain normal air flow when he is experiencing cold-induced asthma?

6) When Mike is experiencing an asthmatic attack, his forced vital capacity (FVC) is 65%, and his FEV1 is 65%. Are these values normal? Knowing how one performs FVC tests, explain these test results in Mike’s case. (Assume that Mike and the doctor have performed an accurate test.)

7) Albuterol is a selective beta-2 adrenergic agonist, which means it specifically activates beta-2 adrenergic receptors on smooth muscle in the airways. How does this improve Mike’s asthma?

Answer 1

Ans1. Boyle's law it's state that the pressure is inversely proportional to its volume at a contant temp.( Example gas in a container or in LPG )

The pressure inside the lungs is called intrapulmonary pressure, pressure of gas exerted on the external environment is atmospheric pressure. Inspiration is a process in which the intercoastal musclr and diaphragm involved, it is a active process. So Boyle's law says that when volume of a gas increse the the pressure decreass and vice versa. When the interpulmomany pressure rises up above the atmospheric pressure the air in the lungs flows out due the pressure gradient. Same when the interpulmomany pressure down than the atmospheric pressure the air flows in the with the help of inhalation.

ANS2. The resistance is varies according to the size of the airways, it has been seems medium or small size airways experience high resistance in comparison to large size airways as they possess Larger diameter.

Airway diameter continous to drop but due the greater cross sectional area of the small airway than the medium size airways the resistance is lower than medium size or other region.

Ans3. Compliance is the lungs ability to expand when air flows into it. It is doner with the help of the recoiling capacity of the lungs after exhalation. Compliance is affected by some diseases such as emphysema or fibrosis or pnemothorax etc.

Alveolar surface tension - the presence not surfactant the alveoli is able to expand and prevent the collapse of alveoli that why immature infant are injected with dexamethasone as they possess lacking of surfactant on the surface of alveolar film.

Airway resistance- it helps for flow of air in the lungs

In the Mike case the resistance increase which causes him the bronchospasm or constriction

Ans4. Air flow is directly proportional to pressure gradient and inversly propertional to resistance. When Pressure gradient increase the air flow is also increase and when resistance increases the air flow decreases.

during inhalation the, the air move in the lungs and intrapulmonary pressure is decrease and against the high resistance. During exhalation, the air flow out of the lungs and intrapulmonary pressure increase.

In the asthma attach the resistance increse due that the airflow Decreases and intrapulmonary pressure affected.

So the intrapulmonary pressure is increase with high resistance with low air flow, so proper airway the intrapulmonary pressure should be Decreases to man normal air flow.

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