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 finds himself with a lingering dry cough and difficulty catching his breath any time he exerts himself – a daily occurrence!  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 handing out, like now, I feel fine.  But as soon as I start to run, I get winded and can’t stop coughing.”  JP listened 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 bronchi-constrict, 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.

Please help answer these 2 questions:

1. In what way do the physical changes Mike need to make alter the pressures required for breathing?  

2. Albuterol is a selective beta-2 adrenergic agonist which means it specifically activates beta-2 adrenergic receptors on smooth muscle in the airways.  Describe adrenergic receptors and  name the neurotransmitter that binds to them.

Answer 1

Ans 1	The decrement in pressure gradient between atmosphere and intrapulmonary pressure causes a decrease in intrapulmonary pressure more than normal. A decrease in the intrapleural pressure tend to increase intrapulmonary pressure.
Ans 2	Albuterol is a selective beta -2 adrenergic agonist. It binds to beta 2 receptor and promotes release of epinephrine (and norepinephrine). It decreases smooth muscle contractility, hyper-reactivity of air ways and bronchodilation.