A 17-year-old student has experienced reversible, periodic attacks of chest tightness with coughing, wheezing, and hyperpnea. She states that expiration is more difficult than inspiration. She is most comfortable sitting forward with arms leaning on some support. X-rays revealed mild overinflation of the chest. Results from laboratory and pulmonary function tests are as follows: • Frequency 20 breaths/min
• Vital capacity (VC) 2.9 L
• FEV1.0 1.4 L
• FEV1.0/FVC 56%
• Functional residual capacity (FRC) 3.89 L
• Total lung capacity (TLC) 6.82 L
• PaO2 70 mm Hg
• PaCO2 26 mm Hg
• Pulse 108 beats/min
• BP 120/76 mm Hg
Intermittent use of a bronchial smooth muscle dilator (1:1000 epinephrine by nebulizer) for several days caused marked improvement, resulting in the following laboratory and pulmonary function tests:
• VC 4.15 L
• FEV1.0 3.1 L
• FEV1.0/FVC >75%
• FRC 3.7 L
• TLC 5.96L
• PaO2 89 mm Hg
• PaCO2 38 mm Hg
• Pulse 129 beats/min BP 122/78 mm Hg
1. What is the disorder of this 17-year-old student?
2. Is this primarily a restrictive or an obstructive disorder? Why?
3. Write the formula for determining residual volume (RV).
4. Determine the residual volume (RV) before and after the use of the bronchodilator.
a. RV before using the bronchodilator:b. RV after using the bronchodilator:
5. Why is expiration more difficult than inspiration in this person?
6. What does the change in pulmonary function after the bronchodilator therapy indicate?
7. Why does the bronchodilator exaggerate the tachycardia?
8. What causes the hypoxemia and the hypocalcemia in this person?
9. A beta2-adrenergic agent was prescribed for further use because it has less cardio stimulatory (beta1) effect. Based on your knowledge of beta1 and beta2 receptors, why is this a good suggestion?
10. An anticholinergic agent was also suggested as a possible nebulizer agent. How might this helps the breathing problem?