Practice Questions -- Answers: Respiratory Ventilation

PRACTICE QUESTIONS -- ANSWERS:  Respiratory Ventilation

1. E. The external intercostals contribute to inspiration and thus affect IRV and TLC and VC. The internal intercostals contribute to forced expiration and thus affect ERV, TLC, and VC. Thus, none of the volumes listed would be normal.

2. C. Normal FEV-1 is 80% or more of VC. Since this child’s VC is 2.0 liters and 80% of 2.0 is 1.6, the FEV-1 should be in the range 1.6-2.0 liters.

3. D. Why is choice C incorrect? Answer: quiet expiration involves elastic recoil only and not active muscle contraction.

4. B. Surfactant reduces lung surface tension, thereby increasing lung compliance.

5. D. Activation of the beta-adrenergic receptors on bronchial smooth muscle cause smooth muscle relaxation, thus increasing airway diameter and reducing airway resistance.

6. D. In emphysema, airway resistance increases in expiration because of airway collapse; lung compliance increases due to loss of lung elastic tissue; intrapleural pressure increases (becomes less negative) because of the increased lung compliance. Of the choices listed, only FEV-1 decreases below normal.

7. B. At the end of inspiration, the lungs are the most stretched and therefore pull back the hardest, causing the intrapleural pressure to become the most negative.

8. A, Above Normal.  Normal RV in an adult male of average size is 1.2 liters.  What conditions might lead such a high residual volume?  (Hint:  consider the effects of emphysema.)

9. C, Normal.

10. B, Below Normal.  The normal range for PEF is 400-600 liters/minute, for an adult, with the exact value depending upon size, age, and sex.