Review Case

1. What type of acid-base disturbance occurred in the Emergency Room?

2. What is the PA02?

3. What is the A-a gradient and what does it tell you?

4. Give at least two mechanisms of hypoxemia in this situation.

5. What does the elevated HCO3 tell you?

Spirometry revealed the following:
FEV1 at 0100=0.5 L (pred 2.9 L); at 0800=0.7 L.
FVC at 0100=Unobt. (pred 3.9 L); at 0800=1.7 L.

Hospital Course

Arterial blood gases are drawn in the Emergency Room and oxygen (2 LPM) by nasal prongs is started.

Gases are repeated at 0300. You commence bronchodilators and begin trimethoprim/sulfamethoxazole.

A gram stain of sputum reveals many PMN's and some alveolar macrophages.

At 0800, the patient feels better, can raise some sputum and is able to sleep.

6. Why begin trimethoprim/sulfamethoxazole? What are the most common pathogens in acute exacerbations of chronic bronchitis?

7. Why did the PaC02 increase at 0300? Should any therapy be altered to diminish the hypercapnia? Should the patient be intubated?

8. Note that the hypoxemia originally presented is easily corrected. What does this suggest as the mechanism of the hypoxemia?

A review of old records reveal the followings:

PFT	1978	1980	1983
FEV1	1.3 L	1.1 L	0.82 L (pred 2.9 L)
FVC	3.0	2.9	1.96 (pred 3.95 L)
RV	3.1	3.4	5.0 (pred 1.6 L)
TLC	6.1	6.9	6.9 (pred 5.57 L)
DCO	10 ml/min/mmHg	20 (pred 20)

9. How does this patient's average yearly decline in FEV1 compare to the normal decline?

10. What do the PFT's say about the relationship of FVC to RV and TLC?

11. Is this patient more like the classic pink puffer (type A) or blue bloater (type B) with COPD? What are the differences in lung physiology between these extremes?

12. What are the mechanisms of slowing of forced expiration in emphysema? Chronic bronchitis? Asthma?

13. What is the driving pressure in terms of Palv, Pel and Ppl? What occurs in emphysema? Explain how this affects forced expiration.

14. Which portion of the expiratory flow-volume curve is effort dependent? Effort independent?

15. Why is the thorax expanded in emphysema?

16. What is the diffusing capacity of carbon dioxide (DCO) in pure chronic bronchitis? Asthma?

Suggested Reading:

1. Matthay, RA. Chronic Airway Diseases. Cecil Textbook of Medicine. 19th edition. WB Saunders Co, 1992, pp 386-394.
2. Murray, JF. Respiratory Failure. Cecil Textbook of Medicine. 29th edition. WB Saunders Co, 1992, pp 452-459.
3. Syllabus on COPD.