Presentation: A 14-year-old girl with cystic fibrosis has complained of an increased cough productive of green sputum over the last week. She also complained of being increasingly short of breath, and she is noticeably wheezing on physical examination.
Arterial blood was drawn and sampled, revealing the following values:
pH | 7.30 |
pCO2 | 50 mm Hg |
pO2 | 55 mm Hg |
Hemoglobin – O2 saturation | 45 % |
[HCO3-] | 24 meq / liter |
Normal Levels of Substances in the Arterial Blood:
pH | 7.40 |
pCO2 (partial pressure of carbon dioxide) | 40 mm Hg |
pO2 (partial pressure of oxygen) | 90 – 100 mm Hg |
Hemoglobin – O2 saturation | 94 – 100 % |
[HCO3-] | 24 meq / liter |
Questions: Choose one of the two sets of questions to serve as your initial response:
1. What causes cystic fibrosis? Describe the pathophysiologic mechanisms of the disease.
2. How would you classify this girl’s acid-base status?
3. How does cystic fibrosis cause this acid-base imbalance?
OR
1. How would the kidneys try to compensate for the girl’s acid-base imbalance?
2. This girl has also had a long history of diarrhea and poor weight gain. Explain why.
3. List some other causes of this type of acid-base disturbance.
