FIO2
PAO2
PaO2
PaCO2
A-a O2
difference
FIO2
helpful?
The Patient: a 59-year-old man
Principal Complaint: shortness of breath
Clinical Examination: This patient entered the emergency room of Brighton Medical Center complaining of shortness of breath. His heart rate was 112 beats/min with a blood pressure of 138/88 mm Hg. His respiratory rate was 35 breaths/min and his breathing was extremely labored. Loud breath sounds with crackling rales were heard over all lung fields. The patient had a rather ashen complexion and his nail beds gave clear evidence of cyanosis. A chest X-ray was ordered and an arterial blood sample showed a hemoglobin concentration of 16 gm/dl with a hematocrit of 52%, a PaO2 of 42 mm Hg and a PaCO2 of 64 mm Hg. The patient was placed in an oxygen tent; his complexion subsequently improved and the cyanosis disappeared.
One-half hour later the physician was called to the patient’s bedside by the nurse, who found the patient to be unresponsive. His respirations were quiet and shallow at a rate of 10 breaths/min. His heart rate was 140 beats/min with a blood pressure of 85/50. The patient was in a deep coma. A call to the laboratory to check the results of the blood tests revealed an arterial PO2 of 56 mm Hg, a PCO2 of 90 mm Hg, a hydrogen ion concentration of 48 nEq/l (pH 7.32), and a bicarbonate concentration of 45 mmol/l.
|
FIO2 |
PAO2 |
PaO2 |
PaCO2 |
A-a O2 |
|
| 21% | 70 | 42 | 64 | 28 |
-- |
| 30% | 101 | 56 | 90 | 45 |
No |
STUDY QUESTIONS:
1. Explain the dramatic change in this patient’s status after admission to the hospital, in the context of the chemical feedback control of minute ventilation. The patient was put on at least 30% of oxygen. This was enough to diminish her hypoxic drive to breath.
2. What type of therapy might have been more appropriate for this patient? Putting her on a much less concentration of oxygen. Start her out with no more than 0.5 l/min O2 by nasal canulla and see if there is an improvement.
3. From the laboratory values provided in the REFERENCE CASE, would you consider the pathophysiology underlying this patient’s condition as chronic or acute? Why? Chronic. On admittance she had an elevated PaCO2 and her A-a difference was high.
4. What would you predict for radiographic findings in this patient? Large diffuse areas from water accumulation.
Last Updated 09/06/01 08:53:27 PM
Return To The MNA 2001 Homepage