Laboratory Data

1. ABGs on room air. Significant hypoxemia suggests cardiac or pulmonary etiology. Relatively normal Pao2 suggests other causes (eg, methemoglobinemia, neurologic disorder, polycythemia). If cardiac cause is suspected, check response to 100% oxygen (hyperoxia test).

2. Hyperoxia test. Administer 100% oxygen to patient for 10-15 minutes, then obtain ABGs and compare to values previously obtained on room air.

a. In patients with cardiac disease, Pao2 will change little with 100% oxygen. Pao2 will remain < 125 mm Hg in cardiac disease.

b. Patients with pulmonary disease will respond to 100% oxygen with an increase in Pao2 to > 150 mm Hg.

c. In those with severe pulmonary disease or persistent pulmonary hypertension, Pao2 may not increase significantly.

3. CBC with differential. May demonstrate polycythemia (hematocrit > 65%), anemia, or evidence of infection.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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