ABG Interpretation - LAB

Question 1

Normal values for ABGs

Answer 1

pH = 7.38 - 7.42 (or 7.35-7.45)
PaCO2 = 38 mmHg to 42 mmHg (or 35 to 45 mmHg)
PaO2 = 85 - 100 mmHg
HCO3 = 22 to 26 mmol/L
BE = +/- 2

Question 2

Respiratory Acidosis

Answer 2

1. Fundamental cause is INCREASE in PaCO2 > 42
   - most commonly due to hypoventilation
   - compensation by kidneys = increasing H+ secetion or reducing HCO3 secretion
   - compensation is slow - 3 to 4 days so you can get partially compensation resp. acidosis

Question 3

Respiratory Alkalosis

Answer 3

1. Fundamental cause = decrease in PaCO2 <38 mmHg
   - usually due to hyperventilation
   - compensation = secretion of HCO3- and/or retention of H+

Question 4

Henderson-Haselbach Equation

Answer 4

pH = pK + log HCO3-/0.03PaCO2

- understand the effect of raising HCO3 or PaCO2 or lowering HCO3 or PaCO2