Lab

Calculated PaCO2

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Calculated PaCO2, Winter's Formula

  • Calculation
  • Calculated PaCO2 in Respiratory Conditions
  1. Increase PaCO2 by 10 mmHg
    1. Acute Respiratory Acidosis: decreases pH 0.08
    2. Chronic Respiratory Acidosis: decreases pH 0.03
  2. Decrease PaCO2 by 10 mmHg
    1. Acute Respiratory Alkalosis: increases pH 0.08
    2. Chronic Respiratory Alkalosis: increases pH 0.03
  • Calculation
  • Calculated PaCO2 in Metabolic Conditions
  1. Metabolic Acidosis with expected compensation
    1. PaCO2 = 1.5 x HCO3 + 8 (+/- 2)
    2. PaCO2Delta = 1.2 x BicarbDelta
    3. PaCO2 will not typically drop below 10 mmHg in respiratory compensation
  2. Metabolic Alkalosis with expected compensation
    1. PaCO2 = 0.7 x HCO3 + 20 (+/- 1.5)
  1. Measured PaCO2 > Calculated PaCO2
    1. Metabolic Acidosis with Respiratory Acidosis
  2. Measured PaCO2 < Calculated PaCO2
    1. Metabolic Acidosis with Respiratory Alkalosis
  • Resources
  1. Calculate pCO2 from pH and Bicarbone (Refactored Henderson-Hasselbach to solve for pCO2 instead of pH)
    1. HendersonHasselbachReversed.html