Lab

Diffusing Capacity

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Diffusing Capacity, Diffusing Capacity of the Lung for Carbon Monoxide, DLCO

  • Background
  1. Capacity of lung to transfer gas across alveoli
  2. Alveoli exposed to Carbon Monoxide
  3. Measure disappearance of Carbon Monoxide from the lung
  • Technique
  • Single-Breath DLCO for patients at rest
  1. Patient takes a full Vital Capacity breath
  2. Inhalation mixture
    1. Carbon Monoxide 0.3% (Used to determine gas transfer)
    2. Helium 10% (Used to determine Lung Volume)
    3. Oxygen 21%
    4. Nitrogen 68%
  3. Breath held to Total Lung Capacity for 10 seconds
  4. Alveolar gas sample taken after washout
  5. Requires baseline Hemoglobin
    1. Results are adjusted based on the Hemoglobin level
    2. Corrected DLCO = DLCO / (0.07 x Hemoglobin)
  • Causes
  • Increased DLCO
  1. Asthma
  2. Left-to-right cardiac shunt
  3. Polycythemia Vera (see below)
  4. Pulmonary Hemorrhage
  • Causes
  • Falsely Abnormal DLCO (if Hemoglobin not 15 g/dl)
  1. See corrected DLCO for Hemoglobin Above
  2. Falsely elevated DLCO
    1. Polycythemia Vera
    2. Early Congestive Heart Failure
  3. Falsely reduced DLCO
    1. Anemia