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

See Also
1. Pulmonary Function Test
2. Lung Volumes
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%
  2. Helium 10% (Used to determine Lung Volume)
3. Breath held to Total Lung Capacity for 5-10 seconds
4. Alveolar gas sample taken after washout
Causes of Decreased DLCO
1. Increased alveolar membrane thickness
  1. Interstitial pulmonary fibrosis
  2. Asbestosis
  3. Sarcoidosis
2. Decreased alveolar membrane area
  1. Pneumonectomy
3. Combination of factors
  1. Emphysema
  2. Bronchiolitis Obliterans with Organizing Pneumonia
Falsely Abnormal DLCO if Hemoglobin not 15 g/dl
1. Falsely elevated DLCO
  1. Polycythemia Vera
  2. Early Congestive Heart Failure
2. Falsely reduced DLCO
  1. Anemia
3. Corrected DLCO = DLCO / (0.07 x Hemoglobin)

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This page was written by Scott Moses, MD, and was last revised 1/26/2008. Please send comments and questions to the editor. Contact information may be found on the page About the Family Practice Notebook. These pages are best viewed with Microsoft Internet Explorer 5.0.