1. An Approach For Spirometry and DLCO Interpretation

2. DL,CO INTERPRETATION
Interpreting the DL,CO, in conjunction with spirometry and lung volumes assessment, may assist in diagnosing the underlying disease.

3. DO NOT USE DLCO/VA or KCO Often Normal in Interstitial Lung Disease
DLCO Interpretation
Low DLCO with normal spirometry
Pulmonary Vascular Disease
Anaemia - correct for Hb
Early ILDs or early emphysema
Chronic pulmonary embolism
Primary pulmonary hypertension
Low DLCO with restriction
Interstitial Lung Disease
Low DLCO with obstruction
Emphysema
COPD
Lymphangioleiomyomatosis
DO NOT USE DLCO/VA or KCO
Often Normal in Interstitial Lung Disease

4. Possible Causes* of High DLCo
Intrapulmonary Haemorrhage
Asthma
Obesity ???
*DLCO is not always high in these patients

5. Adjustments of DL,CO for changes in haemoglobin and carboxyhaemoglobin are important, especially in situations where patients are being monitored for possible drug toxicity, and where haemoglobin is subject to large shifts (e.g.chemotherapy for cancer).

6. Adjusting DL,CO for lung volume using DL,CO/VA or DL,CO/TLC is controversial .
Conceptually, a loss of DL,CO that is much less than a loss of volume (low DL,CO but high DL,CO/VA) might suggest an extraparenchymal abnormality, such as a pneumonectomy or chest wall restriction.
whereas, a loss of DL,CO that is much greater than a loss of volume (low DL,CO and low DL,CO/VA) might suggest parenchymal abnormalities.

7. Degree of severity of decrease in diffusing capacity for carbon monoxide (DL,CO)
Degree of severity DL,CO % pred
Mild >60% and < LLN
Moderate –60%
Severe <40
% pred: % predicted; LLN: lower limits of normal

8. Interpretation Flow Chart
FEV1/FVC VC
Spirometry
Normal
DLCO PV
Disorder
TLC
Restriction
Obstruction
Obstructive &
Restrictive Defects
Chest wall or
Neuromuscular
Disorders
ILD or
Pneumonitis
Asthma or
Chronic
Bronchitis
Emphysema
Chest wall,
Disorders,
Asthma, or
ILD,
Pneumonitis, or
or high
Low
Normal or high

9. Assignment of severity for lung volume disorders
mild
moderate
severe VC
70-90%
50-70%
<50%
TLC
Rest.
Obst.
70-80% %
60-70% %
<60%
>150% RV
55-65% %
45-55% %
<45%
>250%
FRC %
>200%