SPIROMETRYDLCO(3)

Report
An Approach For
Spirometry and
DLCO Interpretation
DL,CO INTERPRETATION
Interpreting
the
DL,CO,
in
conjunction with spirometry and
lung volumes assessment, may
assist in diagnosing the underlying
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
Possible Causes* of High DLCo
 Intrapulmonary
Haemorrhage
 Asthma
 Obesity
???
*DLCO is not always high in these patients
 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).



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.
 Degree
of severity of decrease in
diffusing capacity for carbon
monoxide (DL,CO)

Degree of severity DL,CO

Mild
>60% and < LLN

Moderate
40–60%

Severe
<40
% pred: % predicted; LLN: lower limits of normal
% pred
Interpretation Flow Chart
FEV1/FVC
Normal
Low
VC
VC
Low
Low
Normal
TLC
Normal
TLC
Normal or high
Normal
or high
Low
Restriction
Spirometry
Normal
Normal
Low
Normal
or high
PV
Disorder
Chest wall or
Neuromuscular
Disorders
Obstructive &
Restrictive Defects
DLCO
DLCO
DLCO
Normal
or high
Obstruction
Low
Low
ILD or
Pneumonitis
Normal
or high
Asthma or
Chronic
Bronchitis
DLCO
Low
Emphysema
Normal
or high
Chest wall,
Neuromuscular
Disorders,
Asthma, or
Chronic
Bronchitis
Low
ILD,
Pneumonitis,
or
Emphysema
Assignment of severity for lung
volume disorders
volume
mild
VC
70-90%
50-70%
<50%
Rest.
Obst.
70-80%
60-70%
<60%
120-130%
130-150%
>150%
Rest.
Obst.
55-65%
45-55%
<45%
135-150%
150-250%
>250%
Rest.
Obst.
55-65%
45-55%
<45%
135-150%
150-200%
>200%
TLC
RV
FRC
moderate severe

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