D
LCO or T
LCO (
diffusing capacity or transfer factor of the
lung for
carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
(CO),
) is the extent to which oxygen passes from the
air sacs
Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase in the pneumatization (presence ...
of the
lungs
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side ...
into the
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
. Commonly, it refers to the test used to determine this parameter. It was introduced in 1909.
Mechanism
This test involves measuring the
partial pressure difference between inspired and expired carbon monoxide. It relies on the strong affinity and large absorption capacity of
red blood cell
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...
s for carbon monoxide and thus demonstrates gas uptake by the capillaries that are less dependent on
cardiac output. The measurement of D
LCO is affected by atmospheric pressure and/or altitude and correction factors can be calculated using the method recommended by the American Thoracic Society. Expected D
LCO is also affected by the amount of hemoglobin,
carboxyhemoglobin
Carboxyhemoglobin (carboxyhaemoglobin BrE) (symbol COHb or HbCO) is a stable complex of carbon monoxide and hemoglobin (Hb) that forms in red blood cells upon contact with carbon monoxide. Carboxyhemoglobin is often mistaken for the compound fo ...
, age and sex. The correction for hemoglobin is based on the method of Cotes as recommended by the American Thoracic Society.
DLCO vs TLCO
Generally D
LCO is measured in "ml/min/
kPa
KPA may refer to:
* Keele Postgraduate Association, Keele University, UK, formerly Keele Research Association (KRA)
* Kensington (Olympia) station, London, England, National Rail station code
* Kenya Ports Authority
* ''Kiln phosphoric acid'', a ...
" and T
LCO is measured in "mmol/min/kPa".
Factors affecting DLCO
Decrease
D
LCO is decreased in any condition which affects the effective alveolar surface area:
# Hindrance in the
alveolar wall. e.g.
fibrosis
Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perma ...
,
alveolitis,
vasculitis
Vasculitis is a group of disorders that destroy blood vessels by inflammation. Both arteries and veins are affected. Lymphangitis (inflammation of lymphatic vessels) is sometimes considered a type of vasculitis. Vasculitis is primarily caused ...
# Decrease of total lung area, e.g.
Restrictive lung disease
Restrictive lung diseases are a category of extrapulmonary, pleural, or parenchymal respiratory diseases that restrict lung expansion, resulting in a decreased lung volume, an increased work of breathing, and inadequate ventilation and/or oxygenat ...
or lung resection (partial or total).
#
Chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by long-term respiratory symptoms and airflow limitation. The main symptoms include shortness of breath and a cough, which may or may not produce ...
(Emphysema) due to decreased surface area in the alveoli, as well as damage to the capillary bed
#
Pulmonary embolism
Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream ( embolism). Symptoms of a PE may include shortness of breath, chest pain particularly upon breathin ...
#
Cardiac insufficiency
#
Pulmonary hypertension
#
Bleomycin
-13- (1''H''-imidazol-5-yl)methyl9-hydroxy-5- 1''R'')-1-hydroxyethyl8,10-dimethyl-4,7,12,15-tetraoxo-3,6,11,14-tetraazapentadec-1-yl}-2,4'-bi-1,3-thiazol-4-yl)carbonyl]amino}propyl)(dimethyl)sulfonium
, chemical_formula =
, C=55 , H=84 , N=1 ...
(upon administration of more than 200 units)
# Anemia-due to decrease in blood volume
#
Amiodarone
Amiodarone is an antiarrhythmic medication used to treat and prevent a number of types of cardiac dysrhythmias. This includes ventricular tachycardia (VT), ventricular fibrillation (VF), and wide complex tachycardia, as well as atrial fibril ...
high cumulative dose; more than 400 milligrams per day
# After
chemotherapy
Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothe ...
and
radiotherapy
However, many modern devices compensate for the
hemoglobin
Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyt ...
value of the patient (taken by blood test), and excludes it as a factor in the DLCO interpretation.
Increase
Factors that can increase the D
LCO include
polycythaemia, asthma (can also have normal D
LCO) and increased pulmonary blood volume as occurs in exercise. Other factors are left to right intracardiac shunting, mild left heart failure (increased blood volume) and alveolar hemorrhage (increased blood available for which CO does not have to cross a barrier to enter).
Significance of results
There is no universally recognized reference value range for DLCO as of 2017, but values in the 80%-120% of predicted range based on instrument manufacturer standards are generally considered normal. A D
LCO of less than 60% predicted portends a poor prognosis for lung cancer resection.
FEV1 is of lesser prognostic value for lung resection survival.
[Diffusion lung capacity for carbon monoxide (DLCO) is an independent prognostic factor for long-term survival after curative lung resection for cancer (p n/a)
Michael J. Liptay, Sanjib Basu, Michael C. Hoaglin, Neil Freedman, L. Penfield Faber, William H. Warren, Zane T. Hammoud, Anthony W. Kim. ''Journal of Surgical Oncology''.
Published Online: Oct 1 2009 8:20AM ]
See also
*
Diffusing capacity
Diffusing capacity of the lung (DL) (also known as Transfer factor is another expression for the formerly used diffusing capacity.) measures the transfer of gas from air in the lung, to the red blood cells in lung blood vessels. It is part of a c ...
References
External links
*
{{DEFAULTSORT:Dlco
Diagnostic pulmonology
Respiratory physiology