D_LCO or T_LCO ( diffusing capacity or transfer factor of the lung for

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

(CO),) is the extent to which oxygen passes from the air sacs of the

lungs The lungs are the primary organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the backbone on either side of the heart. Their function in the respiratory syste ...

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 is com ...

. Commonly, it refers to the test used to determine this parameter. It was introduced in 1909.

Mechanism

This test involves measuring the

partial pressure In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal g ...

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), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood cel ...

s for carbon monoxide and thus demonstrates gas uptake by the capillaries that are less dependent on

cardiac output In cardiac physiology, cardiac output (CO), also known as heart output and often denoted by the symbols Q, \dot Q, or \dot Q_ , edited by Catherine E. Williamson, Phillip Bennett is the volumetric flow rate of the heart's pumping output: tha ...

. 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 (chemistry), complex of carbon monoxide and hemoglobin (Hb) that forms in red blood cells upon contact with carbon monoxide. Carboxyhemoglobin is often mistaken ...

, age and sex. The correction for hemoglobin is based on the method of Cotes as recommended by the American Thoracic Society.

D_LCO vs T_LCO

Generally D_LCO is measured in "ml/min/

kPa The pascal (symbol: Pa) is the unit of pressure in the International System of Units (SI). It is also used to quantify internal pressure, stress, Young's modulus, and ultimate tensile strength. The unit, named after Blaise Pascal, is an SI ...

" and T_LCO is measured in "mmol/min/kPa".

Factors affecting D_LCO

Decrease

D_LCO is decreased in any condition which affects the effective alveolar surface area: # Hindrance in the alveolar wall. e.g. fibrosis, alveolitis,

vasculitis Vasculitis is a group of disorders that destroy blood vessels by inflammation. Both artery, arteries and veins are affected. Lymphangitis (inflammation of lymphatic vessels) is sometimes considered a type of vasculitis. Vasculitis is primarily c ...

# Decrease of total lung area, e.g. Restrictive lung disease or lung resection (partial or total). #

Chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by chronic respiratory symptoms and airflow limitation. GOLD defines COPD as a heterogeneous lung condition characterized by chronic respiratory s ...

(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 pulmonary artery, 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 dyspnea, shortness of breath, chest pain ...

# Cardiac insufficiency #

Pulmonary hypertension Pulmonary hypertension (PH or PHTN) is a condition of increased blood pressure in the pulmonary artery, arteries of the lungs. Symptoms include dypsnea, shortness of breath, Syncope (medicine), fainting, tiredness, chest pain, pedal edema, swell ...

# Bleomycin (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, ventricular fibrillation, and wide complex tachycardia, atrial fibrillation, and paroxys ...

high cumulative dose; more than 400 milligrams per day # After

chemotherapy Chemotherapy (often abbreviated chemo, sometimes CTX and CTx) is the type of cancer treatment that uses one or more anti-cancer drugs (list of chemotherapeutic agents, chemotherapeutic agents or alkylating agents) in a standard chemotherapy re ...

and

radiotherapy Radiation therapy or radiotherapy (RT, RTx, or XRT) is a treatment using ionizing radiation, generally provided as part of cancer therapy to either kill or control the growth of malignant cells. It is normally delivered by a linear particle ...

However, many modern devices compensate for the

hemoglobin Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. Hemoglobin ...

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

References

External links

* {{DEFAULTSORT:Dlco Diagnostic pulmonology Respiratory physiology