DLCO

DLCO

DLCO (Diffusing capacity of the lung for carbon monoxide,[1]) is the extent to which oxygen passes from the air sacs of the lungs into the blood. Commonly, it refers to the test used to determine this parameter. It was introduced in 1909.[2]

Contents

Mechanism of The DLCO Test

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 erythrocytes for carbon monoxide and thus demonstrates gas uptake by the capillaries that are less dependent on cardiac output.[3]. The measurement of DLCO is affected by atmospheric pressure and/or altitude and correction factors can be calculated online. Expected DLCO is also affected by the amount of hemoglobin, age and sex and correction factors are available online.

Factors affecting DLCO

Decrease

DLCO is decreased in any condition which affects the effective alveolar surface area:

  1. Hindrance in the alveolar wall. e.g. fibrosis, alveolitis, vasculitis
  2. Decrease of total lung area, e.g. Restrictive lung disease.
  3. Uneven spread of air in lungs, e.g. emphysema.
  4. Pulmonary embolism
  5. Cardiac insufficiency
  6. Pulmonary hypertension
  7. Bleomycin (upon administration of more than 200 units)
  8. Anemia-due to decrease in blood volume

However, many modern devices compensates for the 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 DLCO include polycythaemia, asthma (can also have normal DLCO) and increased pulmonary blood volume as occurs in exercise or congestive heart failure. Other factors are left-to-right pulmonary shunting that occurs in left heart failure, alveolar hemorrhage, and smoking within 24 hours of the test. [4]

Factors affected by DLCO

Decrease

A DLCO of less than 60% predicted portends a poor prognosis for lung cancer resection. FEV1 is of lesser prognostic value for lung resection survival.[5]

References

  1. ^ Macintyre N, Crapo RO, Viegi G, et al. (October 2005). "Standardisation of the single-breath determination of carbon monoxide uptake in the lung". Eur. Respir. J. 26 (4): 720–35. doi:10.1183/09031936.05.00034905. PMID 16204605. http://erj.ersjournals.com/cgi/pmidlookup?view=long&pmid=16204605. 
  2. ^ Hughes J, Bates D (2003). "Historical review: the carbon monoxide diffusing capacity (DLCO) and its membrane (DM) and red cell (Theta.Vc) components". Respir Physiol Neurobiol 138 (2-3): 115–42. doi:10.1016/j.resp.2003.08.004. PMID 14609505. 
  3. ^ Sue DY, Oren A, Hansen JE & Wasserman K (1987). Diffusing capacity for carbon monoxide as a predictor of gas exchange during exercise. N. Engl. J. Med., 316(21):1301-1306.
  4. ^ Ruppel, G. L. (2009). Manual of Pulmonary Function Testing. ISBN 978-0-323-05212-2
  5. ^ 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 DOI: 10.1002/jso.21407

External links

v · d · eRespiratory system, physiology: respiratory physiology
Lung volumes

VC · FRC · Vt · dead space · CC · PEF

calculations: respiratory minute volume · FEV1/FVC ratio

methods of lung testing: spirometry · body plethysmography · peak flow meter · nitrogen washout
Airways/
ventilation (V)
Blood/
perfusion (Q)
Interactions/
ventilation/perfusion ratio (V/Q)
Control of respiration
Insufficiency

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