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Diffusing capacity for carbon monoxide

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DLCOorTLCO(diffusing capacityortransfer factor of thelungforcarbon monoxide(CO),[1]) is the extent to which oxygen passes from theair sacsof thelungsinto theblood.Commonly, it refers to the test used to determine this parameter. It was introduced in 1909.[2]

Mechanism

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This test involves measuring thepartial pressuredifference between inspired and expired carbon monoxide. It relies on the strong affinity and large absorption capacity ofred blood cellsfor carbon monoxide and thus demonstrates gas uptake by the capillaries that are less dependent oncardiac output.[3]The measurement of DLCOis affected by atmospheric pressure and/or altitude and correction factors can be calculated using the method recommended by the American Thoracic Society.[4]Expected DLCOis also affected by the amount of hemoglobin,carboxyhemoglobin,age and sex. The correction for hemoglobin is based on the method of Cotes[5][6]as recommended by the American Thoracic Society.

DLCOvs TLCO

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Generally DLCOis measured in "ml/min/kPa"and TLCOis measured in "mmol/min/kPa".

Factors affecting DLCO

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Decrease

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

  1. Hindrance in thealveolarwall. e.g.fibrosis,alveolitis,vasculitis
  2. Decrease of total lung area, e.g.Restrictive lung diseaseor lung resection (partial or total).
  3. Chronic obstructive pulmonary disease(Emphysema) due to decreased surface area in the alveoli, as well as damage to the capillary bed[7]
  4. Pulmonary embolism
  5. Cardiac insufficiency[8]
  6. Pulmonary hypertension
  7. Bleomycin(upon administration of more than 200 units)
  8. Anemia-due to decrease in blood volume
  9. Amiodaronehigh cumulative dose; more than 400 milligrams per day
  10. Afterchemotherapyandradiotherapy

However, many modern devices compensate for thehemoglobinvalue of the patient (taken by blood test), and excludes it as a factor in the DLCO interpretation.[citation needed]

Increase

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Factors that can increase the DLCOincludepolycythaemia,asthma (can also have normal DLCO) 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).[9]

Significance of results

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There is no universally recognized reference value range for DLCO as of 2017,[10]but values in the 80%-120% of predicted range based on instrument manufacturer standards are generally considered normal.[11]A DLCOof less than 60% predicted portends a poor prognosis for lung cancer resection.FEV1is of lesser prognostic value for lung resection survival.[12]

See also

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References

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  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.PMID16204605.
  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.PMID14609505.S2CID35335150.
  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.doi:10.1056/nejm198705213162103.PMID3574401.
  4. ^American Thoracic society, Single Breath Carbon Monoxide Diffusing Capacity (transfer factor) Recommendations for a Standard Technique- 1995 Update, Am J Respir Crit Care Med. 152 pp 2185-2198 (1995).
  5. ^J.E. Cotes 1993, Lung Function, 5th Edition., Blackwell Scientific Publications, London
  6. ^J.E. Cotes, J.M. Dabbs, P.C. Elwood, A.M. Hall, A. McDonald, and M.J. Saunders. Iron-deficiency anaemia: its effects on transfer factor for the lung (diffusing capacity) and ventilation and cardiac frequency during submaximal exercise. Clin. Sci. 42:325-33 (1972).
  7. ^Bailey, Kristina L. (1 July 2012)."The Importance of the Assessment of Pulmonary Function in COPD".The Medical Clinics of North America.96(4): 745–752.doi:10.1016/j.mcna.2012.04.011.ISSN0025-7125.PMC3998207.PMID22793942.
  8. ^Puri, Sundeep (1 Jun 1995). "Reduced Alveolar–Capillary Membrane Diffusing Capacity in Chronic Heart Failure".Circulation.91(11): 2769–2774.doi:10.1161/01.CIR.91.11.2769.PMID7758183.
  9. ^Ruppel, G. L. (2009).Manual of Pulmonary Function Testing.ISBN978-0-323-05212-2
  10. ^"2017 ERS/ATS standards for single-breath carbon monoxide uptake in the lung"(PDF).European Respiratory Journal.
  11. ^Nguyen, Lam-Phuong; Harper, Richart W.; Louie, Samuel (2016)."Using and Interpreting Carbon Monoxide Diffusing Capacity (Dlco) Correctly".Consultant.
  12. ^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 8:20AMdoi:10.1002/jso.21407
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