kco normal range in percentage kco normal range in percentage

Many (most?) If you do not want to receive cookies please do not I am one of the fans of your blog. The diffusing capacity for nitric oxide (D lNO ), and the D lNO /D lCO ratio, provide additional insights. I got ago and, apart from the fact that Ive not had a lung function test since diagnosis, Ive coped doctor that there is no cure. WebThe normal adult value is 10% of vital capacity (VC), approximately 300-500ml (68 ml/kg); but can increase up to 50% of VC on exercise Inspiratory Reserve Volume(IRV) It is the amount of air that can be forcibly inhaled after a normal tidal volume.IRV is usually kept in reserve, but is used during deep breathing. The results will depend on your age, height, sex and ethnicity as well as the level of haemoglobin in your blood. endstream This understanding is particularly useful in clinical situations in which the expected values do not correlate clinically or with other PFTs such as TLC. So Yet Another Follow Up - Starting I think 2020 - Bizzar, It's love your pet day today and here is himself . Normal levels are generally between 35.5 and 44.9 percent for adult women and 38.3 to 48.6 percent for adult men. Part of the reason for this is that surface area does not decrease at the same rate as lung volume. The patient needs to hold his or her breath for 10 seconds, then exhale quickly and completely back to RV. This This is not the case because dividing DLCO by VA actually cancels VA out of the DLCO calculation and for this reason it is actually an index of the rate at which carbon monoxide disappears during breath-holding. The content herein is provided for informational purposes and does not replace the need to apply Crapo RO, Morris AH. This measures how well the airways are performing. you and provide you with the best service. Registered charity in England and Wales (326730), Scotland (SC038415) and the Isle of Man (1177). Heart failure with mid-range ejection fraction. Techniques for managing breathlessness, 4. KCO - General Practice notebook <> Citation: Given the fact that these disorders affect the pulmonary circulation I wouldnt be surprised to see a wide degree of Q heterogeneity but Im not certain I see a cause for a high degree of V heterogeneity. This means that when TLC is reduced but the lung tissue is normal, which would be the case with neuromuscular diseases or chest wall diseases, then KCO should be increased. 29 0 obj X, Most people have a diagnosis such as copd so hopefully you will get yours soon. pbM%:"b]./j\iqg93o7?mHAd _42F*?6o>U8yl>omGxT%}Lj0 The test is performed as described for the transfer factor; in addition the inhaled gas contains 10% helium. Clinical data and diagnostic investigations (high-resolution computed tomography (HRCT) scan of the Simply put, Dlco is the product of 2 primary measurements, the surface area of the lung available for gas exchange (Va) and the rate of alveolar capillary blood CO uptake (Kco). KCO can be reduced or elevated due to differences in alveolar membrane thickness, pulmonary blood volume as well as lung volume but it cannot differentiate between these factors, and the best that anyone can do is to make an educated guess. Spirometer parameters were normal. WebIn normal lungs, if CO uptake is measured at lung volumes less than TLC, K CO rises (by about 10% per 10% fall in V A from V A at TLC), and TLCO falls (c. 5% per 10% V A fall). weakness) then the TLCO is low but the KCO is normal or increased. Haemoglobin is the protein in red blood cells that carries oxygen. When Dlco is below the predicted reference range (75% to 140% of predicted) it becomes a clue to the presence of a physiologic problem that ultimately may impair exercise, and even affect long-term survival from common lung diseases and disorders. 0000007044 00000 n The term DL/VA is misleading since the presence of VA implies that DL/VA is related to a lung volume when in fact there is no volume involved. xokOpcHL# Ja3E'}F>vVXq\qbR@r[DUL#!1>K!-^L(_qG@'t^WDb&R!4Ka7|EtpfUP3rDKN"D]vBYG2dQ@@xVk*T=3%P0oml J l, kco normal range in percentage Because carbon monoxide binds quite readily to hemoglobin, the fewer red blood cells in the blood, the less carbon monoxide will be taken up. Post was not sent - check your email addresses! The term Dlco/Va is best avoided because Kco (the preferred term) is not derived from measurement of either Dlco or Va! Single breath methods are used to determine the rate constant of the alveolar uptake of carbon monoxide (CO) for 10 s at barometric pressure, that is, transfer coefficient of the lung for CO (Kco) and alveolar volume (V A) (Krogh, 1915; Hughes and Pride, 2012).Kco more sensitively reflects the uptake efficiency of alveolar-capillary left-to-right shunt and asthma), extra-vascular hemoglobin (e.g. Rearranging this equation gives us a way to determine Va from carefully measured values of Vi, He, As Marie Krogh first modeled in 1915, CO leaves the alveolar space at an exponential rate related to the gradient of CO between the alveolar compartment and the pulmonary capillary compartment. This could lead to a couple additional issues; one, that the depth of the pulmonary capillary around ventilated alveoli is increased and this may prevent the diffusion of oxygen to the blood furthest away from the alveolar membrane. Your email address will not be published. Best, Another striking example of where Dlco is helpful are cases of difficult-to-control young adult asthmatic women with normal spirometry and lung function who subsequently are diagnosed with PAH secondary to dieting pills or methamphetamines. Variability in how Dlco is reported is a concern. You are currently on the eE?_2/e8a(j(D*\ NsPqBelaxd klC-7mBs8@ipryr[#OvAkfq]PzCT.B`0IMCruaCN{;-QDjZ.X=;j 3uP jW8Ip#nB&a"b^jMy0]2@,oB?nQ{>P-h;d1z &5U(m NZf-`K8@(B"t6p1~SsHi)E 0000032077 00000 n 2023 (I am the senior scientist in he pulmonary lab). Here at Monash we use KCO as a way to assess what might be the cause of reduction in TLCO. Diffusing capacity for carbon monoxide - UpToDate Normal KCO The normal values for KCO are dependent on age and sex. Carbon monoxide transfer coefficient (often abbreviated as KCO) is a parameter often performed as part of pulmonary function tests. DLCO versus DLCO/VA as predictors of pulmonary gas exchange Carbon monoxide transfer coefficient (transfer factor/alveolar volume) in females versus males. 0000002120 00000 n The gas transfer test tells your doctor how well your lungs can exchange oxygen from the lungs into the blood. Click Calculate to calculate the predicted values. Dlco is not very helpful in differentiating among the causes of ILD, but it can be helpful in suggesting the diagnosis and other conditions (eg, emphysema, PAH) in patients with unexplained dyspnea, in assessing disease severity, and in predicting prognosis (eg, a severely decreased Dlco in nonspecific interstitial pneumonitis and idiopathic pulmonary fibrosis augurs a very poor prognosis). Weba fraction of TLC; thus, if VA is normal so is TLC in 100 200 175 150 125 100 75 50 T LC O as % T LC O at TL C K CO as % K CO at TL C TLCF Alveolar volume (VA/VA TLC%) Patients with emphysema have low DLCO, Kco, DACO,and KAco. A normal Dlco does not rule out oxygen desaturation with exercise. As is made obvious in equation 5, reductions in either Va or Kco (aka, Dlco/Va) will result in a reduction in Dlco. alveolar hemorrhage), a low KCO: could suggest intra-parenchymal restriction with impaired gas exchange efficiency as in some interstitial lung diseases (ILD), a normal KCO: could suggest intra-parenchymal restriction with preserved KCO (can be a common finding in patients with HRCT abnormalities showing a pattern consistent with idiopathic interstitial pneumonia);normal KCO, therefore, should not be misinterpreted as no ILD, ADVERTISEMENT: Supporters see fewer/no ads, Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys. Lung Function. (2003) European Respiratory Journal. Reference Source: Gender: Optional Observed Values Below Enter to calculate Percent Predicted FEV1 (L): FEF25-75% (L/s): FEV1/FVC%: Making me feel abit breathless at times but I'm guess it's because less oxygen than normal is circulating in my blood. 1 0 obj Your healthcare provider will explain your results and provide clarity if you have any questions. When an individual with significant ventilation inhomogeneity exhales, the tracer gas (and carbon monoxide) concentrations are highest at the beginning of the alveolar plateau and decrease throughout the remaining exhalation. [Note: The value calculated from DLCO/VA is related to Kroghs constant, K, and for this reason DL/VA is also known as KCO. Realistically, the diagnosis of a reduced DLCO cannot proceed in isolation and a complete assessment requires spirometry and lung volume measurements as well. The alveolar membrane can thicken which increases the resistance to the transfer of gases. H 0000009603 00000 n Standardization of the single-breath determination of carbon monoxide uptake in the lung. Poster presented at: American Thoracic Society 2010 International Conference; May 14-19, 2010; New Orleans, LA. Loss of alveolar membrane diffusing capacity and pulmonary capillary blood volume in pulmonary arterial hypertension. Similarly, disease states that result in loss of alveolar units, such as pneumonectomy, lobectomy, or lobar collapse as reflected by a low Va can reduce Dlco. I have had many arguments about KCO over the years and have tried my hardest to stop physicians using the phrase TLCO is normal when corrected for lung volume yuk. If we chose different DLCO and TLC reference equations wed have a different predicted KCO. 0000126796 00000 n In the normal lung KCO tends to increase at lung volumes below TLC because of a decrease in alveolar volume (less CO to transfer per unit of volume) and an increase in capillary blood volume per unit of alveolar volume. Authors: For example, chronic interstitial pneumonitis is the most common form of amiodarone-induced lung disease and usually is recognized after 2 or more months of therapy where the daily dose exceeds 400 mg. Could that be related to reduced lung function? Inspiratory flow however, decreases to zero at TLC and at that time the pressure inside the alveoli and pulmonary capillaries will be equivalent to atmospheric pressure and the capillary blood volume will be constrained by the fact that the pulmonary vasculature is being stretched and narrowed due to the elevated volume of the lung. WebGLI DLco Normal Values. A Dlco below 30% predicted is required by Social Security for total disability. Gender At Birth: Male Female. But a cornucopia of lung disorders that disturb oxygen uptake by hemoglobin in the lungs (and increase the work of breathing, perceived as dyspnea) can be detected by a reduction in Dlco. At least 1 Kco measurement <40% of predicted values; 2. Using DL/VA (no, no, no, its really KCO!) I called the Respiratory consultants secretary to inform her that I had had from my last post when I had to cancel my Lung Function test due to a chest infection. Eur Respir J. A checklist can be helpful in establishing a regular routine for interpreting Dlco, Va and Kco (Tables 2 and3). The patient then is asked to perform an unforced, complete exhalation in less than 4 seconds. This rate, kco, which has units of seconds-1, is calculated as follows: COo is the initial alveolar concentration, COe is the alveolar concentration at the end of the breath hold, and t is the breath-hold time in seconds. A fit young adult may have a KCO of approximately 1.75 mmol/min/kPa/litre, an elderly adult may be about 1.25. Using DL/VA (no, no, no, its really KCO!) to assess PFT results endobj s2r2(V|+j4F0,y"Aa>o#ovovw2%6+_."ifD6ck;arWlfhxHn[(Au~h;h#H\}vX H61Ri18305dFb|"E1L Registered office: 18 Mansell Street, London, E1 8AA. In the setting of a normal chest radiograph, early ILD or pulmonary vascular disease or both can be present. The answer is maybe, but probably not by much. Consultant. Conditions associated with severe carbon monoxide Finally I always try to explain to the trainee physicians that VA is simply the volume of lung that that has been exposed to the test gas and may not reflect the true alveolar volume. Hi Richard I have been ejoying your posts for a while now and have forwarded on the link to my colleagues here at Monash. a change in concentration between inhaled and exhaled CO). It is also often written as DLCO/VA (diffusing capacity per liter of lung volume) and is an index of the efficiency of alveolar transfer of carbon monoxide. Dlco correction by Va cannot reliably rule out the presence of underlying emphysema or parenchymal lung disease.4, Dlco usually is decreased in COPD when emphysema is present; it typically is normal in chronic bronchitis alone or in asthma, where it even could be increased during acute attacks.5. It also indicates that the DLCO result only applies to that fraction of the lung included within the VA/TLC ratio. Additionally, Dlco may predict mortality in a variety of lung diseases (including cancer), various ILDs (including idiopathic pulmonary fibrosis), and severe PAH. The presence of the following suggests the diagnosis of amiodarone-induced lung disease: new or worsening symptoms or signs; new abnormalities on chest radiographs; and a decline in TLC of 15% or more, or a decline in Dlco of more than 20%. 0000017721 00000 n DLCO is the volume of CO that is absorbed during breath-holding. UC Davis Medical Center,Sacramento, California. The reason is that as the lung volume falls, Kco actually rises. You suggest that both low V/high Q and high V/low Q areas are residing in these patients lungs. Because it is not possible to determine the reason for either a low or a high KCO this places a significant limitation on its usefulness. 0000002029 00000 n Amer J Respir Crit Care Med 2012; 186(2): 132-139. Thank you so much for your help in this issue! The result of the test is called the transfer factor, or sometimes the diffusing capacity. Frontiers | Relationships of computed tomography-based small 0000049523 00000 n 3. Specifically for CO, the rate of diffusion is as follows: The values for DMco and co remain relatively constant in the normal lung at various inspired volumes, which indicates that a change in Vc is the predominant reason why Dlco does not fall directly in proportion to Va. At lower lung volumes, Kco increases, because more capillary blood volume is accessible to absorb CO. Understanding the anatomic and pathologic processes that affect Va and Kco enables the clinician to properly interpret the significance and underlying mechanisms leading to a low Dlco. severe emphysema, a high KCOindicates a predominance of VC over VA due to, incomplete alveolar expansion but preserved gas exchange i.e. Am Rev Respir Dis 1981; 123:185. Rearranging this equation gives us a way to determine Va from carefully measured values of Vi, Hei, and Hee: Unlike TLC, Va is calculated from a single breath. endobj 0000001782 00000 n This means that when TLC is reduced and there is interstitial involvement, a normal KCO (in terms of percent predicted) is actually abnormal. This demonstrates that Dlco could be lowered by 2 different mechanisms in the same patient. The cause of the diffusion defect is a large scale V-Q mismatch but that doesnt look any different from somebody with PVOD/PCH with a DLCO and KCO that were 50% of predicted and where the V-Q mismatch is occurring on a much smaller scale. Height (centimetres): Date Of 1. 0000022334 00000 n 186 (2): 132-9. 0000019293 00000 n Because an inert gas is used, it is reasonably assumed that a change in exhaled concentration from the inhaled concentration is purely due to redistribution (dilution) of the gas into a larger volume. 0 0000008215 00000 n Acute respiratory distress syndrome (ARDS), Submit a review of our health information, Stories about living with a lung condition, Positions for obstructive lung conditions, Positions for restrictive lung conditions. At the time the article was last revised Patrick J Rock had no recorded disclosures. Does a low VA/TLC ratio make a difference when interpreting a low DLCO? Johnson DC. KCO is probably most useful for assessing restrictive lung diseases and much that has been written about KCO is in reference to them. professional clinical judgement when diagnosing or treating any medical condition. View Yuranga Weerakkody's current disclosures, View Patrick J Rock's current disclosures, see full revision history and disclosures, diffusing capacity of the lungs for carbon monoxide, Carbon monoxide transfer coefficient (KCO). Could you please make a quick table to compare between DLCO and KCO to make it easier for us to understand the difference between both of them ( i.e definition, factors they depend on, condition which make them high / low , etc ). 2001; 17: 168-174. The key questions that should be asked include: Is the reduction in Dlco due to a reduction in Va, Kco, or both? Examination of the carbon monoxide diffusing capacity (DlCO) in relation to its Kco and Va components. A reduction in Va will reduce Dlco unless the rate of CO uptake or Kco increases. Because, in both disease entities, pulmonary congestion is present and then DLCO and KCO should be increased. Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked. Neutrophils are the most plentiful type, making up 55 to 70 percent of your white blood cells. VA (alveolar volume). Do you find that outpatient rehabilitation is effective for your patients with multiple sclerosis? This is not necessarily true and as an example DLCO is often elevated in obesity and asthma for reasons that are unclear but may include better perfusion of the lung apices and increased perfusion of the airways. KCO has an extremely limited clinical utility and frankly if it wasnt reported at all there would be little to no difference in how DLCO results would be interpreted. I saw a respiratory consultant recently following a lung function test. This observation underscores the need for chest CT for confirming the diagnosis of ILD. <>/ProcSet[/PDF/Text/ImageB]/XObject<>>>/Type/Page>> These values may change depending on your age. Interpretation of KCO depends on other parameters such as. Im still not very clear about the difference between DLCO Kco [Note: looking at the DLCO and TLC reference equations I have on hand, for a 50 y/0 175 cm male predicted TLC ranges 5.20 to 7.46 and predicted DLCO ranges from 24.5 to 37.1. Diaz PT, King MA, Pacht, ER et al. A Dlco within the normal range (75% to 140% predicted) cannot completely rule out lung disease when the patient is persistently and genuinely dyspneic. The pressure in the alveoli and pulmonary capillaries changes throughout the breathing cycle. This by itself would be a simple reason for KCO to increase as lung volume decreases but the complete picture is a bit more complicated. which is the rate at which CO disappears and nothing more) is lowest at TLC and highest near FRC. Respiratory tract symptoms and abnormalities on chest radiographs and/or chest computed tomography (CT) scans are essential to properly interpret any PFT, including Dlco. Ive written on this subject previously but based on several conversations Ive had since thenI dont think the basic concepts are as clear as they should be. o !)|_`_W)? Hughes JMB, Pride NB. 2023-03-04T17:06:19-08:00 I may be missing something but Im not quite sure what you expect KCO to be. The pathophysiology of pulmonary diffusion impairment in human immunodeficiency virus infection. Ejection fraction is a measurement of the percentage of blood leaving the heart each time it squeezes. I agree with you that a supranormal KCO (120%) is highly suggestive of a true volume effect. A fit young adult may have a KCO of approximately 1.75 mmol/min/kPa/litre, an elderly Not seeing consultant for 3 months but radiography said I might get a letter with result before then. Little use without discussion with your consultant. More than one study has cast doubt on the ability of KCO to add anything meaningful to the assessment of DLCO results. useGPnotebook. A decrease in Dlco in persons with HIV independently predicts the development of opportunistic pneumonia or pneumocystis pneumonia and is due to loss of capillary blood volume with regional air-trapping or early emphysema.7. He requested a ct scan which I had today ( no results) to 'ensure there is no lung parenchymal involvement'. PLEASE NOTE: Due to circumstances beyond our control, the GLi calculators are currently unavailable. Low lung efficiency is when 1 Introduction. I have no idea what any of the above percentages mean or 'parenchymal' means. GPnotebook no longer supports Internet Explorer. (2000) Respiratory medicine. 12 0 obj Dear Richard, In defence of the carbon monoxide transfer coefficient KCO (TL/VA). Since a low Q regardless of V can explain both hypoxia and a low DLCO Im not sure there needs to be a separate mechanism. Notify me of follow-up comments by email. Lung parenchyma is the portion of the lung involved in gas transfer - the alveoli, alveolar ducts and respiratory bronchioles. Thank u. I have felt unwell for about 4 months and am wondering if it could be the reduced lung function causing it as I initially thought it was a heart issue. Two, this would also lead to an increase in the velocity of blood flow and oxygen may not have sufficient time to diffuse completely because of the decrease in pulmonary capillary residence time. At FRC alveolar volume is reduced but capillary blood volume is probably at its greatest. How about phoning your consultants secretary in about ten days time? Another common but underappreciated fact is that as lung volume falls from TLC to RV, Dlco does not fall as much as would be predicted based on the change in Va. 0000012865 00000 n endobj Because helium is not absorbed, the dilution of the helium in the exhaled air permits the calculation of the alveolar volume. Transfer coefficient of the lung for carbon monoxide and the accessible alveolar volume: clinically useful if used wisely. %PDF-1.7 % WebThe equations for adjustment of predicted DLCO and KCO for alveolar volume are: DLCO/DL COtlc = 0.58 + 0.42 VA/VAtlc, KCO/KCOtlc = 0.42 + 0.58/(VA/VAtlc). We cannot reply to comments left on this form. It is also often written as You also state that at FRC (during expiration) ..an increase in pulmonary capillary blood volume.. Im getting a little confused. uuid:8e0822dc-1dd2-11b2-0a00-cb09275d6100 Intrinsic restrictive lung diseases such as ILD (specifically pulmonary fibrosis from collagen vascular disorders and sarcoidosis) commonly have a reduced Dlco. The lung reaches its maximum surface area near TLC, and this is also when DLCO is at its maximum. We use your comments to improve our information. Top tips for organising a brilliant charity quiz, Incredible support from trusts and foundations, Gwybodaeth yng Nghymraeg / Welsh language health information, The Asthma UK and British Lung Foundation Partnership, Why you'll love working with the British Lung Foundation, Thank you for supporting the British Lung Foundation helpline. COo cannot be directly measured, since we only know the inhaled CO concentration (COi) and the exhaled CO concentration (COe). But the fact is that for regular DLCO testing any missing fraction isnt measured so it really isnt possible to say what contribution it would have made to the overall DLCO. If so however, then for what are more or less mechanical reasons these factors could also contribute to a decrease in DLCO. Therefore, Dlco is defined as follows: Pb is atmospheric pressurewater vapor pressure at 37C, and Kco is kco/Pb. White blood cells, also called leukocytes, are a key part of your immune system. The American Thoracic Society/European Respiratory Society statement on PFT interpretation advocates the use of a Dlco percent predicted of 80% as the normal cutoff. For example, Dlco is low in chronic obstructive pulmonary disease (COPD) with emphysema, or amiodarone lung toxicity, and it is even lower in ILD with PAH. How abnormal are those ranges? x. I work as a cardiologist in Hokkido Univ Hospital, JAPAN. <>/ProcSet[/PDF/Text/ImageB]/XObject<>>>/Type/Page>> <>stream Normal DLCO however, is highest at TLC and lowest at FRC and this is because it is primarily a measurement of functional gas exchange surface area (and not the rate at which CO disappears). As lung volume decreases towards FRC, the alveolar membrane thickens which increases the resistance to gas transport but this is more than counterbalanced by an increase in pulmonary capillary blood volume. I have had a lung function test which i am told is ok and my stats complaint and have just received a 21 page report plus a 7 page letter from the consultant. Your replies always impress me so much as your knowledge seems to know no bounds to the extent that I am curious. |0T2D17p*dl`R,8!^3;t4}a(0bk@|CFE;$4"r4b'7;4@27*'C tb9Cj Your test result is compared to the Thank you so much again for your comments. (2019) Breathe (Sheffield, England). 0000011229 00000 n This rate, kco, which has units of seconds, Confusion arises in how PFT laboratories, by convention, report Dlco and the related measurements Va and Dlco/Va. Check for errors and try again. Just wondering if loads of people have this kind of lung function or if it is something that would cause symptoms of breathlessness and tiredness. Congenital pulmonary airway malformation (CPAM), Coronavirus and living with a lung condition, If you have a lung condition and get coronavirus. These disorders may also cause a thickening of the alveolar-capillary membrane (i.e. At this time the alveolar membrane is stretched and at its thinnest which reduces the resistance to the transport of gases across the membrane. Kco is not the lung CO diffusing capacity. A gas transfer test is used to help diagnose and monitor lung conditions including COPD and pulmonary fibrosis. What does air pollution do to people with a lung condition? ichizo, Your email address will not be published. In this situation, it would be incorrect to state that the Dlco corrects for Va, because the Kco should be much higher. practitioner should be consulted for diagnosis and treatment of any and all medical conditions. Diffusing capacity for carbon monoxide - Wikipedia Learn how your comment data is processed. Dyspnea is the most common reason for ordering a Dlco test, but there are many situations and presentations in which a higher than predicted or lower than predicted Dlco suggests the possible presence of lung or heart disease (Table 1). Webdicted normal values, that is, those recommended by Cotes (1975). <> WebEnter Age, Height, Gender and Race. At least one study has indicated that when the entire exhalation is used to calculate DLCO both healthy patients and those with COPD have a somewhat higher DLCO (although I have reservations about the studys methodology). The specificity and sensitivity of Dlco for specific lung diseases has not been studied extensively until recently, particularly for pulmonary arterial hypertension (PAH) and systemic sclerosis with or without interstitial lung disease (ILD). Any distribution or duplication of the information contained herein is Concise Clinical Review - ATS Journals There is also another minor point that may be skewing the percent predicted DLCO and KCO somewhat. uuid:8e0822df-1dd2-11b2-0a00-aa0000000000 A fit young adult may have a KCO of approximately 1.75 mmol/min/kPa/litre, an elderly adult may be about 1.25. GPnotebook stores small data files on your computer called cookies so that we can recognise Uvieghara AO, Lanza J, Vasudevan VP, Arjomand F. Volume correction for diffusion capacity: use of total lung capacity by either nitrogen washout or body plethymography instead of alveolar volume by single breath methane dilution. Diffusing capacity for carbon monoxide By itself KCO is nothing more the rate at which CO disappears during breath-holding and the reduced DLCO already says theres a diffusion defect. The corrected value is referred to as the DLCO/VA and a normal value is considered to be 80% or more of the predicted value.