Interpretation of increases in the transfer coefficient for carbon monoxide (TLCO/VA or KCO).

Lipscomb, D. J.; Patel, Kanta; Hughes, J. M. B.

doi:10.1136/thx.33.6.728

Cited by 53 publications

(23 citation statements)

References 20 publications

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“…Figure 1 shows that KCO and TL,CO are functions of alveolar expansion [5], cardiac output [8], and haemoglobin concentration [9]. The extensive studies of Stam et al [5] have emphasized that with a reduction in alveolar expansion down to 50% TLC the rise of KCO is linear, although earlier studies [4,10] found a steeper rise at VA v50% VA,max. Despite this increase in KCO, the product KCO6VA (i.e TL,CO) falls as VA declines.…”

Section: Within Individualsmentioning

confidence: 82%

In defence of the carbon monoxide transfer coefficientK_CO(T_L/V_A)

Hughes

Pride²

2001

Eur Respir J

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In defence of the carbon monoxide transfer coefficient KCO (TL/VA). J.M.B.Hughes, N.B.Pride. #ERS Journals Ltd 2001. ABSTRACT: The carbon monoxide transfer factor (TL,CO) is the product of the two primary measurements during breath-holding, the CO transfer coefficient (KCO) and the alveolar volume (VA). KCO is essentially the rate constant for alveolar CO uptake (Krogh's kCO), and in healthy subjects, increases when VA is reduced by submaximal inflation, or when pulmonary blood flow increases. Recently, new reference values were proposed for clinical use which included the observed VA at full inflation; this was claimed to "eliminate the need for KCO".In this commentary, some mechanisms e.g. respiratory muscle weakness, lung resection, diffuse alveolar damage and airflow obstruction, which decrease or increase total lung capacity (TLC) are reviewed.Even when alveolar structure and function are normal, the change in KCO at a given VA varies according to the underlying pathophysiological mechanism. The advantages and disadvantages of normalizing KCO and TL,CO to predisease predicted TLC or to the patient's actual VA (using lack of expansion or loss of alveolar units models) are considered.Examination of carbon monoxide transfer coefficient and alveolar volume separately provides information on disease pathophysiology which cannot be obtained from their product, the carbon monoxide transfer factor. A few years ago, a paper in the European Respiratory Journal [1] concluded that: ". . . the use of TL/VA (the carbon monoxide (CO) transfer coefficient) cannot be justified on scientific grounds". Apart from one letter of disagreement [2], this view that TL/VA (or KCO) is a redundant and misleading measurement has not been challenged. This is surprising because measurements of TL/VA have continued to be published in respiratory journals.The single breath method for measuring CO uptake by the lung, which is used world-wide, was introduced by Krogh [3] in 1915; this measurement was termed diffusion constant. Subsequently the diffusion constant for CO was renamed the diffusing capacity (DL,CO) or the transfer factor (TL,CO), with the uptake being measured at total lung capacity (TLC). Krogh [3] pointed out that TL,CO was the product of two separate measurements, which potentially varied widely (and independently), the rate constant for CO removal from alveolar gas (called the permeability factor (kCO)) and the alveolar volume (VA).kCO is measured as the exponential decay in fractional concentration of CO over a period of breath-holding (BHT):where CO 0 and CO t are the alveolar CO concentrations at the start and finish of the breath-holding period. The units of kCO are s -1 or min -1 . The total CO transfer of the lung is calculated as:where PB and PH2O are the barometric pressure and the water vapour pressure (at 37 ‡C) which standardize for the driving pressure for CO uptake, i.e.the pressure of CO in the alveoli (PA,CO). VA is the alveolar volume measured at standard temperature and pressure, dry (STPD). In modern usag...

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Section: Within Individualsmentioning

confidence: 82%

In defence of the carbon monoxide transfer coefficientK_CO(T_L/V_A)

Hughes

Pride²

2001

Eur Respir J

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Section: Transfer Factor (Diffusing Capacity) Standardized For Alveolmentioning

confidence: 99%

“…Information about the linear model, as applied to data for individuals, was reviewed in 1970; at that time, the average slope of the relationship of TL on VA (the parameter m) was estimated as 0.86 mmol·min -1 ·kPa -1 ·L -1 (2.57 mL·min -1 ·mmHg -1 ·L -1 ) [3]. Subsequent studies have yielded a similar result [5,6].A linear model describing TL at total lung capacity (TLC) on age and VA was applied to population data by GAENSLER and SMITH [7], and a more sophisticated model, …”

mentioning

confidence: 99%

Transfer factor (diffusing capacity) standardized for alveolar volume: validation, reference values and applications of a new linear model to replace KCO (TL/VA)

Chinn¹,

Cotes²,

Flowers³

et al. 1996

Eur Respir J

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Transfer factor (diffusing capacity) standardized for alveolar volume: validation, reference values and applications of a new linear model to replace KCO (TL/VA). D.J. Chinn, J.E. Cotes, R. Flowers, A-M. Marks, J.W. Reed. ERS Journals Ltd 1996.ABSTRACT: Transfer factor (TL) varies with alveolar volume (VA), but not in the manner implied by the carbon monoxide transfer coefficient (KCO (TL/VA)). This paper considers two other simple models (one linear and one exponential) which might standardize TL for VA, and asks the questions: 1) Is either model valid? 2) What are appropriate reference values? and 3) Will the model be useful?The relationship of TL to VA within subjects at different depths of inspiration, and between subjects having lungs of different sizes, were measured and compared. The subjects were asymptomatic, nonsmoking, Caucasian adults, including 31 males assessed in the laboratory and 503 male and female participants in population studies.The linear partial regression coefficients of TL on VA (L corrected for body temperature, atmospheric pressure and water saturation (BTPS)) standardized for height (H) in metres, were similar within-and between-subjects; the coefficients applied over a wide range of values for VA. Inclusion of VA·H -2 as a covariate in the reference equation for transfer factor, in addition to age and height, improves the accuracy of prediction of normal transfer factor compared with current reference values; its use suggests that some of the differences between published values is due to the volume term. The equations can be used clinically, and eliminate the need for carbon monoxide transfer coefficient. Eur Respir J., 1996Respir J., , 9, 1269Respir J., -1277 When an individual subject performs measurements of transfer factor (TL, which is also called diffusing capacity) by the single-breath method, the result is found to vary with the depth of inspiration, and hence with the alveolar volume (VA) during breatholding. This was first observed by KROGH [1] who, in 1915, reported that "with increasing lung volumes above mean capacity, the permeability factor k (i.e. diffusing capacity per unit lung volume) remained practically constant". Based on this observation the carbon monoxide transfer coefficient (KCO), hereafter designated TL/VA, has been equated with transfer factor standardized for alveolar volume. However, subsequent studies, reviewed by STAM and coworkers [2], have shown that between functional residual capacity and total lung capacity, TL/VA was not constant; instead, it was negatively correlated with alveolar volume. On this account, the usefulness of TL/VA as a means for standardizing TL has been questioned [3,4].The Krogh model (TL/VA) can be represented as TL= mVA, where m is a constant. It is invalid because m is not independent of VA. In this paper, two other simple models are considered, an exponential model of the form TL=mVA δ , and a linear model which can be represented as TL=mVA + c ( fig. 1). To be valid, the parameters of the equations should be independe...

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“…A reduction in gas transfer disproportionate to lung volumes may also be indicative of concurrent pulmonary vascular disease [15], especially when accompanied by severe resting hypoxia or major arterial oxygen desaturation with minor exertion. In sharp contrast, DLco and Kco levels 200-300 % above the upper limit of normal, measured using single breath testing, are characteristic features of recent diffuse alveolar hemorrhage syndromes [16]. In the absence of alveolar haemorrhage, a restrictive ventilatory defect combined with a major increase in Kco is a reliable indicator of extra-pulmonary restriction [17].…”

Section: Pulmonary Function Testsmentioning

confidence: 99%

Diagnostic approach to interstitial lung disease

Gogali

Wells

2012

Curr Respir Care Rep

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Interstitial lung disease includes a variety of entities with strikingly diverse natural histories and treated outcomes. Thus, in clinical practice, an accurate diagnosis is essential in order to construct an optimal treatment strategy. The gold standard for diagnosis is now a multi-disciplinary diagnosis, with participation by clinicians, radiologists, and, when applicable, histopatholologists. In non-biopsied cases, the clinical and High Resolution Computed Tomography (HRCT) evaluations are, on average, equally influential. Key clinical information includes the identification of a cause or relevant underlying systemic disease, and the assimilation of serial data allowing definition of the natural history or treated course of disease. In patients undergoing surgical biopsy, clinical and HRCT findings are usually inconclusive and the histological features tend to carry the most diagnostic weight. However, it should be expected that the final diagnosis will differ from the histological diagnosis in a significant minority of patients, when all available information is integrated.

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Interpretation of increases in the transfer coefficient for carbon monoxide (TLCO/VA or KCO).

Cited by 53 publications

References 20 publications

In defence of the carbon monoxide transfer coefficientK_CO(T_L/V_A)

In defence of the carbon monoxide transfer coefficientK_CO(T_L/V_A)

Transfer factor (diffusing capacity) standardized for alveolar volume: validation, reference values and applications of a new linear model to replace KCO (TL/VA)

Diagnostic approach to interstitial lung disease

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Interpretation of increases in the transfer coefficient for carbon monoxide (TLCO/VA or KCO).

Cited by 53 publications

References 20 publications

In defence of the carbon monoxide transfer coefficientKCO(TL/VA)

In defence of the carbon monoxide transfer coefficientKCO(TL/VA)

Transfer factor (diffusing capacity) standardized for alveolar volume: validation, reference values and applications of a new linear model to replace KCO (TL/VA)

Diagnostic approach to interstitial lung disease

Contact Info

Product

Resources

About

In defence of the carbon monoxide transfer coefficientK_CO(T_L/V_A)

In defence of the carbon monoxide transfer coefficientK_CO(T_L/V_A)