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Giovanni Gardini Gardenghi, MD; Claudio Tantucci, MD
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From the Department of Medical and Surgical Sciences, University of Brescia.

Correspondence to: Claudio Tantucci, MD, 1° Medicina, Spedali Civili, Piazzale Spedali Civili, 1, 25123 Brescia, Italy; e-mail: tantucci@med.unibs.it


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestpubs.org/site/misc/reprints.xhtml).


© 2010 American College of Chest Physicians


Chest. 2010;137(5):1253. doi:10.1378/chest.10-0097
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To the Editor:

Regarding our recent article in CHEST (November 2009),1 the hemoglobin (Hb) of the subjects with anorexia was 13 ± 1 g/dL. The diffusing capacity of lung for carbon monoxide (Dlco) values of subjects with anorexia (and controls) were always corrected, according to the following equation proposed by Cotes et al2: Dlco (corrected) = Dlco (observed) × (10.2 + [Hb]) / 1.7 × [Hb], assuming a membrane diffusing capacity/pulmonary capillary blood volume ratio of 0.7 and a reference [Hb] of 14.5 g/dL. Regretfully, we did not mention this correction (which is automatically performed by the computer every time the entered value of Hb is different from 14.5 g/dL) in the Materials and Methods section of our article.

Dr Johnson is perfectly right, because in the article alveolar volume (VA) is erroneously defined as alveolar ventilation, while it is obvious that VA means alveolar volume (in this case obtained by single-breath helium dilution technique).1 We are very sorry about making such a mistake in the manuscript. On the other hand, Dr Johnson made the same mistake referring to a paper by Dr Plummer in a previously published letter to the editor in CHEST.3

There are no doubts that Dlco and the diffusing coefficient of lung for carbon monoxide (Kco) change with VA in opposite and different ways and that these changes are relevant for interpretation of gas transfer in patients with low lung volumes.4 In our subjects with anorexia and controls, however, VA was 99 ± 10% predicted and 103 ± 8% predicted (ie, of VA at total lung capacity = total lung capacity predicted − anatomical dead space predicted), respectively. Thus, there is no substantial reason to recalculate Dlco and Kco in percent predicted of volume-corrected Dlco and volume-corrected Kco. In fact, the values obtained are similar (Dlco: 74 ± 14% predicted vs 75 ± 15% predicted in subjects with anorexia and 95 ± 9% predicted vs 94 ± 9% predicted in controls; Kco: 66 ± 18% predicted vs 66 ± 15% predicted in subjects with anorexia and 82 ± 11% predicted vs 83 ± 10% predicted in controls). Dr Johnson must admit that neither anemia nor VA can explain the difference in Dlco and Kco between subjects with anorexia and matched controls.

We used the European Community for Steel and Coal equations to give the percent predicted of Dlco and Kco, and we agree that those equations seem less consistent for Kco. This applies, of course, for both groups (controls and subjects with anorexia).

By using the formula suggested by Dr Johnson for calculating predicted Kco, actual Kco amounted to 76 ± 18% predicted for subjects with anorexia and 92 ± 11% predicted for controls, nearly equal to Dlco (as percent predicted) for both groups. Therefore, the presentation of our data could be critiqued for Kco in terms of percent predicted, but this does not influence the difference in Kco between subjects with anorexia and matched controls that remains unchanged.

Gardini Gardenghi G, Boni E, Todisco P, Manara F, Borghesi A, Tantucci C. Respiratory function in patients with stable anorexia nervosa. Chest. 2009;1365:1356-1363. [CrossRef] [PubMed]
 
Cotes JE, Dabbs JM, Elwood PC, Hall AM, McDonald A, Saunders MJ. Iron-deficiency anaemia: its effect on transfer factor for the lung (diffusing capacity) and ventilation and cardiac frequency during sub-maximal exercise. Clin Sci. 1972;423:325-335. [PubMed]
 
Johnson DC. DACO and KACO: how to adjust DLCO and KCO for lung volume. Chest. 2009;1354:1111. [CrossRef] [PubMed]
 
Johnson DC. Importance of adjusting carbon monoxide diffusing capacity (DLCO) and carbon monoxide transfer coefficient (KCO) for alveolar volume. Respir Med. 2000;941:28-37. [CrossRef] [PubMed]
 

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References

Gardini Gardenghi G, Boni E, Todisco P, Manara F, Borghesi A, Tantucci C. Respiratory function in patients with stable anorexia nervosa. Chest. 2009;1365:1356-1363. [CrossRef] [PubMed]
 
Cotes JE, Dabbs JM, Elwood PC, Hall AM, McDonald A, Saunders MJ. Iron-deficiency anaemia: its effect on transfer factor for the lung (diffusing capacity) and ventilation and cardiac frequency during sub-maximal exercise. Clin Sci. 1972;423:325-335. [PubMed]
 
Johnson DC. DACO and KACO: how to adjust DLCO and KCO for lung volume. Chest. 2009;1354:1111. [CrossRef] [PubMed]
 
Johnson DC. Importance of adjusting carbon monoxide diffusing capacity (DLCO) and carbon monoxide transfer coefficient (KCO) for alveolar volume. Respir Med. 2000;941:28-37. [CrossRef] [PubMed]
 
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