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Correspondence |

Association of Chronic Mountain Sickness With Abnormal Pulmonary Microcirculation: Importance of Adjusting Predicted Diffusing Capacity of the Lung for Carbon Monoxide for Altitude, Hemoglobin, and Lung Volume FREE TO VIEW

Douglas C. Johnson, MD
Author and Funding Information

From the Spaulding Rehabilitation Hospital.

Correspondence to: Douglas C. Johnson, MD, Spaulding Rehabilitation Hospital, 125 Nashua St, Boston, MA 02114; e-mail: djohnson5@partners.org


Financial/nonfinancial disclosures: The author has 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 (http://www.chestpubs.org/site/misc/reprints.xhtml).


© 2010 American College of Chest Physicians


Chest. 2010;138(3):757-758. doi:10.1378/chest.10-0664
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Published online

To the Editor:

A recent issue of CHEST (February 2010) published findings by Stuber et al1 of large increases in pulmonary hypertension with mild exercise in chronic mountain sickness (CMS). It is important, however, to know whether the findings are associated with abnormal pulmonary microcirculation (using diffusing capacity of the lung for carbon monoxide [Dlco] as proxy). To better evaluate whether CMS has abnormal gas exchange, the authors should report Dlco as percent predicted and properly adjust it for lung volume. The American Thoracic Society recommends adjusting predicted values (not measured values) for altitude and hemoglobin and makes clear that the Dlco/alveolar volume (VA) ratio does not correct for lung volume.2

Dlco and the Dlco/VA ratio change with lung volume as would be expected with changes in surface area for diffusion. Percent predicted for Dlco adjusted for lung volume (Daco) and Dlco/VA ratio adjusted for lung volume (Kaco) also should be reported, using the following equations: Daco predicted = Dlco predicted × (0.58 + 0.42 × VA/VAtlc) and Kaco predicted = Kco predicted × (0.42 + 0.58/(VA/VAtlc)), where Kco = carbon monoxide transfer coefficient and VAtlc = predicted VA at total lung capacity.3

It also would be helpful to know whether CMS affects spirometry (FEV1 and vital capacity) and lung volume (total lung capacity or VA). I hope that the authors will reanalyze their data and report percent predicted Dlco, Kco, and Daco (which = Kaco); VA; and, if spirometry was measured, FEV1 and vital capacity. Finding comparable percent-predicted Daco in patients with and without CMS would strengthen their argument that CMS does not impair pulmonary microcirculation.

Stuber T, Sartori C, Schwab M, et al. Exaggerated pulmonary hypertension during mild exercise in chronic mountain sickness. Chest. 2010;1372:388-392. [CrossRef] [PubMed]
 
Macintyre N, Crapo RO, Viegi G, et al. Standardisation of the single-breath determination of carbon monoxide uptake in the lung. Eur Respir J. 2005;264:720-735. [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

Stuber T, Sartori C, Schwab M, et al. Exaggerated pulmonary hypertension during mild exercise in chronic mountain sickness. Chest. 2010;1372:388-392. [CrossRef] [PubMed]
 
Macintyre N, Crapo RO, Viegi G, et al. Standardisation of the single-breath determination of carbon monoxide uptake in the lung. Eur Respir J. 2005;264:720-735. [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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