0
Correspondence |

Daco and Kaco: How To Adjust Dlco and Kco for Lung Volume FREE TO VIEW

Douglas Clark Johnson, MD
Author and Funding Information

Massachusetts General Hospital, Harvard Medical School Boston, MA

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


The author has reported to the ACCP that no significant 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.chestjournal.org/misc/reprints.shtml).


Chest. 2009;135(4):1111. doi:10.1378/chest.08-2659
Text Size: A A A
Published online

To the Editor:

In an article in the “Topics in Practice Management” section in a recent issue of CHEST (September 2008) entitled “The Carbon Monoxide Diffusing Capacity,” Plummer1 correctly pointed out that lung diffusion capacity corrected for alveolar ventilation (Kco [or ratio of diffusing capacity of the lung for carbon monoxide (Dlco) to alveolar volume (VA)]) is not constant as VA changes. In fact, Dlco and Kco change with VA, as would be expected with membrane conduction varying linearly with surface area (VA2/3) or with VA, and blood conduction not changing.2 Thus, one can “volume correct” Dlco (Daco) and Kco (Kaco). The predicted Daco = predicted Dlco (0.58 + 0.42 VA/VAtlc) and predicted Kaco = predicted Kco (0.42 + 0.58 VA/VAtlc), where VA is the measured VA, and VAtlc is the predicted VA at total lung capacity (ie, the predicted total lung capacity − predicted dead space).2 The percent predicted Daco equals the percent predicted Kaco and provides a good indication of the diffusion capacity of the lung corrected for lung volume.

Just as the predicted Dlco and Kco are adjusted for hemoglobin, the predicted Dlco and Kco should also be adjusted for lung volume. There are specific patterns of the percent predicted Dlco, Kco, VA, and Daco (or Kaco) among lung diseases.2 While patients with interstitial lung disease often have a Dlco < 80% predicted and a Kco > 80% predicted, Daco and Kaco are low. While patients with extrapulmonary restriction but otherwise normal lungs often have low Dlco and elevated Kco levels, Daco and Kaco levels are normal. Patients with emphysema have low Dlco, Kco, Daco, and Kaco.

Dlco studies should go beyond reporting measured, predicted, and percent predicted Dlco, Kco, and VA. Predicted and percent predicted Dlco adjusted for lung volume (ie, Daco) and Kco adjusted for lung volume (ie, Kaco) should also be reported.

Plummer AL. The carbon monoxide diffusing capacity. Chest. 2008;134:663-667. [PubMed] [CrossRef]
 
Johnson DC. Importance of adjusting carbon monoxide diffusing capacity (Dlco) and carbon monoxide transfer coefficient (Kco) for alveolar volume. Respir Med. 2000;94:28-37. [PubMed]
 

Figures

Tables

References

Plummer AL. The carbon monoxide diffusing capacity. Chest. 2008;134:663-667. [PubMed] [CrossRef]
 
Johnson DC. Importance of adjusting carbon monoxide diffusing capacity (Dlco) and carbon monoxide transfer coefficient (Kco) for alveolar volume. Respir Med. 2000;94:28-37. [PubMed]
 
NOTE:
Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging & repositioning the boxes below.

  • CHEST Journal
    Print ISSN: 0012-3692
    Online ISSN: 1931-3543