0
Correspondence |

Elucidating the Ventilation/Perfusion Mismatch and Reduction of Diffusing Capacity for Carbon Monoxide in Chronic Thromboembolic Pulmonary Hypertension FREE TO VIEW

Makoto Takei, MD; Takashi Kawakami, MD; Masaharu Kataoka, MD; Ichiro Kuwahira, MD; Keiichi Fukuda, MD
Author and Funding Information

FINANCIAL/NONFINANCIAL DISCLOSURES: None declared.

aDepartment of Cardiology, Keio University School of Medicine, Tokyo, Japan

bDepartment of Pulmonary Medicine, Tokai University Tokyo Hospital, Tokyo, Japan

CORRESPONDENCE TO: Takashi Kawakami, MD, Department of Cardiology, Keio University School of Medicine, Shinanomachi 35, Shinjuku-ku, Tokyo, 160-8582, Japan


Copyright 2017, American College of Chest Physicians. All Rights Reserved.


Chest. 2017;151(3):725-726. doi:10.1016/j.chest.2016.12.032
Text Size: A A A
Published online

We read with great interest the paper by Akizuki et al in this issue of CHEST. They reported that in patients with chronic thromboembolic pulmonary hypertension (CTEPH), diffusing capacity for carbon monoxide (Dlco) decreased after balloon pulmonary angioplasty (BPA), for mainly the lower lung lobes, and increased after BPA for upper lung lobes. They attributed these changes to the difference in the ventilation/perfusion ratio (V˙ /Q˙ ) between the upper and lower lobes. They hypothesized that BPA of the lower lobes, which have a low V˙ /Q˙ , further led to a decrease in the ratio, which in turn decreased the Dlco. We would like to add some points to this discussion.
As stated by the authors, a low V˙ /Q˙  led to a decrease in Dlco. However, reduced Dlco in CTEPH reflects not only the effect of low V˙ /Q˙  but also dead space ventilation (dead space/tidal volume [Vd/Vt]) in regions with high V˙ /Q˙ . Further, one hypothesis suggests that in patients with CTEPH, a decrease in Dlco also indicates microvascular remodeling. Results of previous reports that Dlco remained unchanged even after successful pulmonary endarterectomy and BPA supported the hypothesis., These points of view suggest that reduced Dlco in patients with CTEPH may be caused by low V˙ /Q˙  as well as high V˙ /Q˙  and microvascular remodeling. Therefore, it is important to distinguish the effects of these three components when discussing Dlco in CTEPH.
To determine changes in V˙ /Q˙  inequality, the multiple inert gas elimination technique is essential in the methods. However, clinical application of the multiple inert gas elimination technique is not easily available for the majority of institutions. If the authors wish to analyze the exacerbation of low V˙ /Q˙ , we suggest using shunt fraction (Q˙ s/Q˙ t) as a surrogate instead of Dlco. Although precise calculation is difficult, the Q˙ s/Q˙ t can be estimated using blood gas analysis in pulmonary and systemic arteries with Fick’s equation. In addition, to estimate the effect of high V˙ /Q˙ , we suggest using dead space ventilation (Vd/Vt) instead of ventilation to carbon dioxide output (V˙ e/V˙ co2). As stated by the authors, V˙ e/V˙ co2 was affected by both Vd/Vt and cardiac output. Vd/Vt may be a more appropriate index for estimation of the improvement in the high V˙ /Q˙  rather than the V˙ e/V˙ co2.
The conclusion of the authors that the effect of BPA differs between the upper and lower lobes because of the difference in the V˙ /Q˙  is very interesting. To obtain further evidence to support this hypothesis, we suggest analyzing the Vd/Vt and Q˙ s/Q˙ t to distinguish the amelioration of high V˙ /Q˙  and deterioration of low V˙ /Q˙  in different lung lobes.

References

Akizuki M. .Serizawa N. .Ueno A. .Adachi T. .Hagiwara N. . Effect of balloon pulmonary angioplasty on respiratory function in patients with chronic thromboembolic pulmonary hypertension. Chest. 2017;151:643-649 [PubMed]journal
 
Takei M. .Kataoka M. .Kawakami T. .et al Respiratory function and oxygenation after balloon pulmonary angioplasty. Int J Cardiol. 2016;212:190-191 [PubMed]journal. [CrossRef] [PubMed]
 
Kapitan K.S. .Clausen J.L. .Moser K.M. . Gas exchange in chronic thromboembolism after pulmonary thromboendarterectomy. Chest. 1990;98:14-19 [PubMed]journal. [CrossRef] [PubMed]
 
West J.B. . Respiratory Physiology: The Essentials.  2012;:- [PubMed] Lippincott Williams & Wilkins Philadelphiajournal
 

Figures

Tables

References

Akizuki M. .Serizawa N. .Ueno A. .Adachi T. .Hagiwara N. . Effect of balloon pulmonary angioplasty on respiratory function in patients with chronic thromboembolic pulmonary hypertension. Chest. 2017;151:643-649 [PubMed]journal
 
Takei M. .Kataoka M. .Kawakami T. .et al Respiratory function and oxygenation after balloon pulmonary angioplasty. Int J Cardiol. 2016;212:190-191 [PubMed]journal. [CrossRef] [PubMed]
 
Kapitan K.S. .Clausen J.L. .Moser K.M. . Gas exchange in chronic thromboembolism after pulmonary thromboendarterectomy. Chest. 1990;98:14-19 [PubMed]journal. [CrossRef] [PubMed]
 
West J.B. . Respiratory Physiology: The Essentials.  2012;:- [PubMed] Lippincott Williams & Wilkins Philadelphiajournal
 
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.

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