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Mina Akizuki, PT; Naoki Serizawa, MD, PhD; Atsuko Ueno, MD, PhD; Nobuhisa Hagiwara, MD, PhD
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FINANCIAL/NONFINANCIAL DISCLOSURES: See earlier cited article for author conflicts of interest.

aDepartment of Rehabilitation, Tokyo Women's Medical University, Tokyo, Japan

bDepartment of Cardiology, Tokyo Women's Medical University, Tokyo, Japan

CORRESPONDENCE TO: Mina Akizuki, PT, Department of Rehabilitation, Tokyo Women's Medical University, 8-1 Kawadacho, Shinjuku-ku, Tokyo 162-0054, Japan


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


Chest. 2017;151(3):726-727. doi:10.1016/j.chest.2017.01.022
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First, we would like to thank Dr Takei and colleagues for their sincere comments. In their letter to the editor regarding our recent paper, they made two important suggestions about analyzing the dead-space/tidal volume (Vd/Vt) and shunt fraction (Qs/Qt) to distinguish the amelioration of high ventilation/perfusion (V˙ /Q˙ ) and deterioration of low V˙ /Q˙  in different lung lobes. We agree that other objective evaluation methods for determining a change in V˙ /Q˙  would aid in supporting our hypothesis that the effect of balloon pulmonary angioplasty (BPA) differs between the upper and lower lobes due to a difference in the V˙ /Q˙ .
After BPA, Vd/Vt measurements in the lower lung field remained unchanged at rest (from 0.36 ± 0.03 to 0.36 ± 0.04) but decreased during exercise (from 0.34 ± 0.04 to 0.32 ± 0.05; P = .030). We observed that the lower lung field became an area that perfused but had poorly ventilated regions (low V˙ /Q˙ ). A reduction in Vd/Vt during exercise appears to have occurred from V˙ /Q˙  matching caused by Vt increases, allowing Vd/Vt to remain unchanged in the upper lung field, which already had sufficient ventilated regions (high V˙ /Q˙ ). Therefore, BPA created more low-V˙ /Q˙  units and decreased diffusing capacity of the lung for carbon monoxide (Dlco) in the lower lung field, which resonates with our hypothesis. Furthermore, Kapitan et al reported that Dlco remained unchanged even after successful pulmonary endarterectomy and BPA., Throughout the duration of BPA, with treatment to both upper and lower lung fields, Dlco was considered to be counterbalanced; further, its reading remained unchanged after BPA.
As Takei et al mentioned, multiple inert gas elimination technique is essential in determining changes in V˙ /Q˙ . However, it is not readily available in a majority of institutions, including ours. We were unable to evaluate V˙ /Q˙  changes using the multiple inert gas elimination technique, and we also did not use blood gas analysis to evaluate the presence of possible intrapulmonary shunts. We can only speculate that the differences in Dlco readings between the upper and lower lobes resulted from the change in the V˙ /Q˙  ratio due to hemodynamic changes.

Finally, we thank Dr Takei and his colleagues again for raising these important concerns in our manuscript. We plan to further investigate the effect of BPA on respiratory function.

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
 
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]
 
Takei M. .Kataoka M. .Kawakami T. .Kuwahira I. .Fukuda K. . Respiratory function and oxygenation after balloon pulmonary angioplasty. Int J Cardiol. 2016;212:190-191 [PubMed]journal. [CrossRef] [PubMed]
 

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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
 
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]
 
Takei M. .Kataoka M. .Kawakami T. .Kuwahira I. .Fukuda K. . Respiratory function and oxygenation after balloon pulmonary angioplasty. Int J Cardiol. 2016;212:190-191 [PubMed]journal. [CrossRef] [PubMed]
 
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