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2264381 
Journal Article 
Abstract 
Measurement of gas transfer components using nitric oxide in post pulmonary endartectomy (PEA) chronic thromboembolic hypertension (CTEPH) patients 
Harlow, L; Oates, K; Ross, RM; Pepke-Zaba, J 
2010 
Yes 
American Journal of Respiratory and Critical Care Medicine
ISSN: 1073-449X
EISSN: 1535-4970 
181 
A1953 
English 
WOS:000208771001161 
is part of a larger document 3452678 Proceedings of the American Thoracic Society 2010 International Conference, May 14-19, 2010, New Orleans
Introduction
A reduced gas transfer factor is frequently observed in patients with CTEPH. Transfer factor for Carbon monoxide (TLCO) is the most widely accepted measure of gas transfer. Previous work has indicated the value of using nitric oxide (NO) to allow the differentiation of diffusing membrane capacity (Dm) and capillary blood volume (Vc); the components of gas transfer. It has been suggested, that transfer factor for nitric oxide (TLNO) is a more accurate reflection of the true Dm than TLCO, due to its greater affinity for haemoglobin and independence from capillary blood volume. To date, many studies have derived Dm and Vc from the Roughton and Forster equation, using triplicate measurements of TLCO at high and low oxygen concentrations. This study uses new technology to measure Dm and Vc, using NO, in a cohort of post PEA CTEPH patients. The aim of the study is to compare the relative contribution of Dm and Vc to the reduction in gas transfer.

Methods
We studied 24 CTEPH patients (14 male, 10 female, mean age 60­+13) post PEA as part of their routine follow up at either 3 months or 1 year. Full lung function were performed and TLNO and Dm were measured directly using single breath for NO and carbon monoxide on a PFTpro system (Viasys). Vc was calculated using the equation 1/DLCO -1/DmCOxqCO=1/Vc. Patients with co-existing parenchymal lung disease were excluded from the study. Predicted values for Dm and Vc were calculated from the equations of Crapo and colleages. Correlations between variables were looked at using Pearsons.

Results
Both Dm and Vc demonstrated a significant correlation with TLCO, however, Vc was reduced more than Dm (57.5%/86.8% respectively). No difference in Dm or Vc was found between smokers and non-smokers. Results are shown in table 1.

*See table in pdf*

Conclusions
The gas transfer in this patient group is still reduced post PEA, despite successful de-bulking of proximal obstructions and normal TLC and RV. The method used in this study is able to distinguish between the two components of gas transfer. In the group studied, Vc is more affected than the alveolar component Dm. The new technology offers a simple patient friendly procedure that can be performed repeatedly allowing measurements of Dm and Vc. This has the potential for improving our understanding of the different components of gas transfer. Further work is warranted in this area. 
American Thoracic Society 2010 International Conference 
New Orleans, LA 
May 14-19, 2010