MMeasurement Of Gas Transfer Components Using Nitric Oxide In Post Pulmonary Endartectomy (PEA) Chronic Thromboembolic Hypertension (CTEPH) Patients

Abstract

2Corresponding author's email: noblel1@yahoo.co.uk 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. ResultsBoth 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. Correlation Matrix Measured Mean ( Sd) + % Pred Mean (Sd) Dm Measured R (P)