Research article

Lung diffusing capacity for nitric oxide and carbon monoxide in relation to morphological changes as assessed by computed tomography in patients with cystic fibrosis

Holger Dressel¹ , Laura Filser¹ , Rainald Fischer² , Katharina Marten³ , Ullrich Müller-Lisse⁴ , Dorothea de la Motte¹ , Dennis Nowak¹ , Rudolf M Huber² and Rudolf A Jörres¹

¹  Institute and Outpatient Clinic for Occupational, Social and Environmental Medicine, Ludwig-Maximilians-University, Ziemssenstr. 1, D-80336 München, Germany

²  Department of Pneumology, Medizinische Klinik Innenstadt, Ludwig-Maximilians-University, Munich, Germany

³  Department of Diagnostic Radiology, University of Göttingen, Göttingen, Germany

⁴  Institute for Clinical Radiology, Medizinische Klinik Innenstadt, Ludwig-Maximilians-University, Munich, Germany

author email corresponding author email

BMC Pulmonary Medicine 2009, 9:30doi:10.1186/1471-2466-9-30

Published:	16 June 2009

Abstract

Background

Due to large-scale destruction, changes in membrane diffusion (Dm) may occur in cystic fibrosis (CF), in correspondence to alterations observed by computed tomography (CT). Dm can be easily quantified via the diffusing capacity for nitric oxide (DL_NO), as opposed to the conventional diffusing capacity for carbon monoxide (DL_CO). We thus studied the relationship between DL_NO as well as DL_CO and a CF-specific CT score in patients with stable CF.

Methods

Simultaneous single-breath determinations of DL_NO and DL_CO were performed in 21 CF patients (mean ± SD age 35 ± 9 y, FEV₁ 66 ± 28%pred). Patients also underwent spirometry and bodyplethysmography. CT scans were evaluated via the Brody score and rank correlations (r_S) with z-scores of functional measures were computed.

Results

CT scores correlated best with DL_NO (r_S = -0.83; p < 0.001). Scores were also related to the volume-specific NO transfer coefficient (KNO; r_S = -0.63; p < 0.01) and to DL_CO (r_S = -0.79; p < 0.001) but not KCO. Z-scores for DL_NO were significantly lower than for DL_CO (p < 0.001). Correlations with spirometric (e.g., FEV₁, IVC) or bodyplethysmographic (e.g., SR_aw, RV/TLC) indices were weaker than for DL_NO or DL_CO but most of them were also significant (p < 0.05 each).

Conclusion

In this cross sectional study in patients with CF, DL_NO and DL_CO reflected CT-morphological alterations of the lung better than other measures. Thus the combined diffusing capacity for NO and CO may play a future role for the non-invasive, functional assessment of structural alterations of the lung in CF.