Exhaled nitric oxide in pulmonary arterial hypertension associated with systemic sclerosis

Zeling Cao; Stephen C Mathai; Laura K Hummers; Ami A Shah; Fredrick M Wigley; Noah Lechtzin; Paul M Hassoun; Reda E Girgis

doi:10.1086/688768

Exhaled nitric oxide in pulmonary arterial hypertension associated with systemic sclerosis

Pulm Circ. 2016 Dec;6(4):545-550. doi: 10.1086/688768.

Authors

Zeling Cao¹, Stephen C Mathai¹, Laura K Hummers², Ami A Shah², Fredrick M Wigley², Noah Lechtzin¹, Paul M Hassoun¹, Reda E Girgis³

Affiliations

¹ Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
² Division of Rheumatology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
³ Division of Pulmonary and Critical Care Medicine, Spectrum Health and Michigan State University College of Human Medicine, Grand Rapids, Michigan, USA.

PMID: 28090297
PMCID: PMC5210065
DOI: 10.1086/688768

Abstract

The fractional exhaled concentration of nitric oxide (FE_NO) has been shown to be reduced in idiopathic pulmonary arterial hypertension (PAH) but has not been adequately studied in PAH associated with systemic sclerosis (SSc). We measured FE_NO at an expiratory flow rate of 50 mL/s in 21 treatment-naive patients with SSc-associated PAH (SSc-PAH), 94 subjects with SSc without pulmonary involvement, and 84 healthy volunteers. Measurements of FE_NO at additional flow rates of 100, 150, and 250 mL/s were obtained to derive the flow-independent nitric oxide exchange parameters of maximal airway flux (J'aw_NO) and steady-state alveolar concentration (CA_NO). FE_NO at 50 mL/s was similar (P = 0.22) in the SSc-PAH group (19 ± 12 parts per billion [ppb]) compared with the SSc group (17 ± 12 ppb) and healthy control group (21 ± 11 ppb). No change was observed after 4 months of targeted PAH therapy in 14 SSc-PAH group patients (P = 0.9). J'aw_NO was modestly reduced in SSc group subjects without lung disease (1.2 ± 0.5 nl/s) compared with healthy controls (1.64 ± 0.9; P < 0.05) but was similar to that in the SSc-PAH group. CA_NO was elevated in individuals with SSc-PAH (4.8 ± 2.6 ppb) compared with controls with SSc (3.3 ± 1.4 ppb) and healthy subjects (2.6 ± 1.5 ppb; P < 0.001 for both). However, after adjustment for the diffusing capacity of CO, there was no significant difference in CA_NO between individuals with SSc-PAH and controls with SSc. We conclude that FE_NO is not useful for the diagnosis of PAH in SSc. Increased alveolar nitric oxide in SSc-PAH likely represents impaired diffusion into pulmonary capillary blood.

Keywords: exhaled nitric oxide; pulmonary arterial hypertension; scleroderma; systemic sclerosis.