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Presentation Number: 1865
Background: Pulmonary arterial hypertension (PAH) and interstitial lung disease (ILD) are major visceral manifestations of systemic sclerosis (SSc). Diffusing capacity for carbon monoxide (DLCO) is a well-validated follow up tool for SSc related pulmonary manifestations. It may also predict the onset of PAH but lacks sensitivity and specificity. In the same way, echocardiography can miss a mild to moderate PAH. Best strategy for PAH screening in SSc, especially in patients with coexisting ILD, is still unknown. Our aim was to study in SSc the relevance of the DLCO-DLNO method which determines the 2 components of diffusion capacity (conductance of alveolar-capillary membrane (Dm) and pulmonary capillary volume (Qc)), according to the presence of ILD or PAH.
Methods: Lung function tests were performed in 26 patients with SSc and included plethysmographic volumes (total lung capacity, TLC) and a DLCO-NO (nitric oxide) test (Medisoft®). This technique determines: DLCO % of predicted values (% pred), Qc % pred, Dm % pred, alveolar volume (VA), Dm/VA and Qc/VA. Patients were classified according to pulmonary HRCT and resting Doppler echocardiography data in 3 groups: normal (n = 10), ILD (n = 9) and suspected PAH defined as a tricuspid gradient > 30 mmHg (n = 7, including 4 with associated ILD). Exclusion criteria were total lung capacity <60 % pred, left ventricular ejection fraction < 55%, chronic thromboembolic disease, Hb <10 g/dl. Statistic analysis was performed by Kruskall Wallis and Mann Whitney tests.
Results: Patients characteristics : mean age = 51 ± 13 yrs; Raynaud’s duration = 11.8 ± 5 yrs, SSc type: 6/26 diffuse and 20/26 limited. Mean TLC was 96.4 ± 19.2 % pred. DLCO-DLNO results are shown in the table.
Conclusion: These data suggest that Qc and Dm assessment by DLCO-DLNO method in SSc may be an interesting tool. Indeed, DLCO alone was not different between patients with or without PAH. Qc/VA ratio was the sole parameter which was significantly lower in patients with PAH than in those with isolated ILD. This parameter evaluates the reduction of pulmonary vascular bed which is a key feature of PAH. Further studies are needed to assess the sensitivity and specificity of this new simple index to detect PAH (isolated or associated to ILD) in a larger population of SSc patients.
DLCO-DLNO results
Methods: Lung function tests were performed in 26 patients with SSc and included plethysmographic volumes (total lung capacity, TLC) and a DLCO-NO (nitric oxide) test (Medisoft®). This technique determines: DLCO % of predicted values (% pred), Qc % pred, Dm % pred, alveolar volume (VA), Dm/VA and Qc/VA. Patients were classified according to pulmonary HRCT and resting Doppler echocardiography data in 3 groups: normal (n = 10), ILD (n = 9) and suspected PAH defined as a tricuspid gradient > 30 mmHg (n = 7, including 4 with associated ILD). Exclusion criteria were total lung capacity <60 % pred, left ventricular ejection fraction < 55%, chronic thromboembolic disease, Hb <10 g/dl. Statistic analysis was performed by Kruskall Wallis and Mann Whitney tests.
Results: Patients characteristics : mean age = 51 ± 13 yrs; Raynaud’s duration = 11.8 ± 5 yrs, SSc type: 6/26 diffuse and 20/26 limited. Mean TLC was 96.4 ± 19.2 % pred. DLCO-DLNO results are shown in the table.
Conclusion: These data suggest that Qc and Dm assessment by DLCO-DLNO method in SSc may be an interesting tool. Indeed, DLCO alone was not different between patients with or without PAH. Qc/VA ratio was the sole parameter which was significantly lower in patients with PAH than in those with isolated ILD. This parameter evaluates the reduction of pulmonary vascular bed which is a key feature of PAH. Further studies are needed to assess the sensitivity and specificity of this new simple index to detect PAH (isolated or associated to ILD) in a larger population of SSc patients.
DLCO-DLNO results
| Normal (n=10) | ILD (n = 9) | PAH (n = 7) | p value | |
| DLCO % pred | 85.1 ± 12.4 | 54.5 ± 23.9 | 42 ± 15.1 | 0.001 |
| Qc % pred | 69.3 ± 16 | 46.9 ± 22.8 | 35.5 ± 17.7 | 0.021 |
| Dm % pred | 91.8 ± 18 | 58.7± 23.8 | 51 ± 17.4 | 0.003 |
| Qc/VA | 11.94 ± 2.67 | 9.06 ± 3.44 | 5.84 ± 1.78 § | 0.002 §: p = 0.03 vs ILD |
| Dm/VA | 12.10 ± 1.78 | 9.77 ± 3.01 | 6.72 ± 0.95 | 0.002 |
G. Denis, None; V. Debroucker, None; E. Hachulla, None; D. Launay, None; N. Bautin, None; R. Matran, None; P. Hatron, None; H. Guenard, None; T. Perez, None.