Labored Breathing

SSc patients with PAH have a disproportionate decline in DLCO relative to decline in FVC. A fall in DLCO may be the first clue to the presence of SSc-PAH, and, if confirmed by serial testing, work-up for PAH is warranted. If the FVC percent predicted is greater than 75% and the ratio of the FVC percent predicted divided by the DLCO percent predicted is >1.4, the patient has predominantly pulmonary vascular disease. Of course, mixed patterns may occur in patients with both ILD and PAH.

Six-Minute Walk Test

The six-minute walk test (6MWT) is a sub-maximal exercise test that yields important information about exercise capacity of the patient and oxygen saturation. (See Figure 1, page 18.) This test is useful to obtain at baseline and, when performed serially, can be used to monitor response to therapy. In some pulmonary conditions, the 6MWT correlates with New York Heart Association functional classification and even predicts mortality. Such correlations have not been demonstrated in SSc, perhaps due to extra-pulmonary features of SSc (e.g., joint pain, muscle weakness, etc.) that often affect ambulation. Nevertheless, the distance walked can be monitored and compared with prior test results for the individual patient. In addition, if exercise-induced hypoxemia is present, supplemental oxygen should be prescribed.

Imaging Studies

Although the chest radiograph is not a sensitive test for detecting early ILD, it may detect lung infiltrates or nodules, pleural disease, lymphadenopathy, or cardiomegaly. High-resolution computed tomography (CT) is a much more sensitive test and should be part of the baseline assessment of all SSc patients. The earliest sign of ILD is a hazy-appearing opacification through which normal lung architecture can be seen (ground-glass opacification). (See Figure 2A, page 18.) With progression, more advanced signs of disease (e.g., honeycombing and traction bronchiectasis) may be seen. (See Figure 2B, page 18.) Patients with a normal CT scan have a good long-term prognosis, whereas those with CT abnormalities tend to worsen if not treated.

Pulmonary thromboembolism rarely occurs in SSc but suspect it in any patient who experiences acute dyspnea or in the patient with risk factors for chronic thromboembolic disease (e.g., sedentary lifestyle or antiphospholipid antibody). Ventilation-perfusion lung scans and CT pulmonary angiography are indicated in such situations.

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Bronchoalveolar Lavage

In years past, SSc-ILD was believed to result from a bland fibrosing process. My lab was among the first to employ bronchoscopy with lavage to obtain cells and proteins from the lower respiratory tract of SSc patients, and these studies provided new insight into the pathogenesis of SSc-ILD.^5,6 Many patients have evidence of an inflammatory process characterized by increased numbers of neutrophils and eosinophils, activated alveolar macrophages, and increased levels of pro-inflammatory and pro-fibrotic cytokines. Cells cultured from bronchoalveolar lavage fluid exhibit the phenotype of an activated myofibroblast with contractile and synthetic properties.⁷ The origin of these cells is not certain, but these activated myofibroblasts are key players in the pathogenesis of SSc-ILD.