Patients with connective tissue disease-associated pulmonary arterial hypertension (CTD-PAH) showed alterations in pulmonary function that could be detected by a pulmonary function test, a study found.

The authors of the study recently published in Disease Markers identified diffusing capacity of the lung for carbon monoxide (DLCO) as an independent predictive factor for CTD-PAH. Almost all (96%) patients experienced a decrease in DLCO, with most (60%) showing a DLCO of less than 60%.

Moreover, 60% of patients showed decreased forced vital capacity (FVC) and total lung capacity (TLC).

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“The reason for lung volume limitation in patients with PAH remains unclear. One explanation is that pulmonary vascular enlargement may have a direct physical effect on the airway, limiting tracheal dilation by mechanical pressure on the airway,” the study authors wrote.

Read more about PAH etiology

Almost all patients (95%) had a forced expiratory volume in 1 second (FEV1)/FVC ratio of greater than 70%. Both FEV1/FVC ratio and TLC improved after treatment for PAH.

In addition, 60% of patients showed decreased maximum expiratory flow at 50% of vital capacity (MEF50), a sensitive marker of small airways. Almost half (42%) presented with a MEF50 of less than 60%, with high-risk patients showing significantly lower MEF50 than low-risk patients.

In contrast to other studies that suggest the use of FVC/DLCO to distinguish PAH from interstitial lung disease, this study found limited use for FVC/DLCO in predicting PAH.

This prospective observational study enrolled 31 patients diagnosed with CTD-PAH (22 patients with systemic lupus erythematosus and 9 patients with systemic sclerosis) at the First Affiliated Hospital of Nanchang University in China. About half (48.4%) of the patients were classified as intermediate risk, while the remaining patients were classified as either low (25.8%) or high (25.8%) risk.


Xiong J, Li J, Huang Y, Yang F, Wu R. The role of pulmonary function test for pulmonary arterial hypertension in patients with connective tissue disease. Dis Markers. 2022;2022:6066291. doi:10.1155/2022/6066291