Diaphragm function does not independently predict exercise intolerance in patients with precapillary pulmonary...

Area of Science:

• Cardiology
• Pulmonology
• Exercise Physiology

Background:

• Exercise intolerance is common in precapillary pulmonary hypertension (PH).
• Diaphragm dysfunction is a suspected contributor to exercise limitation in PH.
• Multimodal evaluation of these factors in PH is limited.

Purpose of the Study:

• To investigate diaphragm function in patients with PH.
• To identify determinants of exercise intolerance in PH.
• To assess the independent contribution of diaphragm dysfunction to exercise limitation.

Main Methods:

• 43 PH patients and 43 controls underwent ultrasound for diaphragm function, spirometry, blood gas analysis, echocardiography for pulmonary artery pressure (PAP), NT-proBNP assay, and cardiac MRI for RVEF.
• Exercise capacity was measured by 6-minute walk distance (6MWD).

Main Results:

• PH patients exhibited significantly lower diaphragm excursion velocity and thickening ratio compared to controls.
• Worse exercise tolerance in PH was associated with poorer diaphragm function, higher NT-proBNP, lower CO2, and lower RVEF.
• Multivariate analysis identified RVEF and NT-proBNP as independent predictors of exercise limitation, not diaphragm function.

Conclusions:

• Patients with PH demonstrate diaphragm dysfunction, which worsens with increasing exercise intolerance.
• Diaphragm dysfunction in PH does not independently predict exercise limitation.
• Right heart dysfunction, reflected by RVEF and NT-proBNP, is the primary factor explaining exercise intolerance in PH.