Association of peak expiratory flow rate with clinical outcomes in pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a rare disease characterized by a progressive increase in pulmonary arterial pressure, leading to right heart failure. In clinical practice, reduced exercise tolerance is commonly observed in patients with PAH. Several studies have identified skeletal muscle abnormalities and muscle weakness as factors contributing to impaired exercise capacity in these patients. Recently, peak expiratory flow rate (PEFR) has been shown to correlate with skeletal muscle mass. Given that PEFR can be easily and noninvasively measured using respiratory function tests, we investigated the relationship between PEFR and prognosis in patients with PAH. We enrolled consecutive untreated patients diagnosed with PAH at Kagoshima University Hospital between July 2005 and July 2024. A total of 85 patients were included and divided into the preserved PEFR group and the reduced PEFR group. There were no significant differences in hemodynamic parameters between the two groups; however, the 6-minute walk distance was significantly shorter (p = 0.0062) in the reduced PEFR group. Kaplan-Meier analysis revealed that the cumulative event-free rate was significantly lower in the reduced PEFR group (Log-rank p = 0.0048). Reduced PEFR was independently associated with poorer outcomes after adjusting for age, plus each of right atrial pressure, cardiac index, and pulmonary vascular resistance. In conclusion, PEFR, a method for measuring skeletal muscle, was associated with poor prognosis in patients with PAH when assessed at the time of diagnosis. PEFR can be easily and repeatedly measured, making it potentially useful for prognostic prediction and exercise rehabilitation in these patients.