Respiratory muscle dysfunction in idiopathic pulmonary arterial hypertension

Abstract

Idiopathic pulmonary arterial hypertension (IPAH) is a pulmonary vasculopathy of unknown aetiology. Dyspnoea, peripheral airway obstruction and inefficient ventilation are common in IPAH. Data on respiratory muscle function are lacking. This prospective single-centre study included 26 female and 11 male patients with IPAH in World Health Organization functional classes II-IV. Mean±SD pulmonary artery pressure was 48.6±16.9 in females and 53.1±22.9 mmHg in males; cardiac output was 3.7±1.3 and 4.2±1.7 L·min-1. Maximal inspiratory pressure (PI,max) was lower in the female patients than in 20 controls (5.3±2.0 versus 8.2±2.0 kPa). In the male patients, PI,max was lower than in 25 controls (6.8±2.2 versus 10.5±3.7 kPa). Maximal expiratory pressure (PE,max) was lower in the female patients than in controls (6.2±2.6 versus 9.5±2.1 kPa), and in male patients as compared to controls (7.1±1.6 versus 10.3±3.9 kPa). There was no correlation between PI,max or PE,max and parameters of pulmonary haemodynamics or exercise testing. The ratio of mouth occlusion pressure within the first 0.1 s of inspiration and PI,max was higher in IPAH than in controls (females 0.067±0.066 versus 0.021±0.008; males 0.047±0.061 versus 0.023±0.016). In conclusion, this study provides the first evidence of inspiratory and expiratory muscle weakness in idiopathic pulmonary arterial hypertension. The pathomechanisms and the prognostic significance should be further investigated. Copyright©ERS Journals Ltd 2005.