Postural relief of dyspnoea is associated with improved neuromechanical coupling in patients with advanced COPD

BACKGROUND: Patients with advanced COPD often report that adopting a specific body posture improves their dyspnoea. Exploring the underlying mechanisms could enhance our understanding of the origin of this symptom and approaches towards its alleviation. METHODS: Pulmonary function tests and detailed sensory-mechanical measurements, including gastro-oesophageal catheter-based crural diaphragm electromyography (surrogate for inspiratory neural drive (IND)) and respiratory manometry, were performed in 16 patients (nine males; mean±sd age 66±7 years) with advanced COPD (mean±sd forced expiratory volume in 1 s 36±16% predicted and residual volume/total lung capacity 55±11%) while adopting their most favourable (MF) and least favourable (LF) postures. RESULTS: The MF postures included sitting upright (56%), sitting with arms on knees in a forward-leaning position (25%), standing (13%) and lying with three pillows (6%). About two-thirds of patients choose the supine posture as the LF posture. There were no significant differences in minute ventilation and inspiratory capacity between MF and LF postures (p>0.05). Compared to LF postures, MF postures were associated with 1) increased dynamic lung compliance, 2) lower transdiaphragmatic pressures and 3) reduced total work of breathing, leading to 4) decreased IND to the diaphragm and 5) improved neuromechanical and neuroventilatory coupling (all p