Cross-sectional assessment of the relationships between dyspnea domains and lung function in diffuse parenchymal lung disease.

BACKGROUND Activity-related dyspnea is the main contributor to the altered quality of life in diffuse parenchymal lung diseases (DPLD). Instruments pertaining to dyspnea are classified as pertaining to domains of sensory-perceptual experience, affective distress or symptom/disease impact; whether these domains are equally related to lung function impairments remains to be established. OBJECTIVES They were to assess the relationships between two domains of dyspnea (sensory-perceptual experience and symptom impact) and pulmonary function tests according to their evaluation of ventilatory demand, capacity and drive in patients suffering from DPLD. METHODS Fifty patients were prospectively enrolled (median age, 58 years; 25 women) and underwent spirometry, body plethysmography, measurements of lung diffusion for carbon monoxide (DLCO) and nitric oxide, maximal airway pressures (capacity and demand assessments), mouth occlusion pressure at 0.1 s (P0.1: respiratory drive assessment) and a 6-min walk test with Borg score assessment (dyspnea: sensory domain). The impact domain of dyspnea was evaluated using the baseline dyspnea index. RESULTS The sensory domain of dyspnea was linked to demand (CO transfer coefficient, kCO) only, while the impact domain was independently linked to demand and capacity (kCO and forced vital capacity, respectively). Among resting pulmonary function tests, both P0.1 and DLCO allowed the assessment of these two domains of dyspnea. CONCLUSIONS In DPLD, the sensory-perceptual domain of dyspnea is mainly linked to alterations in ventilatory demand while the impact domain is related to both demand and capacity. DLCO that assesses both demand and capacity and P0.1 were the strongest correlates of dyspnea.