Cross-Sectional Assessment of the Relationships between Dyspnea Domains and Lung Function in Diffuse Parenchymal Lung Disease

Abstract

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 (DL<smlcap>CO</smlcap>) and nitric oxide, maximal airway pressures (capacity and demand assessments), mouth occlusion pressure at 0.1 s (P_0.1: 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, k<smlcap>CO</smlcap>) only, while the impact domain was independently linked to demand and capacity (k<smlcap>CO</smlcap> and forced vital capacity, respectively). Among resting pulmonary function tests, both P_0.1 and DL<smlcap>CO</smlcap> 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. DL<smlcap>CO</smlcap> that assesses both demand and capacity and P_0.1 were the strongest correlates of dyspnea.