The alveolar to arterial oxygen partial pressure difference is associated with pulmonary diffusing capacity in heart failure patients

In chronic heart failure (HF), the alveolar-capillary membrane undergoes a remodeling process that negatively affects gas exchange. In case of alveolar-capillary gas diffusion impairment, arterial desaturation (SaO₂) is rarely observed in HF patients. At play are 3 factors: overall pulmonary diffusing capacity (assessed as lung diffusion for CO, DLCO), global O₂ consumption (VO₂) and alveolar (A) to arterial (a) pO₂ gradient (AaDO₂). In 100 consecutive stable HF patients, DLCO, resting respiratory gases and arterial blood gases were measured to determine VO_2, paO₂, pAO₂ and AaDO₂. DLCO was poorly but significantly related to AaDO₂. The correlation improved after correcting AaDO₂ for VO₂ (p 2 and AaDO₂ were independently associated with DLCO (p 2 and pAO₂. AaDO₂/VO₂ showed a higher gradient in patients with lower DLCO. AaDO₂ increase and VO₂ reduction allow preventing low SaO₂ in HF patients with reduced DLCO. Accordingly, we suggest considering AaDO₂ and VO₂ combined and reporting AaDO₂/VO₂.