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 (SaO) is rarely observed in HF patients. At play are 3 factors: overall pulmonary diffusing capacity (assessed as lung diffusion for CO, DLCO), global O consumption (VO) and alveolar (A) to arterial (a) pO gradient (AaDO). In 100 consecutive stable HF patients, DLCO, resting respiratory gases and arterial blood gases were measured to determine VO paO, pAO and AaDO. DLCO was poorly but significantly related to AaDO. The correlation improved after correcting AaDO for VO (p<0.001, r=0.49). Both VO and AaDO were independently associated with DLCO (p<0.001). Patients with reduced DLCO showed no differences as regards paO and pAO. AaDO/VO showed a higher gradient in patients with lower DLCO. AaDO increase and VO reduction allow preventing low SaO in HF patients with reduced DLCO. Accordingly, we suggest considering AaDO and VO combined and reporting AaDO/VO.