Dependence of oxygen consumption on oxygen delivery in patients with chronic congestive heart failure

We previously have shown that in patients with adult respiratory distress syndrome (ARDS) oxygen consumption (VO2) is linearly related to oxygen delivery (DO2) below a threshold DO2 of 21 ml/min/kg. To evaluate this relationship in chronic congestive heart failure (CHF), we studied eight patients with chronic CHF at baseline and during treatment with nitroglycerin. The resting DO2 and VO2 were 10.7 +/- 2.3 ml/min/kg and 3.8 +/- 0.87 ml/min/kg, respectively. In our eight patients, we found a significant relationship between changes in VO2 and in DO2 (delta VO2 = 0.16 + 0.34 X delta DO2, r = 0.84, n = 29). There was no significant relationship between DO2 and mixed venous oxygen tension (PvO2, r = 0.16), nor was there a significant relationship between cardiac output (Qt) and PvO2 (r = 0.21). We conclude that in patients with chronic CHF, changes in VO2 appear to be dependent on changes in DO2. This may represent an adaptive tissue response to chronically reduced systemic oxygen transport.