Chest
Volume 92, Issue 3, September 1987, Pages 447-450
Journal home page for Chest

Clinical Investigations
Dependence of Oxygen Consumption on Oxygen Delivery in Patients with Chronic Congestive Heart Failure

https://doi.org/10.1378/chest.92.3.447Get rights and content

We previously have shown that in patients with adult respiratory distress syndrome (ARDS) oxygen consumption ( V˙o2) is linearly related to oxygen delivery ( D˙o2) below a threshold Do, 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 Do, and Vo, 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 Vo, and in Do, (ΔV˙o2=0.16+0.34×ΔD˙o2,r=0.84,n=29). There was no significant relationship between Do, and mixed venous oxygen tension ( Pv¯O2, r = 0.16), nor was there a significant relationship between cardiac output ( Q˙t) and Pv¯O2, (r = 0.21). We conclude that in patients with chronic CHF, changes in Vo, appear to be dependent on changes in D˙o2. This may represent an adaptive tissue response to chronically reduced systemic oxygen transport.

Section snippets

METHODS

We studied eight patients with chronic stable CHF (NYHA functional class 3 or 4 for more than one year) despite conventional therapy (digitalis and diuretics). None of the patients had peripheral edema. Patients were admitted to the coronary intensive care unit for hemodynamic monitoring and further management of their heart failure. A 7.5-F Swan-Ganz balloon floatation catheter (Edwards Laboratories) was placed under fluoroscopic and/or pressure guidance in the pulmonary artery of each

RESULTS

Salient patient characteristics are shown in Table 1. Table 2 demonstrates mean physiologic data obtained at baseline and at peak oxygen delivery. All patients had normal arterial oxygenation. Body temperature was constant and normal at the times of gas exchange and hemodynamic measurements. There was a significant increase in Q˙t, D˙o2 and V˙o2 after treatment with nitroglycerin, while all other parameters were unchanged. Figure 1 demonstrates the significant linear relationship

DISCUSSION

In most states of health and disease, any reduction in D˙o2 is compensated by local mechanisms that maintain constant V˙o2 and thereby fulfill the normal metabolic requirements of the tissues. The principal mechanism is increased oxygen extraction, which may be mediated by shifts in the oxyhemoglobin dissociation curve,9 or by changes in peripheral vasoregulation whereby blood flow is shifted to areas of high oxygen extraction.10 These mechanisms reduce Cv¯O2 and consequently

ACKNOWLEDGMENT

The authors would like to thank Dr. Andrew Wachtel and Ms. Elaine Mickle for their support in carrying out this project, and Ms. Debra Craig for secretarial assistance.

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Manuscript received December 12; revision accepted March 2.

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