[The DO2/VO2 relationship: and approach to cellular metabolism in "crisis" situations].
Difference in oxygen content b/w arterial and venous blood VO2 = CO x x VO2/DO2 x Ratio of oxygen uptake to delivery Usually % Uptake is. Basic concepts: The Relationship between VO2 and DO2 and the concept . results of a careful clinical evaluation and some paraclinical tests including meas -. CPB Calcs · pH-BE-K Calcs · Pressure Calcs · Quiz and Survey · Resource Library Critical to these relationships are two bits of information that should be DO2 = CaO2 x Q, where q is blood flow (either cardiac output or arterial pump flow) Oxygen consumption (VO2) is easy if you think of it in terms of the difference.
The pO2 contributes very little to the oxygen content of blood, having little impact on arterial blood oxygenation. The PaO2 should be used more for assessing pulmonary or oxygenator gas exchange. Note that the saturation percentage gets converted to decimal format and, for convenience, we ill round off to two decimal points.
The small difference between the answer can be accounted for variations in "rounding".
- Oxygen Extraction Ratio
- [The DO2/VO2 relationship: and approach to cellular metabolism in "crisis" situations].
In our example using the lab data, the DO2 is as calculated: It is sometimes preferred to calculate DO2 by indexing it to body surface area. In this case, Q would represent the cardiac or pump index rather than output. The equation, making use of mathematical shortcuts is as follows: In our case, Q would represent the pump index, which is 2.
Think of it in terms of the ratio percentage of what is presented to the tissues and what is used.
Simply put, is is the ratio of oxygen consumption to oxygen delivery, both of which have already been calculated. Secondly, fever, pain, stress etc. Pulmonary artery catheterization allows obtaining true mixed venous oxygen saturation SvO2 while measuring central venous oxygen saturation ScvO2 via central venous catheter reflects principally the degree of oxygen extraction from the brain and the upper part of the body.Using oxyHb and Fick to calculate VO2max
SvO2 reflects the relationship between whole-body O2 consumption and cardiac output. Indeed, it has been shown that the SvO2 is well correlated with the ratio of O2 supply to demand. The central venous catheter sampling site usually resides in the superior vena cava.
Thus central venous blood sampling reflects the venous blood of the upper body but neglects venous blood from the lower body i. As shown below, venous O2 saturations differ among several organ systems since they extract different amounts of O2.
Determinants of Cardiac Output and Principles of Oxygen Delivery
The primary cause of the lower O2 extraction is that many of the vascular circuits that drain into the inferior vena cava use blood flow for nonoxidative phosphorylation needs e. However, SvO2 and ScvO2 change in parallel when the whole body ratio of O2 supply to demand is altered. The difference between the absolute value of ScvO2 and SvO2 changes under conditions of shock. During cardiogenic or hypovolemic shock mesenteric and renal blood flow decreases followed by an increase in O2 extraction in these organs.
In septic shock, regional O2 consumption of the gastrointestinal tract and hence regional O2 extraction increases despite elevated regional blood flows. On the other hand, cerebral blood flow is maintained over some period in shock. This would cause a delayed drop of ScvO2 in comparison to SvO2, and the correlation between these two parameters would worsen.
Some authors therefore argued that ScvO2 cannot be used as surrogate for SvO2 under conditions of circulatory shock.