Oxygen delivery (DO2) and consumption (VO2) graph

Q: Why does it help to read the Oxygen delivery (DO2) and consumption (VO2) graph in reverse?

Answer: It helps a lot more if the following graph is read from right to left!

In the normal healthy state (of oxygenation balance), oxygen consumption remains constant over a range of DO2, and decreases only when DO2 falls below a critical level, called critical DO2. 

Pathologic changes caused by any condition, such as sepsis or systemic inflammatory responses, cause increased VO2 and subsequently impaired peripheral oxygen utilization, resulting in a pathologic (or earlier) critical DO2.

The following graph illustrates the same concept in various pathological diseases, either alone or in combination, such as anemia, heart failure, or Multi-Organ Dysfunction Syndrome (MODS).

#oxygen-delivery

#hemodynamics

References:

1. Wolff CB. Normal cardiac output, oxygen delivery and oxygen extraction. Adv Exp Med Biol. 2007;599:169-82. doi: 10.1007/978-0-387-71764-7_23. PMID: 17727262.

2. Cain SM. Acute lung injury. Assessment of tissue oxygenation. Crit Care Clin 1986; 2:537.