The Importance of Orthostatic Intolerance in the Chronic Fatigue Syndrome

[Hutan]

a bit more on Shock Index

As far as I can see, even if exercising strenuously, the shock index shouldn't rise significantly.

Rady MY, Smithline HA, Blake H, et al. A comparison of the shock index and conventional vital signs to identify acute, critical illness in the emergency department. Ann Emerg Med. 1994;24:685–690. [PubMed]

In people, a value of greater than 0.9 is indicative of serious illness, requiring immediate treatment and close monitoring.

http://www.cdemcurriculum.org/index.php/ssm/show_ssm/approach_to/shock (2015)

Shock is a broad term that describes a physiologic state where oxygen delivery to the tissues is inadequate to meet metabolic requirements, causing global hypoperfusion. It may also be thought of as an imbalance between tissue oxygen supply and demand.

A normal <shock> index ranges from 0.5-0.7; repeated values >1.0 indicate decreased left ventricular function and are associated with higher mortality.

Types of Shock
Hypovolemic (most common) Decreased circulatory volume e.g. Hemorrhage or fluid loss
Cardiogenic Impaired heart pump function e.g. Acute coronary syndrome, valve failure, dysrhythmias
Distributive Pathologic peripheral blood vessel vasodilation e.g. Sepsis, anaphylaxis, neurogenic
Obstructive Non-cardiac obstruction to blood flow e.g Pulmonary embolus, tension pneumothorax, tamponade

Understanding the primary cause is important to guide treatment, but the end results of shock (circulatory collapse and end organ damage) are the same for all.

To me that suggests that if your shock index is over 1 then your priority should be sitting/lying down and getting oxygen back to your body. But I'm not a doctor. It would be very interesting to get the view of a doctor who uses the shock index about the significance of an intermittently high shock index.