Related Experiment Video
Updated: Nov 7, 2025

Supramaximal Intensity Hypoxic Exercise and Vascular Function Assessment in Mice
Published on: March 15, 2019
Acute normobaric hypoxia does not increase blood or plasma viscosity
Michael Buono1, Kaitlyn Rostomily1
1School of Exercise and Nutritional Sciences, San Diego State University, San Diego, CA, USA.
Background:
It has previously been reported that chronic hypoxia increases blood viscosity. The increase is usually attributed to polycythemia-induced increases in hematocrit. However, the effect of acute hypoxia in humans on blood viscosity is unknown.
Objective:
Therefore, the purpose of this study was to determine the effect of acute hypoxia, independent of changes in hematocrit, on blood and plasma viscosity.
Methods:
Nine healthy volunteers breathed room air for 30 min, followed by 30 min of breathing 15% oxygen. Blood samples were collected at the end of both the normoxic and hypoxic conditions. Blood viscosity, plasma viscosity, and hematocrit were measured in each sample.
Results:
The mean±SD hemoglobin oxygen saturation significantly (P < 0.05) decreased from 98±1% during normoxia to 87±2% during hypoxia. Hematocrit was essentially identical for the two conditions (42.1% vs. 42.0%). Blood viscosity was not significantly different for the two conditions with a mean of 2.89±0.17 cP during normoxia and 2.83±0.19 cP during hypoxia. Likewise, plasma viscosity was not significantly different for the two conditions with a mean of 1.19±0.04 cP during normoxia and 1.19±0.05 cP during hypoxia.
Conclusion:
Such results suggest that acute normobaric hypoxia, independent of changes in hematocrit, does not increase blood or plasma viscosity.
Related Concept Videos
Oxygen Transport in the Blood
Hypoxia
Types of Hypoxia
There are four primary types of hypoxia, each resulting from a different cause:
1. Anemic hypoxia: This type occurs due to insufficient oxygen delivery caused by a lack of red blood cells (RBCs) or RBCs with abnormal or...
Hyperpnea and Hyperventilation
Acute Respiratory Failure-II
The underlying physiological abnormalities that contribute to hypoxemic respiratory failure include:
Autoregulation of Blood Flow
Chemical Signaling in Autoregulation
Chemical signaling operates at the precapillary sphincter level, inciting either contraction or relaxation....
Chemical Factors Affecting Respiration Centers
CO2 has a potent influence on respiration and is strictly regulated....

