Blood shift

Blood shift has at least two separate meanings:

Free diving


When the body is immersed, the diving reflex will contract the circular muscle in blood vessels of the arms and legs, reducing the total volume of blood vessels in the body. Therefore, a greater proportion of blood volume will remain in the torso, moved mainly in the pulmonary artery. This results in an increase in blood pressure, and shrinkage of the alveoli. The increased external pressure creates a pressure differential with the lungs, leading to a further influx of venous blood into the lung cavity. The blood vessels in the lungs expand and fill, and the alveoli contract still further.[1]

Practical implications

The maximum diving depth of the free diver is mainly determined by the ratio of the residual volume (RV) to the total lung capacity (TLC). The blood shift causes the lungs' capillary volume to expand resulting in a reduction of the residual volume and thus in an increase of the maximum possible depth. A redistribution of about 1.53 liters of blood to the pulmonary blood vessels has been shown. [1]


  1. 1 2 Claus-Martin Muth: Apnoetauchen - Gibt es medizinische Besonderheiten? 8. Bonner Tauchersymposium, 23. Februar 2008. (German)

Further reading

This article is issued from Wikipedia - version of the 11/4/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.