Spleen contraction elevates hemoglobin concentration at high altitude during rest and exercise

Area of Science:

• Physiology
• Altitude Medicine
• Sports Science

Background:

• Hypoxia and exercise independently stimulate spleen contraction.
• The spleen stores erythrocytes that can be released to enhance oxygen transport.

Purpose of the Study:

• To investigate spleen volume and hemoglobin concentration changes during rest and exercise at varying altitudes.
• To understand the spleen's role in erythrocyte mobilization under hypoxic conditions.

Main Methods:

• Eleven healthy lowlanders performed a step test at 1370m, 3700m, and 4200m.
• Spleen volume was measured using ultrasound, and hemoglobin via Hemocue.
• Cardiorespiratory variables were monitored throughout the study.

Main Results:

• Spleen volume decreased with increasing altitude and further with exercise.
• Hemoglobin concentration increased with altitude and during exercise, but the increase was smaller at 4200m compared to 3700m.
• Spleen volume and hemoglobin returned to baseline levels after 10 minutes of rest.

Conclusions:

• The spleen contracts at rest and during exercise at high altitudes to enhance oxygen delivery.
• Reduced hemoglobin response at the highest altitude suggests maximal spleen recruitment at rest and during exercise.