Effect of altitude exposure on platelets

Area of Science:

• Physiology
• Aerospace Medicine
• Hematology

Background:

• Decompression from depth is known to decrease platelet counts.
• The effects of altitude-induced decompression and exposure on platelet function are not fully understood.

Purpose of the Study:

• To investigate the impact of simulated and natural altitude decompression on circulating platelet counts and survival.
• To explore the potential mechanism of platelet sequestration in the pulmonary vascular bed.

Main Methods:

• Human subjects underwent simulated altitude decompression (20,000 ft) without hypoxia.
• Platelet counts and autologous platelet survival were measured post-decompression.
• Subjects were exposed to natural high-altitude environments (9,800 ft and 17,600 ft).
• Rabbits received homologous, chromium-51-labeled platelets after decompression (hypoxic and nonhypoxic).

Main Results:

• A significant (P < 0.01) 10% drop in platelet count occurred for three days after simulated altitude decompression.
• Four out of five subjects showed shortened platelet survival after exposure.
• Natural high-altitude exposure led to significant mean platelet count decreases of 7% (9,800 ft) and 25% (17,600 ft) on day 2.
• Platelet counts returned to baseline by day 5 in the natural environment.
• Decompressed rabbits showed increased lung radioactivity with labeled platelets, suggesting pulmonary sequestration.

Conclusions:

• Altitude decompression, like depth decompression, causes a reduction in circulating platelet count.
• Platelet sequestration in the pulmonary vascular bed is a likely mechanism for altitude-induced thrombocytopenia.
• Further research is warranted to understand the clinical implications of these findings for individuals exposed to high altitudes.