Agnirva Space Premier League - Expedition #31765: Breathing in Space: Understanding Exhaled Nitric Oxide Levels on the ISS

When astronauts breathe in space, it's not quite the same as breathing on Earth. One of the most fascinating ways scientists monitor astronaut health is through a simple breath test measuring exhaled nitric oxide (NO). The Exhaled Nitric Oxide-1 experiment, led by Professor Dag Linnarsson of the Karolinska Institute, sought to understand how microgravity affects nitric oxide levels in the lungs.

Nitric oxide is a naturally occurring gas produced in our airways. On Earth, measuring exhaled NO is commonly used to assess inflammation in the respiratory tract—especially for conditions like asthma. But what happens to this biomarker in space, where the lungs must adapt to an entirely different gravitational context?

During Expeditions 12 through 17, astronauts aboard the ISS participated in this ESA-sponsored study. Using equipment developed by Aerocrine in Sweden, crew members exhaled into specialized devices that captured their breath samples for later analysis. The results were surprising. Exhaled nitric oxide levels were significantly lower in microgravity than on Earth.

This decrease may be due to changes in lung physiology caused by the absence of gravity. On Earth, gravity helps blood and gases distribute evenly across the lungs. In microgravity, that balance is disrupted, potentially affecting how gases like NO are produced and exhaled. This has critical implications for astronaut health, especially during long-term missions.

Understanding these changes helps scientists develop better countermeasures for respiratory issues in space. It also has terrestrial applications. The findings could lead to improved diagnostics for respiratory diseases by highlighting how environmental factors influence biomarker levels. It’s a classic example of space research coming full circle—advancing science both in orbit and on the ground.

What makes this study stand out is its focus on a non-invasive, practical diagnostic tool. In the constrained environment of a spacecraft, simplicity and reliability are crucial. Breath analysis offers both, making it an attractive method for continuous health monitoring during extended missions.

Ultimately, Exhaled Nitric Oxide-1 laid the groundwork for future studies of respiratory function in space, paving the way for better understanding of human adaptation to life beyond Earth. As we prepare for deep space missions to the Moon and Mars, these kinds of physiological studies will be critical to ensuring crew health and mission success.

Get certified with over 100 hours of immersive, self-paced learning in astronomy, cosmology, space technology, and climate science through the Agnirva Space Internship Program. Join, complete virtual projects, and earn a digital certificate to showcase your space fluency in interviews, resumes, and beyond.