Pulmonary nitric oxide in astronauts before and during long-term spaceflight

Area of Science:

• Space Medicine
• Respiratory Physiology

Background:

• Astronauts face risks from toxic dust exposure during space missions.
• Exhaled nitric oxide partial pressure (PENO) is a non-invasive biomarker for airway inflammation.
• Lung NO turnover is influenced by gravity and gas density, factors altered in space.

Purpose of the Study:

• To investigate the impact of microgravity and reduced atmospheric pressure on exhaled nitric oxide partial pressure (PENO) in astronauts.
• To assess PENO as a monitor for lung health changes during spaceflight.
• To evaluate the effect of different atmospheric pressures on PENO measurements.

Main Methods:

• Ten astronauts were monitored pre-flight (1 G) and inflight (microgravity).
• Measurements included PENO at 50 mL/s (PENO50), alveolar NO, and airway NO flux.
• Six astronauts were also studied at reduced atmospheric pressure (0.7 ata).

Main Results:

• PENO50 decreased over time during the observation period (p=0.0284).
• PENO50 was significantly lower in microgravity (1.65 mPa) compared to 1 G (2.28 mPa), a 27% reduction.
• Reduced atmospheric pressure did not affect PENO50 but increased airway NO contribution.

Conclusions:

• Observed PENO50 changes suggest initial airway inflammation that resolved over time.
• Baseline PENO50 for astronauts should be established under relevant gravity conditions.
• PENO monitoring may require adjustments based on gravity and atmospheric pressure during space missions.