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Nitric oxide in single-breath exhalation in humans
1Hermann Rahn Laboratory of Environmental Physiology, Department of Physiology, School of Medicine and Biomedical Science, University, Buffalo, NY 14214, USA.
The Japanese Journal of Physiology
|August 1, 1997
Summary
Nitric oxide (NO) exhaled air results from airway formation and alveolar clearance. This study shows NO is lower in late exhaled air, indicating diffusion in alveoli clears NO.
Area of Science:
- Pulmonary physiology
- Respiratory medicine
- Biomedical engineering
Background:
- Nitric oxide (NO) plays a role in airway function.
- Measuring exhaled NO (VNO) is complex due to gas mixing.
- Alveolar gas collection is challenging in human subjects.
Purpose of the Study:
- To test if exhaled NO (VNO) is determined by airway production and alveolar clearance.
- To investigate the diffusion of NO in the alveoli.
- To understand NO dynamics in the respiratory tract.
Main Methods:
- Utilized a single-breath technique in 5 healthy volunteers.
- Analyzed early and late fractions of exhaled air.
- Measured carbon dioxide fraction (FECO2) to differentiate gas origins.
- Compared NO concentration and VNO after inspiring NO-free and NO-containing gas (510 ppb).
Main Results:
- NO concentration and amount were significantly lower in the late exhaled air fraction compared to the early fraction.
- This difference was observed regardless of whether subjects inspired NO-free or NO-containing gas.
- FECO2 profiles confirmed the distinct origins of early (conducting airways/transition zone) and late (alveolar) exhaled air fractions.
Conclusions:
- Nitric oxide (NO) is continuously produced in the conducting airways and/or transition zone.
- NO is acquired by both inhaled and exhaled air within these regions.
- NO is effectively cleared by diffusion within the alveoli, reducing its concentration in the late exhaled air.