Related Experiment Videos
Impact of volume-dependent alveolar diffusing capacity on exhaled nitric oxide concentration
1Department of Chemical and Biochemical Engineering and Materials Science, University of California, Irvine, 92697-2575, USA.
Annals of Biomedical Engineering
|October 16, 2001
Summary
Exhaled nitric oxide (NO) levels may indicate lung inflammation. A new model shows that the diffusing capacity for NO (D(NO,alv)) increases with lung volume, explaining the steady NO concentration at exhalation.
Area of Science:
- Pulmonary Physiology
- Biomarker Discovery
- Respiratory Medicine
Background:
- Exhaled endogenous nitric oxide (NO) is a potential biomarker for pulmonary inflammation.
- Previous models assumed constant alveolar nitric oxide flux (J(max,alv)) and diffusing capacity (D(NO,alv)).
Purpose of the Study:
- To investigate the impact of a volume-dependent diffusing capacity for NO (D(NO,alv)) on exhaled NO concentration.
- To incorporate the volume dependence of D(NO,alv) into a two-compartment model of NO exchange.
Main Methods:
- Utilized a two-compartment model for nitric oxide (NO) exchange dynamics.
- Incorporated a newly established relationship where D(NO,alv) increases with alveolar volume (VA): D(NO,alv) = 48*VA(2/3) ml/min/mmHg.
Main Results:
- The study demonstrates that D(NO,alv) is not constant but increases with alveolar volume (VA).
- The plateau in exhaled NO concentration is explained by a constant ratio of J(max,alv)/D(NO,alv).
- This constant ratio implies a volume dependence of J(max,alv) similar to D(NO,alv), likely due to decreasing alveolar surface area during exhalation.
Conclusions:
- The volume dependence of D(NO,alv) significantly impacts exhaled NO concentration dynamics.
- A constant ratio of J(max,alv)/D(NO,alv) is the likely mechanism for the end-exhaled NO plateau.
- This finding necessitates re-evaluation of NO exchange models in respiratory research.