Submitted on December 23, 2008
Revised on March 18, 2009
Accepted on March 18, 2009
THE EFFECT OF POSTURE-INDUCED CHANGES IN PERIPHERAL NITRIC OXIDE UPTAKE ON EXHALED NITRIC OXIDE
Sylvia A.B. Verbanck1*, Yannick Kerckx2, Daniel Schuermans3, Claire Marie de Bisschop4, Herve Guenard, Robert Naeije5, Walter Vincken3, and Alain Van Muylem6
1 Academic Hospital University of Brussels
2 Universite Libre de Bruxelles
3 University Hospital UZ Brussel
4 Poitiers University, Sport Sciences Faculty
5 Free University of Brussels, Belgium
6 Erasme University Hospital
* To whom correspondence should be addressed. E-mail: sylvia.verbanck{at}uzbrussel.be.
Airway and alveolar NO contributions to exhaled NO are being extracted from exhaled NO measurements performed at different flow rates. In order to test the robustness of this method and the validity of the underlying model, we deliberately induced a change in NO uptake in the peripheral lung compartment by changing body posture between supine and prone. In 10 normal subjects, we measured exhaled NO at target flows ranging 50-350ml/s in supine and prone postures. Using two common methods, bronchial NO production (Jaw(NO)) and alveolar NO concentration (FANO) were extracted from exhaled NO concentration versus flow or flow-1 curves. There was no significant Jaw(NO) difference between prone and supine, and a significant FANO decrease from prone to supine ranging 23-33% depending on the method used. Total lung capacity was 7% smaller supine than prone (p=0.03). Besides this purely volumetric effect, which would tend to increase FANO from prone to supine, the observed degree of FANO decrease from prone to supine suggests a greater opposing effect which could be explained by the increased lung capillary blood volume (Vc) supine versus prone (p=0.002) observed in another set of 11 normal subjects. Taken together with the relative changes of NO and CO transfer factors, this Vc change can be attributed mainly to pulmonary capillary recruitment from prone to supine. Realistic models for exhaled NO simulation should include the possibility that a portion of the pulmonary capillary bed is unavailable for NO uptake, with a maximum capacity of the pulmonary capillary bed in the supine posture.
