GE Analytical Instruments ©2006 10-1 DLM 14291 Rev. A
10. NASAL NITRIC OXIDE
The concentration of nitric oxide in the nasal cavities, paranasal sinuses, and other
cavities is measured using a trans-nasal flow of low NO air while the subject
performs an oral exhalation against resistance to elevate the soft palette,
eliminating air from the lower airways. With the NOA 280i, this is performed using
an external vacuum pump with a flow control device, a nasal olive, and a sampling
line equipped with a tee for sidestream sampling by the NOA
The American Thoracic Society has published “Recommendations for Standardized
Procedures for the Online and Offline Measurement of Exhaled Lower Respiratory
Nitric Oxide and Nasal Nitric Oxide in Adults and Children-1999” (Am J Respir Crit
Care Med Vol 160. pp 2104–2117, 1999).
The recommended procedure uses two nasal olives with a central lumen that are
securely placed in the nares. The subject inserts a mouthpiece with expiratory
resistance, inhales to total lung capacity, and then orally exhales while
maintaining a mouth pressure of 10 cm H
2
O. While the oral exhalation is occurring,
air is aspirated at a flow rate of 3 L/min via one of the nasal olives while a supply
of low NO air is provided via the other olive.
An NO plateau should be achieved under these conditions within ~20 seconds If an
NO plateaus is not obtained at 3 L/min, higher flows (3–6 L/min) can be used. The
transnasal flow used for the collection should be recorded with each nasal NO
measurement.
Recommended Setup
The setup for nasal nitric oxide measurements consists of:
• A vacuum source capable of drawing 3-6 L/min.
• A rotometer or other flow control device for regulating the flow into the
vacuum source.
• Tubing to connect the vacuum source.
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