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9.6 Nasal nitric oxide measurement
For completion, I am going to briefly cover nasal NO although I did not measure this
parameter as part of my research. Presentation of standard techniques for this measurement
commenced in 1999 (American Thoracic Society and Association. 1999), with minor
amendments in 2002 and 2005 (Baraldi, de Jongste et al.2N2; American Thoracic Society
and European Respiratory Society 2005). The NO concentration is far greater in the nose than
the lower respiratory tract and is measured in parts per million as opposed to parts per billion
(Alving, Weitzberg et al. 1993; Gerlach, Rossaint et al. 1994; Lundberg, Farkas-Szallasi et al.
1995). NO concentration is even higher in the para-nasal sinuses (Lundberg, Rinder et al.
1994; Lundberg, Farkas-Szallasi et al. 1995; Haight, Qian et al. 2000).
Table 9.3: The recommended standard for nasal NO measurement
The current recommended technique for measurement of nasal NO is:
o tho subject is seated
o two nasalolives are placed with a central lumen in the nares.
o these must be of sufficient size to occlude the nostril.
o d sdlTrple is aspirated continuously at a constant rate from one narus.
o gas is entrained via the other narus giving a trans-nasal flow in series.
o a target sampling airflow of 0.25 to O.3Umin is recommended.
. oropharyngeal and lower airway contamination is prevented by one of the methods
suggested (see paragraph below).
. mean NO values are calculated for a stable plateau of greater than ten seconds or five
breaths (Silkotf, Chatkin et al. 1999; Ratjen, Kavuk et al. 2000).
o the higher flow rate (compared to exhaled oral sampling) at 0.25-3Umin allows a steady
plateau levelof NO concentration in subjects within 20-30 seconds.
This trans-nasal flow reflects the most cornmon method of measurement. An alternative is to
have continual aspiration of both nares; one to discard and one to measure. Velum closure can
be achieved in a number of ways; the most common is to slowly exhale orally against a
resistance similar to the exhaled NO recommendation (Arnal, Didier et al. 1997; Kharitonov,
Rajakulasingam et al. 1997; Silkofl McClean et al. 1997; Dubois, Douglas et al. 1998;
Silkoff, Chatkin et al. 1999). Other options that have also been effective are purse-lip
breathing via the mouth (Rodenstein and Stanescu 1983), breath-holding with the velum
closed (Kimberly, Nejadnik et al. 1996) or voluntary elevation of the soft palate by a trained
subject (Giraud, Nejadnik et al. 1998). Of note for nasal NO measurements, healthy adults
have significantly better repeatability than healthy children (Kharitonov, Walker et al. 2005).
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