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9.1 Introduction
Chapter 9: Exhaled and nasal NO to today
Having already presented my own research and preliminary discussion around the findings,
this chapter reviews where the research on exhaled NO had reached by 2000 and describes the
continued progression in this field to 2006. I will begin with a review of the official
statements from two international respiratory societies - the European Respiratory Society
(ERS) and American Thoracic Society (ATS) - both of which aimed to standardise the
techniques of NO measurement. I will present what is now known regarding NO in health and
in respiratory diseases in adults, children and infants. In the final paragraph I will give my
opinion as to where I believe this information is most useful.
9.2 Technical factors affecting results across research groups
By the end of the 1990s, exhaled and nasal NO had been measured in many groups; in normal
subjects (both adult and paediatric populations), as well as in those with asthma, non-
asthmatic atopy, chronic obstructive pulmonary disease (COPD), chronic bronchitis, cystic
fibrosis (CF), ciliary disorders, bronchiectasis and interstitial lung disease. As alluded to in
previous chapters, some findings remained consistent across the research groups. The best
examples of consistency in exhaled oral NO results were the high levels measured in steroid
naive asthmatics compared to normal controls which reduced with steroids, and the lower NO
levels in asthmatics already on inhaled or oral corticosteroids. For nasal NO measurements,
the most consistent findings were the low levels seen in patients with primary ciliary
dyskinesia and CF. However, other results were not consistent across research groups and
even when conclusions were similar, the absolute levels of exhaled NO were very different. It
was this discrepancy that led to the commencement of the methodological studies discussed in
the previous chapters. There were many reasons for the differences in the absolute levels that
were reported. I will list here what I believe constituted the main sources of variation.
1. Modification of analysers - the early analysers had been modified from machines
originally developed to measure NO in pollution using the chemiluminscence reaction,
similar to the machine that I adapted. The analysers used at that time included:
o Aerocrine AB, PO Box L024, Solna, Sweden.
o CLA 510s, Horiba, Kyoto, Japan.
o CLD 700AL, Eco Physics, AG, Basal or Duerten, Switzerland.
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