Assessment of nasal and bronchial inflammation:
Rhinitis (allergic and non-allergic), SP and asthma are diseases that are characterized by processes whose pathogenesis is based on inflammation. Inflammation of the airways can be assessed directly or indirectly. The techniques for assessing inflammation directly can be divided into invasive techniques and non-invasive techniques.
Within invasive techniques we include those which require nasal or bronchial endoscopy such as biopsy. However, the applicability of these invasive methods has many limitations because they are not without risks and/or complications. They also require considerable experience to implement. It is therefore very important to develop and validate new methods that allow us to non-invasively detect inflammation of the upper and lower airways.
Nitrous oxide (NO): Is synthesized from the amino acid L-arginine by the action of the enzyme nitric oxide synthase (NOS). Three isoforms of this enzyme are known: nNOS or NOS1, which predominates in nervous tissue; iNOS, inducible NOS or NOS2, induced by an agent that activates the immune system; and eNOS, endothelial NOS or NOS3, constituent of the vascular endothelium. Since iNOS is found in different cells of the respiratory tract and is induced by various inflammatory cytokines, NO is considered to be an excellent marker for airway inflammation. Thus, just as exhaled nitric oxide (FeNO) is considered a good non-invasive marker of inflammation of the lower airways, nasal nitric oxide (nNO) potentially appears be a good marker of nasal inflammation.
Nasal nitric oxide (nNO): Some authors describe reference values for nNO up to one hundred times higher than those for FeNO. However, until now normal levels of nNO in different nasal diseases and in healthy individuals have not been established because the published results vary widely. Dotsch et al. in 1996 published a series of 67 healthy subjects in which they found mean nNO values in a healthy population of 96±47 ppb. A year later Ferguson studied 82 healthy patients and published mean normal values of nNO of 1197±361 ppb. Additional papers were published subsequently, but the results remained quite diverse.
As for the reference values in patients with rhinitis, data published so far are also contradictory. Some authors show that nNO is higher in patients diagnosed with rhinitis, especially in patients with AR. However, other studies have not observed differences in levels of nNO in patients diagnosed with rhinitis compared to the normal population.
The electronic nose: Is a new technique which is based on the detection of VOCs present in the gas phase of the human respiration and that can be detected by chromatography and mass spectrometry sensors. It consists of a device made up of several nanosensors that when exposed to volatile particles undergo specific changes in their electrical resistance, resulting in a pattern or profile of VOCs by logarithmic regression. These VOC patterns can be used as non-invasive biomarkers of several biochemical processes that occur in different diseases whose pathogenesis is based on inflammation. For example, in diseases of the airways they have been used successfully in comparing patterns of VOCs in patients with chronic obstructive pulmonary disease (COPD) and asthma. This technique's potential applicability in biomedicine is enormous.
In short, both measuring nNO and determining patterns of VOCs by the electronic nose are non-invasive methods that can help in the diagnosis and monitoring of certain respiratory diseases. However, in the case of nNO currently available studies show very different and conflicting results and in the case of the determination of VOCs by electronic nose there are very few papers published to date. It is therefore vital to design a study that allows us to clarify the potential utility of non-invasive markers of inflammation such as determination of nNO and determination of the different patterns of VOCs by electronic nose in healthy patients, in patients diagnosed with AR and non-allergic rhinitis and in patients with associated SP and asthma.
Working Hypothesis: Rhinitis, SP and asthma are prevalent diseases that cause considerable morbidity. Since the substrate of these diseases lies in inflammation, our group of investigators believe that the study of inflammation is one of the most interesting aspects for assessment and management of these diseases. Similarly to how measuring FeNO is being used as a good marker of bronchial inflammation, measuring nNO and determining patterns of VOCs by the electronic nose could also be two good non-invasive markers of upper and/or lower (in the case of VOCs) airway inflammation. However, although in recent years there have been some studies on the origin, function and utility of measuring nNO and the use of the electronic nose in respiratory disease, there are still many questions that remain in reference to these two techniques.
