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Simulated postnasal mucus fails to reproduce the symptoms of postnasal drip in rhinitics but only in healthy subjects.

BACKGROUND
Post nasal drip (PND) is a very common symptom associated with upper respiratory tract disorders. While easy to visualize, the concept of PND due to an increased volume of secretions which move from the posterior nasal choanae into the posterior nasopharynx/oropharynx may be overly simplistic. PND could also be associated with altered viscosity of nasal secretions. An alternative hypothesis is that the sensation of PND is due to mucosal inflammation resulting in heightened cough or irritant throat sensory dysfunction. The impact of viscous secretions on the symptoms of PND is assessed.


METHODS
Healthy subjects and rhinitis patients were recruited. Patients were asked about PND symptoms with a 9 item PNDSS questionnaire at baseline and after the insertion of two different viscosities of artificial mucus utilizing hydroxypropyl methylcellulose at 1% and 4%.


RESULTS
Sixty six patients were recruited. As expected, rhinitics had an increased sense of PND compared to healthy subjects at baseline. However, only healthy subjects could detect the increased viscosity of secretions and where rhinitics failed to respond. Cough was not induced in either group.


CONCLUSION
The mechanisms of PND in chronic patients and those with rhinitis are likely to have other aetiologies other than simply increased or more viscous secretions.