Subjective perception of nasal breathing

Nasal obstruction is a very common nasal complaint in clinical practice. The mechanism of nasal breathing perception is poorly understood and controversial. Currently, there is no reliable tool for measuring nasal perception of air flow. This thesis aims to develop an understanding of nasal perception pathway, identify factors contributing to nasal perception and develop a new reliable measuring tool.

Empty nose syndrome (ENS) is a well-known condition characterized by paradoxical sensation of nasal obstruction despite wide empty nasal space. The explanation of this condition can enhance the understanding of nasal perception mechanism, therefore pathophysiology of ENS was studied. (Chapter 2) The nasal perception is driven by the nasal mucosal ‘cooling’ which connected to brainstem control center and specific region of cerebral cortices including emotional processing area. Our experiment found that the effect of emotional control and psychogenic modulation on nasal perception is likely to be the explanation of the discordance between subjective and objective findings in ENS and may potentially be its cause.

The utility of objective airway test on structural obstruction was studied in patients who underwent nasal obstruction surgery. (Chapter 3) Nasal resistance demonstrates higher correlation of the impact of surgery with patient reported outcomes on the obstructed side. The control of ‘disease factor’ is deemed successful when an improvement in unilateral nasal resistance by 0.2 Pa/cm3/s or total resistance by 0.1 Pa/cm3/s is achieved.

Despite achieving the desired outcome in controlling the ‘disease factor’, persistent nasal obstruction also depends on ‘patient factor.’ The ‘patient factor’ associated with poor surgical outcome from the turbinate surgery was studied by comparing ENS and non-ENS patients. (low or high benefit) (Chapter 4) High psychogenic function, disproportionate subjective nasal complaints and the presence of reflux symptoms were shown to be characteristic of ENS. The new measuring tool called ENS12Qs was developed accordingly. (Chapter 5) This 12-item questionnaire utilized in this study to differentiate ENS from non-ENS cases can potentially be used to clinically identify patients at risk of developing poor surgical outcome ‘before’ it occurs.

In conclusion, this thesis provides the understanding and insight of subjective nasal perception. Psychogenic factor is the major contributor on subjective nasal perception and could explain the paradoxical finding between subjective perception and objective nasal airway test. The poor psychogenic function found in ENS led to the development of subjective measurement tool which provides a comprehensive and reliable subjective nasal perception assessment.