The diving reflex in non-eosinophilic non-allergic rhinitis.

The usual nasal response to head submersion in aquatic mammals is an increase in resistance to airflow, the so-called diving reflex. Although less well developed in humans, it is nevertheless present. It is likely to occur due to a relative increase of parasympathetic over sympathetic control of the nasal vasculature. Non-eosinophilic non-allergic rhinitis is thought to be due to a similar imbalance and we have attempted to establish whether the diving reflex is abnormal in this condition. Sixteen normal subjects and 18 subjects with non-eosinophilic non-allergic rhinitis (NENAR) underwent simulated diving using the ‘cold face test'. Expiratory total nasal airway resistance (ETR) was measured before and after the test by means of active anterior rhinomanometry. There was no significant increase in ETR in the normal group but a significant increase in ETR in the NENAR group (pre-test median ETR—0.464 kPa.s.l−1, post-test median ETR 0.667 kPa.s.l−1, (Wilcoxon's signed rank test P < 0.05). The change in median ETR in the NENAR group was also significantly higher than the median change in ETR in the normal group (Mann-Whitney, extract probability P= 0.04). We conclude the nasal airway response to simulated diving in NENAR is abnormal.