THE DIVING REFLEX IN NON-EOSINOPHILIC NONALLERGIC RHINITIS

The usual nasal response to head submersion in aquatic mammals is an i ncrease in resistance to airflow, the so-called diving reflex. Althoug h less well developed in humans, it is nevertheless present. It is lik ely to occur due to a relative increase of parasympathetic over sympat hetic control of the nasal vasculature. Non-eosinophilic non-allergic rhinitis is thought to be due to a similar imbalance and we have attem pted to establish whether the diving reflex is abnormal in this condit ion. 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 measure d before and after the test by means of active anterior rhinomanometry . There was no significant increase in ETR in the normal group but a s ignificant increase in ETR in the NENAR group (pre-test median ETR-0.4 64 kPa.s.l(-1), post-test median ETR 0.667 kPa.s.l(-1), (Wilcoxon's si gned 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 nor mal group (Mann-Whitney, extract probability P = 0.04). We conclude th e nasal airway response to simulated diving in NENAR is abnormal.