Treatment of nasal inflammation decreases the ability of subjects with asthma to condition inspired air

The effect of nasal structure on olfactory function in patients with OSA

The aim of this study was to investigate the relationship between nasal structure and olfactory function in patients with obstructive sleep apnea (OSA). Olfaction and nasal structure of 76 adults with OSA diagnosed by polysomnography were measured using acoustic rhinometry and the Sniffin, Sticks (SS) smell test at Anzhen Hospital, a major academic center in Beijing, China. We tested the hypothesis that nasal structure in these patients would correlate with objectively measured olfactory performance. Minimum cross-sectional area (MCA) of the nose was significantly correlated with SS composite score (r = 0.434, p < 0.001), a result that was driven by two of the test's three components: olfactory threshold (OT) (r = 0.385, p = 0.001) and olfactory discrimination (OD) (r = 0.370, p = 0.001) but not olfactory identification (OI) (p > 0.05). Additionally, nasal volume (NV) was associated with composite SS score (r = 0.350, p = 0.002), a finding driven by OT (r = 0.283, p = 0.014). These data suggest that nasal structure affects parameters of olfactory function, likely via alterations in nasal airflow. Thus, anatomic abnormalities and diseases involving airflow (such as OSA) may cause, in part, olfactory dysfunction that is amenable to treatment. We speculate that surgery that alters nasal volume and MCA may improve olfactory performance.

Upper airways reactions to cold air

Cold air-induced rhinitis is a common complaint of individuals with chronic allergic or nonallergic rhinitis and those with no chronic nasal disease. It is characterized by rhinorrhea, nasal congestion, and nasal burning that appear within minutes of exposure to cold air and dissipate soon after exposure is terminated. The symptoms of cold-air rhinitis are reproduced experimentally with nasal cold-air provocation. This procedure has shown that nasal mast cell activation and sensory nerve stimulation are associated with the development of nasal symptoms. Sensory nerve activation generates a cholinergic reflex that leads to rhinorrhea; therefore, anticholinergic agents are highly effective in treating cold-air rhinitis. Experimental data suggest that individuals with nasal cold-air sensitivity may have reduced ability to compensate for the water loss that occurs during exposure to cold air. Therefore, the symptoms of cold air-induced rhinitis may reflect the activation of compensatory mechanisms to restore mucosal homeostasis.

Familial aggregation of nasal conditioning capacity

In our previous studies on nasal conditioning, we observed a large variability among individuals to condition inspired air. Although we previously investigated various physiological parameters (age, sex, nasal mucosal temperature, heart rate, blood pressure, and nasal volume) that might underlie these differences, we have been unable to explain this variability. Many proteins and molecules, which are under genetic control and could affect nasal conditioning, are involved in water transport,. In this study, we hypothesized that familial factors may contribute to the differences in nasal conditioning capacity (NCC). We performed a prospective study of 47 sibling pairs. Cold dry air was delivered to the nose, and the total water gradient (TWG) was calculated to determine the NCC. We found a highly significant intraclass correlation of 0.53 (P < 0.0001) between sibling pairs for the TWG. These results suggest that there is a familial basis for nasal conditioning and a large enough genetic component to search for genes explaining the observed correlation.

Alpha-adrenoreceptor blockade with phenoxybenzamine does not affect the ability of the nose to condition air

The primary function of the nose is to warm and humidify air. We have previously shown that raising nasal mucosal temperature by immersing feet in warm water increases the amount of water evaporated by the nose as air passes through it (nasal conditioning capacity; Abbott D, Baroody F, Naureckas E, and Naclerio R. Am J Rhinol 15: 41-45, 2001). To investigate further the effect of nasal mucosal temperature on nasal conditioning capacity, we raised the temperature through alpha-adrenoreceptor blockade by intranasally administering phenoxybenzamine. We hypothesized that blocking alpha-adrenoreceptors during inhalation of cold, dry air would lead to an increase in nasal blood flow, surface temperature, and nasal conditioning capacity, as measured by the water gradient. After appropriate pilot studies, we performed a double-blind, placebo-controlled, two-way crossover study in nine nonatopic, healthy subjects by studying the effect of treatment with intranasal phenoxybenzamine. Nasal mucosal temperature increased significantly after administration of phenoxybenzamine and was associated with a significantly smaller net decrease in nasal mucosal temperature after exposure to cold, dry air (P < 0.05). However, there were no significant differences in nasal conditioning capacity between treatments (P > 0.05). Phenoxybenzamine decreased the symptom of rhinorrhea after exposure to cold, dry air (P < 0.05), but congestion was not different between individuals given phenoxybenzamine and placebo (P > 0.05). Our data demonstrate that phenoxybenzamine, despite raising mucosal temperature and not affecting nasal volume, did not affect the ability of the nose to warm and humidify air.