Abstract
Adequate perception of nasal airflow (i.e., nasal patency) is an important consideration for patients with nasal sinus diseases. The perception of a lack of nasal patency becomes the primary symptom that drives these patients to seek medical treatment. However, clinical assessment of nasal patency remains a challenge because we lack objective measurements that correlate well with what patients perceive.The current study examined factors that may influence perceived patency, including air temperature, humidity, mucosal cooling, nasal resistance, and trigeminal sensitivity. Forty-four healthy subjects rated nasal patency while sampling air from three facial exposure boxes that were ventilated with untreated room air, cold air, and dry air, respectively. In all conditions, air temperature and relative humidity inside each box were recorded with sensors connected to a computer. Nasal resistance and minimum airway cross-sectional area (MCA) were measured using rhinomanometry and acoustic rhinometry, respectively. General trigeminal sensitivity was assessed through lateralization thresholds to butanol. No significant correlation was found between perceived patency and nasal resistance or MCA. In contrast, air temperature, humidity, and butanol threshold combined significantly contributed to the ratings of patency, with mucosal cooling (heat loss) being the most heavily weighted predictor. Air humidity significantly influences perceived patency, suggesting that mucosal cooling rather than air temperature alone provides the trigeminal sensation that results in perception of patency. The dynamic cooling between the airstream and the mucosal wall may be quantified experimentally or computationally and could potentially lead to a new clinical evaluation tool.
Highlights
The subjective sensation of nasal airflow, or nasal patency, is of great importance to patients with nasal sinus disease
To test whether nasal patency sensation is mediated by nasal mucosal cooling rather than by air temperature or humidity alone, we examined whether the computed total nasal mucosal heat loss (q) during breathing was a better predictor of nasal patency than temperature or relative humidity (RH) alone, using Equation 1: q~V r1⁄2DH(Cend {Cin)zcP(Tend {Tin), ð1Þ
The third hypothesis of this study examined whether factors such as lateralization thresholds to butanol, nasal resistance, or minimum airway cross-section area (MCA), measured by rhinomanometry and acoustic rhinometry, respectively, contributed as alternative or confounding factors in modulating perceived nasal patency
Summary
The subjective sensation of nasal airflow, or nasal patency, is of great importance to patients with nasal sinus disease. A perception of a lack of nasal patency is the primary symptom that drives these patients to seek medical treatment. This subjective perception often bears little relationship to the actual physical resistance to airflow in the nose. Despite the plausible role of trigeminal cool receptor input in perception of nasal patency, factors that stimulate or modulate this signal remain unclear. We hypothesized that if air humidity significantly influences perceived patency, it would suggest that mucosal cooling, which is the combination of both conductive heat loss (driven by temperature gradient) and evaporative heat loss (driven by water vapor pressure gradient), is the actual underlying factor contributing to the sensation of nasal patency, rather than temperature alone (hypothesis 2). We believe that clinical assessment and improvement of subjective nasal patency will be enhanced by fully understanding the underlying mechanisms that influence the perception of patency
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