Endonasal thermal imaging of the nasal cavity

<p dir="ltr">Traditionally, the perception of nasal obstruction was assumed to be inadequate airflow or the sensation of increased airflow resistance through the nostrils. However, surgical experience dictates that simply providing nasal airflow/decreased resistance does not always overcome "nasal obstruction". Direct airflow analysis from respiratory efforts or airflow resistance (rhinomanometry) has been the primary method for objectifying the perception of nasal breathing. However, objective tests that evaluate resistance and cross-sectional area correlate poorly with subjective nasal obstruction. Additionally, no airflow receptors have been identified in the nose. Increasing evidence suggests that nasal breathing is caused by the mucosal cooling of the sensory receptors across the nasal cavity during inspiration. Changes in nasal temperature can predict the patient-reported perception of nasal breathing and reveal a more significant correlation than the nasal resistance and cross-sectional area.</p><p dir="ltr">Miniaturized and infrared thermocouples have been utilized in previous studies to measure intranasal mucosal temperature. Nevertheless, the outcome is inconsistent, possibly due to mucosal irritation from the sensor after contact. Additionally, it is challenging to position the contact sensor on the inferior turbinates or nasal septum. Non-contact thermal sensing, such as an infrared camera (IR), may be preferable. Therefore, this thesis aims to develop the endonasal thermal image of the nasal passage and assess the intranasal mucosal temperature with the subjective perception of nasal breathing and objective measurement of nasal airflow.</p><p dir="ltr">A cross-sectional analysis of a single cohort of consecutively recruited and clinically evaluated patients with nasal obstruction were recruited. Intranasal mucosal temperatures were extracted from the thermal endonasal image of the nasal passage generated from the infrared radiometric thermal camera (FILR VS290). The mid-expiration and mid-inspiration temperature data (internal nasal valve area, nasal cavity area, inferior turbinate area, and overall airway (mean value)) were compared to the patient-reported nasal breathing (visual analog scale (VAS), Nasal Obstruction Symptom Evaluation (NOSE) scale) and nasal airway resistance (NAR) pre-and post-decongestion.</p><p dir="ltr">33 patients (age 33.94±11.65 years, 39.4.% female, 66 nasal cavities) were included. Mid-expiration temperature (ExT) of all areas were higher than mid-inspiration temperature (InT) at both pre-and post-decongestion states. ExT post-decongestion of three areas and overall airway were lower than ExT pre-decongestion. No statistically significant correlations were found between intranasal mucosal temperature, subjective perception of nasal breathing, and objective measurement of nasal airflow at pre-and post-decongestion states.</p><p dir="ltr">Additionally, A prospective study of adult patients with nasal obstruction managed with nasal airway surgery was performed. Intranasal mucosal temperatures were determined using the thermal endonasal image of the nasal passage produced by the infrared radiometric thermal camera (FILR VS290). A comparison was made between the mean values of ExT and InT temperature data (internal nasal valve, nasal cavity, inferior turbinate, and overall airway (mean value)) and VAS, NOSE scale and NAR before and after surgery.</p><p dir="ltr">7 patients (35.14±16.45 years, 57.14.% female, 14 nasal cavities) were included. All NOSE, VAS, and NAR improved after surgery. ExT, InT, and the difference between ExT and InT of three areas and overall airway were similar between pre-and post-surgery. No statistically significant correlations were found between intranasal mucosal temperature, VAS, NOSE, and NAR at pre-and post-surgery except for the difference between ExT and InT of overall airway and NOSE pre-operative.</p><p dir="ltr">In conclusion, this thesis establishes that endonasal thermal imaging, utilizing infrared radiometric thermal cameras, has the potential to assess the perception of nasal breathing in patients with nasal obstruction in pre- and post-decongestion states. However, it cannot demonstrate the difference in intranasal mucosal temperature between pre-operative and post-operative states in nasal airway surgery. More precise thermal imaging of the nasal passage is essential if mucosal temperature is to be a reliable measure of nasal obstruction in a clinical setting.</p>