Mouth breathing – A predictor for patient satisfaction after nasal septoplasty?*

Background: No reliable marker exists to predict septoplasty outcome. Most patients suffering from nasal airway obstruction (NAO) caused by a deviation of the nasal septum report a bothersome mouth breathing and dryness. In this study our aim was to assess, whether mouth breathing could be objectified in these patients and whether mouth breathing could predict septoplasty outcome. Methods: A monocentric, prospective case-control study of 21 patients was conducted. The proportion of mouth breathing was measured in a blinded manner. As a measurement of patient satisfaction, subjective symptoms preand postoperatively, were assessed by using VAS, NOSE and SNOT-20 score. In the patient group an additional acoustic rhinometry and a clinical examination of the nose were performed. Results: With a mean of 25% (SD = 20%) the proportion of mouth breathing in patients with NAO did not differ significantly from the proportion in controls without NAO, with a mean of 27% (SD = 23%). Analysis of subjective scores revealed a significant reduction of subjective symptoms after septoplasty. A higher preoperative proportion of mouth breathing correlated with more remaining postoperative NAO. Conclusions: The percentage of mouth breathing is no different in patients with symptomatic septal deviation than in control patients. Mouth breathing in patients with NAO, evaluated for septoplasty, could be a negative predictive factor for patient satisfaction after nasal septoplasty. Mouth breathing in these patients should be observed carefully because more preoperative mouth breathing should make one more hesitant to consider septoplasty.


Surgical procedure
The surgeries were performed by different surgeons at the ENT department. Either by fully trained surgeons or by trainees with the supervision of a board-certified ENT surgeon trained at our institution.

Data collection
To measure the proportion of mouth breathing, the consulta- The remaining time was divided into "mouth breathing" (mouth open) and "nose breathing" (mouth closed). The percentages mentioned, reflect "mouth breathing" divided by the sum of "mouth breathing and nose breathing". In a next step the videos were blinded by the first examiner (C.B.) and analyzed by a second examiner (N.B.). Videos with a proportion of mouth breathing time differing more than 10% between the two analyses (6/20 patients and 3/15 controls), were watched again by both of the examiners together and a consensus was found.
The Sino-Nasal Outcome Test-20 German Adapted Version (SNOT-20 GAV) (12) is a 20-item measure to assess primary and secondary rhinological symptoms, as well as the quality of life.
For each of the 20 questions participants had to provide a value between 0 (no problem) and 5 (problem as bad as it can be). The maximum attainable SNOT-20 GAV score is 100.
The Nasal Obstruction Symptom Evaluation scale in German language (D-NOSE) (14) is a 5-item measure to assess nasal airway obstruction, as well as restriction in quality of life due to nasal symptoms. For each of the 5 questions the participants had to provide a value between 0 (no problem) and 4 (severe problem).
The maximum attainable D-NOSE score is 100.
As suggested by Ciprandi et al., we used the Visual Analog Scale (VAS) to additionally evaluate nasal airway obstruction (18) . Each participant had to provide a value between 0 (no nasal airway obstruction) and 10 (nasal airway obstruction couldn't be worse).
The scores were also assessed in the control group in order to exclude control patients with NAO, defined as a SNOT-20 score of ≥ 25, accepting a mild nasal airway obstruction in control patients (11) .
In the patient group, an acoustic rhinometry and a clinical examination of the nose were performed additionally prior to septoplasty. Acoustic rhinometry was performed using Otopront (Germany) Rhino-Sys rhinometer and its software 2.81.
The acoustic rhinometry was performed by trained nurses, according to instructions given by the manufacturer. We measured the minimal cross-sectional area 1 + 2 (MCA), and nasal volume 1 + 2 (Vol) for both sides of the nose. All of the measurements were performed prior to and after nasal decongestion. Nasal decongestion allowed us to evaluate structural, as well as mucosal components of nasal airway obstruction (19) . For statistical analysis only the values (MCA 1, MCA 2, Vol 1, Vol 2, total MCA (MCA 1 + 2) and total Vol (Vol 1 + 2)) after decongestion on the narrower side of the nose were used. Only decongested values were used in order to evaluate the structural, and not the mucosal component of acoustic rhinometry data. The study population for acoustic rhinometry data analyses slightly differed from the study population of the nine patients mentioned above. On one patient, who underwent septoplasty, no acoustic rhinometry was performed, so he or she could not be included in acoustic rhinometry analyses. On one patient, who did not undergo septoplasty and on one patient who did not reply to the questionnaires, an acoustic rhinometry was performed, so they could get included in the analyses. The study population for acoustic rhinometry analyses finally consisted of 10 patients.
The preoperative clinical examination of the nose was performed during the consultation by ENT consultants and ENT residents of the Department of Otorhinolaryngology, Head and Neck Surgery at the University Hospital of Zurich. The degree of septal deviation was categorized into 0 (none), 1 (mild), 2 (moderate) and 3 (severe). All of the 9 patients, who underwent septoplasty, suffered from an either moderate or severe deviation of the nasal septum.
Only after the end of the consultation, the video recording and the completion of the 3 questionnaires, patients and controls were informed of the hypothesis and the design of the study.

Statistical analysis
All statistical analyses were performed with an α-error of 5%, The normality of distribution was tested by using the Shapiro-Wilk test. Comparisons of continuous variables with a normal distribution were performed, using a Student t-Test. Comparisons of continuous variables with a non-normal distribution and of non-normally distributed categorical data pre-and postoperatively were performed using a Wilcoxon signed-rank Test.
Correlations between two continuous variables were calculated using a Pearson correlation. Correlations between continuous and categorical data were calculated using a Spearman rank correlation.

Results
In total, the study included nine patients with NAO, undergoing septoplasty/functional septorhinoplasty and twelve control patients, without nasal symptoms. The male to female ratio of the patients with NAO was 6:3, the ratio of the control patients was 7:5. The average age in the patient group was 37.56 ± 12.41 years and 50.67 ± 16.00 years in the control group. It was planned to include ten patients with NAO, undergoing septoplasty, but the situation due to the COVID-19 pandemic complicated Table 1. Demographic factors and mean values of objective and subjective data pre-and postoperatively within the groups.

Characteristics
Nasal airway obstruction group (n = 9) Control group (n = 12) the testing of additional patients. Table 1 summarizes demographic factors, as well as mean values of objective and subjective data pre-and postoperatively.
As  level, all of the significant results, mentioned above, still showed statistical significance.

Discussion
In this study, our aim was to investigate mouth breathing as an objective predictive factor for patient satisfaction after septoplasty. All of our patients showed a reduction of subjective symptoms post-compared to preoperatively. It could be demonstrated that there is no difference in mouth breathing between patients with or without nasal airway obstruction. Another main finding was that a higher percentage of preoperative mouth breathing correlated with more remaining nasal airway obstruction after septoplasty.
Mouth breathing is a common symptom reported by patients with nasal airway obstruction, suspected to be caused by a deviation of the nasal septum and is one reason to indicate a septoplasty. Previous studies have reported high patient satisfaction after septoplasty (20,21) . In line with these results, a significant reduction of subjective symptoms three months postoperatively could be proven in our study. Even though several studies evaluating potential septoplasty outcome predictors have been conducted, there is still no reliable predictive factor for patient satisfaction after septoplasty (3) . Mouth breathing has never before been evaluated as a potential predictive factor for septoplasty outcome.
Van Egmond et al. demonstrated that septoplasty is an effective method to treat nasal airway obstruction, offering subjective and objective postoperative benefits to patients with a septal deviation (5) . As this previous study has shown, we could also observe a significant reduction of subjective symptoms (VAS, NOSE, and SNOT-20 score) post-compared to preoperatively, in all of our patients. In comparison to Tjahjono et al., our patients showed a higher absolute pre-and postoperative NOSE score, but the difference (deltaNOSE) was comparable to our results.
Pre-and postoperative VAS score and consequentially also deltaVAS values showed equivalent results (22) . In comparison to

Prus-Ostaszewska et al. SNOT-20 values pre-and postoperatively
and deltaSNOT-20 were comparable to results of the present study (23) . Clinical examination of the nose postoperatively showed either a straight septum or a slight remaining nasal deviation in every patient and none of them had the intention to undergo revision surgery. All of these findings suggest that our surgical technique was adequate and effective.
The comparison of mouth breathing between patients and controls did not show any difference. Patients without nasal airway obstruction even had a slightly higher mean proportion of mouth breathing than patients with relevant nasal airway obstruction. In other words, mouth breathing is an inadequate marker to discriminate between patients with nasal airway obstruction and patients without nasal symptoms.
A possible explanation for our findings could be an impaired endonasal trigeminal perception, causing the sensation of nasal airway obstruction, a finding Saliba et al. has demonstrated for patients with chronic rhinosinusitis (24) . We demonstrated recently (25) that better endonasal trigeminal perception is directly linked to higher postoperative patient satisfaction after sep- toplasty. An acoustic rhinometry measurement of our control patients would have been an interesting addition to our present measurements. Acoustic rhinometry measurements of control patients with comparable values to measurements of patients  In comparison to Kjaergaard et al. (26) , no association of the subjective sense of nasal obstruction and acoustic rhinometry measurements could be found in the present study. Although the degree of septal deviation correlated with acoustic rhinometry findings, acoustic rhinometry does not seem to be an appropriate objective measure to predict nasal airway obstruction and patient satisfaction after septoplasty.
In contrast to our expectations, a significant correlation of preoperative mouth breathing and postoperative patient satisfaction in patients with NAO, measured using NOSE score, was found. More preoperative mouth breathing correlated with a higher postoperative NOSE score, more remaining postoperative nasal airway obstruction and less patient satisfaction.
According to Chambers et al., nasal valve dysfunction can be an indicator for insufficient improvement of nasal airway obstruction after septoplasty (27) . In the present study the nasal valve was carefully assessed preoperatively but we cannot exclude effects of a potential nasal valve dysfunction on the outcome.
Overall, it could be suggested that mouth breathing is an inap-

Conclusion
This is the first study to investigate prediction of septoplasty outcome using mouth breathing measurements. Despite the small study population, we were able to demonstrate that more mouth breathing in patients with nasal airway obstruction can indicate to an altered nasal trigeminal perception or a co-existing inflammatory pathology and can predict poorer