To our knowledge this is the first real-life study to describe the management of MNO using both subjective and objective criteria in MNO isolated or associated to upper airway inflammatory diseases (AR or CRSwNP). The main findings of this study were: 1st) Medical treatment by intranasal corticosteroids achieved a minor improvement in subjective NO outcomes in all subjects while in CRSwNP the response to medical treatment was higher potentially due to the inflammatory component. 2nd) Nasal corrective surgery is the treatment of choice in MNO, both isolated and associated to upper airway inflammatory diseases (AR and CRSwNP). 3rd) LoS is more frequent in MNO with upper airway inflammatory disease, particularly in CRSwNP with clear improvement after surgery. 4th) Both subjective and objective criteria are needed to assess and optimal management of MNO since both subjective (NO/LoS/NOSE/CQ7) and objective (endoscopy score) outcomes showed strong positive correlations at baseline and after treatment. And 5th) AcR did not correlate with subjective outcomes or clinical examination, except in CRSwNP patients.

A long debate persists about the usefulness of subjective and objective methods for making decisions on the management of patients with NO. Establishing standards and ranges of symptom scales and questionnaires is essential to measure the success of an intervention and its impact on QOL [5, 6, 17, 18•].

This study shows that at baseline, subjective NO in all MNO groups was higher than previously reported, especially in CRSwNP [17, 19]. This finding might be due to the moderate-severe NO (Likert) used as inclusion criteria.

After medical treatment, there was a slight clinical NO improvement in patients with MNO, with or without upper airway inflammatory disease, in accordance with other authors [8, 20]. These data suggest that intranasal corticosteroids have a minor effect on MNO [21••] and potentially may delay the surgical treatment [8].

In our study, surgery was the optimal choice showing an improvement not only in subjective but also in objective outcomes, fulfilling success criteria previously reported [17], with a change in NO-VAS ≥ 3 and a clear reduction of NOSE (≥ 30). These changes were observed to be higher in CRSwNP which can be justified by both the correction of MNO and the resection of NP. This is in accordance with previous works [22] where symptoms assessed with CQ7 such as facial pressure, nasal congestion, and headache improved significantly after surgery. Other studies have reported that surgery increases the costs at short-term but have proven to be cost-effective at long term and more successful than non-surgical management of MNO in adults [8, 20].

Concerning to LoS, this symptom was present at baseline in all the MNO groups, predominantly in CRSwNP patients. LoS is one of the major symptoms for the clinical diagnosis of CRSwNP in both the American and the European rhinosinusitis guidelines (EPOS 2020 – IRCAR2021) [23, 24••] and also considered as a clinical marker of severity [25, 26]. Other authors [23, 27] have also correlated LoS with the degree of nasal congestion being medical treatment (i.e. intranasal corticosteroids and short course of systemic corticosteroids) clearly recommended in olfactory dysfunction secondary to CRS. In this study, LoS improved only after surgery in all subjects but more significantly in CRSwNP, which supports the impact of both inflammatory and mechanical factors in this symptom [28, 29]. Our findings suggest that improvement in smell may be related to improved conduction of odorants to the olfactory neuroepithelium.

A main finding of this study was also the high positive correlation between all subjective scales (VAS/NOSE/CQ7) at baseline, medical and surgical treatments. According to some authors [5, 18•], these scoring systems are useful because they are capable of determining subjective changes (follow-up) in the assessment of treatment effects (1B: strong recommendation, moderate quality of evidence). Similarly, these scales correlated with some objective outcomes. However, the NO subjective outcomes did not correlate with NPS in CRSwNP subjects, as reported in other studies [30,31,32] but in contrast with others [33]. Furthermore, a small correlation was found between NPS and CT findings (LMS) in agreement with some authors [34] but in disagreement with others who reported some correlation [31]. Some studies have reported an uncertain correlation between AcR and NO subjective score systems [5, 17]. In our study, only some correlation between NO-VAS and Vol0-5 was found in CRSwNP patients.

Finally, our study has allowed us to design an algorithm to guide the most appropriate MNO management (diagnosis and treatment) in daily clinical practice (Fig. 3).

Mechanical nasal obstruction (MNO) management algorithm. Abbreviations: AR, Allergic rhinitis; CRSwNP, Chronic rhinosinusitis with nasal polyps; CQ7, Congestion Quantifier Questionnaire 7; FESS, Functional endoscopy sinus surgery; MNO, mechanical nasal obstruction; NO, Nasal obstruction; NOSE, Nasal Obstruction and Septoplasty Effectiveness; SP, septoplasty; VAS, Visual Analogue Scale. * If the score is 2, it must correspond to one of the 3 structures studied (obstructive lower left and/or right turbinate enlargement and/or septal deformity)

This real-life study is, to our knowledge, the first to demonstrate the effect of medical and surgical treatments in MNO alone or associated to upper airway inflammatory diseases, either AR or CRSwNP. It also proves that nasal symptoms, measured by VAS, NOSE and CQ7, highly correlated with each other and with objective outcomes, easy to use in clinical practice.

Our own MNO score by clinical examination with nasal endoscopy facilitated the data collection, being practical and easy to interpret. However, this classification will require further validation.

Regarding objective methods, AcR (easier and faster to perform) is the only objective test available at our hospital. This is the reason why methods such as anterior rhinomanometry was not used for the study. Trying to avoid bias, one investigator alone confirmed and interpreted the data.

As a main limitation, the assessment of the patients was based on the subjective perception derived from clinical anamnesis and examination by different researches from the same team, which can lead to some differences in data collection. ENTs who performed the nasal endoscopy were not blinded to the procedures performed to the patients or the rest of scales since the study was done in daily clinical practice. Physical examination was performed with rhinoscopy and nasal endoscopy following the same criteria evaluation with specific features to evaluate nasal septum and inferior turbinate and modified Lildholdt score for patients with CRS with NP to avoid bias in terms of interpretation. This MNO score by clinical examination with nasal endoscopy facilitated the data collection, being practical and easy to interpret. However, this classification will require further validation.

Likewise, surgery was not carried by a single surgeon but by the rhinology surgical team using the same standardized technique.

In addition, although QOL questionnaires were not used, NOSE and CQ7 scales reflect symptoms that would influence QOL.

In daily clinical practice, medical treatment by intranasal corticosteroids is not useful in MNO alone but it may help when associated to comorbid upper airway inflammatory disease. Nasal corrective surgery is the treatment of choice in MNO, both isolated and associated to upper airway inflammatory diseases, either AR or CRSwNP. The therapeutic indication for MNO should be based on both subjective and objective outcomes while AcR, an objective assessment, may be useful but as complementary examination.