Obstructive sleep apnea hypopnea syndrome (OSAHS) is a common disorder characterized by recurrent episodes of airway obstruction as a consequence of repetitive collapse of the upper airway (UA) during sleep time. This condition is seen in approximately 4% of the general population, with a higher prevalence in men (4–6%) compared to women (2–4%). Patients diagnosed with OSAHS have a decreased quality of life (QoL) and increased morbidity and mortality compared to the non-affected population.1
The OSAHS occurs during sleep time, producing a decrease in oxyhemoglobin saturation, microaurousals, excessive daytime sleepiness and behavioral and metabolic disorders, resulting in serious health consequences, such as increased cardiovascular risk and metabolic syndrome. OSAHS is due to collapses in the UA that worsen during sleep time.
The UA permeability requires the interaction of multiple anatomical, structural, and neuromuscular factors. As a part of the UA, nasal obstruction can intensify snoring and sleep apnea by increasing nasal resistance to airflow, which generates negative pressure within the UA.2 On the other hand, nasal obstruction creates a dependency on mouth breathing, which itself increases resistance to airflow in the UA.3 Although the pathophysiological mechanisms for this phenomenon are unclear, it is possible that nasal pressure receptors may have a role in controlling the position of the soft palate. In addition, the posterior movement of the mandible during the nocturnal mouth opening modifies the action of the dilatative muscle of the pharynx decreasing its effectiveness, which could increase the collapse of the UA.4
Several medical and surgical therapeutic options have been evaluated in order to improve nasal breathing and OSAHS. The UA surgery helps to reduce the respiratory resistance, described as one of the main factors contributing to continuous positive airway pressure (CPAP) intolerance, which is the most common treatment of OSAHS. Except for mild cases of exclusive OSAHS, nasal surgery is not effective for the treatment of this condition. However, nasal surgery, mainly, septoplasty and turbinoplasty, is commonly used in OSAHS as an “optimization surgery,” which aims is to improve the nasal area for greater tolerance of CPAP.5 According to Starling's theory, any resistance at the nasal level will favor greater resistance at the pharyngeal level. Therefore, although nasal surgery will not achieve a significant reduction in apnea-hypopnea index (AHI), it may allow to achieve a reduction in the CPAP pressure necessary to improve tolerance and QoL.5 Previous studies including metaanalysis have shown improvement in CPAP tolerance after nasal surgery,5–9 and highlight the importance of nasal surgery in the prevention and adherence to the CPAP.5 Considering this point, authors such as Rotenberg et al10 proposed redefining the timing of nasal surgery in the treatment of OSAHS: after failure due to CPAP intolerance, or better, before starting the CPAP to guarantee its use.
Identifying the location of obstruction of the UA can be challenging. Nonetheless, this identification is crucial to obtain an effective surgery in patients with OSAHS. In order to improve the examination of the UA, drug induced sleep endoscopy (DISE), is a very helpful tool to establish the topographic diagnosis, identifiying the zone(s) of obstructions and collapses in patients with OSAHS.11,12 The aim of our study is to evaluate the effects of nasal surgery in the UA collapse using DISE in a group of patients with OSAHS.
Following Institutional Board Review, patients who underwent nasal surgery were prospectively identified from a cohort of individuals diagnosed with OSAHS at the Otolaryngology Department of a University Hospital between November 2015 to December 2016. All participants were informed about the study and consent was obtained.
The inclusion criteria were limited to patients between 18 and 70 years, with mild to severe OSAHS (AHI >15) demonstrated by formal laboratory polysomnography (PSG), and severe septal deviation confirmed by endoscopy and anterior rhinomanometry (Rhinolab. 4 Rhino 4- Phase Rhinomanometer. Freiburg, Germany). Patients with previous surgeries for OSAHS, allergy to propofol, and obesity with BMI >35 were excluded.
The study protocol included extensive medical history with Epworth Sleepiness Scale (ESS) and a systematic UA evaluation with a video-flexible endoscopy at the outpatients ENT clinic, including tonsil size grading, obtained using the Friedman staging system for OSAHS, Friedman tonsil position (FTP), Mallampati score, lingual tonsil hypertrophy scale according to Friedman (LTH) and Müller maneuver. This evaluation was performed by the 1st author, with the patient seated, as well as in supine position.
Septoplasty was indicated when severe septal deviation was found during examination, confirmed by nasal endoscopy and assesed by anterior rhinomanometry. All patients underwent nasal endoscopy, anterior rhinomanometry, PSG, and DISE before surgery and 3 months after the procedure was completed.
The DISE was performed consistently by the 1st author, in the operating room, starting with the patient in supine position.12 For sedation, 2% propofol syringe infusion pump with target-controlled infusion (TCI) was used, with a target concentration of 2ng/mL with progressive increases of 0.2 to 0.5 ng/mL as required. Sedation level was monitored using bispectral index (BIS) (BIS Quatro. Covidien ILC MA). When the patient was asleep and actively snoring (BIS between 70 and 50), video-flexible endoscopy (TGH Endoscopia. MACHIDA ENT-30PIII, Spain) was used to assess the UA, visualize the area of collapse in real time and to record the findings continuously. During DISE, the head was 1st turned to the right, then to the left and, finally, the mandibular advance maneuver was performed. The findings were observed for a minimum of 2 cycles in each segment and for each maneuver. The NOHL classification of Vicini et al published in 2012, was used to report the findings.11
All the patients of our study underwent nasal surgery, which included: septoplasty and turbinoplasty with radiofrequency probe. Septoplasty was performed by the 1st author according to a modified Cottle's technique with the use of a photophore, respecting the right upper superior tunnel without dissecting. The surgical technique was standardized and included a hemitransfixion incision followed by an elevation of the septal mucoperichondrium in both sides, addressing all areas of deviation and reshaping or removing the deviated part of the cartilage. Associated turbinoplasty with radiofrequency probe (TGH Endoscopia. BM-780 II. Radiofrequency Unit, Spain) under endoscopic control with a 0 degree optic was also performed as required. The radiofrequency probe was inserted into the tail, body and head of the inferior turbinate, at a fixed power of 2, during 8 seconds.
Postoperative UA examination was carried out in the outpatient clinic at 1 and 4 weeks, followed by 3, 6 and 12 months after surgery. A video-flexible endoscopy was performed during postoperative follow-ups. Three months after nasal surgery, it confirmed the absence of edema prior of DISE. DISE was then repeated in all cases consistently by the 1st author.
The DISE video recordings were analyzed consistently by the same ENT surgeon, who was blinded to the demographic and polysomnographic data. The findings were characterized by the site and degree of obstruction of UA, through a categorization system based on previous studies as described in Table 1 (Supplemental Digital Content, http://links.lww.com/SCS/A804).2 Possible location of obstruction were oropharynx (Fig. 1), hypopharynx (Fig. 2A), and epiglottis (Fig. 2B). The degree of obstruction was determined for each location according to Vicini et al11 and was classified for oropharynx and hypopharynx as non-collapse (0%), partial collapse (< 75%) or complete collapse (> 75%) and for epiglottis as no collapse or collapse.
A descriptive analysis was carried out to estimate the measures of central tendency (means and median) and dispersion (range, standard deviation and percentiles 25–75) of the quantitative variables and the frequency distribution of the qualitative variables. Normality was assessed with Kolmogorov Smirnov and Shapiro Wilk. McNemar test was used to analyze the changes in the pattern of UA obstruction visualized by DISE. A P < 0.05 was considered statistically significant. SPSS 22.0 (SPSS Inc, Chicago, IL) was used for all the analysis.
Initially, 37 patients were eligible for the study. Three patients were excluded because they were lost during follow up. A total of 34 cases were included in the study and underwent both DISE and PSG, before and after surgery. The majority of patients were male. The median age for the entire cohort was 42.8 ± 14 years, and BMI of 28.4 ± 5 kg/m2. All patients had a diagnosis of OSAHS, distributed as follows: mild (55.9%), moderate (17.6%), and severe (26.4%). Fifteen cases were intolerant to CPAP. Patients characteristics of the entire cohort are shown in Table 2 (Supplemental Digital Content, http://links.lww.com/SCS/A804).
Surgical success with subjective and objective improvement in nasal obstructions was found in all cases without significant complications. Nasal surgery resulted in a significant decrease in nasal resistance, as measured by rhinomanometry, from 0.58 + 0.4 Pa/cm3 /s to 0.15 + 0.06 Pa/cm3/s. Regarding the optimization of CPAP, nasal surgery was effective in 12 cases (80%) of those 15 cases that were intolerant to CPAP, that then became tolerant to CPAP after nasal surgery.
After 12 months, there was no significant difference between preoperative weight and postoperative weight. However, ESS score was significantly lower, from 8.4 ± 5 to 6.5 ± 5 (P < 0.05). AHI decreased after nasal surgery, but this difference was not significant (mean of 26.7 to 19 events/h, P > 0.05).
The DISE was performed in all patients without complications during or after the procedure, with mean duration of 9.3 minutes (range 5–18 minutes). Findings during DISE before and after nasal surgery are shown in Table 3 (Supplemental Digital Content, http://links.lww.com/SCS/A804).
Before nasal surgery, a majority of the subjects demonstrated multilevel obstruction (74%), mainly at the oropharyngeal and hypopharyngeal levels. After nasal surgery, only 50% patients showed multilevel collapse, a significant difference (Supplemental Digital Content, Table 3, http://links.lww.com/SCS/A804). Among patients with single-level collapse, the oropharynx was the most common location of obstruction. It became significantly more frequent after nasal surgery was done (41% vs 21%, P < 0.05).
Changes in UA collapses during DISE after nasal surgery were identified at different anatomical levels. At the oropharynx level collapses during DISE did not changed significantly: the number of patients without collapse increased, those with partial collapse decreased and those with total collapse remained the same (P 0.267). However, at the hypopharynx level there was a significant change in the UA collapses: the number of patients without collapse increased, those with partial collapse decreased and those with total collapse also decreased (P 0.028). Finally, at the larynx level, changes did not reached statistically significant difference: the number of patients without collapse during DISE decreased, whereas those with collapse increased (P 0.278). Therefore, nasal surgery significantly altered the UA functional findings in the hypopharynx, but not significantly in the oropharynx or the larynx.
Addiditonally, we observed that performing a mandibular advancement maneuver during DISE improved retrolingual collapse in 71% before nasal surgery, and in 85% after surgery (P < 0.5).
In this study, we conducted a prospective evaluation of 34 patients with OSAHS which underwent DISE before and after nasal surgery, with the aim to evaluate the effects of this procedure in the collapse of the UA. Our results suggest that performing DISE after nasal surgery may modify the surgical plan for OSAHS surgery, especially when a multilevel collapse in the UA is observed preoperatively.
These findings may be explained by the theory of respiratory physiology. According to Starling's theory, decreasing nasal resistance, the flow in the nose improves changing the pressures in the UA. This justifies the improvement in patients from multilevel collapse to single level collapse.3,4 A similar interpretation is known as the Bernoulli effect: which describes that when inhaled air passes through a narrow UA and, thus at a higher speed, distal intraluminal pressure decreases, generating a higher negative pressure that causes the collapse of that area.4 Therefore, when managing patients with OSAHS with multilevel obstruction at DISE, we can consider performing nasal surgery as a 1st step10; then, after a 2nd DISE, we may propose a new surgical plan that would be better targeted, improving surgical results and also reducing the concerns about associated complications after multilevel surgery.
Our observation of significant changes at the hypopharynx level can be explained by the dynamic interaction between the palate and the base of tongue during apnea, where the tongue moves backward and exerts a posterior force that collapses the soft palate. This effect could be decreased by reducing nasal resistance.13 As Victores & Takashima2 reported in a retrospective review of 24 patients, the repetition of DISE after nasal surgery should only be proposed in patients with retropalatal obstruction and without obstruction of the base of tongue; they could obtain an improvement in palatal collapse after nasal surgery modifying their surgical plan.
They also observed that edema resolved 3 months after nasal surgery, and thus changes observed in the UA during DISE collapses were not related to postoperative edema, as we have also found in our study.2 Similarly, in a prospective study of 35 patients who underwent PSG and a morphological examination of the UA before and after nasal surgery, Morinaga et al14 observed that nasal surgery was effective in reducing the AHI of patients with a wide retroglossal space and a high palate. In another study evaluating the influence of mouth opening on UA collapsibility in 6 healthy sleeping volunteers, Meurice et al4 observed that patients with retroglossal obstruction were less likely to improve obstruction in the UA by decreasing nasal resistance after nasal surgery.
Several studies suggest that CPAP may be ineffective in the treatment of patients with OSAHS with epiglottis collapse because it will further push the epiglottis down into the laryngeal entry.15 The use of DISE has led to the discovery of more cases of epiglottic obstruction. These findings can be attributed to the ability of the test to detect this finding in comparison with the previous methods. However, DISE can produce a greater degree of pharyngeal muscle relaxation, resulting in an exaggerated image of obstruction.12 The prevalence of the epiglottis obstruction was reported in varying percentages by other authors reach up to 73%. In our study, we have found that the epiglottic collapse did not change after nasal surgery was performed.
Our findings are consistent with previous reports, that suggest that nasal surgery does not completely cure OSAHS, but significantly helps to tolerate CPAP and improve hypersomnolence.8,9 As other publications, our results showed that septoplasty did not improve AHI following Sher criteria. The surgical success rate according to the classic definition of Sher et al16 is quantified with a postoperative reduction of the AHI of at least 50% and/or a final postoperative AHI below 20. In a meta-analysis including 13 studies, Li et al8 showed that nasal surgery may reduce drowsiness and snoring during the day but its efficacy in the treatment of OSAHS limited. Similar findings have been reported in patients with nasal obstruction and OSAHS, where isolated nasal surgery significantly improved hypersomnolence, without significantly improving the AHI.9 Moreover, in a meta-analysis including 587 patients, the authors observed that improvement in hypersomnolence and AHI after isolated nasal surgery, but the improvement in AHI was slightly significant.17
Despite of these results, nasal surgery plays an important role in the management of OSAHS patients, because most of them report an improvement in Qol.18 and daytime hypersomnolence.6,8,9,17 Consistent with these findings, the present study showed improvement in ESS. As previously reported, daytime hypersomnolence is associated with an increased risk of traffic and work accidents.1 Nasal surgery could help to reduce these risks, especially in patients who can not tolerate CPAP and are not candidates for multilevel surgery. The treatment of nasal obstruction should be considered a crucial component in the management for patients with OSAHS, by decreasing snoring of patients.19 Snoring was not evaluated in this study, however there is evidence of the relationship between nasal surgery and snoring improvement.7 This improvement in snoring has been correlated with morphological characteristics of the oropharynx during the preoperative examination in the consultation. As reported by Li et al7, small tonsil is considered a good prognostic factor for the improvement of snoring after nasal surgery. However, our data did not associate this small tonsil relation with postoperative improvement at the oropharyngeal level.
The UA surgery helps to reduce respiratory resistance, which is one of the causes of the intolerance of CPAP, the most common treatment of OSAHS. Nasal surgery can reduce the level of pressure making the CPAP more tolerable5 which correlates with our findings. Sleep time is usually based on ventilation through the nose3, if we breathe with our mouths open during sleep, resistance increases and thus the collapse of the UA. In a cohort of 33 patients nonresponders to previous OSAHS surgery, Kezirian20 found that 1/3rd of them opened their mouths during DISE. The degree of mouth opening was not evaluated in this study, the implications for surgical treatments are not entirely clear, and therefore, future investigations are needed.
One of the limitations of our study is that postoperative DISE was performed 3 months after nasal surgery. The optimal time to perform DISE after nasal surgery is not well established. Other studies that evaluated nasal surgery in OSAHS reexamined patients 3 months after surgery, confirming absence of edema.2,7 Nevertheless, the assessment of changes in DISE findings after nasal surgery may not be the same in the long term. Furthermore, the system used to classify the morphology of the UA was based on a subjective measure of the degree of obstruction; further studies could be developed using quantitative techniques to evaluate the dimensions of the UA.21 In addition, our results might have been limited by a small sample size. Although it is the largest study of its kind, larger and more- detailed investigations will be useful. Others studies with longer follow-up could provide a more detailed evaluation of the effects of nasal surgery in UA during DISE.
This study suggest that nasal surgery may improve hypopharyngeal collapses observed during DISE in patients with OSAHS. Thus, an improvement in nasal obstruction may also modify the surgical plan based on UA functional findings in OSAHS patients. Therefore, clinicians should consider performing DISE after nasal surgery, especially when a multilevel collapse in the UA is observed preoperatively.
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