Starling Resistor

First of all, an increase in Rn does contribute to the total resistance of the upper airway, regardless of the fact that Rn during sleep is not as important as during the awake state. Therefore, the increase in total upper airway resistance is not very strong but existing.

In contrast to the nose, the larynx and the trachea, there are no bony and cartilaginous structures in the pharynx, which can protect airway patency. This is the reason why the pharynx may act like a Starling resistor. An increased preload in terms of an increased Rn may increase the suction force, leading to pharyngeal obstruction. Trials using single-sides nasal dressings were able to induce apneas in healthy volunteers. However, the total number of induced apneas was not adequate to induce clinically relevant obstructive sleep apnea (OSA). ^{12 , 13 , 14}

Another study used allergic rhinitis as a more physiological model for partial nasal obstruction. Sleep studies conducted during and out of pollen season showed significantly more apneas during pollen season. ¹⁵ Again the results were statistically significant, but in absolute numbers (apnea index 0.7 vs. 1.7) the effect was too little to induce a clinical significant OSA.

Against this background partial nasal obstruction is more likely able to worsen a preexisting OSA than to trigger it by itself.

Switch to Oral Breathing

In case of complete nasal obstruction, a switch to oral breathing is necessary. As seen in healthy subjects, mouth opening increases the critical closing pressure of the upper airway and thus enables airway obstruction. ¹⁶ In other words, mouth breathing is the less stable breathing route. Besides that, upper airway resistance during sleep is higher in mouth breathing as compared to nasal breathing. ¹⁷ In a study conducted by Zwillich et al, 2 out of 10 healthy subjects developed a clinically significant OSA after nasal packing on both sides, whereas there was almost no change in the remaining 8 subjects. ¹⁸ Obviously there seems to be a subgroup of patients (20% in this study), in which the switch from nasal to oral breathing generates OSA, while in the majority of patients nothing happens. In the cited study those subjects developed OSA, who already showed a few apneas with unblocked noses.

Drop Out of Nasal Reflexes

Nasal reflexes mediated by the trigeminal nerve are assumed to maintain upper airway patency. It has been shown several times that both central and obstructive apneas occur after the use of local anesthesia within the nose. ^{19 , 20} The study of White et al describes the occurrence of severe OSA in 3 out of 10 healthy subjects after local anesthesia. ¹⁹ The other 7 subjects did not show any effect at all. Using placebo instead of local anesthesia, no patient developed OSA.

Again there seems to be a subgroup of patients in which nasal reflexes seem to play an important role in maintaining upper airway patency, whereas this correlation cannot be shown in the majority of subjects.

Nitric Oxygen

A significant amount of nitric oxygen (NO) is produced within the nose and especially within the paranasal sinuses, and from here it mixes with the inspired air depending on the intensity of nasal breathing. ²¹ NO is a potent bronchial dilator and increases the oxygen content of the blood. ²² In addition, NO is thought to have several functions such as keeping up the muscular tone, neuromuscular control of the pharynx, breathing stimulation, and regulation of sleep. So far, the role of NO in the pathogenesis of OSA has not been understood well enough to give a final conclusion about it.

To sum it up, nasal obstruction indeed seems to be associated with snoring and apneas. However, a distinct correlation between the severity of OSA and the amount of nasal obstruction could not have been found so far. ²³ In short, the nose contributes only little or in few individuals to the pathogenesis of OSA.

Nasal Decongestives

Two studies investigating the effects of xylometazoline ^{24 , 25} did not show any changes in apnea–hypopnea index (AHI) as compared to placebo, although Rn is significantly decreased in the xylometazoline groups. The earlier study reported a subjective improvement on the quality of sleep. ²⁴ In contrast the more recent study did not find any effect of xylometazoline on the quality of sleep. ²⁵

Topical Corticosteroids

Topical corticosteroids improve both the subjective and the objective quality of sleep, and daytime performance in patients with allergic rhinitis. ^{26 , 27 , 28} In doing so, the improvement of subjective parameters correlates with objective nasal patency.

A randomized crossover trial included 13 patients with OSA. Each patient was treated for 4 weeks with local fluticasone and for another 4 weeks with placebo. An objective sleep study was done after each treatment section. ²⁹ After treatment with fluticasone the AHI decreased from 30.3 ± 31.9 at baseline to 23.3 ± 21.3, whereas there was no effect after placebo treatment. Once again, a subgroup of two patients benefitted strongly from the fluticasone treatment, while the other patients showed little or no effect.

Another randomized, controlled, crossover study compared the effects of a tramazoline plus dexamethasone nasal spray versus placebo in 21 sleep apneics without subjectively impaired nasal breathing. ³⁰ Treatment was given for 1 week each. A sleep study and a rhinoresistometry were performed at the beginning and at the end of each treatment period. The authors described a significant reduction of Rn, and several breathing parameters in the verum group as compared to placebo. In the verum group the AHI decreased from 31.1 at baseline to 25.0 after treatment. Figures for placebo were 31.1 and 29.8, respectively.

In contrast, a third randomized controlled trial (RCT) comparing fluticasone and placebo did not show any differences between the two treatments. ²⁶

The RCT done by Craig et al indicated that topical corticosteroids are able to reduce the AHI in adults immediately. The amount of reduction is low, and long-term data are currently not available.

Nasal Dilators

There are external and internal nasal dilators (▶Fig. 7.1). ▶Table 7.1 summarizes current data from objective polysomnographies (PSGs). Altogether there are data about 194 cases. A significant effect of nasal dilators on AHI cannot be seen so far.

▶ Table 7.1 Influence of internal and external nasal dilators on AHI

Authors	Dilator	N	AHI with	AHI without	P value	EBM
Höijer et al (1992) 33	Internal	10	18	6.4	0.008	3b
Metes et al (1992) 34	Internal	10	46	44	NS	4
Kerr et al (1992) 24	Internal + ND	10	64.9	63.2	NS	4
Hoffstein et al (1993) 35	Internal	15	35.4	33.9	NS	4
Wenzel et al (1997) 36	External	30	38.1	40	NS	3b
Todorova et al (1998) 37	External	30	26.2	24.1	NS	4
Bahammam et al (1999) 38	External	12	8.9	7.4	NS	1b
Gosepath et al (1999) 39	External	26	26.3	31.7	0.031	4
Schönhofer et al (2000) 31	Internal	21	37.4	36.1	NS	4
Djupesland et al (2001) 40	External	18	12.2	9.3	<0.05	4
Amaro et al (2012) 32	External	12	38	39	NS	3b
All		194	30.93	30.28		B
Abbreviations: AHI, apnea–hypopnea index; EBM: evidence-based medicine; ND: nasal decongestive; NS, not significant.

Two of the studies cited in ▶Table 7.1 also provide subjective data concerning daytime sleepiness. ^{31 , 32} In both studies the Epworth Sleepiness Score (ESS) was significantly reduced when the patients used nasal dilators as compared to baseline without dilators, although there was no change in AHI.

Postoperative Care

In case of nasal surgery the severity of OSA has significant impact on postoperative care and monitoring. This is why sleep apnea patients undergoing surgery under general anesthesia or sedation are generally at an increased risk for perioperative complications. ^{41 , 42 , 43} This perioperative risk is particularly increased if the OSA is treated surgically, as postoperative bleeding, swelling, and nasal packings need to be taken into account.

There are two publications dealing with specific complications after nasal surgery with nasal packings in patients with OSA. ^{44 , 45} All patients were kept in the recovery room for several hours. All complications occurred within the first few hours after surgery. This is why it is recommended to monitor all patients in the recovery room for 4 hours postoperative. If no complications are seen during this period, the patient is safe to shift to the regular ward. Vice versa, if complications occur, the patient should be monitored overnight. ⁴⁶

Outcomes

Snoring is a subjective complaint. Its disturbing character not only depends on its physical sound intensity, but also on psychoacoustic parameters such as roughness, sharpness, and loudness. ⁴⁷ In addition, the perception of snoring depends on multiple parameters concerning the patient’s bed-partner such as sleep quality, hearing impairment, psychological characteristics, and others. This is why the annoyance of snoring is difficult to measure in an objective way. As a consequence, there are almost no reliable data about the objective impact of nasal surgery on snoring, which could have been summarized at this point.

Considering that the nose is almost never the origin of snoring sounds, the authors made the experience, that there are much more effective surgeries in other parts of the upper airway to treat simple snoring than nasal surgeries. Actually, the majority of patients do not or only hardly benefit from nasal surgeries in terms of reduction of snoring frequency or intensity. As a consequence, authors recommend performing nasal surgeries to treat snoring without any other complaints. As stated in Chapter 7.4.2, nasal surgery has a lot of positive effects on sleep quality, recovery during sleep, and daytime symptoms in patients with nasal pathologies. Thus, we perform nasal surgery in patients with objective nasal pathologies and/or in patients with either nonrestorative sleep and/or subjectively impaired nasal breathing.

If a patient only snores without any of the symptoms mentioned earlier, we recommend a topodiagnosis (e.g., drug-induced sleep endoscopy) to detect the site of generation of snoring sounds in order to identify a more successful kind of surgery.

Outcomes

Altogether 30 studies have been identified, which include 772 patients with pre- and postoperative objective sleep studies before and after isolated nasal surgery in patients with OSA. Out of these studies four are case series. ▶Table 7.2 summarizes the current available data. Out of these 30 studies, only 5 showed significant changes in AHI after nasal surgery. For the entire group of 772 patients the mean AHI decreased, not significantly, from 33.3 at baseline to 30.4 after nasal surgery. In other words, nasal surgery has either very limited or no effect on OSA severity. Accordingly, we did not see any effect of additional nasal surgery in our group of 70 patients (N = 52 without vs. N = 18 with additional nasal surgery), who underwent multilevel surgery for OSA. ⁷⁸ In this context, the only RCT is of particular interest. ⁶³ The study compared a surgical group (N = 27) with a placebo group (sham operation; N = 22). There were no significant changes in AHI in both groups. Significant changes were seen only in the surgical group, namely reduction of Rn seated and in supine position, reduction of the Epworth Sleepiness Scale (ESS) score, and an increase in nasal breathing.

In the vast majority of cases it does not seem possible to significantly reduce the AHI with nasal surgery alone. Accordingly, several other reviews concerning this topic report the same result. ^{79 , 80 , 81}

In contrast to the AHI, the respiratory disturbance index (RDI) seems to be affected by nasal surgery. The RDI is calculated as the number of apneas, hypopneas, plus respiratory-related arousals per hour of sleep. In other words, the RDI is at least as high as the AHI, but mostly higher. Two case series present RDI data. ^{59 , 76} Both studies describe a significant reduction of RDI, namely 39.0 to 29.1 ⁵⁹ and 28.8 to 17.1, ⁷⁶ respectively. As heterogeneity between the two studies is low, the results seem reliable. In conclusion, nasal surgery may be able to reduce respiratory related arousals in patients with OSA.

Focusing on subjective outcome parameters, nasal surgeries show huge effects. All in all, 14 studies (N = 361 patients; ▶Table 7.2) provide data concerning daytime sleepiness as measured with the ESS. In mean the ESS score fell from 10.9 before to 7.0 after nasal surgery, indicating a significant reduction of daytime sleepiness in these patients. A review published by Li and colleagues described similar data. ⁷⁹

Other publications report a highly significant improvement of quality-of-life parameters after isolated nasal surgery in sleep apnea patients, using the “Snore Outcome Survey” ⁶⁴ or the “SF-36.” ⁸² A recent study investigated 61 sleep apneics before, and 3 months after nasal surgery using the NOSE-questionnaire, the Pittsburgh Sleep Quality Index, and other questionnaires. ⁸³ The patients benefited in all dimensions measured.

To sum it up, isolated nasal surgery has various measurably subjective benefits in sleep apnea patients resulting in a more restorative sleep. However, the severity of OSA as defined in AHI can only be reduced in single cases.