Lack of association of impaired upper airway sensation with the presence or absence of obstructive sleep apnoea or chronic rhinosinusitis in World Trade Center responders

OBJECTIVE

Examine sensory function of the upper airway in four groups of subjects recruited from the World Trade Centre General Responder Cohort (WTCGRC), with/without obstructive sleep apnoea (OSA), and with/without chronic rhinosinusitis (CRS).

METHODS

Upper airway sensory function was determined using 2-point discrimination (2-PD) and vibration threshold (VT) in 163 WTCGRC subjects with both OSA and CRS (cases), OSA or CRS alone and without OSA or CRS (controls). Presence of OSA was determined from clinical sleep studies or home sleep testing. Presence of CRS was determined by nasal symptom questionnaire. The relationship between the presence of OSA and CRS and upper airway sensory impairment was assessed using linear regression analysis with each of 2PD and VT sensory threshold values as the dependent variable; OSA, CRS and their interaction were the independent variables. Age, gender and body mass index were covariates in the statistical model. The primary analysis was comparison of OSA+CRS versus controls (no OSA and no CRS) evaluated by linear contrasts.

RESULTS

There were no differences in 2-PD or VT in those with OSA+CRS, OSA and CRS alone or controls. However, both 2-PD and VT were significantly higher in the WTCGRC controls compared with values seen in historical controls using the same methodology (median 2-PD 13.0; CI (11.0 to 13.5) vs 10.5; CI (8 to 11); VT: mean±SEM (9.3±0.6 vs 2.2±0.1)).

CONCLUSION

While no differences were found in upper airway sensation between cases of OSA and CRS versus controls in the WTGRC population, there was evidence of impaired upper airway sensation in the WTGRC overall.

Characteristics of pharyngeal paraesthesia symptoms in patients with obstructive sleep apnoea

PURPOSE

This study aimed to investigate pharyngeal paraesthesia symptoms in patients with obstructive sleep apnoea (OSA).

MATERIAL AND METHODS

Patients with snoring and suspected OSA as well as age-matched controls were recruited. All participants underwent nocturnal polysomnography (PSG) and pharyngeal paraesthesia assessment using the Glasgow-Edinburgh throat scale (GETS). The incidence and severity of pharyngeal paraesthesia symptoms were compared between the groups.

RESULTS

A total of 280 patients who snored or were suspected of having OSA and 35 healthy, age-matched controls were recruited. The total pharyngeal paraesthesia symptom score was significantly higher in the OSA group than in the healthy group (12 [5, 23] vs. 3 [0, 9]; p < 0.001). The most frequent pharyngeal paraesthesia symptoms in the snore patients were Q7 (catarrh down the throat) and Q3 (discomfort/irritation in the throat), which are related to the irritability of the throat. The incidence of Q7 (OSA, 58% vs. controls, 14%; χ² = 23.66; p < 0.001), Q3 (OSA, 46% vs. controls, 3%; χ² = 23.07; p < 0.001), Q1 (feeling of something stuck in the throat; OSA, 33% vs. controls, 6%; χ² = 11.00; p = 0.001), Q6 (swelling in the throat; OSA, 31% vs. controls, 0%; χ² = 14.53; p < 0.001), Q9 (want to swallow all the time; OSA, 20% vs. controls, 6%; χ² = 6.28; p = 0.012), Q5 (throat closing off; OSA, 24% vs. controls, 6%; χ² = 6.16; p = 0.013), and Q2 (pain in the throat; OSA, 23% vs. controls, 6%; χ² = 5.32; p = 0.021) was significantly higher in the OSA group than in the controls CONCLUSIONS: Patients with obstructive sleep apnoea have higher pharyngeal paraesthesia symptoms scores and tend to have irritated throats compared to healthy controls.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03506178.

Palatal Sensory Function Worsens in Untreated Snorers but not in CPAP-Treated Patients With Sleep Apnea, Indicating Vibration-Induced Nervous Lesions

BACKGROUND

Signs of both motor and sensory nervous lesions have previously been shown in the upper airway of patients with OSA and habitual snorers. Snoring per se may damage all upper airway neurons over time, thereby causing progression to manifest sleep apnea. To test this hypothesis, nonsnoring subjects, untreated snorers, and CPAP-treated patients underwent repeated sensory testing of the soft palate in a prospective long-term study.

METHODS

Cold detection threshold (CDT) testing at the soft palate and lip with a thermode and nocturnal respiratory recordings were performed in 2008 to 2009 with retesting 6 to 7 years later.

RESULTS

In 25 untreated snorers, palatal CDT worsened from a median (25th-75th percentile range) 4.2°C (3.2-5.9) to 11.0°C (7.0-17.4) (P < .001). The apnea-hypopnea index increased from a median 7.0 to 14.0 events/h (P < .05). There was no significant correlation between changes in CDT and the apnea-hypopnea index. In 21 nonsnoring control subjects, palatal CDT increased from a median 3.2°C to 5.6°C (P < .005). In 19 CPAP-treated patients, palatal CDT did not significantly change; eight patients had improved values. CDTs worsened significantly more in the snorers group than in the control subjects (P < .05) and the CPAP-treated patients (P < .001). There was no significant difference between control subjects and CPAP-treated patients.

CONCLUSIONS

CDT worsened considerably over time in untreated snorers, significantly more than in nonsnoring control subjects and CPAP-treated patients. Untreated snorers therefore risk developing poor sensitivity in the upper airway. In contrast, efficient treatment of OSA seems to protect the sensory innervation, as the CPAP-treated group maintained their sensitivity to cold and, in some cases, the sensitivity even improved.

Quantitative Evaluation of the Function of the Sensory Nerve Fibers of the Palate in Patients With Obstructive Sleep Apnea

STUDY OBJECTIVES

To quantitatively evaluate the functional integrity of sensory nerve fibers of the palate in patients with obstructive sleep apnea (OSA) using the Neurometer system.

METHODS

A total of 32 patients with OSA and 18 healthy control patients were included in the study. All participants were selected based on medical history, physical examination, and nocturnal polysomnography (PSG) and divided into two groups. The palatal sensory status of participants was examined with a Neurometer current perception threshold (CPT) system. The system was used to deliver an electrical stimulus at three different frequencies (2,000 Hz, 250 Hz, and 5 Hz) by an investigator blinded to the PSG results.

RESULTS

There were no significant differences in the CPT values of the hard palate between the patients with OSA and control patients at any of the three stimulation frequencies. The differences in the CPT values of the soft palate between these groups failed to show any statistical significance at 250 Hz and 5 Hz. However, the patients with OSA showed significantly higher CPT values of the soft palate at 2,000 Hz than the age-matched healthy control patients (256.56 ± 129.34 versus 372.13 ± 152.06; P = .009).

CONCLUSIONS

Our study revealed an impairment of 2,000 Hz-related sensory nerve function of the soft palate among patients with OSA. The CPT test could be a useful tool for the quantitative and selective assessment of the sensory nerve function in patients with OSA. Additional research is required to evaluate the different types of sensory nerve dysfunctions among such patients.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Title: The Effects of Nasal Airflow on Upper Airway Dilator Muscles During Sleep; Identifier: NCT03506178; URL: https://clinicaltrials.gov/ct2/show/NCT03506178.

CITATION

An Y, Li Y, Chang W, Gao F, Ding X, Xu W, Han D. Quantitative evaluation of the function of the sensory nerve fibers of the palate in patients with obstructive sleep apnea. J Clin Sleep Med. 2019;15(9):1347-1353.

Systematic review of the different aspects of primary snoring

Primary snoring, also known as simple or non-apnoeic snoring, is regarded as the first stage of sleep disordered breathing without severe medical consequences for the snorer and co-sleeper. Although it is a highly prevalent phenomenon in the general population, our knowledge is limited because of the lack of a consensus on terminology. This systematic review of the aspects used in the definitions of simple/primary snoring was conducted to obtain an inventory of current practices and compare these definitions with the conceptual definition of the American Academy of Sleep Medicine. PubMed and Web of Science were searched from July 2016 onwards without any language limitations, and 362 references were obtained. After selection based on titles, 39 remained, among which 29 contained a definition or reference to a definition. In 69% of the studies, a cut-off <5 apnoea/Hypopnoea events per hour of sleep on the Apnoea-Hypopnoea Index was used. Despite this tendency, the cut-offs ranged from 0 to <15/h. Unfortunately, the cut-off and occasional requirements did not match the conceptual definition of the American Academy of Sleep Medicine. A consensus must be reached on an operational and clinically relevant definition based on the clear conceptual definition.

Investigation of smell and taste function in patients with obstructive sleep apnoea syndrome

Objective

This study investigated the relationship between disease severity and taste and smell functions in patients with obstructive sleep apnoea syndrome.

Methods

A total of 65 patients with recurrent upper airway obstruction during sleep were included. Participants were divided into four groups according to apnoea-hypopnoea index, obtained on polysomnography. Smell and taste tests were performed on these patients.

Results

A significant difference was observed between the smell thresholds of the groups for the identification test (p = 0.016). In the taste test, significant differences were observed between the groups in terms of sweet, sour, salty and bitter taste test thresholds (p = 0.029, p = 0.0005, p = 0.001 and p = 0.017, respectively).

Conclusion

As sleep apnoea severity increased (according to the apnoea-hypopnoea index) in obstructive sleep apnoea syndrome patients, the taste and smell thresholds decreased due to the effect of neuropathy and inflammation in the upper respiratory tract.

Desmin and dystrophin abnormalities in upper airway muscles of snorers and patients with sleep apnea

BACKGROUND

The pathophysiology of obstruction and swallowing dysfunction in snores and sleep apnea patients remains unclear. Neuropathy and to some extent myopathy have been suggested as contributing causes. Recently we reported an absence and an abnormal isoform of two cytoskeletal proteins, desmin, and dystrophin, in upper airway muscles of healthy humans. These cytoskeletal proteins are considered vital for muscle function. We aimed to investigate for muscle cytoskeletal abnormalities in upper airways and its association with swallowing dysfunction and severity of sleep apnea.

METHODS

Cytoskeletal proteins desmin and dystrophin were morphologically evaluated in the uvula muscle of 22 patients undergoing soft palate surgery due to snoring and sleep apnea and in 10 healthy controls. The muscles were analysed with immunohistochemical methods, and swallowing function was assessed using videoradiography.

RESULTS

Desmin displayed a disorganized pattern in 21 ± 13% of the muscle fibres in patients, while these fibers were not present in controls. Muscle fibres lacking desmin were present in both patients and controls, but the proportion was higher in patients (25 ± 12% vs. 14 ± 7%, p = 0.009). The overall desmin abnormalities were significantly more frequent in patients than in controls (46 ± 18% vs. 14 ± 7%, p < 0.001). In patients, the C-terminus of the dystrophin molecule was absent in 19 ± 18% of the desmin-abnormal muscle fibres. Patients with swallowing dysfunction had 55 ± 10% desmin-abnormal muscle fibres vs. 22 ± 6% in patients without swallowing dysfunction, p = 0.002.

CONCLUSION

Cytoskeletal abnormalities in soft palate muscles most likely contribute to pharyngeal dysfunction in snorers and sleep apnea patients. Plausible causes for the presence of these abnormalities is traumatic snoring vibrations, tissue stretch or muscle overload.

Sensory Innervation of the Human Soft Palate

The human soft palate plays an important role in respiration, swallowing, and speech. These motor activities depend on reflexes mediated by sensory nerve endings. To date, the details of human sensory innervation to the soft palate have not been demonstrated. In this study, eight adult human whole-mount (soft palate-tongue-pharynx-larynx-upper esophagus) specimens were obtained from autopsy. Each specimen was bisected in the midline, forming two equal and symmetrical halves. Eight hemi-specimens were processed with Sihler's stain, a whole-mount nerve staining technique. The remaining eight hemi-soft palates were used for immunohistochemical study. The soft palatal mucosa was dissected from the oral and nasal sides and prepared for neurofilament staining. Our results showed that the sensory nerve fibers formed a dense nerve plexus in the lamina propria of the soft palatal mucosa. There was a significant difference in the innervation density between both sides. Specifically, the oral side had higher density of sensory nerve fibers than the nasal side of the soft palate. The mean number and percent area of the sensory nerve fibers in the mucosa of the nasal side was 78% and 72% of those in the mucosa of the oral side, respectively (P < 0.0001). The data presented here could be helpful for further investigating the morphological and quantitative alterations in the sensory nerves in certain upper airway disorders involving the soft palate such as obstructive sleep apnea (OSA) and for designing effective therapeutic strategies to treat OSA. Anat Rec, 301:1861-1870, 2018. © 2018 Wiley Periodicals, Inc.

Neuropathic changes in the tongue protruder muscles in patients with snoring or obstructive sleep apnea

OBJECTIVE

Both myopathic and neuropathic tongue protruder muscle changes have been demonstrated to occur in obstructive sleep apnea (OSA) patients using different methods. We tried to elucidate this dilemma using quantitative electromyographic (EMG) methods.

METHODS

In a group of consecutive patients with suspected OSA a full overnight polysomnography (PSG) and quantitative needle EMG of the tongue protruder, biceps brachii and vastus lateralis muscles were performed. EMG findings were compared to control subjects.

RESULTS

Of 23 patients, 8 were classified as simple snorers and the remaining 15 as OSA patients by PSG. Motor unit potential (MUP) parameters obtained in tongue protruder muscles, but not biceps brachii or vastus lateralis muscles, were significantly larger in patients compared to controls. However, no correlation was found between tongue protruder muscle MUP parameters and patient characteristics.

DISCUSSION

Our study confirmed previous findings of neuropathic changes in the tongue protruder muscles of OSA patients, and extended these to simple snorers. Changes were limited to the upper airway muscle, and could not been explained by the severity or duration of the sleep breathing disorder. The possible role of denervation injury caused by the upper airway vibrations should be tested in the future by appropriately designed studies.

Neuromuscular function of the soft palate and uvula in snoring and obstructive sleep apnea: A systematic review

OBJECTIVE

A collapsible upper airway is a common cause of obstructive sleep apnea. The exact pathophysiology leading to a more collapsible airway is not well understood. A progressive neuropathy of the soft palate and pharyngeal dilators may be associated with the progression of snoring to OSA. The purpose of this study is to systematically review the international literature investigating the neurophysiologic changes in the soft palate and uvula that contribute to progression from snoring to OSA.

METHODS

PubMed/MEDLINE and 4 other databases were systematically searched through July 4, 2017. Eligibility: (1) Patients: controls, snoring or OSA patients (2) Intervention: neuromuscular evaluation of the palate and/or uvula (3) Comparison: differences between controls, snoring and OSA patients (4) Outcomes: neuromuscular outcomes (5) Study design: Peer reviewed publications of any design.

RESULTS

845 studies were screened, 76 were downloaded in full text form and thirty-one studies met criteria. Histological studies of the soft palate demonstrated diffuse inflammatory changes, muscular changes consistent with neuropathy, and neural aberrancies. Sensory testing studies provided heterogeneous outcomes though the majority favored neuronal dysfunction. Studies have consistently demonstrated that increasing severity of snoring and sleep apnea is associated with worsening sensory nerve function of the palate in association with atrophic histological changes to the nerves and muscle fibers of the soft palate and uvula.

CONCLUSIONS

Recent evidence highlighted in this systematic review implicates the role of neurogenic pathology underlying the loss of soft palate and/or uvular tone in the progression of snoring to sleep apnea.

Upper Airway Vibration Perception in School-Aged Children with Obstructive Sleep Apnea

STUDY OBJECTIVES

Children with the obstructive sleep apnea (OSA) have impaired upper airway two-point discrimination compared to controls. In addition, blunted vibration threshold detection (VT) in the palate has been recognized in adults with OSA, but has not been studied in children. Both findings are indicative of a defect in the afferent limb of the upper airway dilator reflex that could prevent upper airway dilation secondary to airway loading, resulting in airway collapse. We hypothesized that children with OSA have impaired palate VT compared to controls, and that this improves after OSA treatment.

METHODS

Case-control study. Children with OSA and healthy non-snoring controls underwent polysomnography and palate VT measurements. Children with OSA were retested after adenotonsillectomy.

RESULTS

29 children with OSA (median [interquartile range] age = 9.5 [7.5-12.6] years, obstructive apnea-hypopnea index [OAHI] = 11.3 [5.7-19.5] events/h, BMI z = 1.8 [1.3-2.1]) and 32 controls (age = 11.2 [9.3-13.5] years, P = 0.1; OAHI = 0.5 [0.1-0.7] events/h, P < 0.001; BMI z = 1 [0.3-1.7], P = 0.004) were tested. OSA palate VT (1.0 [0.8-1.5] vibration units) was similar to that of controls (1 [0.8-1.3], P = 0.37). 20 children with OSA were retested 4.4 (3.2-7.1) months after treatment. OAHI decreased from 13.1 (5.8-19) to 0.6 (0.2-2.5) events per hour (P < 0.001) postoperatively, but palate VT did not change (before = 1 [0.7-1.5], after = 1.2 [0.8-1.4], P = 0.37).

CONCLUSIONS

Children with OSA and controls have similar palate VT. Unlike in adults, palate VT does not seem to be affected by childhood OSA.

Assessment of Change in Palatal Sensation in Obstructive Sleep Apnea Patients by Using Two-Point Palatal Discrimination

Objectives.

Patients with obstructive sleep apnea syndrome (OSAS) have impaired responses to inspiratory resistive loading during sleep. This may be due, in part, to a change in the upper airway sensation. Therefore, we hypothesized that patients with OSAS have diminished upper airway sensation due to snoring.

Methods.

A total of 53 participants were selected based on clinical evaluation and polysomnography. Two-point discrimination was measured with modified calipers in the tongue and soft palate.

Results.

A total of 10 participants were included in the control group, 12 participants in the simple snoring group, and 27 participants in the OSAS group. There were 12 patients in the impaired sensation group of the OSAS group. On comparing polysomnography, patients with impairment of their palatal sensory input in two-point discrimination (TPD) had a more protracted duration of the longest snoring episode than those with simple snoring and normal sensation. Patients with decreased sensory input in TPD had longer average duration of snoring episodes and relative snoring time than those with simple snoring and normal sensory input in cold uvular TPD. Comparison of the cold uvular TPD for normal sensation and impaired sensation in patients with OSAS after treatment showed a different trend.

Conclusion.

Impaired sensation of the soft palate was correlated with the longest snoring episode duration, average snoring episode duration, and relative snoring time. It is helpful in detecting the early stage of neural degradation in OSAS patients by assessing snoring components of polysomnography and TPD in the soft palate.

Simple snoring: not quite so simple after all?

Simple snoring (SS), in the absence of obstructive sleep apnoea (OSA), is a common problem, yet our understanding of its causes and consequences is incomplete. Our understanding is blurred by the lack of consistency in the definition of snoring, methods of assessment, and degree of concomitant complaints. Further, it remains contentious whether SS is independently associated with daytime sleepiness, or adverse health outcomes including cardiovascular disease and metabolic syndrome. Regardless of this lack of clarity, it is likely that SS exists on one end of a continuum, with OSA at its polar end. This possibility highlights the necessity of considering an otherwise 'annoying' complaint, as a serious risk factor for the development and progression of sleep apnoea, and consequent poor health outcomes. In this review, we: 1) highlight variation in prevalence estimates of snoring; 2) review the literature surrounding the distinctions between SS, upper airway resistance syndrome (UARS) and OSA; 3) present the risk factors for SS, in as far as it is distinguishable from UARS and OSA; and 4) describe common correlates of snoring, including cardiovascular disease, metabolic syndrome, and daytime sleepiness.

Palatal sensory threshold reflects nocturnal hypoxemia and airway occlusion in snorers and obstructive sleep apnea patients

STUDY OBJECTIVES

Upper airway sensory deficit has been reported to be associated with snoring or obstructive sleep apnea. There are limited data on the correlation between disease severity and upper airway sensation. In this study, we investigated the relationship between clinical parameters and standardized palatal sensory threshold (SPST) using Semmes Weinstein monofilaments.

METHODS

We recruited 40 snorers and 19 control subjects. Palatal sensory threshold was measured in all study subjects, using Semmes Weinstein monofilaments. Standardized palatal sensory threshold was determined by subtraction of hard palate sensation from uvular sensation. All subjects with snoring underwent a modified Muller maneuver during wakefulness before polysomnography.

RESULTS

SPST was higher in snorers than in control subjects, but did not differ according to the severity of obstructive sleep apnea. Patients with higher SPST (≥ 0.45 g/mm(2)) were older and had more severe hypoxemia indices: lower nadir oxyhemoglobin saturation (SpO2) and higher percentage of sleep time at < 90% SpO2. Adjusted for age, sex, neck circumference, and body mass index, SPST was correlated with the apnea-hypopnea index and hypoxemia indices. With a cutoff value ≥ 0.45 g/mm(2), the sensitivity of SPST for nocturnal hypoxemia (nadir SpO2, < 80%) was 81.3%. Patients with higher SPST (≥ 0.45 g/mm(2)) showed more airway occlusion in modified Muller maneuver, than those with lower values.

CONCLUSIONS

The SPST measured using Semmes Weinstein monofilaments reflects nocturnal hypoxemia and airway occlusion. This test provides a potential tissue marker of the severity of hypoxemia in patients who snore.

Ambient temperature and obstructive sleep apnea: effects on sleep, sleep apnea, and morning alertness

STUDY OBJECTIVES

The aim of the study was to investigate the effect of ambient temperature on sleep, sleep apnea, and morning alertness in patients with obstructive sleep apnea.

DESIGN

Randomized controlled trial.

SETTING

In-hospital investigations.

PARTICIPANTS

Forty patients with obstructive sleep apnea naïve to treatment, with an apnea-hypopnea index of 10-30.

INTERVENTIONS

Three different nights in room temperatures of 16°C, 20°C, and 24°C.

MEASUREMENTS

Overnight polysomnography and Karolinska Sleepiness Scale.

RESULTS

The obstructive apnea-hypopnea index was 30 ± 17 at 16°C room temperature, 28 ± 17 at 20°C, and 24 ± 18 at 24°C. The obstructive apnea-hypopnea index was higher at 16°C room temperature versus 24°C (P = 0.001) and at 20°C room temperature versus 24°C (P = 0.033). Total sleep time was a mean of 30 min longer (P = 0.009), mean sleep efficiency was higher (77 ± 11% versus 71 ± 13% respectively, P = 0.012), and the patients were significantly more alert according to the Karolinska Sleepiness Scale (P < 0.028) in the morning at 16°C room temperature versus 24°C. The amount of sleep in different sleep stages was not affected by room temperature.

CONCLUSIONS

Untreated patients with obstructive sleep apnea sleep longer, have better sleep efficiency, and are more alert in the morning after a night's sleep at 16°C room temperature compared with 24°C, but obstructive sleep apnea is more severe at 16°C and 20°C compared with 24°C.

CLINICAL TRIAL INFORMATION

This study is registered in ClinicalTrials.gov number NCT00544752.