|Year : 2015 | Volume
| Issue : 1 | Page : 31-35
Obstructive Sleep Apnoea: A Roar in the Snore
Gopinadh Anne, Sandeep Chiramana, Geetha Bhavani Paluri, B Sridevi, Sampath Chowdhary Anche, Srujana Zakkula
Department of Prosthodontics, Sibar Institute of Dental Sciences, Guntur, Andhra Pradesh, India
|Date of Web Publication||19-Oct-2015|
Geetha Bhavani Paluri
Department of Prosthodontics, Sibar Institute of Dental Sciences, Guntur, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Sleeping is an important physiological role in our day to day life. A good laugh and a long sleep are the best cures in the doctor's book. Sleep disorders of the upper airway result from any condition or disease that causes its partial or complete obstruction when a patient assumes a supine position and goes to sleep. Sleep disorders, particularly untreated obstructive sleep apnoea (OSA) can be associated with motor vehicle accidents, poor work performance in the office or workplace, and also makes a person prone to occupational accidents and reduced quality of life. Comprehensive management of upper airway sleep disorders requires an interdisciplinary approach. A prosthodontist can play a significant role as the team member in the interdisciplinary approach for the management of upper airway sleep disorders. The present article focuses on the history, clinical examination, investigations, and management of OSA.
Keywords: Apnea-hypopnea index, continuous positive airway pressure, obstructive sleep apnea, polysomnography
|How to cite this article:|
Anne G, Chiramana S, Paluri GB, Sridevi B, Anche SC, Zakkula S. Obstructive Sleep Apnoea: A Roar in the Snore. J Dent Allied Sci 2015;4:31-5
|How to cite this URL:|
Anne G, Chiramana S, Paluri GB, Sridevi B, Anche SC, Zakkula S. Obstructive Sleep Apnoea: A Roar in the Snore. J Dent Allied Sci [serial online] 2015 [cited 2019 Aug 25];4:31-5. Available from: http://www.jdas.in/text.asp?2015/4/1/31/167538
| Introduction|| |
Obstructive sleep apnea (OSA) is a common problem that affects a person's breathing during sleep. In patients with OSA, air cannot flow normally into the lungs. The block in airflow is usually caused by the collapse of the soft tissues in the upper airway and tongue during sleep.
| Types of Sleep Disorders|| |
Snoring is a common sleep disorder which occurs as a result of the base of the tongue or soft palate or both approximating the posterior wall of the pharynx. The obstruction happens when a patient falls asleep or assumes a supine position when oropharyngeal musculature is relaxed. ,
Apnoea is defined as cessation of airflow during sleep, which lasts for at least 10 s until the body reacts with a bigger breathing effort to overcome the problem with oxygen desaturation of more than 3% and/or associated with arousal. This cycle happens over and over throughout the night, interfering with the normal sleep pattern.
Hypopnea is defined as a reduction in amplitude of airflow of >50% of baseline measurement, for at least 10 s with accompanying oxygen desaturation of at least 3% and/or associated with arousal.
OSA refers to the occurrence of at least five apnoeas or hypopneas per sleep hour (Apnea-Hypopnea Index [AHI] >5/h), resulting in sleep fragmentation and decrease oxygen saturation.
Grading of sleep apnea
Sleep specialists categorize sleep apnea by the number of events per hour: 
- Mild - 5-15 events/h
- Moderate - 15-30 events/h
- Severe - Over 30 events/h.
| Pathophysiology of Sleep Disorders|| |
Sleep is not a homogenous state and is divided into two states: Nonrapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. In REM sleep, the brain activity is same as when a person is awake. NREM sleep is divided into four stages. Stages 3 and 4 represent a deeper level of sleep and are required to refresh the brain. REM and NREM sleep alternate cyclically through the night at intervals of 90-120 min.
During REM sleep, there is a generalized inhibition of skeletal muscles including intercostals, accessory, and pharyngeal dilators. Thus, ventilation during REM is virtually dependent on diaphragmatic function, and upper airway function is more precarious than during NREM.
The resistance of the system is increased and at the same time both chemical and mechanical sensors are depressed. Considerable individual variation exists in the threshold for arousal in response to chemical and mechanical/behavioral drive. This variation in responsiveness may be an important risk factor for OSA.
Pathophysiologic mechanism of snoring and OSA, although fully not understood can be explained by either the obstacle theory or the Bernoulli theory. According to the obstacle theory, an increased negative pressure during inspiration retracts the structures of the pharynx and makes them vibrate in the airflow to produce snore and possible obstruction in OSA.
The Bernoulli theory assumes that according to the principle of Bernoulli (1738), the velocity of streaming air is higher and the pressure lower at a constriction of a tube compared with the larger part. This may cause inward suction of the pharyngeal structures in a constricted area and snores by the vibration of wall structures. 
| Risk Factors for Obstructive Sleep Apnea|| |
The increased prevalence of SDB in the elderly appears to plateau after 65 years. Mechanisms proposed for the increased prevalence of sleep apnoea in the elderly include increased deposition of fat in the parapharyngeal area, lengthening of the soft palate, and changes in body structures surrounding the pharynx. 
Imaging studies have revealed that men have increased fat deposition around pharyngeal airway as compared with women.  Besides, hormonal differences may play a role in the predisposition to abnormal breathing during sleep.  Premenopausal women are relatively protected from OSA even if they have other known risk factors for OSA. In a cross-sectional prevalence study, it shows a 4-fold higher prevalence of at least moderate OSA in postmenopausal women as compared with premenopausal women. And interestingly, in postmenopausal women taking hormonal replacement therapy, the prevalence of OSA is similar to premenopausal women. 
Obesity is the major risk factor for the development of OSA, it is thought to be associated with anatomic alterations that predispose to upper airway obstruction during sleep, by increasing adiposity around the pharynx and body. Central obesity has been associated with a reduction in lung volume, which leads to a loss of caudal traction on the upper airway, and hence, an increase in pharyngeal collapsibility. 
Family history and genetic predisposition
Obesity is closely associated with OSA and itself aggregates in families. Craniofacial morphology represents another mechanism by which genetics may influence the development of OSA, the bony and soft tissue structures that are seen from one generation to another in different families, including specific craniofacial disorders, for example, Pierre-Robin syndrome, these patients have micrognathia, glossoptosis, and cleft palate, the tongue tends to prolapse backward, leading to airway obstruction. 
Smoking and alcohol consumption
Smoking is associated with a higher prevalence of snoring and sleep-disordered breathing (SDB). It can well be explained by the cigarette induced airway inflammation and damage which could change the structural and functional properties of the upper airway, and increasing the risk of collapsibility during sleep. Alcohol relaxes upper airway dilator muscles, increases upper airway resistance, and may induce OSA in susceptible subjects. ,
| Diagnosis of Obstructive Sleep Apnoea|| |
Clinical presentation of obstructive sleep apnoea
Common physical findings in patients with obstructive sleep apnea hypopnea syndrome [Table 1] and [Table 2]
Airway evaluation in obstructive sleep apnoea
Static radiologic imaging techniques, such as X-ray cephalometry, computed tomography (CT) scanning, and magnetic resonance imaging (MRI), have been used mostly to detect differences in airway anatomy. Dynamic scanning protocols (e.g., ultrafast CT or cine MRI) and multiple pressure recordings have been used to gain insights into the mechanism and level of airway obstruction.
Clinical examination and clinical scores
Anatomic and static clinical findings were the first parameters to be evaluated to improve treatment success.
Case details should be recorded on a SDB examination form which should include body mass index (BMI), neck size, alcohol consumption and sedative usage details, sleep position, frequency and intensity of snoring, and subjective assessment on Epworth sleepiness scale [Table 3]. 
Friedman et al. developed a clinical 4° staging system incorporating the tonsil size, the position of the soft palate, the tongue size, and the BMI.
| Investigations|| |
Lateral cephalograms are used to analyze skeletal and soft tissue characteristics of patients with OSA. The following findings in OSA patients can only be a selection while performing a lateral cephalogram: Longer soft palates reduced minimum palatal airway widths, increased thickness of the soft palate, differences in calculated craniofacial scores, increased pharyngeal lengths, retroposition of the mandible or the maxilla, micrognathia, increased mid-facial heights, and differences in hyoid bone position. The hyoid bone has been found to be more inferiorly placed in OSA patients.
Computed tomography scanning
Compared to lateral X-ray cephalometry, CT scanning significantly improves soft tissue contrast and allows precise measurements of cross-sectional areas at different levels, as well as three-dimensional reconstruction and volumetric assessment.
CT scanning has provided valuable insights into the pathophysiology of SDB and plays a major role in its management.
Magnetic resonance imaging
Compared to lateral X-ray cephalometry or CT scanning MRI offers various advantages, such as excellent soft tissue contrast, three dimensional assessments of tissue structures, and lack of ionizing radiation. The latter has made MRI the imaging technique of choice in the assessment of children with SDB. Numerous authors have demonstrated that the mechanism and level of airway obstruction can be visualized by MRI, even under natural sleep. 
Videoendoscopy during spontaneous sleep
Videoendoscopy during spontaneous sleep is performed to improve patient selection for the different treatments available and may also be performed in combination with overnight sleep recordings. Because videoendoscopy during spontaneous sleep allows the assessment of the upper airway during different sleep stages and lacks the side effects of sedating drugs, this method may be considered superior to videoendoscopy under sedation. 
Acoustic reflection test
Acoustic reflection test can be used to determine the airway obstruction and also the corresponding effect of mandibular advancement and protrusion on the upper airway.  In this test, the sound wave is projected into the airway and is reflected back through the tube to a computer which creates graph that determines the location of the obstruction.
Polysomnogram (PSG) is considered the gold standard test for diagnosis of OSA. The test involves overnight recording of sleep, breathing pattern, and oxygenation. The study records analysis of apnoea, oxygen saturation, body position, change heart rate, snoring, desaturation relations, and sleep staging. The recordings include electroencephalography, electrooculography, electromyography, and electrocardiography. PSG provides the AHI scores which are an estimation of apnoeic-hypopnoeic episodes per hour of sleep. Based on these scores, OSA is grouped into four categories: 
- Mild OSA (10-20 AHI)
- Moderate OSA (20-30 AHI)
- Severe OSA (30-40 AHI)
- Very severe (more than 40 AHI).
A PSG will provide the apnea index, the hypopnea index, the apnea-sleep ratio (the percentage of time spent in apneic state), the apnea-hypopnea sleep ratio (the percentage of sleep time spent in apneic and hypopneic states), and the AHI or respiratory disturbance index. This information is necessary to properly diagnose and determine the course of treatment for a patient.
Spirometry is a pulmonary function test. It is a simple method of studying pulmonary ventilation by recording movements of air into and out of lungs. The test determines the inspiratory flow rate, expiratory flow rate, forced vital capacity (FVC), ratio of forced expiratory volume in 1 s to FVC, and other ventilation rates.
| Influence of Tooth Loss on Obstructive Sleep Apnoea|| |
Edentulism has been shown to produce anatomical changes in craniofacial structures and hypothesized to increase OSA. The following anatomical changes ensue due to loss of teeth:
- Decrease in vertical dimension of occlusion
- Change in position of mandible
- Change in position of hyoid bone
- Impaired function of oropharyngeal musculature such as loss of tone in soft palate and pharynx, macroglossia.
| Treatment Protocols|| |
The management protocol includes behavioral modifications sleep position change and weight control by modification in lifestyle. Definite modalities include continuous positive airway pressure (CPAP), surgery to enlarge upper airway and orthognathic surgery for bringing the mandible and maxillae forward and oral appliances. Complete dentures for edentulous patients help restore face height and better control on the lower jaw thereby helping in normal breathing. 
It includes body weight control, sleep position changes, and stopping of sedatives/alcohol.
- Obese patients should be encouraged to lose weight and attempt to reach BMI of 25 or close to it
- Patients may be asked to lie on their side and place a pillow behind them so that they cannot roll onto their back to a supine position. Another alternative is to sew a tennis ball in the center of the back of the pyjamas to serve the same purpose
- The elimination of alcohol and sedatives at least 3 h before sleep has been recommended because of the depressant effect of the drugs on the central nervous system.
Continuous positive airway pressure
This involves continuously pumping room air under pressure through a sealed gauge or nose mask, which passes through the upper airway to the lungs. However, CPAP suffers from poor patient compliance because of portability problems, pump noise, dryness of airway, and mask discomfort. Patients who are unable to be compliant with a nasal mask due to claustrophobia, headaches, mask leaks, eye irritation, and sinusitis may benefit by using oral mask ventilation with oral positive airway pressure (OPAP). OPAP delivered through an oral appliance is a treatment alternative to nasal CPAP. 
A number of surgical procedures have been practised to increase and stabilize the upper airway caliber. These include: Maxillomandibular advancement, palatouvulo-pharyngoplasty, laser assisted uvulopalatoplasty, hyoid suspension, genioglossus advancement, tongue-based suspension sutures, and midline glossectomy. 
Oral appliances are indicated for use in patients with primary snoring, mild and moderate OSA, and who do not respond or are not appropriate candidates for treatment with behavioral measures such as weight loss or sleep position change. 
The effects of mandibular advancement on upper airway anatomical relationship are: 
- Elevates the base of the tongue
- Tenses the palatoglossus muscle and pulls the soft palate forward
- Decompress tissues around the pharynx and allows the pharynx to expand
- Helps stabilize lateral pharyngeal wall by applying tension to pharyngomandibular raphe which is coupled to pharyngeal constrictors
- Splays the tonsillar arches formed by palatoglossus and palatopharyngeal muscles which leads to further stabilization of lateral pharyngeal wall.
Mandibular advancement device
It is the one with fixed mandibular advancement or titratable/adjustable mandibular advancement appliances.
Mandibular advancement devices (MADs) with fixed/recorded mandibular advancement are:
- Monoblock appliances
- A simple splint
- Karwetzky activator
- Twin block appliance
- Removable Herbst appliance
- Twin block.
All these appliances are made with the mandible in a requisite protrusive position. Karwetzky activator is one of the most widely used fixed MAD in the management of OSA. Karwetzky activator is a tooth- and tissue-borne activator which is split along the occlusal plane and joined by two "U" loops made of 0.9 mm stainless steel wire in the lingual acrylic area of first molars. This design permits lateral and vertical jaw movements during sleep. This appliance can be easily made in a dental laboratory.
The research on this design has lead to the improvisation and development of tongue stabilizing device (TSD) which is made of soft medical silicone for comfort and works by holding the tongue forward by gentle suction, preventing it from falling back against the back of the throat and thus keeping the airway open during sleep. TSD does not attach to the teeth; it is more of a vestibular appliance. This device actively pull or hold the tongue in a position more anterior than the normal resting tongue position. The bulb protrudes anteriorly to and between incisor teeth and beyond the lips, which by means of negative pressure holds the tongue forward during sleep. Passive mandibular advancement also occurs. This appliance has been found effective in snoring and OSA.
Tongue repositioning manoeuvre with oral shields
The appliance is an improvisation of oral screens by attaching a funnel anteriorly which is covered by a membrane. The membrane funnel oral shields enables the patient to form negative intraoral pressure during and after deglutition and thus continuously train a tongue position at hard palate with close tongue velum contact which is needed for posterior mouth closure. This concept has been found to be effective in training of nasal breathing, oral rest position, and nocturnal assistance of mouth closure.
Titratable mandibular advancement devices
These are preferred for their inbuilt system by which mandibular protraction can be titrated or sequentially advanced in the sagittal plane until the acceptable level of subjective improvement occurs.  Titratable mandibular advancement helps in slowly moving the mandible either anteriorly or posteriorly using the adjustable mechanism until successful results are achieved with the minimum possible protrusive position.
| Conclusion|| |
The interplay between anatomic, functional, and neural factors that influence the upper airway patency during wakefulness and sleep is still unclear. This may be due to the missing data linking sleep studies using polysomnography and three-dimensional imaging studies performed during wakefulness and natural sleep conditions. Although the role played by the prosthodontists is still in its infancy, there is much to learn and understand in the rapidly evolving field of sleep medicine. The growing interest of prosthodontists in sleep medicine has contributed immensely toward effective prevention and treatment of OSA and sleep bruxism for each patient based on his/her individual requirement.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]