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IMAGE 2010-11 ISSN: 2229-5658 Vol No: 11 ISSUE No: 4 15 OBSTRUCTIVE SLEEP APNEA - A REVIEW Dr Shruthi C S, Reader, Dept of Prosthodontics and Implantology M R Ambedkar Dental College and Hospital Bangalore, Dr Vinod Kumar R, Professor, Dept of Conservative Dentistry and Endodontics Dayanand Sagar College of Dental Sciences Bangalore.,Dr .Upendranath Reddy,Senior Lecturer, Dept of Conservative Dentistry and Endodontics Pulla Reddy Dental College Kurnool.,Dr Paras, Reader, Dept of Conservative Dentistry and Endodontics JSS Dental College and Hospital Mysore. Abstract Obstructive sleep apnea is characterized by repetitive episodes of pharyngeal collapse with increased airflow resistance during sleep. It appears to have multiple contributing causes and patients who have this disease are at risk for many deleterious conditions, including chronic snoring, hypertension, excessive daytime sleepiness, decreased libido, fatigue, and an increased tendency for accidents. Children may also exhibit poor school performance and hyperactivity. The proper recognition and treatment of these patients is critical. Key Words: Sleep Apnea, Snoring, Mandibular Advancement Appliance. INTRODUCTION Sleep apneas are classified into three types; obstructive, central, and mixed. Central apneas are characterized by the simultaneous cessation of both airflow and respiratory effort. Obstructive sleep apnea (OSA) is characterized by repetitive episodes of pharyngeal collapse with increased airflow resistance during sleep. During mixed apnea, a central respiratory pause is followed by obstructed ventilatory efforts. An arousal is a change in sleep to a lighter stage and/or an actual awakening. Apnea is defined as a cessation of airflow (breathing) lasting for at least 10 seconds. Hypopnea is a 50% reduction in airflow for 10 seconds or more, usually associated with a fall in blood oxygen saturation. The Apnea Index (AI) is the number of apneic episodes per hour of sleep. The total number of apneic and hypopneic episodes per hour of sleep is referred to as the Apnea-Hypopnea Index (AHI) or the Respiratory-Disturbance Index (RDI). 1 Up to 25% of adults have OSA (i.e., an apneañhypopnea index (AHI) _5/h) and roughly 10% of all adults have moderate to severe disease (i.e., an AHI _15/h). 2 OSA is associated with higher rates of cardiovascular and cerebrovascular morbidity and mortality as well as excessive daytime sleepiness, fatigue and PROSTHODONTICS & ORAL MEDICINE neurocognitive deficits. When left untreated, the mortality rate for severe OSA approaches 30% at 15 years. Upper Airway Sleep Disorders Upper airway sleep disorders (UASDs) are conditions that occur in the upper airway that diminish sleep time and/or sleep quality. USAD syndromes described in the literature include sleep apnea syndrome, and upper airway resistance syndrome (UARS). 3 Snoring is a common symptom of these syndromes. Sleep apnea syndrome is a sleep interference disorder characterized by apneic and possibly hypopneic events, resulting in low oxygen levels to the lungs (hypoxia), blood oxygen desaturation, and a sleep arousal or awakening. UARS is a condition that can cause the clinical manifestations of sleep apnea syndromes and yet, the patient exhibits no apnea or hypopnea events. These patients exhibit a narrowing of the upper airway that requires a greater effort on their part to breathe. Physiology of Upper Airway Sleep Disorder The term upper airway includes the structures of the hypopharynx, oropharynx, and nasopharynx (Fig. 1). As illustrated in Figure 1, the upper airway is a nonrigid soft tissue structure with minimal bony support. The negative pressure during inspiration tends to cause a change in shape of the airway, which is resisted to a large extent by Visit: http://image.idakunnamkulam.com/ The International Journal of Indian Dental Association, Kunnamkulam Branch. Indexed in Journals Master List of IC TM
IMAGE 2010-11 ISSN: 2229-5658 Vol No: 11 ISSUE No: 4 16 the activity of the tensor veli palatini and the genioglossus muscles in a individual normal . Fig. 1. Upper airway space of Fig. 2. Upper airway anatomy of OSA patient patient with normal anatomy. reveals complete closure of airway Most snoring and obstructive sleep apnea (OSA) patients have an initially compromised airway space that is often caused by obesity but may be caused by any condition that impinges on the space. The genioglossus and tensor veli muscles may have increased activity in the awake OSA patients and thus help maintain the shape of the upper airway. 4 However, when the patient assumes a supine position and goes to sleep, there is a decrease in the activity of the genioglossus and tensor veli palatini muscles that results in a decreased airway space. 5 This decrease in airway size may result in an increase in the velocity of the air passing through the airway, increasing the degree of subatmospheric pressure. The combination of increased negative pressure and decrease in muscle activity allows the tongue and soft palate to move toward and often contact the posterior wall of the oropharynx, resulting in a decreased airway space. If the blockage is not complete, the increase in airflow velocity during inspiration and expiration may cause the soft tissues, particularly the uvula, to vibrate (Fig. 2). For other patients, this combination of negative pressure, decreased muscle activity and movement of tongue and soft palate toward the posterior wall of the pharynx, results in a complete blockage of the airway (Fig. 3). The resulting conditions may be snoring and/or OSA. 6 Any anatomic abnormality of the nose, nasopharynx, oropharynx, larynx, and oral cavity may also cause the initial reduction of airway space. These conditions may include obesity, polyps, tumors, edema of the epiglottis, adenotonsillar hypertrophy, and other structural changes in the upper airway. Obstructive Sleep Apnea OSA is still a poorly recognized medical condition the cause of which is multifaceted. Any obstructive condition coupled with assuming the supine position may cause a blockage of the upper airway. Anatomic alterations may reduce airway space in moderate-to-severe OSA patients, 7 and include posteriorly positioned maxillae and mandibles, steep occlusal planes, overerupted anterior teeth, large gonial angles, anterior open bites in association with long tongues, posteriorly placed pharyngeal walls, retrognathic mandibles, large tongue and soft palate, large airway volumes, and anteroposterior discrepancies between the maxilla and mandible. Micrognathia, acromegaly, and Downís syndrome may also be predisposing conditions. Blockage of the airway causes an apnea and/or hypopnea event(s) and results in Visit: http://image.idakunnamkulam.com/ The International Journal of Indian Dental Association, Kunnamkulam Branch. Indexed in Journals Master List of IC TM
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