Obstructive Sleep Apnea : Role Of A Dental Surgeon

All About Sleep

Sleep is defined as a period of rest for the body and mind during which consciousness are in partial or complete abeyance and the bodily functions are partially suspended. An average human being requires 8 hours of sleep (range:4 to 10 hours). There are two main types of sleep:

• Non Rapid Eye Movement (NREM):It is also known as quiet sleep
• Rapid Eye Movement:It is also known as active sleep or paradoxical sleep.

Various Stages in Sleep Cycle: The various stages of sleep are as follows: NREM STAGE 1: At the beginning of the sleep cycle, Stage 1 is a light stage of sleep that could be regarded as a transition phase between wakefulness and sleep. This phase lasts for a brief period of around 5 to 10 minutes, and if someone were awakened during this stage, they might report that they were not really asleep. NREM STAGE 2: The second stage of sleep is referred to as Stage 2 and persists for roughly 20 minutes. In this stage, you become less conscious of your surroundings, your body temperature drops, and your breathing and heart rate become more regular. People typically spend half of their total sleep in this stage. NREM STAGE 3: During Stage 3 sleep:

• Muscles relax
• Blood pressure and breathing rate drop
• The deepest sleep occurs in this stage
• Bedwetting and sleepwalking can occur in this stage

REM SLEEP: Also known as Stage 4, during this stage:

• Brain activity increases
• The body becomes relaxed and immobilized
• Dreams occur
• Eyes move rapidly

People generally spend nearly 20% of their entire sleep in this stage. Sequence of Sleep: Sleep begins with stage 1 and progresses to stage 2 & stage 3. After stage 3, stage 2 sleep is repeated before entering REM sleep. Once REM sleep is over, the body returns to stage 2. Sleep cycles through these stages approximately four or five times throughout the night. On an average, we enter REM sleep approximately 90 minutes after falling asleep. The first cycle of REM sleep lasts only for few minutes, but each cycle becomes longer. REM sleep can lasts upto an hour.

All About Sleep Apnea

OBSTRUCTIVE SLEEP APNEA (OSA): Obstructive Sleep Apnea (OSA) is a sleep disorder that involves cessation or significant decrease in airflow in the presence of breathing effort. It is the common type of Sleep Disordered Breathing (SDB) and is characterized by recurrent episodes of upper airway collapse during sleep. UPPER AIRWAY RESISTANCE SYNDROME (UARS):Upper Airway Resistance Syndrome (UARS) is caused by slowing or blocking of air in the nasal passages during sleep, disrupting it & causes fatigue. Definitions Of Respiratory Events:-- APNEA: Apnea is defined by the American Acadey Of Sleep Medicine (AASM) as the cessation of airflow for atleast 10 seconds. --HYPOPNEA: Hypopnea is defined as recognizable transient reduction (but not complete cessation) of airflow for 10 seconds or longer. Pathophysiology Of Obstructive Sleep Apnea (OSA) Obstructive Sleep Apnea (OSA) is caused by soft tissue collapse in the pharynx. Transmural pressure is the difference between intra-luminal pressure & surrounding tissue pressure. If transmural pressure decreases, the cross sectional area of the pharynx decreases too. If this pressure passes a critical point, pharyngeal closing pressure is reached. Exceeding pharyngeal critical pressure causes tissue collapsing inward and the airway gets obstructed. Different Types Of Sleep Apnea:-- OBSTRUCTIVE: The airway becomes narrowed, blocked or floppy in this type of apnea. --CENTRAL: There is no blockage of the airway, but the brain doesn't signal the respiratory muscles to breathe. --MIXED: Combination of obstructive & central sleep apnea. Etiology Of Obstructive Sleep Apnea:1) ANATOMIC FACTORS: -- Enlarged tonsils.

• Volume of the tongue.
• Soft tissue.
• Length of soft palate.
• Abnormal positioning of the maxilla & mandible.

2) STRUCTURAL FACTORS: -- Retrognathia & Micrognathia due to

• Mandibular hypoplasia.
• Brachycephalic head form.
• Pierre Robin Syndrome.
• Down Syndrome.
• Marfan Syndrome.
• High arched palate.

##Nasal Obstruction: Polyps, Septal deviation, Tumors ,Trauma and Stenosis. ##Retropalatal Obstruction: Elongated, posteriorly placed uvula ,tonsil and adenoid hypertrophy. ##Retroglossal Obstruction: Macroglossia & tumor 3) NON STRUCTURAL RISK FACTORS

• Obesity.
• Sedative state.
• Alcohol use.
• Supine sleep position.
• Hyperthyroidism.
• Acromegaly.