Thursday, September 29, 2022

Obstructive Sleep Apnea (OSA)

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Sleep apnea & hypopnea is a sleep disorder in which cessation/ reduction of respiratory effort at the nostril level for a few seconds to a few minutes. It is subdivided in central, obstructive & mixed types. Obstructive sleep apnea (OSA) is the commonest subtype. Sedentary lifestyle, faulty eating habits & lack of physical activities are the predisposing factors for obesity. The collection of fat within & around the upper aerodigestive tract reduces the dimensions of the airway lumen which increases the turbulence in the air current. Snoring is induced by turbulent airflow during sleep. The snoring loudness increases with the severity of airway narrowing. The anatomical abnormalities (nasal, nasopharyngeal, oropharyngeal, hypopharyngeal & laryngeal) is generally responsible for OSA in young patients. Abnormal anatomy can worsen the symptoms of obesity-related OSA. The commonly found anatomical abnormalities are a deviation of the nasal septum, hypertrophy of inferior turbinate’s, adeno-tonsillar hypertrophy, retrognathia, weak epiglottis & mass lesions of upper aerodigestive tract (nasal polyposis, bulky tongue). The reduced muscle strength secondary to the fat deposition in & around the upper aerodigestive tract is unable to maintain the adequate airway lumen required for healthy sleep. The moderate to excessive narrowing of the airway lumen, easy collapsibility of pharyngeal part of airway & induced negative pressure distal to the site of obstruction generates partial to complete blockage of the airway. The oxygen level in blood decreases in OSA due to the reduced volume of available air for gas exchange at the lung alveoli level. The arousal episodes occur during sleep due to induced signals from the brain when blood oxygen level reaches below a threshold level. Poor sleep induces excessive daytime sleepiness, morning headache, dry mouth, inattentiveness & irritability are the common presenting symptoms. OSA has a great impact on quality of life at school, working place & at home. Daytime sleepiness increases the chances of road traffic & household accidents. The induced negative pressure in the airway, episodic fall in blood oxygen level affects almost all of the body systems. OSA increases the risk of stroke, & heart attack by many folds. Polysomnography helps in differentiating OSA from other mimicking diseases.

A multidisciplinary approach is required to manage the OSA. A detailed airway assessment is required from the ENT doctor for anatomical features. The site of airway narrowing is determined by a combination of clinical assessment with site localizing investigations. Apneograph, sleep MRI & DISE are investigations used by ENT surgeons to localize the site of obstruction. The site-directed surgery increases the long term effectiveness of surgery. The majority of anatomical abnormalities are correctable by surgical intervention. Young age OSA can be completely reversed by surgical correction in abnormal anatomy patients. The severity of obesity related to OSA can be reduced by a healthy lifestyle, regular exercise, balanced diet & correction of the sleeping position. PAP therapy is mostly followed treatment for obesity-related OSA. The machine maintains the blood oxygen level during obstructive episodes but the long term compliance falls around 50%. The correction of abnormal anatomy can remove and/or increase the compliance of PAP therapy. Surgical success is persistent if an OSA patient follows a healthy lifestyle.

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