osa - Obstructive sleep apnea : recent advances and future...

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Obstructive sleep apnea : recent advances and future trends Ajay Handa Dept of Pulmonary Medicine
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• Sleep physiology • Historical aspects • Clinical profile • Polysomnography • Management • Recent advances • Future directions
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Sleep physiology • Sleep is a period of bodily rest with reduced awareness of the environment • Two phases of sleep –REM, NREM • NREM and REM sleep bouts alternate with each other throughout night (average cycle length is 90 mins)
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REM sleep • Rapid eye movements • Generalized hypotonia of muscles • Irregular rate and depth of respiration Marked suppression of hypothalamic regulation of homeostasis
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NREM sleep • Normal muscle tone • Regular respiration • Four stages of NREM sleep based on EEG • Stage 1- small amplitude high frequency waves resembling awake state • Stage 4- large amplitude and lowest frequency waves approaching REM
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EEG record
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Functions of sleep • “Restoration of body” – as metabolic and energy demands are reduced. But what is restored ? • NREM - replenishes cerebral glycogen stores • REM – restoration of depleted noradrenergic neurons • Consolidation of memory and improved learning !!
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Resp effects of NREM sleep • depresses activity of respiratory pump muscles • markedly depresses activity of airway dilator muscles upper airway obstruction • resultant decreased ventilation causes PaCO2 to rise by 5-6 mmHg • fall in PaO2 in sleep does not affect healthy individuals. • causes significant hypoxemia in COPD patients who may require supplemental oxygen during sleep not during waking hours.
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•CO 2 Apnea threshold increased during NREM sleep . • Awake AT is 20 mmHg ,increases to 40 mmHg in NREM. • In hypoxic patients who may be hypocapnic during NREM there are increased chances of having central sleep apneas(CSA) upper airway obstruction due to reduced tone of dilator muscles may cause OSA usually stage 1,2 of NREM
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Reduced CO 2 responsiveness • Due to reduced CO 2 sensitivity of central chemo receptors ( change in membrane properties of neurons ) • Reduced activity of respiratory motor neurons due to withdrawal of excitatory effects of wakefulness on these neurons. • Contribute to the hypoventilation that occurs during sleep
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Resp effects of REM sleep • Profound atonia all muscles • Thoracic muscles are more depressed than abdominal muscles • Irregular respirations result but average ventilation changes little compared to wakefulness
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Resp effects of REM sleep • Increased upper airway obstruction due to hypotonia of dilator pharyngeal muscles • Considerable suppression and disorganized activity of diaphragm • OSA episodes and oxygen desaturation are longer and more severe than NREM
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Cardiovascular effects of REM • Marked fluctuations in sympathetic outflow • Bidirectional changes in HR and BP • Sinus bradycardia, sinus arrest have been reported • Adverse cardiac events such as arrhythmia, Ac MI , sudden death may occur in pt with CAD
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osa - Obstructive sleep apnea : recent advances and future...

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