Distinguish between an obstructive and central apnea using a polysomnograph.
Compare the flow and effort curves. An obstructive apnea will show effort without an appropriate increase in flow, while central apnea will not reveal significant effort.
Why does the flow curve spike wildly following an obstructive event?
Increased hypercapnia eventually drives higher and higher respiratory impulses.
What is hypopnea?
Decreased breathing due to obstruction or decreased drive. Distinguish from apnea, where no flow occurs.
Why is OSA pose a threat to cardiovascular health?
OSA causes diastolic dysfunction; negative intrathoracic pressure generated against a closed airway increases venous return, impeding LV filling.
What happen to sympathetic nerve activity and BP in OSA?
What risks do these pose?
Increased incidence of CV diseases (arrhythmia, pulm-HTN, systemic-HTN, MI, valvular disease, pro-coagulant state) in patients with OSA, as well as respiratory and nervous dysregulations.
Explain why both pressure and temperature flow-sensors are used in polysomnography.
Temperature flow sensors are less reliable (may give false positives due to nasal eddy currents, blood pulsing, etc)
What is Cheyne-stokes breathing?
When does it occur?
An abnormal pattern of breathing (crescendo-decrescendo). Increased CO2 during apnea causes overcompensatory respiratory increases.
Seen often in central sleep apneas, sometimes even when awake!
Why does heart failure contribute to central sleep apnea?
Decreased output causes longer blood transit times, which means that the chemoreceptor response time is longer.
Pulmonary congestion increases pressure which irritates pulmonary receptors.
How does a narcoleptic patient present on an MSLT?
How does a normal patient present?
Narcoleptic patients fall asleep rapidly (<5min onset) and achieve REM sleep more often than not.
Normal patients take at least 10min to fall asleep and achieve REM 1 or fewer times (out of 5).
Describe the etiology and pathophysiology of narcolepsy.
Narcolepsy is associated with hypocretin-producing neuron loss. Most cases are sporadic but risk is increased with affected family members. Other factors include stage of development and environment (trauma, infection, behavior)
What is the source of the circadian rhythm?
Through what hypothalamic structure does it signal?
The suprachiasmatic nucleus (SCN).
Signals through the subparaventricular zone, to the dorsomedial nucleus, to the lateral hypothalamus and ventrolateral preoptic nucleus.
Maybe not high-yield.
How might a patient with nighttime REM intrusion present?
How might a patient with daytime REM intrusion present?
REM intrusion into night resulting in inappropriate motor inhibition >> Sleep paralysis.
REM intrusion into daytime results in cataplexy and/or hypnagogic hallucinations.
What tests are good for evaluating periodic limb movement disorders?
What can precipitate these disorders?
Actigraphy & Polysomnography (reveal hundreds of limb movements which prevent REM sleep).
Iron deficiency, diabetes, nerve disorders (eg Restless Legs syndrome)
Distinguish between delayed-sleep and advanced-sleep phases.
Delayed-phase: Sleep later, rise later. Typical of teenagers.
Advanced-phase: Sleep earlier, risk earlier. Apparently familial.
*Note: Shift-work can result in either*
Who can present with non-24-hour sleep phases?
The retinally blind (remember, signaling to the SCN is separate from that which goes to the visual cortex).
And the people locked in my basement.
How will a patient with insomnia or cognitive impairment present on actigraphy?
Disorganized and fragmented sleep patterns. No apparent rhythm.
What occurs in REM behavior sleep disorder?
Distinguish this from sleepwalking, talking etc.
The usual muscle paralysis is absent; patients tend to react to and act out their dreams physically.
Sleep walking/talking/eating generally occurs during non-REM sleep.
What are the signs of a night terror?
During what phase of sleep do they occur?
High voltage delta wave arousal with increased HR.
Occurs during stage 3 (deep) sleep.
Distinguish between a nightmare and night terror.
Nightmares occur late during sleep, are often remembered, awaken the person and make it difficult to return to sleep.
Night terrors often do not awake the person, who will often return to sleep and may not be aware of others during or after. Occurs during first hours of sleep.
How can an obstructive sleep apnea be treated?
Lifestyle modifications (regular sleep patterns, weight reduction)
Use of a CPAP to maintain positive airway pressure (prevent collapse).