Sleep d/o breathing

Question 1

Normal sleep physiology

Answer 1

• Sleep occurs in cycles: stage 1-> 2-> 3-> REM is 1 cycle
• Usually 3 cycles per night, with earlier stages becoming shorter and REM becoming longer as night progresses
• During sleep tidal volume greatly decreases and RR increases, but overall minute ventilation decreases
• Despite this, there is no increase in pCO2
• End tidal O2 decreases and end tidal CO2 increases

Question 2

Central sleep apnea

Answer 2

• Problem w/ sensor or central controller
• Sensor problem: CHF (cheyne stokes breathing)
• Controller problem: CCHS, respiratory depressants (narcotics/BZDs/Barbs), premature infants (immature brain stem)

Question 3

CHF on breathing

Answer 3

• CHF leads to cheyne stokes breathing, which is a pattern of repeating labored breathing followed by periods of apnea
• This is due to circulatory delay from the HF: increased pCO2 leads to hyperventilation (exaggerated response) which causes the pCO2 to drastically drop
• Then there is the apnea (due to low pCO2) which starts the cycle over again b/c of the rise in pCO2

Question 4

Controller problem central sleep apnea

Answer 4

• CCHS leads to respiratory arrest during sleep, associated w/ PHOX2B gene (damage to central chemosensitivity)
• Can be acquired via brainstem injury

Question 5

Obstructive sleep apnea vs central sleep apnea

Answer 5

• To differentiate central sleep apnea from obstructive sleep apnea use an effort belt
• If effort belt shows sudden absence of chest/abdomen movement then the sleep apnea is due to central problem
• If the effort belt continues to show movement of the body but no movement of air, the problem is obstruction

Question 6

Obstructive breathing during sleep

Answer 6

• Progression: snoring-> upper airway resistance syndrome-> obstructive sleep apnea
• Upper airway changes: pharyngeal dilator muscles have decreased tone during sleep (narrows the pharynx)

Question 7

Causes of obstructive sleep apnea

Answer 7

-Extraluminal positive tissue pressure: fat deposition (obese), small mandible/pharyngeal anatomy, enlarged tonsils or adenoids

Question 8

Risk factors for upper airways obstruction

Answer 8

• Male, post menopausal women, age
• Asian > black > hispanic > caucasian
• Obese
• Large neck circumference
• Carniofacial morphology
• Genetic predispositions

Question 9

Consequences of sleep apnea

Answer 9

• Hypoxemia and reperfusion injury: endothelial dysfxn, oxidative stress, inflammation
• Increased sympathetic surges: cardiac stress and insulin resistance
• Multiple arousals leading to sleep deprivation

Question 10

Cardiovascular complications

Answer 10

• Afib
• HTN (systemic and pulm)
• CVAs, CAD
• CHF
• Insulin resistance

Question 11

Rx for obstructive sleep apnea

Answer 11

• Surgery, positive airway pressure, oral appliance
• Rx improves BP, glc control, alertness, ED
• Lowers CV risk