Sleep Disordered Breathing

Question 1

Definition + primary signs/symptoms of sleep apnea

Answer 1

Hypersomnolent, snoring, males, daytime sleepiness, polycythemia ← Signs/Symptoms

Definition: > 5 episodes apnea/hr, sleepiness during day

Question 2

Characteristics of an apnic event

Answer 2

• Air flow down
• PaO2 down
• PaCO2 up
• Hypoxia, hypercapnea = induced Pulmonary vaso constriction (pulmonary hypertension) + sympathetic nerve firing - constricting peripheral vasculature (systemic hypertension).
• Apnic event must be 10 seconds. Can be up to 60 seconds.

Question 3

Epidemiology of apnea

Answer 3

• apnea w/>5 episodes/hour ==> @ 25% of adult men and 9% of adult women
• many are asymptomatic ==> increased apnea frequency ==> increased symptoms
• obseity directly associated with severity and onset of obstructive sleep apnea

Question 4

Pathophysiology of obstructive apnea

Answer 4

• hallmark = pharyngeal occlusion during sleep
• lipid accumulation @ soft tissue of the pharynx ==> upper airway narrowing
  
  • during wakefulness, high levels of electromyographic tone activates pharyngeal dilator muscles and maintains patency
  • During sleep, electromyographic tone is lost ==> predisposingupper airway collapse
• Facial anatomy appears to be pivotal in the development of sleep apnea.

Question 5

Apnic event impact on blood gases

Answer 5

• arterial hypoxemia and hypercapnia ==> sympathetic hyperexcitation + CV changes
• Peripheral vascular resistance increases during an apnea ==> transient systemic hypertension
• arterial hypoxemia causes precapillary pulmonary vasoconstriction and its accompanying pulmonary hypertension.
• Vagal tone (via cartoid body hypoxic stimulation) also increases during an apnea (breath holding) resulting in bradycardia

Question 6

Clinical features/complications of OSA

Answer 6

• systemic hypertension (during wakefulness)
  
  • often normal blood gases
• may present w/ CHF or cor pulmonale
• increased risk for: cerebral vascular accidents, CHF, CAD

Question 7

Therapeutic approach to apnea

Answer 7

• maintenance of pharyngeal patency during sleep
• weight loss
• continous positive airway pressure (CPAP) = mask device worn during sleep ==> delivers positive pressure into nasal/oral pharynx