Pathophysiology of sleep apnea

Definition - absence of spontaneous breathing or cessation of breathing

Causes/ pathophysiology:

1. obstruction of the upper airway (obstructive apnea)
2.impaired CNS respiratory drive (central apnea)

1. obstructive sleep apnea

(a) physiology of muscles of pharynx
-during inspiration- these muscles keep the airway open + allow the air to flow in
-during sleep - these muscles relax but the airway remains open ENOUGH to allow
adequate airflow (uncompromised breathing)

(b) pathophysiology
- in MINORITY ppl- have an especially narrow passage + relaxation of the muscles of
pharynx causes the airway to completely close (air cant flow )
-if the obstruction is incomplete, turbulent flow + vibration occur resulting in SNORING
-if narrowing progresses to the point of OCCLUSION or near occlusion, subjects will
increase inspiratory effort to try to breathe until the effort awakens* them but they have
no recollection (*long enough for the muscles to open the airway again)
- then a series of deep breaths are taken before the subjects rapidly returns to sleep,
snores and becomes apneoic once more.
- thus, resulting in fragmented, restless sleep +

-increase risk of stroke and hyprtension
-increses daytime drowsiness
-increase sympathetic activity
-increase heart rate

2. central sleep apnea

-disorders that cause cessation of the ventilatory drive during sleep include:

I) damage to the central resp centres
II) abnormalities of the neuromuscular apparatus

-patients may have decreased ventilation when they are awake although they are fully capable of normal VOLUNTARY breathing.
-during sleep, their breathing disorders worsen
-thus, resulting in more frequent episodes of apnea
-lead to decrease PO2 and increase in PCO2 (critical level is reached which will stimulate respiration)
-further results in restless sleep (with clinical features similar as seen in obstructive sleep apnea).


Prepared by : SRI MURNIATI and MADHURA