Apneas and Sleep Disordered Breathing

What is sleep disordered breathing?

The term Sleep Disordered Breathing (SDB) covers a range of disorders characterized by abnormalities in breathing during sleep.  Sleep-induced partial obstruction of the upper airway (at the throat) is the most common form of SDB, and is identified by the occurrence of snoring.  This well-known sound is generated when the partially obstructed airway vibrates during breathing efforts.  The severity of the obstruction that is indicated by snoring varies from mild to severe. Although snoring often occurs without any reduction in blood oxygen, it can be an important source of sleep disruption.

Obstructive sleep apnea (OSA) is the most serious form of SDB and typically occurs after long-standing snoring. In patients with OSA, the upper airway closes completely during sleep. This leads to arousals, disruption of sleep and diminished blood oxygen levels.  In the early stages of OSA the subject’s sleep is dominated by heavy obstructed snoring with only a few episodes of complete obstruction. As the disorder progresses there are typically repeated episodes of obstructive apnea throughout the night.

It is estimated that OSA affects up to 20% of the adult population, and is associated with hypertension, stroke, congestive heart failure and Type 2 diabetes. Snoring and obstructive apnea are also very common in childhood when adenotonsillar enlargement peaks in the 2 – 5 year old age range.  The American Academy of Sleep Medicine reports that the prevalence of OSA is approximately two percent in otherwise healthy young children. Chronic snoring occurs in almost 10% of children of both sexes.

“Apnea” means temporary absence or cessation of breathing. Obstructive apneas are caused by a physical obstruction, such as collapse of the upper airway when muscles relax during sleep. During an apnea the natural reaction of the body is to make bigger efforts to breathe.  Eventually this will cause the subject to wake up briefly, which causes the airway to return to normal again, allowing them to breathe, and then fall back to sleep. A person may have many obstructive apneic events during the night, leading to many arousals, disruption of sleep and diminished blood oxygenation.

Apneas may also be caused by a problem in the relay of breathing signals from the brain. These apneas are known as “central apneas”, as the problem relates to the central nervous system.  “Mixed” apneas are a combination of obstructive and central apneic events.