Obstructive sleep apnea (OSA) is the most common type of sleep apnea and is caused by complete or partial obstructions of theupper airway. It is characterized by repetitive episodes of shallow or paused breathing during sleep, despite the effort to breathe, and is usually associated with a reduction in blood oxygen saturation. These episodes of decreased breathing, called "apneas" (literally, "without breath"), typically last 20 to 40 seconds.
Individuals with OSA are rarely aware of difficulty breathing, even upon awakening. It is often recognized as a problem by others who observe the individual during episodes or is suspected because of its effects on the body. OSA is commonly accompanied withsnoring. Some use the term obstructive sleep apnea syndrome to refer to OSA which is associated with symptoms during the daytime. Symptoms may be present for years or even decades without identification, during which time the individual may become conditioned to the daytime sleepiness and fatigue associated with significant levels of sleep disturbance. Individuals who generally sleep alone are often unaware of the condition, without a regular bed-partner to notice and make them aware of their symptoms.
As the muscle tone of the body ordinarily relaxes during sleep, and the airway at the throat is composed of walls of soft tissue, which can collapse, it is not surprising that breathing can be obstructed during sleep. Although a very minor degree of OSA is considered to be within the bounds of normal sleep, and many individuals experience episodes of OSA at some point in life, a small percentage of people have chronic, severe OSA.
Many people experience episodes of OSA for only a short period. This can be the result of an upper respiratory infection that causes nasal congestion, along with swelling of the throat, or tonsillitis that temporarily produces very enlarged tonsils. The Epstein-Barr virus, for example, is known to be able to dramatically increase the size of lymphoid tissue during acute infection, and OSA is fairly common in acute cases of severe infectious mononucleosis. Temporary spells of OSA syndrome may also occur in individuals who are under the influence of a drug (such as alcohol) that may relax their body tone excessively and interfere with normal arousal from sleep mechanisms.
We researched this topic for you and found the following best online resources. They are categorized into basic, advanced, and research level based on the extent of information you need. You will be taken to the respective websites by pressing on the links below.
http://www.hindawi.com/journals/ijhy/2013/193010/ akram khan, nimesh k. patel, daniel j. o’hearn, and supriya khan, “resistant hypertension and obstructive sleep apnea,” international journal of hypertension, vol. 2013, article id 193010, 6 pages, 2013. doi:10.1155/2013/193010
http://www.hindawi.com/journals/pm/2013/521087/ carlos zamarrón, luis valdés cuadrado, and rodolfo álvarez-sala, “pathophysiologic mechanisms of cardiovascular disease in obstructive sleep apnea syndrome,” pulmonary medicine, vol. 2013, article id 521087, 16 pages, 2013. doi:10.1155/2013/521087
http://www.hindawi.com/journals/sd/2014/768210/ georgia andreou, filippos vlachos, and konstantinos makanikas, “effects of chronic obstructive pulmonary disease and obstructive sleep apnea on cognitive functions: evidence for a common nature,” sleep disorders, vol. 2014, article id 768210, 18 pages, 2014. doi:10.1155/2014/768210