OSA or Obstructive sleep apnea is the most common type of sleep apnea and is characterized by what causes the stop or pause on breathing, in this case, a muscle may be blocking the air path. It shows repeated episodes of complete or partial obstructions of the upper airway during sleep, despite the effort to breathe, and is usually associated with a reduction in blood oxygen saturation.
The prevalence of OSA in the general adult population varies depending on the definition but is approximately 15 to 30 percent in males and 5 to 15 percent in females (when OSA is defined as an apnea-hypopnea index [AHI] greater than five events per hour of sleep)
The pathophysiological causes of OSA likely vary considerably between individuals. A narrowed upper airway is very common among OSA patients and is usually in adults due to nonspecific factors such as fat deposition in the neck, or abnormal bony morphology of the upper airway. There is a variety of defective respiratory control mechanisms are found in OSA, including impaired chemical drive, defective inspiratory load responses, and abnormal upper airway protective reflexes.
This article also reviews the effects of sleep on respiratory mechanics, the determinants of UA patency, and the pathophysiology of UA obstruction during sleep. The pathophysiology of OSA in children and the clinical features, diagnosis, and treatment of OSA in children and adults are reviewed separately.
Effects of sleep in respiratory mechanics:
Sleep is affected by different physiologic changes relevant to the flow of air. Sleep is viewed as a quiet resting period, judging by the limited movement, decreased responsiveness, and the passive appearance of a sleeping individual.
It is also connected to a decrease in metabolic rate, loss odd the wakefulness drive to breathe and ventilatory motos of the muscles including the upper airway muscle. Furthermore, the loss of the wakefulness drive to breathe renders respiration during sleep critically dependent on the level of chemoreceptor and mechanoreceptor stimuli and hence susceptible to central apnea and to upper airway obstruction.