The human airways allow speech, swallowing and breathing. They are made up of soft muscles and tissues and do not contain any bony structures that allows them to be flexible. When this passage collapses during sleep, it could be due to loss in muscle tone, or a defect in the framework such as fat accumulation around the tongue or soft palate. This causes the person to choke during sleep.
Obstructive sleep apnea (OSA) is a choking sensation that happens when a lack of oxygen causes the body to repeatedly wake up and gasp to open up the airways. This is a protective mechanism.
How does having OSA cause hypertension?
Many researchers have identified sleep apnea as a factor in high BP. When there are low levels of oxygen in the body, it activates the autonomic nervous and hormonal systems that are responsible for controlling BP. The blood vessels begin to narrow and other bodily changes occur, leading to high BP.
Almost half of OSA sufferers develop hypertension. This link is so strong that it prompted the Joint National Committee on High Blood Pressure to cite sleep apnea as a cause in secondary hypertension.
Empirical Evidence Linking OSA with Hypertension
A study published in the New England Journal of Medicine found that middle age adults who were not treated for obstructive sleep apnea had a 2 to 3 fold higher risk of having high blood pressure within an 8 year period.
A Canadian study found that for each episode of sleep apnea that occurred per hour, the chance of developing hypertension also went up by 1%. In addition, for every ten percent drop in nighttime oxygen levels, the percentage of acquiring hypertension went up by 13%. Further, this Sleep Heart Health Study found that in severe OSA cases, both the systolic and diastolic blood pressure readings were higher and consequently nighttime blood pressure. The rise in high BP was in proportion to the severity and presence of OSA. These individuals also had higher daytime levels of blood pressure.
How does treating OSA reduce the risk of developing hypertension?
Using Continuous Positive Airway Pressure for treating OSA has a positive effect on reducing the risk of developing hypertension. In CPAP therapy, gentle streams of air are pumped into the airways, preventing them from collapsing during sleep. Many research studies have demonstrated that people with moderate-to-severe sleep apnea who are treated with nasal CPAP had lower blood pressure reading during the night and day.
In a HIPARCO trial study conducted in several centres, patients with OSA and high blood pressure who were not responding to conventional treatment, received CPAP therapy for 12 weeks. This caused a reduction in a 24-hour mean as well as diastolic blood pressure. It also improved blood pressure patterns at night. A 4-hour use of the CPAP machine is required each night in order for a significant decrease in BP levels.
What are the benefits of using CPAP in hypertension?
Using CPAP leads to a reduction in BP amongst all patients, regardless of whether they are using antihypertensive medications. Patients who refuse CPAP and are offered supplemental oxygen instead, do not experience the same benefits as those using CPAP.
Using CPAP effectively reduces sleep apnea related symptoms and comorbidities such as type 2 diabetes and heart disease.
If you are experiencing high BP levels and are unable to get sound sleep, you should visit a qualified sleep doctor to rule sleep apnea.