Causes and consequences of blood pressure alterations in obstructive sleep apnea

Article Abstract:

Obstructive sleep apnea (OSA) is a temporary cessation of breathing during sleep, lasting 10 seconds or more, due to collapse of the upper airway. The diagnosis is made if more than 5 apnea episodes occur per hour or more than 30 episodes occur during the night. In previous studies, hypertension was found to be more common in patients with OSA than in the general population. Patients with OSA were also found to experience elevations of blood pressure during sleep. A review of the literature on blood pressure variations and daytime hypertension in OSA patients found that changes in blood pressure during sleep are common in OSA patients. Blood pressure elevation was observed more often than decreased blood pressure. In addition, daytime hypertension was more common in OSA patients, occurring in 48 to 96 percent of patients studied; in contrast, hypertension occurs in only 20 to 25 percent of the general population. In some studies of hypertensive patients, 18 to 35 percent suffered from OSA, compared with 0 to 13 percent of normotensives (persons with normal blood pressure). However, other studies have found no difference between hypertensives and normotensives in the rate of OSA. Treatment of OSA by tracheostomy (surgical creation of an external opening in the windpipe) or other means often abolishes the blood pressure variation during sleep, indicating that some event during apnea is responsible for the elevation in blood pressure. The event is thought to be hypoxia (low oxygen content in the body), which results from the cessation of breathing. Bodily efforts to overcome apnea and initiate breathing (inspiratory efforts) can also elevate blood pressure. Activation of the sympathetic nervous system, which raises blood pressure, has been documented in OSA patients during episodes of apnea. OSA is more common in obese persons than in nonobese, and weight loss decreases episodes of apnea. In conclusion, patients with OSA experience abnormal variations in blood pressure that are probably caused by activation of the sympathetic nervous system due to hypoxia and to ineffective inspiratory efforts. The possible association between OSA and daytime hypertension warrants further study. (Consumer Summary produced by Reliance Medical Information, Inc.)

Care and treatment, Complications and side effects, Physiological aspects, Obesity, Sleep apnea syndromes, Sleep apnea

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National high blood pressure education program working group report on ambulatory blood pressure monitoring

Article Abstract:

Ambulatory blood pressure monitoring (ABPM) is a technique for taking many blood pressure readings over a 24-hour period while the patient continues with normal activities. It is useful in certain situations, for example, detecting those with ''white coat'' or ''office'' hypertension (high blood pressure readings only when measured in the doctor's office). It is also useful in other situations, including evaluation of: borderline hypertension with target organ damage; episodic hypertension; and hypertension resistant to drug therapy. ABPM is not appropriate for the diagnosis and management of most patients with hypertension, especially when there is target organ damage or other risk factors. Studies of ABPM found that it was more accurate in diagnosing hypertension than casual blood pressure monitoring, and its usefulness in predicting those at higher risk of heart attack is being studied. It has proved useful in research and clinical situations, such as monitoring the effects of drugs taken to lower high blood pressure, especially since blood pressure taken in the doctor's office may be affected by the timing of when the patient last took the medications. Charges for ABPM range from $100 to $300, but some doctors charge as much as $500. Two different techniques are currently used for ABPM, but they have never been compared to determine which is better under which conditions. Nor is there a standard for the frequency of the readings, or for analysis of the data. Three more changes would also be helpful: a simple, standard diary for the patient to complete; a more reliable microphone that is easier to position; and smaller and quieter recording devices that would not interfere with the patient's sleep or other activities. Further studies of ABPM will determine average ranges of data for different age, race, and sex groups. This information can then be used to determine the risk of heart attack and other heart problems, as well as the usefulness of drug therapy. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Reports, Hypertension, Diagnosis, Measurement, Blood pressure measurement, National High Blood Pressure Education Program Coordinating Commission

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