SLEEP APNEA
Two new studies shed light on the syndrome.
Two recent studies of sleep apnea address its possible effects on the cardiovascular system and the effectiveness of a particular treatment.
In the first, an observational cohort study, researchers investigated whether obstructive sleep apnea is a significant risk factor for stroke and death, independent of other confounding factors for stroke, such as high blood pressure, atrial fibrillation, sex, and a history of smoking. Over a period of approximately three years, 1,022 patients at least 50 years of age and without a history of stroke, myocardial infarction, or tracheostomy were enrolled. All patients completed a questionnaire concerning sleep and underwent a study in which various physiologic measurements were taken during sleep. Patients with five or more events of apnea or hypopnea per hour were considered to have obstructive sleep apnea-the control group patients had four or fewer such events.
Among the 68% of the study sample patients who had obstructive sleep apnea, there were higher rates of obesity, hypertension, and diabetes, as compared with the control group. Following up the subjects after a mean interval of 3.4 years, the researchers found that stroke or death from any cause occurred in the obstructive sleep apnea group at an unadjusted rate of 3.86 events per 100 person-years, compared with 1.3 such events in the control group. When confounding risk factors were controlled for, the rates were 3.48 and 1.6, respectively, still statistically significant. A further analysis revealed that the risk of stroke or death increased with severity of the syndrome.
In the second study, a large randomized trial conducted in 11 Canadian institutions, researchers sought to determine whether the use of continuous positive airway pressure (CPAP) in patients with both heart failure and central sleep apnea could improve survival. Included in the study were patients with New York Heart Association class II, III, or IV heart failure who were receiving maximal medical management and who had at least 15 apneic or hypopneic events per hour during sleep, the majority of which were determined to be central, not obstructive. Central sleep apnea was defined as the absence of inspiration (as determined by tidal volume and chest motion) for 10 seconds or longer. Patients were randomized into either a control group or the CPAP intervention group. Those in the intervention group received CPAP at increasingly higher levels (as much as 10 cm of water, a level "shown to attenuate central sleep apnea," according to the study authors) for no less than six hours per night.
The first study underscores the necessity of appropriate treatment of obstructive sleep apnea, as it is an independent risk factor for stroke and death. Yet in the second, CPAP, a primary treatment modality used in sleep apnea, was not found to have any substantial effect on survival in patients with heart failure. The two studies illustrate the need for further research and a better understanding of the syndrome, especially in light of its demonstrated adverse consequences.
Yaggi HK, et al. N Engl J Med 2005; 353(19):2034-41; Bradley TD, et al. N Engl J Med 2005;353(19):2025-33.
MUSIC THERAPY FOR DECREASING PATIENT STRESS
A new study is currently examining its effectiveness.
Nurses at an Indianapolis, Indiana, health care organization are using music as an experimental adjunctive therapy for hospitalized patients and outpatients, according to Susan McAlister, MSN, RN, director of nursing quality and regulatory compliance at Clarian Health Partners.
In collaboration with the Indianapolis Symphony Orchestra, an innovative project was conceived in which the orchestra licensed the right to reproduce its recordings of musical compositions to the health care system in exchange for health services for its members, such as hearing tests and other screenings. The nurses and music therapists searched the medical literature for guidance on therapeutic types of music. They made selections according to established principles of music therapy, recommending, for example, that the beat and tempo of the music proceed at a rate slower than the average human pulse rate. Once the compositions were selected, a CD entitled "Art in Healing" was produced, the packaging of which included printed materials concerning guided imagery techniques.
Researchers are studying the effects of the musical intervention in three groups. The first group consists of patients struggling with smoking cessation after a long history of the habit, who had been receiving biofeedback treatment and were given the recording to further decrease tension and anxiety. The second group of patients consists of pregnant women confined to hospital bed rest because of prenatal complications. Because the women often have difficulty getting comfortable, the nurse researchers hope that the music will induce relaxation. The third group consists of postoperative patients who listen to the CD as an adjunctive analgesic therapy to help manage postoperative pain. The researchers plan to analyze the effectiveness of the intervention according to anxiety inventory scales in the first two groups and pain scales and physiologic indicators, such as vital signs, in the third. The CD is also being broadcast on the hospital's television network, so that all patients can have the opportunity to listen to it.
[beta]-BLOCKER THERAPY FOR GASTROESOPHAGEAL VARICES
Timolol doesn't prevent their development and may be dangerous.
Although [beta]-blockers are known to reduce portal pressure, it was revealed in a recent study that one such agent, timolol, did not significantly deter the development of gastroesophageal varices in a group of patients with portal hypertension and cirrhosis.
Approximately 213 patients between 19 and 74 years of age were enrolled in the study over the course of six years, none of whom had gastroesophageal varices at the time, as determined by endoscopy, and all of whom had cirrhosis and portal hypertension (a hepatic venous pressure gradient [HVPG] of at least 6 mmHg). To determine the amount of timolol to be used in each study subject, an initial dose of 5 mg was titrated until the baseline resting heart rate declined by 25% or was reduced to less than 55 beats per minute or a daily dose of 80 mg was reached. Upon randomization, 108 and 105 patients were placed in the timolol and placebo groups, respectively. The primary outcome measures were the development of gastroesophageal varices, variceal bleeding, or substantial bleeding attributable to portal hypertensive gastropathy. After the initial examination, the researchers conducted follow-up assessments of the patients at four weeks after randomization, at three months, and then every three months subsequently.
The results of the study showed that after a median follow-up interval of almost 55 months, both groups of patients, clinically comparable upon enrollment, had reached the primary outcome measures at nearly equal rates, 39% in the timolol group and 40% in the placebo group. Other measured outcomes, such as the rates of liver transplantation and death, also did not differ significantly. However, among patients in the timolol group there was a notably greater number of other serious adverse events, none resulting in death.
The researchers also observed a higher rate of gastroesophageal varices or variceal hemorrhage among patients with an HVPG greater than 10 mmHg at baseline or HVPG that increased more than 10% from that point.
Comparably, among those with the baseline HVPG less than 10 mmHg or whose HVPG decreased more than 10%, there was a lower rate of those outcomes. The researchers note that the results underscore the value of the HVPG as a reliable indicator of the development of gastroesophageal varices or variceal hemorrhage, and conclude that [beta]-blocker therapy does not significantly prevent those outcomes in patients with cirrhosis and portal hypertension and is associated with the incidence of serious adverse events.
Groszmann RJ, et al. N Engl J Med 2005;353(21):2254-61.