2006年12月19发表在《睡眠》十二月刊上一项新的研究表明：阻塞性睡眠呼吸暂停（OSA）导致的白天嗜睡与心功能下降是紧密相关的。
加州大学圣地亚哥分校的研究者们发现OSA导致的白天嗜睡和较差的心脏血流动力学的表现是密切相关的。该研究得主要负责人，Joel Dimsdale医学博士告诉Medscape说：“我们的研究表明心排出量和白天嗜睡的关系是非常强的，超过了其他所有变量。”
虽然OSA与心血管病的发病率和死亡率增加的关系已经众所周知，该实验第一次在未确诊有心血管疾病的患者中研究白天嗜睡与心脏血流动力学表现二者之间的关系。
常见情况
Dimsdale博士说OSA是一个十分常见的疾病，由它所继发的疲劳状态会增加个体工业操作和车祸的风险，还常出现工作欠佳。但是这项研究表明那些都是心血管功能下降的结果。
这项观察性研究的对象包括86个患者-68个男性和18个女性-平均年龄47岁。所有患者可疑为OSA而且通过多功能睡眠记录仪确诊。
用阻抗心动描记法测量安静状态下的每搏输出量和心搏出量，而且用体表面积换算为心搏量和心脏指数。用ESS积分法测量白天嗜睡的程度，高分表示白天嗜睡的时间长。
Dimsdale博士提到：这项实验表明ESS积分越高，心搏量和心脏指数越小。他说：“这些病人并不知道自己有心脏病。但是当我们测量他们的心排出量时我们发现那些白天嗜睡得分较高的病人和那些患有OSA但白天嗜少的病人相比，有着更加不利的血流动力学状态。”
主诉睡眠不好
他还补充道，“即使控制了年龄、性别、种族、呼吸障碍指数和平均血氧饱和度，ESS评分和较差的每搏输出量及心排出量都是相关的而且有显著性。”
Dimsdale博士注意到在没有确诊心脏病之前， OSA患者并没有常规进行心功能检查。他说，一方面来说，这可能是因为很多临床医生错误的认为心功能评定需要侵入性技术。但心阻抗图已被证实是一个可信赖的代替心导管术的方法，提供了一个非侵入性方法来筛选这样的病人。
Dimsdale博士提到，基于这个研究结果，病人抱怨的白天嗜睡现象不应该被轻视。他说，“我们的结果提示类似的抱怨应该被注意而且不仅仅只给一些关于睡眠卫生学或者安眠药等忠告。在确立的完整的临床建议建之前，仍然需要一些实验以确定这些结果是否可以被重复。这将是很有价值的，可以发现阻塞性睡眠呼吸暂停的标准疗法-持续性正压通气-是否可以改善心功能。 ”
http://www.medscape.com/viewarticle/549556
Daytime Sleepiness Caused by OSA Strongly Linked to Impaired Cardiac Function
Caroline Cassels
December 19, 2006 — Daytime sleepiness caused by obstructive sleep apnea (OSA) is independently associated with decreased cardiac function, a new study published in the December issue of Sleep suggests.
Researchers at the University of California, San Diego found a robust link between OSA-related daytime sleepiness and compromised cardiac hemodynamic performance.
"Our results suggest the relationship between cardiac output and [daytime] sleepiness is very strong, surpassing that of any other variable," the study's principal investigator, Joel Dimsdale, MD, told Medscape.
While the relationship between OSA and increased cardiovascular morbidity and mortality is well-known, this is the first study to examine the association between daytime sleepiness and cardiac hemodynamic performance in patients without established cardiovascular disease.
Common Condition
OSA, said Dr. Dimsdale, is an extremely common condition. Its subsequent fatigue places individuals at increased risk for industrial as well as automobile accidents and suboptimal work performance. But this study suggests there are also cardiovascular consequences.
The observational study included 86 patients — 68 men and 18 women — with an average age of 47 years. All were suspected of having OSA and underwent confirmatory diagnostic polysomnography.
Noninvasive stroke volume and cardiac output were measured using impedance cardiography and corrected for body surface area to yield both stroke and cardiac indexes. Daytime sleepiness was quantified using the Epworth Sleepiness Scale (ESS), with a higher score suggesting more daytime sleepiness.
According to Dr. Dimsdale, the study showed that the higher the ESS score, the lower the stroke and cardiac indexes.
"These patients did not have known cardiac disease. However, when we measured their cardiac output we found those with greater daytime sleepiness scores had a more adverse hemodynamic profile than those with sleep apnea who were less affected by daytime sleepiness," he said.
Sleep Complaints Not Benign
Even after age, sex, ethnicity, respiratory disturbance index, and mean sleep oxygen saturation were controlled for, the relationship of the ESS score with both compromised stroke index and cardiac output persisted and was significant, he added.
Dr. Dimsdale noted that in the absence of established cardiac disease, cardiac function is not routinely measured in OSA patients. In part, he said, this may be due to the fact that many clinicians mistakenly believe that assessments of cardiac function require invasive techniques.
However, impedance cardiography, which has been shown to be a reliable alternative to cardiac catheterization, offers a noninvasive method of screening such patients.
Dr. Dimsdale said that, based on the study's results, patients' complaints of daytime sleepiness should not be taken lightly.
"Our results suggest such complaints need to be considered carefully and not merely relegated to advice to use sleep hygiene or sleeping pills. Rather, sleep should be formally assessed and the question of whether the heart is performing appropriately should also be determined," he said.
However, he added, before firm clinical recommendations can be made, other studies are required to determine whether these results can be replicated.
It would also be worthwhile, he said, to find out whether continuous positive airway pressure, the standard treatment for OSA, improves cardiac function.
http://www.medscape.com/viewarticle/549556
编辑：蓝色幻想
