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LWB K34 0-c 08_ pp177-203.qxd 6/29/09 10:16 PM Page 177 Aptara Inc.
CHAPTER
S S S S Sleep
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Kathy P. Parker / Rebecca A. Gary /
Sandra B. Dunbar
INTRODUCTION in thee early mor ining hours 1 13,14 (Fig. 8-3). In fact, a coontinuum
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Physiological changes that accompany normal sleep may have ad- arousal state) provides a background for all waking endeavors and
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verse fefffects on patients with cardiovascularr disease, a dnd because is is a far moree important dimension of human function than com-
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cardiac patients as a group also have a high prevalence of sleep ab- monly recognized. Many adults are chronically sleepy in the day-
normalities, attention to sleep in overall cardiovascular care has time because of insufficient or disrupted night-time sleep. The
become increasingly important. 1,2 Cardiovascular nurses are well problem may initially go unnoticed when masked by stimulating
positioned to assess sleep patterns, identify poor sleep quality and factors such as movement, excitement, high motivation, or
quantity, intervene to prevent sleep loss, educate and counsel car- hunger. However, daytime sleepiness can be unmasked by situa-
diovascular patients regarding sleep, and work with the interdisci- tional factors such as boredom, a warm dark room, or a prolonged
plinary team to assure treatments for sleep and sleep-related prob- dull task. 13 Although poor nocturnal sleep can cause sleepiness,
lems. To assist nurses in helping patients with cardiovascular abnormal daytime sleep can also adversely affect nocturnal sleep.
disease achieve adequate, restful, and restorative sleep, this chap- Thus, a complete assessment includes an examination of noctur-
ter reviews normal sleep and sleepiness, changes in cardiopul- nal and daytime sleep/wake patterns.
monary and other system functions during sleep, sleep problems
commonly seen in patients with cardiovascular disease, and ap- Stages of Sleep
propriate management.
Typical EEG patterns during wakefulness and sleep are shown in
Figure 8-2. During relaxed wakefulness with the eyes open, the
NORMAL SLEEP EEG consists predominantly of mixed frequency (cycle per sec-
ond; Hz), low-voltage activity (low amplitude), or desynchronized
Sleep and Sleepiness brain-wave activity. Rapid eye movements (REMs) and blinks
may occur, and muscle tone is usually at its highest level. With
The human need for sleep has been recognized throughout the eyes closed, alpha waves are often noted (8 to 12 Hz). 15
centuries, and few physiological phenomena have received as Sleep onset is heralded by a general slowing of the EEG activ-
much attention from scholars, scientists, poets, and other literary ity and the emergence of delta waves (4 to 7 Hz) during more
figures. Before the twentieth century, sleep was thought to be a than 50% of the epoch. Sleep then progresses through several
simple, passive phenomenon—a state often described as existing stages of nonrapid eye movement (NREM) and rapid eye move-
3
between waking and death. Although much remains to be fully ment (REM) sleep and cycles (an NREM/REM cycle) that are
understood about the topic, the modern study of sleep has re- well described and form characteristic patterns in individuals and
vealed some of its secrets. Sleep is now understood as an active groups. NREM sleep is divided somewhat arbitrarily into three
process regulated by a multiplicity of behavioral, neuroendocrine, stages based on the EEG pattern. Sleep depth increases from stage
and central nervous system factors. 4,5 Insufficient and/or poor 1 to stage 2 to slow wave sleep (SWS; deep sleep; previously de-
quality nocturnal sleep and daytime sleepiness adversely affect im- fined as stages 3 and 4) based on the fact that the sleeper becomes
portant clinical outcomes. 6–9 Numerous primary sleep disorders 10 more difficult to awaken.
have been recognized, and the field of sleep medicine is now a In stages 1 and 2, or light sleep, the EEG consists of relatively
bona fide, empirically based subspecialty. 11 low-amplitude waves with a predominant frequency of 2 to 7 Hz.
The modern definition of sleep is “a reversible behavioral state High, narrow, vertex, sharp waves may appear late in stage 1.
of perceptual disengagement from and unresponsiveness to the Stage 2 is identified by two sporadic waveforms that stand out
4
environment.” Sleep is further defined according to behavioral from the background EEG: sleep spindles and K complexes. Sleep
and physiological criteria. Behavioral criteria include quiescence, spindles are waxing–waning bursts of waves in the 12 to 14 Hz
closed eyes, decreased response to external stimuli, recumbent po- range. 4,12 They originate in the thalamus and are thought to
4
sition, and reversible unconsciousness. Physiological criteria are reflect impulses that inhibit the relay of sensory information to
16
based on recordings from a polysomnogram that includes elec- the cerebral cortex. K complexes consist of a sharp negative wave
troencephalography (EEG), electro-oculography (EOG), and (upward deflection by EEG) followed by a slower positive wave
electromyography (EMG) 12 (Figs. 8-1 and 8-2). (downward deflection). 17 They occur spontaneously and in
Daytime sleepiness refers to the tendency or propensity to fall response to mild external stimuli, such as sounds. SWS is differ-
asleep during the day. In normal individuals, sleepiness typically entiated by the percentage of slow (0.5 to 2 Hz), high-amplitude
13
has a biphasic circadian rhythm, with an increased sleep tendency ( 75 V) EEG waves (referred to as synchronized brain-wave
in the mid-afternoon and, as is well known to nightshift workers, activity). They account for 20% to 50% of the waves in each
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