Sleep
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Review Comparative Study
The role of actigraphy in the study of sleep and circadian rhythms.
In summary, although actigraphy is not as accurate as PSG for determining some sleep measurements, studies are in general agreement that actigraphy, with its ability to record continuously for long time periods, is more reliable than sleep logs which rely on the patients' recall of how many times they woke up or how long they slept during the night and is more reliable than observations which only capture short time periods. Actigraphy can provide information obtainable in no other practical way. It can also have a role in the medical care of patients with sleep disorders. ⋯ In conclusion, the latest set of research articles suggest that in the clinical setting, actigraphy is reliable for evaluating sleep patterns in patients with insomnia, for studying the effect of treatments designed to improve sleep, in the diagnosis of circadian rhythm disorders (including shift work), and in evaluating sleep in individuals who are less likely to tolerate PSG, such as infants and demented elderly. While actigraphy has been used in research studies for many years, up to now, methodological issues had not been systematically addressed in clinical research and practice. Those issues have now been addressed and actigraphy may now be reaching the maturity needed for application in the clinical arena.
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This paper reviews the efficacy of auto-titrating continuous positive airway pressure (APAP) for treatment of obstructive sleep apnea. It is based on a review of 30 articles published in peer review journals conducted by a task force appointed by the American Academy of Sleep Medicine to develop practice parameters for use of APAP devices for treatment of obstructive sleep apnea (OSA). The data indicate that APAP can be used to treat many patients with OSA (auto-adjusting) or to identify an effective optimal fixed level of continuous positive airway pressure (CPAP) for treatment (auto-titration). ⋯ There is conflicting evidence for and against the premise that treatment with APAP increases acceptance and adherence compared to fixed CPAP. In studies demonstrating an increase in adherence with APAP, there was similar improvement in measures of daytime sleepiness as with fixed CPAP treatment. Further studies are needed to determine if APAP can increase acceptance or adherence with positive pressure treatment in patients with OSA.
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Decrease of respiratory muscle capacities in neuromuscular disease can lead to chronic respiratory failure with permanent alveolar hypoventilation. Respiratory centers elaborate a strategy of breathing dedicated to prevent overt respiratory muscles fatigue. This strategy may worsen chronic hypercapnia. ⋯ The effects of atonia are amplified by a very low reactivity of respiratory centers. Nocturnal mechanical ventilation improves nocturnal hypoventilation and daytime arterial blood gases (ABG). Mechanism of improvement in ABG and how nocturnal hypoventilation and diurnal hypoventilation interact, are still a matter of debate.
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Recent studies show that central sleep apnea occur in about 40% of patients with heart failure and systolic dysfunction. The pathophysiological consequences of central sleep apnea may contribute to morbidity and mortality of heart failure. Three treatment modalities, oxygen, continuous positive airway pressure and theophylline have been shown to decrease periodic breathing modestly with considerable improvement in arterial oxyhemoglobin desaturation, and variable effects on sleep characteristics. However, long-term effects of central sleep apnea and its treatment on the natural history of heart failure remain to be determined.
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The mammalian circadian oscillator, located in the suprachiasmatic nuclei of the anterior hypothalamus, serves as the principal source of rhythmic temporal information for virtually all physiologic processes in the organism, including the alternating expression of sleep and wakefulness. Recent studies, in both animal models and human subjects, have demonstrated the important modulation of sleep and wakefulness mediated by the circadian clock. Independent of other factors, notably prior sleep-wake history, the circadian clock potentiates wakefulness (and alertness) at one phase of the diurnal cycle, while facilitating sleep and its attendant processes at the opposite phase. ⋯ This response can be prevented or overridden with extraordinary avoidance of sunlight or with provision of artificial light of sufficient duration and intensity to negate the sunlight signal, an approach shown to be effective in the treatment of shiftwork sleep disruption. Practical issues sharply limit the application of artificial lighting to all shiftwork settings, however, and the role for a pharmacological chronobiotic agent capable of accomplishing the same end is potentially very large (Copinschi et al., 1995; Jamieson et al., 1998). For example, the effects of zolpidem vs. placebo on sleep, daytime alertness, and fatigue in travelers who complain of jet lag was co