Description

Sleep can be defined as a periodic and reversible state of disengagement from the environment. It consists of an active process that involves multiple, complex physiological and behavioral mechanisms of the central nervous system. It is also a natural process highly conserved during evolution, which is critical for health and well-being, being essential for rest, repair, and for the survival of the individual. Sleep is controlled by a circadian system that drives 24-h periodicity, and a homeostatic system that ensures that adequate amounts of sleep are obtained, and it can be assessed in terms of quantity (total sleep time, and time spent in each sleep stage), quality (fragmentation, sleep stage changes, wake after sleep onset, EEG sleep patterns), and distribution over the 24-h cycle.

The ICU can be a hostile and stressful environment for patients. From the point of view of ICU survivors, a stay in the critical care unit represents a traumatic event in their lives and the environment does not favor rest, due to the equipment (alarms from monitors and life-supporting devices) and human factors (staff conversations), all related to therapy and care.

In critically ill patients, sleep and circadian rhythms are markedly disturbed. Abnormalities include sleep deprivation and disruption, as well as altered sleep architecture, and loss of normal oscillations of melatonin and cortisol. These alterations have been associated with delirium, fatigue, and higher mortality. In addition, sleep disturbances may remain after hospital discharge and have been consistently associated with psychological comorbidities, which may contribute to the low quality of life observed in ICU survivors. Patient factors for sleep deprivation in ICU are the type and severity of the underlying illness, the pathophysiology of the acute illness, pain (from procedures or the underlying condition), and stress/anxiety. Most of these factors are intrinsic to ICU patients and therefore, difficult to modify. However, factors associated with the ICU environment, such as exposure to inadequate levels of light and noise during the day and night, or inflexible schedules of daily care activities, have also been reported to have a major role in sleep disturbance. For decades these aspects of ICU care had received little attention but in recent years there has been increasing interest in changing this reality.

A limited number of studies have evaluated interventions targeting sleep optimization in the ICU. The most studied strategy to date has been the use of eye masks and/or earplugs, however, studies report poor tolerance for them. A more complex but interesting intervention to restore circadian rhythm is the application of a dynamic light system, that ensures low light at night and higher levels of light at the daytime. In terms of noise, an interesting alternative is to apply auditory masking to avoid intense cortical stimuli secondary to annoying noises, and therefore prevent awakenings. These strategies have been reported to have some positive impacts on sleep in ICU, but sleep has only been assessed by qualitative methods. In addition, they have been tested as isolated interventions, and not as part of a more comprehensive approach.

A proposal is an interdisciplinary approach, which targets different environmental factors and integrates experts from different fields. Although the concepts of dynamic light and sound masking are well known, our proposal includes the local design of solutions based on these concepts. This study also chose to use the highest standard for sleep measurements (PSG), which has been one of the main limitations of previous research in this field. It is hoped that the intervention will be effective in improving sleep. Although this study is underpowered to study the potential impacts of the strategy on mortality or ICU length of stay, if the intervention proves to be effective in improving sleep, a larger-scale study could follow. But even if the intervention proves not to be effective, the data collected about sleep and about long-term neuropsychological outcomes in our ICU population will be highly relevant to advance our understanding of the relation between these variables, and for the planning of future studies.

The hypothesis is that the use of a multifaceted intervention of environmental control in the ICU, based on dynamic light therapy, auditory masking, and rationalization of ICU nocturnal patient care activities, is associated with improved quantity and quality of sleep, assessed by polysomnography and other semiquantitative methods, compared to standard care.