The research was carried out in randomized controlled experimental type in order to determine the effect of light in ICU on patients' sleep quality and physiological parameters. The cases were assigned to the experimental and control groups according to the simple randomization method.

The research universe; Between May 2019 and December 2019, sick individuals who were admitted to the 5 isolation rooms in the Reanimation Intensive Care clinic in the education and research hospital in Istanbul were formed. The research sample is; As a result of the power made for the study to be experimentally designed; a total of 148, with a minimum of 74 for each group. In collecting data; Patient Information Form, Numerical Pain Rating Scale, Richards Campbell Sleep Scale, Glaskow Coma Scale, Richmond Agitation Sedation Scale, Bedside Monitors were used to measure physiological parameters. The data obtained as a result of the research were made using the package program named SPSS (IBM SPSS Statistics 24).

Sleep causes temporary, partial and periodic interruption of the organism's interaction with the environment, is a physiological condition that affects many systems. That sleep activity is a vital and important activity for individuals.They emphasized and sleep; the alternating state of inertia and inertia, around the human a situation where they do not respond to the events that took place. initiation and maintenance through the function of many cortical and subcortical brain regions. People sleep on average one third of their lives They spend it. The sleep of a normal adult person consists of night sleep and It lasts an average of 7 to 9 hours, with a sleep time of four to six 90 to 100 minutes. Non-REM (NREM) and REM sleep change cyclically. In the sleep-wake cycle in man, the most basic and determinant is the circadian rhythm. Circadian The rhythm refers to changes in the physiological and biological processes of the organism for about a day. The main center that regulates the circadian rhythm is located in the anterior hypothalamus as a double structure. suprachiasmatic nucleus (SKN). Light is the most important rhythm editor. Other regulators are social and are physical activities. Florence Nightingale and Virgina Henderson in love and day rhythm; defined the patient as two important factors in supporting the health of the individual. In the regulation of the circadian rhythm, the light and dark cycle in the external environment is important. The synthesis and release of melatonin is stimulated in the dark at night, and during the day by the effect of light It is suppressed. N-acetyl transferase (NAT) enzyme is effective in melatonin formation. Melatonin The main task of the hormone is to protect the biological rhythm of the body. In this context; lighting, circadian rhythm and sleep are related.

Health care institutions and especially intensive care units, in terms of physical environment and lighting the patient can affect the circadian rhythm of the individual, change the release of melatonin and as a result can affect sleep patterns and cognitive performance. In our country, in terms of physical environment lighting, it does not support circadian rhythms. As a result, sick individuals in the ICU are asleep The therapeutic effect of sleep because they spend a significant amount of time they need to be awake can not benefit sufficiently. In addition, in the ICU, many There is a factor. These factors are; pain, physical condition, drug therapy, fear of death, environmental noise, pleasant non-smells, invasive interventions, loss of privacy and family disability. In the study of, the greatest stress of the sick individuals in the ICU One of the causes was found to be sleeping problems. In the literature, especially in health care institutions In patients with ICU inpatient, sleep activity has a negative effect on both duration and quality. shows that it is affected In admission to the ICU, when environmental factors are not suitable, the patient especially the sleep activity of the individual is impaired and this process occurs even after the patient is discharged from YBU, can continue. One of the biggest reasons for this; Physical environment and lighting of ICUs in terms of disruption of circadian rhythms of sick individuals. The presence of night light suppresses the level of melatonin, which is normally the highest at night. Melatonin level is accepted as an indicator of circadian rhythm. Artificial lighting is a known factor in the disruption of the circadian rhythm. Sick individuals in the ICU, 24 hours it is exposed to artificial light throughout a cycle. Artificial lighting, health of the sick individual health care to help professionals continue their care and treatment practices It is applied at high levels for 24 hours in institutions such as ICU. Its as a result, daylight is often obscured / eliminated in ICUs and artificial lighting are added. Researches conducted, unnatural night disruption of circadian rhythms with illumination causes health problems related to sleep activity. It is also sufficient and relaxing non-sleep, negatively affects the immune system, wound healing process and cognitive functions of the sick individual. It affects in the same direction, increases the level of stress and delays its recovery. Sick individuals in the ICU are concerned with serious illnesses or injuries and care and treatment. The illness of the symptoms lies. Today, long-term health of an illness or injury in an ICU It is known to cause problems. Some of these problems are sleep problems due to lighting and circadian rhythm disturbances. our Country Study to determine the effect of environmental factors related to lighting on sleep problems in ICU There is. Nurses who continue the care and treatment of sick individuals in ICU, diagnosing problems early, identifying primary nursing diagnoses, existing stressors important role such as reduction, ensuring the necessary environmental regulation to create a therapeutic environment, and they have responsibilities. In this context, this research is based on YBU. to determine the effect of light on sleep quality and physiological parameters in individuals and nursing will be carried out to guide its applications.

Inclusion Criteria:

• 18 years of age or older,
• Not having a problem in terms of consciousness and sense organs
• A score of 9 or above on the Glaskow Coma Scale (GCS),
• Richmond Agitation-Sedation Scale (RASS) score was determined as -1,0,1.

Exclusion Criteria:

• Be under the age of 18
• Having a problem in terms of consciousness and sense organs,
• A GCS score below 9,
• Receiving inotropic support,
• Being fully sedated,
• Having a chronic disease such as chronic heart disease, dementia, psychosis,
• Identified as having severe brain injury.

The principle of "loyalty and confidentiality" was adhered to by assuring individuals that their identities and personal information obtained from them would not be disclosed to anyone other than the researcher or that the information would not be allowed to be accessed by anyone other than the intended purpose.