Iran Journal of Nursing

1. Introduction
Brain injury is one of the causes of death and disability in developed countries, including the United States. One and a half million people die each year because of brain injuries. Following a brain injury, a person experiences severe and various complications, including sensory, physical, motor, cognitive, and behavioral disorders, as well as impaired levels of consciousness. Most patients experience brain damage based on the severity of the coma. These people are more likely to be admitted to the intensive care units. The longer the duration of the coma and the greater the severity of the dysfunction, the poorer would be the prognosis for complete recovery. For example, if coma lasts longer than 6 hours, the chances of severe brain damage, and naturally, more complications will increase. Patients with severe disturbances of consciousness whose Glasgow coma scale (GCS) is between 3 and 8 require respiratory care and are admitted to intensive care units. It can be said that the primary and common causes of hospitalization of patients in special wards are coma and decreased level of consciousness. The patient admitted to the intensive care unit suffers from sensory deprivation due to the nature of these wards, reduction of environmental stimuli, and long hospital stay. Sensory deprivation is one of the most common threats to patients after coma and hospitalization. Despite brain damage as the primary problem, deprivation of environmental stimuli can cause more damage to the patient’s mental and perceptual processes. Sensory deprivation as an important complication can make it difficult for patients admitted to intensive care units to recover. It also causes problems such as long-term hospitalization of patients, imposing high costs on the family and society, and generally affects the quality of life of the patient and the family. 
Studies show that the processes of brain regeneration and recovery begin at the beginning of brain damage and are influenced by internal and external factors. The internal factor is the release of nerve growth factor, and the external factor is environmental stimulation. Therefore, environmental stimuli can result in the reconstruction and improvement of neurological function and can rehabilitate comatose patients with brain damage. The use of pharmacological methods to control stress in patients with brain injury leads to a further reduction in their level of consciousness and cognitive activity. In contrast, non-pharmacological methods can increase the level of consciousness of these patients. So the use of a sensory stimulation program has been suggested in recent years to reduce the complications of brain injury, accelerate brain regeneration, and prevent sensory deprivation in these patients. Using the sensory stimulation program by awakening the reticular activating system promotes brain healing or in healthy axons under the influence of these stimuli, lateral interfaces (lateral buds) are created that facilitate the reorganization of brain activity. If these stimuli are appropriate, the recovery rate from the coma will rise. The use of sensory stimulation for patients in coma is one of the essential nursing care in the intensive care unit. Still, the care of entirely dependent patients limits the time for purposeful and meaningful stimulation by nurses. On the other hand, the presence of family members on the bed of comatose patients can be a good source to cause these stimulations. Therefore, in this study, family auditory stimulation was used for patients. 
This study aimed to determine the effect of sensory stimuli with a familiar sound, and patient’s auditory preferences on the level of consciousness of comatose patients admitted to intensive care units.
2. Materials and Methods
The present study is quasi-experimental that was performed on 45 patients admitted to the intensive care unit of selected hospitals in Ahvaz City, Iran, in 2021. The patients who met the inclusion criteria were randomly divided into two intervention groups and a control group. Sampling was performed for six months. It lasted from August 2020 to January 2021.
The intervention was performed for 3 days from the beginning of hospitalization and twice a day (6 times in total) at 10 AM and 3 PM at the patient’s bedside. 
 Routine care and routine sounds were provided for the control group. The patient’s level of consciousness was evaluated 15 minutes before and 15 minutes after the intervention in all three groups. The instrument for assessing patients’ level of consciousness was GCS. Descriptive and inferential statistical methods were used to analyze the data.
3. Results
A total of 70 patients were initially selected according to the inclusion criteria, and then 25 patients were excluded from the study because of death, surgery, or transfer to the ward. Finally, 15 patients were in the familiar voice intervention group, 15 patients in the auditory preferences intervention group, and 15 patients in the control group. The Chi-square test results showed no statistically significant difference between the three groups regarding the frequency distribution of sex, level of education, diagnosis of disease, and cause of hospitalization. Also, the results of 1-way analysis of variance showed that the mean age and GCS score on the first day of hospitalization and before the intervention was not statistically significant between the three groups. The mean level of consciousness of the auditory preferences and familiar voice groups after the intervention was significantly higher than the control group (P<0.05). However, there was no significant difference between the two groups of auditory preferences and familiar voice (P<0.05).
4. Conclusion
Considering that the effect of a familiar voice and auditory preferences has been more than unfamiliar sound, it is recommended to provide a program of auditory stimulation with a familiar voice and auditory preferences for patients in intensive care units. Therefore, it is recommended to provide an auditory stimulation program with the voice of a close family or auditory preferences for comatose patients in intensive care units to create a stress-free environment for the patient and family. 

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the ethics committee of the Islamic Azad University, Najafabad Branch (Code: IR.IAU.NAJAFABAD.REC.1399.057). All ethical principles are considered in this article. The participants were informed about the purpose of the research and its implementation stages. They were also assured about the confidentiality of their information. They were free to leave the study whenever they wished, and if desired, the research results would be available to them.

Funding
This study was extracted from the MA. thesis of the first authorat the Research Center for the Development of Nursing and Midwifery Sciences, Najafabad Branch, Islamic Azad University, Najafabad.

Authors' contributions
Conceptualization, editing and finalization of writing, supervision and project management: Fatemeh Salmani; Methodology: Fatemeh Salmani, Mina Jozi, Sahar Vanuni; Validation: Fatemeh Salmani, Mina Jozi; Analysis: Fatemeh Salmani; Research, sources, draft writing: Sahar Vanuni.

Conflict of interest
The authors declared no conflict of interest.

Acknowledgments
We would like to thank the esteemed officials of the Islamic Azad University, Najafabad Branch, as well as all the participants in the research.


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