The neonatal period is defined as the first 28-day period of postnatal life. This period is stated as the transition period in which the newborn tries to adapt to extrauterine life, is sensitive and dynamic. One of the most common problems that occur during this period when the newborn experiences biochemical and physiological changes is respiratory failure. Respiratory failure is a cause of mortality and morbidity in the newborn. Therefore, the etiology should be determined quickly and intervened early. Newborns with or without respiratory failure need mechanical ventilation support to provide ventilation.

Mechanical ventilation is a life support system developed to support or fulfill normal lung functions. Mechanical ventilation is frequently used in infants hospitalized in the Neonatal Intensive Care Unit (NICU), to improve respiratory failure, to ensure adequate gas exchange, and to solve other problems. Newborns connected to mechanical ventilator, separation from the family in the intensive care environment, noise of the devices, invasive interventions, etc. They experience stress because they are exposed to painful stimuli due to many medical diagnosis and treatment procedures. These painful stimuli are a powerful source of stress. Stress is a factor that increases the susceptibility to physical and mental tension and illness due to physical, chemical or emotional factors. As a result of the stress experienced by newborns in the NICU due to painful stimuli, the secretion of glucocorticoids, especially cortisol, increases, long-term neurodevelopmental problems occur, and adverse events such as increase in heart rate, increase in catabolization and decrease in oxygen saturation values may occur.

Pain affects the endocrine system physiologically and activates the hypothalamic-pituitary-adrenal (HPA) axis, which is the body's main stress control mechanism. The function of the HPA axis and the resulting changes in cortisol levels in acute or chronic pain have been demonstrated by many studies. It has been reported that newborns with pain have higher cortisol levels and higher cortisol responses. It has been stated that this situation is associated with stressful events, there is an interaction between stress and pain, pain sensitivity increases in stressful situations, and the HPA axis is activated in case of stress, causing the release of glucocorticoids such as cortisol. In stressful situations, cortisol levels increase in newborns. Since the salivary cortisol level in newborns reflects the plasma cortisol level, it has been stated that determining the cortisol level is a reliable method in evaluating stress.

It is recommended to use pharmacological and non-pharmacological methods together to reduce pain and stress and minimize pain during short-term, mild and moderately painful procedures in newborns in the intensive care unit. Among non-pharmacological methods, non-nutritive sucking has vital importance in controlling pain, providing comfort and neurobehavioral control, increasing physiological stability and oxygenation, reducing stress, effective functioning of the digestive system and reducing the risk of aspiration. In the literature many painful procedures (circumcision, vaccination, IV catheterization, lumbar puncture test) of pacifier use It is reported that it provides an analgesic effect and reduces stress during In this context, it is stated that pacifier use has a calming effect and reduces stress for newborns and it is emphasized that it reduces salivary cortisol levels.

The endogenous analgesic effect of the pacifier; When a pacifier is placed in the mouth of the newborn, the sucking reflex is activated via a non-opioid mechanism, resulting in tactile sensitivity and stimulation of mechanical receptors. Since sucking prevents swallowing, it protects the baby against aspiration. Pacifier use in stressed newborns who also have tachycardia; It contributes to the calming of the newborn by causing stability in heart rate and increasing oxygenation. In this respect, the behavioral organization of newborns using pacifiers such as self-consolation and soothing develops, the time spent for sleep and wakefulness levels increase, the baby's energy consumption decreases and the discharge time is shortened. Smith et al. (2022) reviewed the NICU environment and published clinical practice guidelines recommending non-pharmacological methods to prevent pain and stress in neonates. Various non-pharmacological methods, including non-nutritive absorption, have been proposed in this guideline. The use of pacifiers in NICUs is recommended in the treatment plan of stressed newborns with poor sucking, swallowing and breathing coordination, as it helps neurobehavioral organization and maturation and supports calming. In addition to the benefits of pacifier use, there are also some risks such as otitis media, dental malocclusion, suffocation, allergies, increased caries risk, infections. However, when the mother and baby are separated and the benefits of the pacifier are evaluated, pacifier use is recommended for newborns. It is stated that the baby admitted to the NICU has a risk of losing its sucking reflexes as a result of being separated from the mother for a long time, and it is reported that non-nutritive sucking should be used to protect the sucking reflex, increase physiological stability and reduce stress. The Baby-Friendly Hospital Initiative, launched in 1990 by the World Health Organization (WHO) and the United Nations International Children's Emergency Fund (UNICEF) to promote and support breastfeeding, established the principles of "Ten Steps to Successful Breastfeeding". It was realized that these principles, which rejected the use of pacifiers in the future, did not take into account the separation of the mother and the baby, and it was suggested that this situation should be brought to the agenda. As a matter of fact, the "Ten Steps to Successful Breastfeeding" application was revised in 2013, and the use of pacifiers was recommended considering the special situations in which the newborn and mother were separated. In the literature prevent delays in nutritional development of newborns in ICUs who have to be separated from their mother, motor organization, supporting the development of neurobehavioral maturity levels, etc. The use of pacifiers is strongly recommended in justified cases. Painful and invasive procedures for follow-up, diagnostic and therapeutic purposes are an inevitable part of care in the intensive care unit. An effective pain and stress management is the main goal of nursing care and is based on a comprehensive assessment of the pain and stress of the newborn. Appropriate assessment of pain response and stress level directly affects and guides treatment. Physiological changes such as an increase in heart rate, respiratory rate, blood pressure and intracranial pressure, decrease in oxygen saturation, sweating in the palms, change in respiratory pattern, differentiation in skin color and pupil size are observed in newborns as a result of painful stimuli activating the sympathetic nervous system. The salivary cortisol level is a simple method used and recommended to evaluate the stress level of newborns. It is important to implement planned interventions in case of newborn stress. Nurses and other healthcare professionals have the responsibility to prevent or minimize the pain and stress of the newborn during procedures. The nurse's being with the patient for a long time contributes to the healing process by providing the evaluation and reduction of the patient's pain and stress.

Many studies have been found in the literature on the evaluation of pain and stress in newborns connected to mechanical ventilation, but it has been observed that there are no studies on the use of pacifiers in newborns connected to mechanical ventilation. Since pacifiers produced in the market are not suitable for mechanical ventilators it is planned to use the prototype of the pacifier shield designed by the researcher for newborn babies in this project.