BACKGROUND: Endotracheal suctioning of respiratory secretions is one of the most common causes of pain and discomfort in Intensive Care Unit environment. The electrical properties of the skin, also known as electrodermal activity (EDA), are considered as an indirect measure of autonomous nervous system.AIM: This study explores EDA changes during endotracheal suction in sedated adult critical care patients; and compares these changes to other monitoring parameters.MATERIALS AND METHODS: Skin conductance variability, selected hemodynamic and respiratory parameters, bispectral index (BIS) and ambient noise level, were monitored during 4 hour routine daytime intensive care nursing and treatment in an adult Intensive Care Unit. 4h-measurements were divided into 2 groups, based upon the sedation level (group A: Ramsay sedation scale 2-4 and group B: 5-6 respectively) of the patients. Selected recordings before and after endotracheal suction (stress events) were performed. Seven stress events from Group A and 17 from Group B were included for further analysis. Patients' demographics, laboratory exams and severity scores were recorded. Pain status evaluation before every event was also performed via 2 independent observers.RESULTS: In both groups the rate of EDA changes was greater than in other monitoring parameters. Yet, in group A only selected parameters were significantly changed after the start of the procedure, while in group B, every parameter showed significant change (p<0.05). Groups were similar for other co-founding factors.CONCLUSION: EDA measurements are more sensitive to stress stimuli, than cardiovascular, respiratory or even BIS monitoring. Deeper sedation seems to affect more the intensity of EDA changes during suction.