Some evidence suggests that nonverbal patients experience
 stressful, unpleasant, and potentially negative experiences during their time
 in intensive care units. These include pain, fear, sleep deprivation,
 nightmares, inability to speak, and feelings of isolation and loneliness. Among
 these negative experiences, pain has emerged as a leading stressor for
 intensive care units patients. The
 patient self report is the most reliable source of pain assesment, intensive
 care unit  patients are unable to self
 report because of intubation and sedation. For this reason, there must be
 scales which include verbal and non-verbal parameters, behavioral responses to
 pain in intensive care units. Critical care nurses play the most important role
 in evaluation and relief of pain in intensive care patients since they are the
 staff who spend time most with the patients and follow them closely.