Thirty four infants were enrolled in this study based on the following inclusion criteria : age between 29 to 37 weeks of gestational age , birth weight 1200 grams or more , having an endotracheal tube , no congenital anomalies , no seizures diagnosis , no chest tubes , no intracranial hemorrhage higher than degree II , not receiving opiates and sedatives four hours before intervention and not receiving any painful procedure at least half an hour before the intervention .