The nurse is providing care during the immediate postoperative period for a client that had a radical neck dissection. the best method to assess for stridor is:

The nurse needs to listen with a stethoscope over the trachea.
A stridor is a high-pitched sound which can be heard over the trachea. It is a sound which indicates a disrupted airflow, probably caused by a swelling in the airway. A radical neck dissection is an operation for cancer of the oropharynx or salivary glands. One of the biggest risk after this surgery is airway obstruction. A stridor will indicate a probable post-operational problem. 

If it's a smaller child or infant, place one on the middle of the chest and on the child's back. (if it is a bigger child with enough room for two, place one on the upper right/your left of the chest, and one on the lower left/your right) the pads should never touch each other. 

Iguess it you with your back