How does the ear convert mechanical signals to electrical signals?

Mr rogers is 2 days postoperative of a thoracotomy of removal of a malignant mass in his left chest. his pain is being managed via epidural catheter with morphine. as the nurse assumes care of mr rogers, he is alert and fully oriented and states that his current pain is 2 on a 1 -to-10 scale. his vital signs are 37.8-92-12, 138/82. what are benefits of epidural versus systemic administration of opioids? the nurse monitors mr roger’s respiratory status and vital signs every 2 hours. what is the rationale for this frequent assessments? the nurse monitors mr rogers for what other complications of epidural anelgesis?