The purpose of the study is to determine whether remifentanil influence the pharyngeal phase of swallowing using using pressure and impedance recordings. The purpose is also to compare remifentanil to morphine and younger to elderly volunteers.

Remifentanil and other opioids are widely used as anesthetic sedation during minor surgical procedures and as pain relief in postoperative patients when the patient is spontaneously breathing and the airway is not secured by endotracheal intubation. In a previous study (not yet published) we showed that remifentanil induce pulmonary aspiration in healthy volunteers and the aim of this study is to objectively determine weather remifentanil infusion in healthy volunteers influence the pharyngeal phase of swallowing. The purpose is also compare the effect of remifentanil to morphine and younger volunteers to elderly volunteers. To assess this question we are going to study 24 volunteers, 12 younger and 12 elderly, who are randomised to receive remifentanil infusion with target concentration 3 ng/ml during 30 minutes at one occasion and an injection of morphine (younger: 0.1 mg/kg, elderly 0.07 mg/kg) at the other. The volunteers are asked to swallow 10 ml normal saline several times both before and after opioid administration and pharyngeal motility is parallelly recorded using combined manometry and impedance catheter placed transnasally into to the pharyngo-esophageal segment. Any subjective swallowing difficulties are also recorded.

Inclusion Criteria:

• 18-30 or 65 < year old healthy volunteers from both sexes.
• Have signed and dated Informed Consent.
• Willing and able to comply with the protocol for the duration of the trial.

Exclusion Criteria:

• Pharyngoesophageal dysfunction
• Known history of cardiac, pulmonary or neurological disease
• Ongoing medication
• Allergies to or history of reaction to remifentanil, fentanyl analogues or other ingredients
• Pregnancy or breast feeding
• BMI > 30
• Previous participation in a medical clinical trial where opioid has been used or have during last 30 days participated in any other medicinal clinical trial or in a trial where follow-up in not complete.