The purpose of the study is to test the hypothesis that patients who suffer from moderate-to-severe OSA have increased pain thresholds and are more sensitive to the analgesic effects of opioids compared to patients with normal sleep-related breathing physiology. We will evaluate the effect of remifentanil, a short acting mu-opioid receptor agonist, on pain using an experimental heat and cold-induced pain tests, and compare it between volunteers with and without a polysomnography (PSG)-based diagnosis of obstructive sleep apnea.