The use of opioid medications in our community is quite common and can cause serious breathing problems, particularly during sleep. The goal of this project is to investigate the effects of opioids on upper airway muscle activity, respiratory control, and breathing during sleep in patients with obstructive sleep apnoea. These studies will help us to understand reasons why breathing responses to opioids vary between individuals and which sleep apnoea patients are most at risk of developing breathing complications during sleep.