Obese subjects ages 10-18 years with OSA will be recruited from sleep clinic. As per standard clinic care, once a subject is diagnosed with OSA on a PSG they are reviewed in sleep clinic to discuss CPAP therapy. Families will be approached to participate in this study during the subject's regularly scheduled clinical visit. Obese subjects meeting eligibility criteria will be recruited from the sleep clinic. The patients agreeing to CPAP therapy will be invited to take part in the study.

As per current standard clinical care, CMC diagnosed with moderate to severe OSA following a clinically indicated baseline PSG who have had a previous adenotonsillectomy or who are not considered candidates for surgery are reviewed in sleep clinic to discuss the prescription of CPAP for OSA. CMC subjects' meeting eligibility criteria will be recruited from the sleep clinic. The patients agreeing to CPAP therapy will be invited to take part in this study.

HHF is an integrated flow generator that delivers heated and humidified air or oxygen at high flow rates via a soft nasal cannula using an open circuit. HHF via the Fisher and Paykel myAIRVO 2 device will be initiated as per The Hospital for Sick Children's sleep laboratory standard protocol by a sleep technician or respiratory therapist (RT) during an overnight polysomnography. Nasal prongs will be selected that are less than fifty percent of the subject's nares. The lowest flow rate of HHF will be selected and titrated upwards until clinical effect is achieved, to a maximum flow of 60L/minute, as per standard clinical care.

Determine whether a participant's AHI changes with HHF vs CPAP

Determine whether COMFORT scale scores differ between HHF and CPAP