The main objective of this study is to evaluate the efficacy of high-flow nasal cannula (HFNC) therapy in children with OSA.

Children and adolescents aged 6 to 18 years old with a diagnosis of moderate-to-severe OSA requiring CPAP therapy will be recruited.

In phase 1 study, eligible subject will be recruited for HFNC therapy titration with PSG to assess treatment efficacy. After titration, if HFNC therapy is shown to be effective, the participants will be recruited into the phase 2 intervention period to evaluate the compliance and quality of life with HFNC therapy. At baseline and follow-up visits, neurobehavioural and quality of life surveys will be completed, compliance data will be obtained.

Background: Obstructive sleep apnoea (OSA) is prevalent in school-aged children and is associated with significant morbidities. Poor compliance with positive airway pressure therapy remains an issue and leads to suboptimal treatment in children with OSA. Alternative therapeutic strategy is needed to manage this group of patients more effectively.

Objective: To evaluate the efficacy of high-flow nasal cannula (HFNC) therapy in children with OSA.

Hypothesis: The investigators hypothesize that HFNC therapy is effective in reducing the severity of OSA in children.

Design: A 2-phase study - phase 1 is a single arm study to evaluate the efficacy of HFNC therapy in children with OSA, phase 2 is an intervention period to evaluate the compliance and quality of life with HFNC therapy.

Subjects: 46 children and adolescents aged 6 to 18 years old with a diagnosis of moderate-to-severe OSA requiring CPAP therapy.

Methods: In phase 1 study, eligible subject will be recruited for HFNC therapy titration with PSG to assess treatment efficacy. After titration, if HFNC therapy is shown to be effective, the participants will be recruited into the phase 2 intervention period to evaluate the compliance and quality of life with HFNC therapy. At baseline and follow-up visits, neurobehavioural and quality of life surveys will be completed, compliance data will be obtained.

Primary outcome measure: Efficacy of the HFNC therapy, as defined by the change in OAHI from baseline to that with HFNC therapy.

Expected results: Efficacy data to determine whether HFNC therapy can be an alternative therapy for children with OSA.

Inclusion Criteria:

• Diagnosis of moderate-to-severe OSA requiring CPAP therapy (Moderate-to-severe OSA is defined as an OAHI ≥ 5 events per hour and reported history of habitual snoring of 3 nights or more per week)

Exclusion Criteria:

• Syndromal diseases;
• Cranio-facial anomalies;
• Pathological central apnoea, chronic respiratory failure or neuromuscular disease as they would require bilevel PAP;
• Secondary obesity e.g. Prader-Willi syndrome, Cushing's syndrome;
• History of pneumothorax or pneumomediastinum;
• Prior use of PAP or HFNC therapy;
• Refusal to use non-invasive ventilation.