To undertake normative data collection of existing clinical algorithms using existing oximetry technology.

Paediatric patients who are undergoing routine diagnostic pulse oximetry, will be approached to also wear an additional oximeter at the same time so that comparisons between two oximeters and their clinical algorithms can be compared.

Inclusion Criteria:

• All children who have been referred for a clinical overnight pulse oximetry test

Exclusion Criteria:

• Families who do not understand written English if an interpreter is not present for clinical reasons
• Times when the kit is already being used for another recruit
• If children do not attend with the legal guardian and so informed consent cannot be signed
• Patient is deemed too unwell by clinical team to be approached about the research

All children aged 1 month - 16 years who are undergoing an overnight pulse oximetry investigation.