Table 1 Categorical factors assessed for influence on oximeter accuracy

Location of measurement (ED, HDU, ward, or outpatient department)

Position of the oximeter probe (finger or ear)

Recognised condition associated with chronic respiratory failure (chronic obstructive pulmonary disease, obesity hypoventilation syndrome, bronchiectasis, cystic fibrosis, neuromuscular disease and chest wall deformities such as severe kyphoscoliosis)

Current tobacco smoking status (current versus ex or non-smoker)

Skin pigmentation (based on modified Fitzpatrick scale with patient skin colour classified as either: Light (Type I to Type II), Medium (Type III to Type IV) or Dark (Type V to Type VI))

Diabetes Mellitus