Results of hypoxic challenge test (15% fractional inspired oxygen for 20 min) with revised SIGN grading (see Appendix 3)
| Hypoxic challenge test (HCT) result | Recommendation |
| Pao2 ≥6.6 kPa (>50 mm Hg) or Spo2 ≥85% | In-flight oxygen not required (C) |
| Pao2 <6.6 kPa (<50 mm Hg) or Spo2 <85% | In-flight oxygen required at 2 l/min via nasal cannulae (C) |
Pao2, arterial oxygen tension; Spo2, oxygen saturation.