Blood-Injection-Injury (B-I-I) Specific Phobia Affects the Outcome of Hypoxic Challenge Testing

BACKGROUND: Blood-injection-injury (B-I-I) phobia is capable of producing inaccurate hypoxic challenge testing results due to anxiety-induced hyperventilation.

CASE REPORT: A 69-yr-old woman with a history of hypersensitivity pneumonitis, restrictive spirometry, exercise desaturation requiring supplementary oxygen on mobilizing, reduced DLco, and B-I-I phobia was referred for hypoxic challenge testing (HCT) to assess in-flight oxygen requirements. HCT was performed by breathing a 15% F_Io₂ gas mixture, simulating the available oxygen in ambient air onboard aircraft pressurized to an equivalent altitude of 8000 ft. S_po₂ fell to a nadir value of 81% during HCT, although it rapidly increased to 89% during the first of two attempts at blood gas sampling. A resultant blood gas sample showed an acceptable Po₂ outside the criteria for recommending in-flight oxygen and a reduced Pco₂. Entering the nadir S_po₂ value into the Severinghaus equation gives an estimated arterial Po₂ of 6 kPa (45 mmHg), which was felt to be more representative of resting values during HCT, and in-flight oxygen was recommended.

DISCUSSION: While hyperventilation is an expected response to hypoxia, transient rises in S_po₂ coinciding with threat of injury are likely to be attributable to emotional stress-induced hyperventilation, characteristic of B-I-I specific phobia and expected during the anticipation of exteroceptive threat, even in normal subjects. In summary, should excessive hyperventilation be detected during HCT and coincide with transient increases in S_po₂, HCT should be repeated using S_po₂ only as a guide to the level of hypoxemia, and S_po₂ maintained using supplementary oxygen in accordance with alternative methods described in guidelines.

Spurling KJ, McGoldrick VP. Blood-injection-injury (B-I-I) specific phobia affects the outcome of hypoxic challenge testing. Aerosp Med Hum Perform. 2017; 88(5):503–506.