{
  "abstract": "Introduction A hypoxic challenge test (HCT) is often used to determine whether individuals with pre-existing respiratory conditions require in-flight supplementary oxygen (Coker et al., Thorax; 77: 329-350).A 69-year-old male (BMI: 43.1 kg/m2) was referred for a HCT to assess his requirement for in-flight supplementary oxygen following two previous episodes of deterioration during air travel. His clinical diagnoses included chronic obstructive pulmonary disease, tracheobronchomalacia, obstructive sleep apnoea and ischaemic heart disease. A previous baseline electrocardiogram (ECG) demonstrated sinus rhythm with 1st degree atrio-ventricular block (figure 1a).Methods The patient underwent a HCT in accordance with the British Thoracic Society Clinical Statement on air travel (Coker et al., Thorax; 77: 329-350) and was commenced on a fraction of inspired oxygen of 15% via a face mask.Results During phase 1 of the HCT the patient desaturated from 93% to 84%, coinciding with nausea, light-headedness, and drowsiness. The test was terminated prematurely, and a capillary blood gas (CBG) was attempted, but was unsuccessful. Despite recovery of oxygen saturation to >90%, the patient demonstrated signs of clinical deterioration becoming unresponsive to verbal stimuli, prompting a peri-arrest call. Supplementary oxygen was commenced at 2L/min, and a repeat CBG demonstrated a pH of 7.47, PO2 of 11kPa and PCO2 of 3.56kPa, consistent with hyperventilation. An ECG demonstrated sinus rhythm with intermittent second-degree atrioventricular block Mobitz type I (Wenckebach) ( figure 1b). The patient was admitted as an inpatient and experienced further pre-syncopal episodes before a dual-chamber permanent pacemaker was implanted two days later.Conclusion This case suggesting hypoxia during a HCT may unmask underlying atrioventricular conduction abnormalities, beyond its traditional role in determining the need for supplemental oxygen. The development of second-degree atrioventricular block during hypoxia highlights the importance of close monitoring, early escalation in response to clinical deterioration and the potential need for electrocardiogram monitoring during a HCT in those with known cardiovascular disease.Abstract P18 Figure 1a) Resting ECG demonstrating sinus rhythm with 1t degree atrioventricular block. b) Sinus rhythm with 2nd degree Mobitz Type I atrioventricular block (Wenckebach) following hypoxic challenge test.",
  "authors": [
    {
      "affiliations": [
        "Royal Papworth Hospital, Cambridge, United Kingdom"
      ],
      "name": "Fridah Kinoti-Ronoh"
    },
    {
      "affiliations": [
        "Royal Papworth Hospital, Cambridge, United Kingdom"
      ],
      "name": "Beverley Moseley"
    },
    {
      "affiliations": [
        "Royal Papworth Hospital, Cambridge, United Kingdom"
      ],
      "name": "Joshua Barnes"
    }
  ],
  "title": "P18 From hypoxic challenge testing to permanent pacemaker: a case of hypoxia-induced atrio-ventricular block",
  "uid": "3a9a2a93-5fe4-5b00-9219-66d7df98b9e9"
}