Is there an alternative to pre-flight hypoxic challenge testing in scoliotic patients?

SummaryIntroductionHypoxic challenge testing (HCT) is not readily available in all hospitals. It has recently been shown that resting oximetry does not reliably predict the results of HCT in patients with extrapulmonary restrictive lung disease. We assessed other clinical tests to see if they might be used as an alternative screen for HCT.MethodsPeople with primary thoracic scoliosis were recruited. Resting SpO2, arterial blood gases (ABG’s), lung function and shuttle walking test (SWT) were measured. All subjects underwent HCT breathing an inhaled oxygen fraction of 15% for 20 min, or until SpO2 fell below 85%, when ABG’s were taken.ResultsFourteen people (5 male) with thoracic scoliosis, Cobb angle 93 (31)°, aged 65 (8.5) years, FEV1 0.86 (0.4) L, FVC 1.2 (0.4)L were studied. The resting SpO2 was 96 (2) %, PaO2 9.2 (1) kPa and PaCO2 6.1 (0.4) kPa. HCT was positive in 11 subjects (PaO2 <6.6 kPa). Eight of 11 HCT positive subjects had a resting SpO2 > 95%. Positive correlation was found between SpO2 at SWT termination and PaO2 following HCT (r = 0.56, p = 0.02). Those with saturations of 92% or under at SWT termination had positive HCT.ConclusionsDespite normal resting SpO2 subjects with thoracic scoliosis may have positive HCT. Current recommendations for air travel do not accurately identify these people. Desaturation following a SWT may provide a useful screening tool, however a low threshold for performing HCT on people with thoracic scoliosis prior to air travel is warranted.