Exercise-induced desaturation in subjects with non-cystic fibrosis bronchiectasis: laboratory-based tests versus field-based exercise tests

OBJECTIVE: To investigate the validity of field walking tests to identify exercise-induced hypoxemia and to compare cardiorespiratory responses and perceived effort between laboratory-based and field-based exercise tests in subjects with bronchiectasis. METHODS: This was a cross-sectional study involving 72 non-oxygen-dependent participants (28 men; mean age = 48.3 ± 14.5 years; and mean FEV(1) = 54.1 ± 23.4% of the predicted value). The participants underwent cardiopulmonary exercise testing (CPET) on a treadmill and constant work-rate exercise testing (CWRET) on the same day (1 h apart). In another visit, they underwent incremental shuttle walk testing (ISWT) and endurance shuttle walk testing (ESWT; 1 h apart). Desaturation was defined as a reduction in SpO(2) ≥ 4% from rest to peak exercise. RESULTS: CPET results were compared with ISWT results, as were CWRET results with ESWT results. There was no difference in the magnitude of desaturation between CPET and ISWT (−7.7 ± 6.3% vs. −6.6 ± 5.6%; p = 0.10) and between CWRET and ESWT (−6.8 ± 5.8% vs. −7.2 ± 6.3%; p = 0.50). The incremental tests showed an agreement in the magnitude of desaturation in the desaturation and no desaturation groups (42 and 14 participants, respectively; p < 0.01), as did the endurance tests (39 and 16 participants; p < 0.01). The magnitude of desaturation was similar among the participants who did or did not reach at least 85% of the maximum predicted HR. CONCLUSIONS: Field exercise tests showed good precision to detect desaturation. Field tests might be an alternative to laboratory tests when the clinical question is to investigate exercise-induced desaturation in subjects with bronchiectasis.