A novel, noninvasive assay shows that distal airway oxygen tension is low in cystic fibrosis, but not in primary ciliary dyskinesia.

OBJECTIVES: Oxygen tension affects the biology of aerobic and denitrifying organisms. Using a novel, fast-response sensor, we developed a noninvasive procedure to measure pO2 in distal human airways. We hypothesized that distal pO2 would be low in cystic fibrosis (CF) airways.

MATERIALS AND METHODS: We measured the fraction of expired oxygen (FEO2 ) in real time using a fast laser diode analyzer in healthy subjects and in patients with CF, asthma, and primary ciliary dyskinesia (PCD). Subjects slowly exhaled to residual volume (RV), where the nadir of FEO2 (NFO) was recorded. Values were compared to peripheral oxygen saturation (Sa O2 ), expired CO2 at RV, FEV1 , FEV1 /FVC, and FEF25-75 . We also measured the effect of supplemental oxygen on FEO2 .

RESULTS: Seventy-four subjects completed the study. Seven additional subjects could not perform the maneuver. Mean (±SD) NFO values for controls (n = 29), CF patients (n = 23), asthma patients (n = 15), and PCD patients (n = 7) were 13.4 ± 1.1%, 12.4 ± 1.2%, 13.3 ± 1.1%, 14.4 ± 0.6%, respectively. NFO in CF was lower than in controls (P = 0.0162), and NFO in PCD was higher than in CF (P = 0.0007). Asthma results were heterogeneous. Oxygen caused a dose-dependent increase in NFO (P < 0.0005; n = 3; r2  = 0.91). NFO values were positively associated with FEV1 (P = 0.0009), FEV1 /FVC (P = 0.0019) and FEF25-75 (P = 0.0155), but there was no association with Sa O2 .

CONCLUSIONS: Distal airway pO2 is lower in CF than in controls. This may reflect absorption of oxygen in partially plugged acinar units, and/or increased epithelial oxygen consumption. Distal airway pO2 can be precisely titrated to treat infections.