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 (F_EO2) 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 F_EO2 (NFO) was recorded. Values were compared to peripheral oxygen saturation (S_aO₂), expired CO₂ at RV, FEV₁, FEV₁/FVC, and FEF_25‐75. We also measured the effect of supplemental oxygen on F_EO2.

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 FEF_25‐75 (P = 0.0155), but there was no association with S_aO₂.

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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.