Multiple breath washout (MBW) and oxygen-enhanced MRI techniques use acute exposure to 100% oxygen to measure ventilation heterogeneity. Implicit is the assumption that breathing 100% oxygen does not induce changes in ventilation heterogeneity, however, this is untested. We hypothesized that ventilation heterogeneity decreases with increasing inspired oxygen concentration in healthy subjects. We performed MBW in 8 healthy subjects (4 female, 4 male, Age=43±15y) with normal pulmonary function (FEV1=98±6% predicted) using 10% Argon as a tracer gas and oxygen concentrations of 12.5%, 21% or 90%. MBW was performed in accordance with ERS-ATS guidelines. Subjects initially inspired air followed by a wash-in of test gas. Tests were performed in balanced order in triplicate. Gas concentrations were measured at the mouth, Argon signals rescaled to mimic a N2 washout, and analyzed to determine the distribution of specific ventilation (SV). Heterogeneity was characterized by the width of a log-Gaussian fit of the SV distribution and from Sacin, and Scond indices derived from the phase III slope. There were no significant differences in the ventilation heterogeneity due to altered inspired oxygen: histogram width (hypoxia 0.57±0.11, normoxia 0.60±0.08, hyperoxia 0.59±0.09, P=0.51), Scond (hypoxia 0.014±0.011, normoxia 0.012±0.015, hyperoxia 0.010±0.011,P=0.34) or Sacin (hypoxia 0.11±0.04, normoxia 0.10±0.03, hyperoxia 0.12±0.03,P=0.23). Functional residual capacity was increased in hypoxia (P=0.04) and deadspace increased in hyperoxia (P=0.0001) compared to the other conditions. The acute use of 100% oxygen in MBW or MRI is unlikely to affect ventilation heterogeneity in normal subjects provided alterations in FRC and deadspace are taken into account.
- mutiple breath washout
- oxygen enhanced imaging
- ventilation heterogeneity
- Copyright © 2016, Journal of Applied Physiology