> a) The O2 blender of bellavista regulates the FiO2 mix to reach the desired concentration over one breath. Within the breath the O2 concentration may fluctuate slightly while in average the desired FiO2 will be achieved.
> b) The O2 measurement in both, bellavista and CITREX is processed and averaged to avoid fluctuation of the value.
> c) Having zero flow (or very small flow) during one phase of the breath means that this portion of gas remains in the circuit for a while and influences the FiO2 measurement without ever reaching the patient.
> d) This is what happens during zero PEEP where the base flow becomes almost zero. The gas delivered at the end of inspiration remains in the circuit and will be measured by CITREX during the entire exhalation period. At the same time there will already be fresh gas inside bellavista, measured by the bellavista O2 cell.
> e) This creates the observed effect which has no influence on the patient.