The influence of absorption and ionization on high-order
harmonic generation in a gas-filled hollow fiber is analyzed
within the framework of slowly varying envelope approximation.
Harmonic spectra and pressure dependencies are calculated
for high-order harmonic generation in hollow fibers filled
with different rare gases. Ionization of the gas filling
the fiber gives rise to self-phase modulation of the pump
pulse, changing the phase mismatch within the pump pulse
and shifting the maxima in pressure dependencies of high-order
harmonics.