  Line asymmetries and shifts are a powerful tool for studying velocity fields
in the stellar photospheres. Other effects, however, could also generate
asymmetries blurring the information of the velocity patterns. We have studied
the shifts and asymmetries induced in the profiles of spectral lines by
pressure effects. The best theoretical and experimental data on line broadening
and shifts caused by collisions with atomic hydrogen were used to analyze the
NaI D and three CaI lines. Line bisectors of synthetic spectra computed with
accurate data for the NaI and CaI lines are compared with very high resolution
high signal-to-noise ratio solar spectra and indicate that pressure broadening
reproduces the wings of the observed lines, but pressure shifts introduce
neither asymmetries nor shifts comparable to the observed ones.
