  I consider the generic model independent predictions of the theory of quantum
cosmological perturbations. To describe the stage of cosmic inflation, where
these perturbations are amplified, the hydrodynamical approch is used. The
inflationary stage is completely characterized by the deviation of the equation
of state from cosmological constant which is a smooth function of the number of
e-folds until the end of inflation. It is shown that in this case the spectral
index should deviate from the flat one at least by 3 percent irrespective of
any particular scenario. Given the value of the spectral index the lower bound
on the amount of the gravitational waves produced is derived. Finally the
relation between effective hydrodynamical description of inflation and
inflationary scenarios is discussed.
