  The shift and broadening of the resonance lines in spectrum of the
antiprotonic helium atoms $\bar{p}\mathrm{He}^{+}$ located in fluid and
superfluid $^4$He have been calculated. The contributions to the shift and
broadening from collective degrees of freedom in liquid $^4$He have been
estimated using the phenomenological response function. Effects due to the
interaction of $\bar{p}\mathrm{He}^{+}$ with a single $^4$He atom have been
calculated in the quasistatic approximation using the experimental pair
correlation function. It has been shown that an implanted
$\bar{p}\mathrm{He}^{+}$ atom establishes a good probe of liquid helium
properties, since this atom practically does not change the target structure.
