documentclass{article}

usepackage{pgfplots,pgfplotstable}
pgfplotsset{compat = 1.15}

begin{document}

pgfplotstableread
{
    x   y
    1   10
    2   20
    3   30
}data

pgfplotstablegetelem{0}{y}ofdata
Value is pgfplotsretval

begin{tikzpicture}
begin{axis}[xbar]
pgfplotstablegetelem{0}{y}ofdata
addplot coordinates {(pgfplotsretval,1)};
end{axis}
end{tikzpicture}

end{document}