  The pressure dependence of the critical temperature $T_c$ and upper critical
field $H_{c2}(T)$ has been measured up to 19 GPa in the layered superconducting
material 2H-NbSe$_2$. Relating the behavior of $H_{c2}(T)$ to Fermi surface
parameters, we find that the electron phonon coupling of the 2D Nb 4d derived
bands shows a peak at 5 GPa when the charge density wave (CDW) order is
suppressed. On the other hand, $T_c(P)$ shows a bell shaped curve with a
maximum at 10.5 GPa, well above the pressure for the suppression of the CDW
order. Changes in the band structure produce this shift in the maximum of
$T_c(P)$, demonstrating that 2H-NbSe$_2$ shows important differences with
respect to other compounds where $T_c$ has a maximum in the temperature-density
phase diagram shaped by the suppression of another, non-superconducting, ground
state.
