You don't need to alter sprites, you need to alter the range of the lifebar.
0 refers to the position of the X axis and most lifebars have their end point aligned to that, so
range = 0,144
would be a 144 pixel lifebar draining between 0 and 144 pixels. If you cover it up so there are say... 40 pixels of that lifebar not visible you would do
range = 40,104
and get the correct effect. I suggest you try that out, it may take some trial and error.