Use a text editor to edit the "ENGINE_SETTINGS.XML" file in the directory. "\Steam\SteamApps\common\Alien Isolation\DATA". Locate the following lines.

[Setting name="Level of Detail"]
[Quality name="Ultra" float="1.0" precedence="4"/]
[Quality name="High" float="0.9" precedence="3"/]
[Quality name="Medium" float="0.75" precedence="2"/]
[Quality name="Low" float="0.6" precedence="1"/]
[/Setting]

...and change them to:

[Setting name="Level of Detail"]
[Quality name="Ultra" float="2.0" precedence="5"/]
[Quality name="Very High" float="1.0" precedence="4"/]
[Quality name="High" float="0.9" precedence="3"/]
[Quality name="Medium" float="0.75" precedence="2"/]
[Quality name="Low" float="0.6" precedence="1"/]
[/Setting]