What Does This Oxygen Level In A COPD Patient Indicate?

I have severe copd am doing a week s trial on bipap machine not getting no sleep with it noisey and claustrophobic I av been sleeping a lot prior to the machine also av little energy .on oxygen 15hours a day my oxygen levels r approx 88 -90 Would this machine prolong my life The respiratory nurse told me I would av to use it every night for 4 hours if machine approved after trial I am 66years old My carbon dioxide levels are high