Unplug the sensor from the wiring harness, and get a special O2 sensor socket from the auto parts store (some loan them out for free) and remove the old sensor from the exhaust bung. If the sensor won't budge, try more penetrating oil or attempt the removal with the engine warm (be careful not to burn yourself).
However, a mattress that is too soft is just as bad for low back pain as a mattress that is too firm. In a 2005 study, The Journal of the Canadian Chiropractic Association pointed out that in a survey, 76% of orthopedic surgeons recommended firm mattresses.
A lumbar cushion is a specially designed support pillow used for providing added support to the lower back, thus relieving or reducing lower back pain aggravated by prolonged periods of sitting. Typically, a lumbar cushion is contoured to conform to the natural curve of the lower back when seated. People who have lower back pain or muscle tension may benefit from using a support pillow at their office desk, in the car, or at home.