The total number of HBOT treatment sessions required and the overall longevity of effects depend upon the condition being treated and the severity of symptoms. It is known that the oxygen levels return to baseline 4 hours post HBOT session. However, downstream effects on a molecular level from HBOT can continue on for much longer. Because this therapy is used to treat a wide range of conditions and ailments, the effects vary from patient to patient. Talk to your doctor to find out what your specific treatment plan entails and how long you can expect the effects to last.