What you are experiencing is very normal after pneumonia!
Pneumonia is inflammation of the lung. This is most commonly due to an infection. Since you had bacterial pneumonia, inhaling bacteria was the cause of your infection and antibiotics would help. Additional treatment for pneumonia may include rest, fluids, oxygen, and inhaled medicine depending on the nature and severity of your symptoms.
Recovery from pneumonia varies based on the germ, your overall health, and how soon effective treatment is started. It may be months after finishing the course of antibiotics, until your oxygen level is consistently above 90% and you’re back to your busy active self. It is possible for inflammation or irritation to remain in the lungs for 6 to 8 weeks after the actual infection is gone. A low oxygen level and weakness may linger. These should gradually improve and eventually go away completely. So it is a good sign that your oxygen level is staying above 90% when you are resting! You should let your doctor know if they worsen or do not go away. A follow-up chest x-ray is helpful to show that the pneumonia has completely gone away, but it will not show inflammation that is still in your lungs. This is most likely the cause of your lingering low oxygen level and weakness. To know if it is really safe to take the oxygen off at night, talk with your doctor about having your oxygen level checked with an oximeter during the night while you sleep. There would be no harm in continuing to use the oxygen at night until you are able to talk with your doctor.
It is difficult to tell you exactly when you will return to your full strength. Generally it will take you at least as long as the pneumonia has caused you to be less active. Certainly the physical conditioning that will occur with the aerobic activity that your doctor has suggested will help to shorten your return to your usual activity level. Muscles that are physically conditioned use oxygen and energy in the most efficient way possible. You should progressively increase your aerobic activity to the point that you are able to tolerate.
Things to do to keep you from getting pneumonia in the future include good medical control of other lung and sinus problems, good hand washing, and not smoking. Pneumovax 23 and Pnu-Immune® 23 are a polyvalent pneumococcal vaccine that can prevent pneumonia caused by 23 pneumococcal strains of bacteria. Getting a flu shot in the autumn of each year may keep you from getting pneumonia as a complication of the flu. Talk with your doctor about these preventative measures. The key is to seek medical care promptly! Please read our Pneumonia MedFact at http://www.nationaljewish.org/medfacts/pneumonia.html for more information.