Thanks for your question on Health Care Magic.
I can understand your concern.
Normal
oxygen saturation of body is more than 95%. So 66% saturation is considered as very low.
Pneumonia is common cause for low oxygen saturation.
Pneumonia if uncontrolled and extensive can cause collapse, consolidation and
pleural effusion.
All these causes non functioning of involved lung.
So oxygenation (main function of lungs) is hampered.
This is having poor prognosis. Body can not sustained for long time with this much low oxygen level.
After sometimes
kidney, heart and brain start loosing their functions due to low oxygen saturation.
So his condition is extremely serious. Prognosis in such cases is very poor.
So discuss with your doctor and start vigorous treatment to control pneumonia.
Hope I have solved your query.
Wishing good health to your husband. Thanks.