Is your husband injecting or taking meds for his diabetes? How low is his blood sugar readings after meals? I'm betting that he needs an intervention at perhaps the emergency room if his blood sugar is low. Low blood sugar affects every organ of the body. The O2 readings you report would concern me very much, and I'd suggest going to an emergency facility as soon as possible.
Recently I was hospitalized for surgery to my stomach, and my blood sugar levels fell, followed by my by blood pressure (much lower than what you report), and my O2 level dropped into the high 80% areas. Once my blood sugar was stabalized and my meds for CHF were adjusted, everything came back to acceptable levels.
I'd suggest your husband be checked as soon as possible. Do keep us informed.
I was hospitalized with congested heart failure, and I was in the ICU for several days and involved was removing the fluids for the lungs and stabilizing the oxygen level. Normal oxygen level for me at the time of my hospital discharge was in the low 90's which is not a medical problem.
If the level of oxygen in an individual's body is too low, mild to severe complications can occur. The person may experience fatigue and have a grayish blue skin hue. The primary symptom of low oxygen, however, is shortness of breath. This may be accompanied by dizziness, fainting or disorientation.
Your husband should seek medical attention for the low oxygen level and treatment for a weak heart. Hope this helps, and if you have any further questions you are welcome to respond. Take care.