Last week I told you about the case of a 55 year old man with rest pain and a TCOM of 35mmHg on his anterior leg. Because he had been sleeping in a chair due to rest pain, he had some edema of his leg. In order to know whether a low oximetry value is due to ischemia or edema, you have two options:
- Have the patient breath oxygen. Breathing 100% oxygen from a non-rebreather face mask should increase the TCOM value to >100mmHg. This patient had a TCOM of only 49mmHg when breathing oxygen, so we know that his low baseline TCOM value is due to ischemia.
- Perform a “leg drop test”. In patients with ischemia, the TCOM will increase when you do this. The Leg Drop Test: This is the slight but measureable increase in TCOM when the patient is allowed to hang his leg down.
The Oxygen Challenge Test: This is the increase in TCOM when the patient starts breathing oxygen (the value increases from only 35 to 49 mmHg which is a poor response but the curve shows the small increase.)
The Leg Drop Test: This is the slight but measureable increase in TCOM when the patient is allowed to hang his leg down.
I called the vascular surgeon who had seen him previously and asked for an urgent consultation. The patient decided not to see the vascular surgeon urgently. He returned to clinic 14 days later with acute ischemic changes to the limb, a large area of exposed tendon and severe pain. He was emergently hospitalized for an amputation.