Straight Talk Tuesday

The 2014 Margolis paper questioned the effectiveness of hyperbaric oxygen therapy for diabetic foot ulcers. There are a lot of ways that “effectiveness” can be defined. Even if it’s not the best way to think about it, let’s consider “cost-effectiveness” because most of us have a vague idea of what that means. When is HBOT NOT cost-effective? I can think of 3 scenarios right off the top of my head: 1) when we provide HBOT to patients who were going to get well anyway (that’s “inappropriate” care because it is unnecessary care), 2) when we provide HBOT to patients who can’t be helped (that “inappropriate” care because it is futile), 3) when we give patients more treatments than they need to achieve the desired benefit (that’s “Excessive” care because it’s wasteful).

So how can we reduce unnecessary HBOT? Let’s start by trying to predict who will get well without HBOT. TCOM is not too bad at doing this (skin perfusion pressure –SPP- may be even better). Because hypoxia is often the final common denominator for wound failure, it is easier to find a value below which a wound will NOT heal than to find a value above which a wound is reliably predicted TO heal. Nevertheless, sea level air TCOM values can be used to separate out the wounds that are not likely to heal spontaneously from the ones that are likely to heal spontaneously. How can we reduce futile HBOT? In-chamber TCOM remains the best single predictor of this. In-chamber TCOM is 75% accurate at predicting benefit from HBOT in DFUs. Among patients with an in-chamber TCOM >200 mmHg, 78.3% benefited from HBOT compared to those with an in-chamber TCOM <100 mmHg. Only 18% of those benefited. There are other things we know. For example, DFU patients with interrupted treatment course had twice the amputation rate. Only 58% of patients with renal failure (RF) received benefit from HBOT, a far worse outcome than non-renal failure patients (p<0.0001). Also, in RF patients, the number of ulcers decreased the likelihood of benefit. Among RF patients with 2 or more ulcers, only 30% improved. I think this raises the question of whether we should provide HBOT to renal failure patients with 2+ ulcers. Sadly, the 5 year survival rate of RF patients after a major amputation is only 14%, so if we fail to salvage their limb, it’s a death sentence.

In 2007 we published a mathematical model that predicted the likelihood of a positive outcome of HBOT for a DFU patient based on the following factors: patient age, years of diabetes, ulcer Wagner grade, air TCOM, and pack/year smoking history. As far as I know it was the first time anyone tried to use modeling to predict benefit from HBOT. At the time there was no interest in this at all, even from private insurance companies. Eight years later it appears that insurers would rather stop treating all patients rather than find a way to identify those who might benefit. I think it’s time to start talking about modeling again. To do that we have to become comfortable with the idea that we are going to be effectively “rationing” scarce resources, but the alternative appears to be to deny treatment to all patients in a category. I grant you that deciding to treat no one is “fair” from a certain perspective, but I’d rather try to help the patients we can. What do you think?

Fife CE, Buyukecakir C, Otto G, et al. The predictive value of transcutaneous oxygen tension measurement in diabetic lower extremity ulcers treated with hyperbaric oxygen therapy: a retrospective analysis of 1144 patients. Wound Rep Regen 2002; 10:198-207.