April 12, 2013

Oxygen Treatment May Not Help Foot Ulcers

This was somewhat of a shocker when I received the email mail recently from a reader in Great Britain, and then later finding it in a newsletter. I have been following several news outlets about hyperbaric oxygen therapy for different types of topics, but had not seen this coming. I will admit at first I did not believe it and had to read it several times. I appreciate the reader for having alerted me to this as I may have missed this study otherwise.

Reuters Health reported this and I will attempt to analyze the study for materials not in the press release. The results of this study do call into question results of previous studies, but this study seems to vary and be about foot ulcers only. The prior studies were more centered on wounds and skin problems in areas above the ankle. This is a distinction that may or may not be valid, but still needs to be evaluated. Dr. Stephen Thom, a professor at the Perelman School of Medicine in Philadelphia was very realistic in his analysis and how this needs to be reviewed to see what differences there are.

Please note that HBO (hyperbaric oxygen) and HBOT (hyperbaric oxygen therapy) are usable interchangeably, although HBO may not be as rigorous in its application. This possible variable needs to be explored. The study authors did state that further study is needed to understand the current results and the effects of oxygen treatments. They are also concerned that the people chosen from the National Healing Corporation (NHC) may have had more severe problems although they tried to compensate for that.

Covariates are a continuous control variable that is observed rather than manipulated, but can affect the outcome included age, sex, wound duration at enrollment, wound size at enrollment, Wagner grade, number of wounds on the patient, wound location, history of neuropathy, history of wound recurrence, and history of osteomyelitisor abscess. Osteomyelitis is an infectious, usually painful inflammatory disease of bone that is often of bacterial origin and may result in death of bone tissue.

To minimize bias the researchers used a PS approach. The propensity score (PS) is the conditional probability of assignment to a particular treatment given a vector of observed covariates. This allowed the researchers to achieve balance on observed covariates between treatment groups so that the treatment groups were more comparable. The PS provides a summary value for the potential measured confounders.

The PS represents a summary value of the potential covariates for each patient and is defined, regardless of the actual treatment choice, as the probability that each patient would receive the treatment of interest given the background covariates of that subject. The PS model was used to balance a number of baseline covariates such as age, sex, wound age, wound size, Wagner wound grade = 2, the number of wounds on the patient, history of neuropathy, history of wound recurrence, and history of osteomyelitis or abscess. Importantly, wound age, wound size, and Wagner wound grade = 2 at first visit are highly predictive of the likelihood that a subject will heal and has been used in other PS studies of wound therapies.

Wagner Grading System for Diabetic Foot Infections is the following:
- 0 - Intact Skin
- 1 - Superficial ulcer of skin or subcutaneous tissue
- 2 - Ulcers extend into tendon, bone, or capsule
- 3 - Deep ulcer with osteomyelitis, or abscess
- 4 - Gangrene of toes or forefoot
- 5 - Midfoot or hindfoot gangrene
This study does point out how important it is to have our feet examined on a regular basis to head off problems before they get to this stage. I hope that this study is not reflective of other problems we may encounter with hyperbaric oxygen therapy in the future. I will be looking for more studies to see if there are further problems, or if it is the foot ulcers that are the problem.

For a past blog on hyperbaric oxygen therapy, read my blog here. 

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