ASK THE EXPERT: DR. JEFFREY NIEZGODA
ASK THE EXPERT
Dr. Jeffrey Alan Niezgoda, MD, FACHM, MAPWCA, CHWS, is dedicated to excellence in wound, vascular, and regenerative clinical services as the founder and President Emeritus of AZH Wound & Hyperbaric Medicine. He is the President & CMO of WebCME, an international educational company providing wound care and hyperbaric education. Dr. Niezgoda is the President of the American Professional Wound Care Association and Past-President of the American College of Hyperbaric Medicine.
Can you discuss how you use the oxygenation information from SnapshotNIR to change or confirm your clinical decision-making?
Prior to having near-infrared spectroscopy (NIRS) in the SnapshotNIR device, a lot of decision-making was based on direct observations of the tissues over time. We didn't have the ability to look minute-to-minute, or after a certain treatment modality was implemented, whether there was any impact on the tissues.
The way that I've been using SnapshotNIR clinically, for assessment of tissue oxygenation, is on an almost instantaneous basis to see how the patient is responding to the therapies, like hyperbaric oxygen treatment, for example. I obtain a pre-treatment image and then a post-treatment image and can compare the oxygenation of that tissue. It's very helpful in using that to determine whether the patient has had a response. Years ago, all we had was a TCOM evaluation which was a very laborious and challenging process because it took a lot of extra time to get the electrode and the chamber wired. Additionally, you just had that single focal electrode that was measuring and giving feedback, so, if you were in an area of inflammation, an area of edema, or in an angiosome that wasn't well perfused, you would get a reading that wasn't necessarily accurate of the global tissue change that was happening in the extremity around that wound. Now, with SnapshotNIR, we can bring the patient into the hyperbaric chamber, capture a picture and look at those pre- and post-treatment images to review the extent of the tissue oxygenation that occurred following treatment.
That has been very, very helpful in determining whether the patient is responding, and even more, we now have preliminary data to suggest that those changes can be predictive of future outcomes. In other words, if the patient oxygenates diffusely in that area with very high values, that does tend to predict a very good outcome.
We have also been using SnapshotNIR to assess the oxygenation of other interventions in the clinic in addition to HBOT. We use a lot of ultrasound debridement in the clinic, and we use the NIRS device to check the outcomes of tissue oxygenation and the response to the ultrasound. We can see that therapy stimulation results in increased oxygenation following an ultrasonic debridement.
Finally, another modality that we've been using in the clinic is shockwave treatment. The various shockwave devices we use have been shown to have a direct impact on the tissue, the sub-wound vessels, and the sub-wound tissues. We've noticed that some of these therapies can augment tissue oxygenation following treatment and SnapshotNIR is an ideal point-of-care tool to assess that. We look at the changes in tissue oxygenation over time and it's very helpful to be able to do that on a day-to-day, treatment-by-treatment, and minute-by-minute basis to measure the changes and the response of the tissue to the various treatments we administer.
What is your opinion on using SnapshotNIR versus TCOM?
Using TCOM, you’re obtaining a localized single-point estimate of oxygenation of the tissue. SnapshotNIR measures tissue oxygenation and perfusion but provides an evaluation of the entire wound and peri-wound region. The image and data is much more expansive. There are certainly pros and cons for both TCOM and SnapshotNIR, but if you look at the scorecard comparing the two devices, SnapshotNIR wins hands down. There are many drawbacks to using transcutaneous oximetry which makes TCOM an outdated and inferior tool when compared to SnapshotNIR.
TCOM only provides a discrete single electrode analysis of tissue oxygenation. You can certainly use three or four leads around the wound, depending on the type of TCOM device, but you're still only getting a single value from each lead. We know that the single TCOM lead readings and values can be inaccurate in demonstrating what is actually happening in the tissues because of various physiological and patient factors. For example, if a patient has a cigarette prior to the TCOM exam, that could throw the values off. If the patient has an infection in the area, or edema or inflammation, that can provide inaccurate readings. If the patient’s extremity is cold, the readings can be impacted. These are drawbacks when performing a TCOM test. Additionally, the testing also requires an experienced and trained technician to administer it properly and in an exact fashion to obtain the most accurate answers, and even then, several things out of our control, as I have mentioned, can impact or influence the readings.
Alternatively, SnapshotNIR is very quick and easy to use. Just about anyone can be trained to take Snapshot images and interpret the entire image or area of capture. When looking at a diabetic foot ulcer, for example, we can capture the entire foot and even the distal extremity in the image. It provides a global view of that tissue which is much more valuable clinically than a single focal point. SnapshotNIR does not appear to have the same technical and physiologic limitations as TCOM. That is a significant difference and advantage.
Other than research purposes, we have not done TCOM testing or evaluation in our center for about three years. SnapshotNIR has replaced TCOM in our center and I think that this is also happening at many other centers. I believe that SnapshotNIR has great potential to become the TCOM replacement or the preferred alternative to transcutaneous oximetry across the globe. The information is much more robust with SnapshotNIR and clinically useful. Tissue assessment with TCOM has been compared to SnapshotNIR in several studies and the comparison of data obtained correlates very well. We've also done research in comparing these devices and agree that the comparison is very favorable.
How do you use the hemoglobin view on SnapshotNIR? Especially the deoxyhemoglobin and the oxyhemoglobin? What does that mean to you clinically when you're using those?
We've been using the hemoglobin view largely for research purposes, attempting to determine how it can complement our clinical evaluation of the patient. We find that those values are helpful, especially when patients have venous congestion syndromes due to venous insufficiency with a stagnation of blood in the leg, or in patients with edema and swelling due to lymphedema. Venous insufficiency and lymphedema present together very often clinically. We are finding that when we treat those patients with either an aggressive lymphedema decongestion program or good venous insufficiency management, we can improve the swelling and edema in the leg. This appears to correlate with improved hemoglobin numbers. I think that the HGB view on SnapshotNIR, both oxygenated and deoxygenated hemoglobin, helps us to evaluate and monitor improvements and trends over time and the response to the venous or lymphatic therapy.
These are interesting initial observations because, until SnapshotNIR, we had no way of imaging these patients. We could certainly measure limb growth and look at the amount of fluid remaining in the tissue but we had no way to look deeper into the tissues and determine how venous congestion and edema were impacting the patient. There is still a lot of work to be done in this area to really determine how valuable this hemoglobin view tool will be and what parameters we should use in evaluating these patients, however, I think SnapshotNIR will be more commonly used in the area of venous and lymphedema management as we gain more information.
Does SnapshotNIR meet an unmet need as far as assessing microvascular versus macrovascular?
SnapshotNIR does a nice job of giving you a good assessment of the microvasculature and the subdermal tissue oxygenation especially at the wound site or in the peri-wound region that exists in a patient. If you look at the gold standards for evaluating macro vessel disease, like ABI, duplex ultrasound, or angiography, when these are combined with SnapshotNIR, you have a much clearer and broader picture of the patient’s overall arterial status. Working together, these technologies create a synergy in looking at the macro and microvessels and providing a much clearer picture of the angiosomal and tissue oxygenation that is occurring in that extremity.
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