Professor Peter Vowden

I'm Peter Vowden. I'm a consultant vascular surgeon in Bradford. I also hold an honorary chair at the University of Bradford looking at wound care and wound care research. I've been a consultant now for 21 years. We've got a large hospital-based wound care clinic that my wife runs that looks after both venous and arterial ulcers and we have a shared diabetic foot clinic we run with podiatrists. If you take a patient who has venous disease, the basic problem is that the venous pressure at the ankle remains elevated and that has a long-term effect on the capillary circulation. The cause of the venous disease can either be after a deep vein thrombosis or because of simple superficial venous disease. The net result is basically the same, and that is something called chronic venous hypertension. That has an effect on blood flow. The capillary blood flow is slowed because the outflow resistance to the circulation is higher, and that results in relative stasis. The secondary effect is the development of edema. The other effects that occur are extravasation of protein-rich exudate into the tissues and that was the original theory about the cuffing of capillaries and the effect that had on oxygen transfer. We now know that in addition to that there is relative activation of white cells and migration of activated white cells into the tissue, and that in itself causes problems by activating an inflammatory response. So the overall result is a decrease in capillary density, a restriction in capillary blood flow, an exaggerated inflammatory process, and this in turn leads to a reduced tissue oxygen level. And if we look at some of the original work done, for instance, by Stacy, they were able to show there that tissue oxygen levels were reduced in the skin of the lower leg, and that that could be corrected by applying compression, which alleviated some of the problems with edema and improved the rate of capillary blood flow. So it's a complex theory, but what it does is to result in extravasation of red cells, gives you the staining, an inflammatory process which gives you the symptoms of varicose eczema, weakening of the skin so that relatively minor trauma can lead to damage which can then propagate itself into what we recognise as a venous leg ulcer. We've learnt a lot about the endovenous treatment of varicose veins. So nowadays we have three separate methods of treating, what in fact four, we've got basic compression, giving people hosiery, will increase venous return and provide some protection in terms of recurrent venous ulceration. We know that we can treat venous disease surgically and we've done that for years, but that is an operation and clearly some of the patients who have venous leg ulcers are elderly and not necessarily fit for an operation. Recently we've been able to treat venous disease by carrying out endovenous ablation and there are a number of different techniques but basically we seal the incompetent vein and valve which prevents the increase in venous pressure at the ankle and allows the skin to recover to a degree and reduce the risk of ulceration. We can also do that by something called foam sclerotherapy which is an advancement in the way that we do the old-fashioned treatment of injecting varicose veins. How do you select the patients? Well, anybody that has superficial venous disease and an intact deep venous system is undoubtedly suitable for some form of corrective venous surgery. In addition, not all the patients who have got an element of deep venous disease should be excluded from some of the benefits of very localised venous surgery. So you may be able to treat a localised perforator vein, even in somebody who has had a deep vein thrombosis. But the more complex the deep venous disease, the more difficult it is to select patients for venous surgery. And that's why ultrasound duplex examination of the venous system is very important for patients who have venous leg ulceration and why the recently published Royal Society of Medicine guidelines, for instance, have suggested early referral for all patients with skin damage related to venous disease so that they can be screened by a vascular surgeon for their suitability for venous intervention. I think it's very important to have some measure of peripheral vascular function before you start applying compression and it is one of the components you need to take into consideration when you're diagnosing what type of venous leg ulcer it is. Certainly if you have poor perfusion, whether you measure that by Doppler, by tissue oxygen levels, by toe pressures, then you will get poor wound healing and that applies whether it's a diabetic foot ulcer, whether it's a venous ulcer. The method that you use is more important if you are planning to apply compression. The reason for that is that Doppler gives you an overall measure of limb blood pressures. It doesn't give you a compartment measure and if you recall your anatomy there are three arteries that reach the ankle. Doppler just takes the pressure in the best one. That doesn't mean to say that perfusion is adequate in all areas. So you can measure the ankle-bacal pressure index very easily using an automated system and in fact we use that as our routine screening test but for some patients you must still be prepared to selectively measure the blood pressure in all the vessels if you're going to get a true measure of their lower limb perfusion. Now clearly for a 20 year old patient who's got a venous leg ulcer that is less important than it is for an 80 year old patient who's got a history that would suggest claudication who also has a venous leg ulcer. The fact is as soon as the patient starts to mobilise their calf muscle activity is far greater than any compression you're going to get from measuring the blood pressure at their ankle. My general rule is that by two weeks it is safe to do a Doppler. It is probably safe before then. Certainly these patients will benefit from compression, particularly in the early phases after their deep vein thrombosis, and those patients with an extensive deep vein thrombosis you may well need to plan life long for use of compression hosiery. Those patients clearly will need repeat testing on a regular basis if they fall into that elderly group that I described earlier. Vascular calcification tends to occur more in the medium sized arteries than in the very small digital vessels. The reason for that is probably related to the variation in tissue within the arterial wall and there isn't as much tissue that would attract calcium in the smaller vessels. You do get a more accurate representation by measuring toe pressure. Toe pressures do not however tell you what's happening to those vessels in the calf. So it's a very good measure in a diabetic where most of the ulcers are on the foot and therefore the foot is a relevant area. It's not necessarily the best measure when you're wanting to treat a venous leg ulcer on the calf where you may be more concerned about the perfusion in say the anterior compartment of the leg rather than what's going on in the foot.