Thursday, June 18, 2015

Why Digital Pulse?

Why take Digital Pulses? by KC La Pierre

What is the Digital Pulse? Digital in this instance denotes the digit or foot and pulse refers to the pumping of blood through an artery or vein entering or exiting the foot. To be more precise, the digital pulse is taken or referenced at what is called the V.A.N. apparatus. V.A.N. stands for Vein, Artery, and Nerve. V.A.N. describes the physical conformation of the vascular structures located in a specific location on the pastern of the horse.

If you were to place your fingers on the front of the pastern, mid way between the coronary band and the fetlock (ankle), and slowly slide them towards the inside of the pastern, your fingers would slip into a slight hollow. This is the location where you would take the digital pulse.
The digital pulse is a reliable indicator of what is occurring within the vasculature of internal foot, including whether inflammation may be present within the confines of the hoof capsule.
In the normal horse at rest, locating a pulse at the V.A.N apparatus can often be difficult, as it is very faint, this because systolic pressure (arterial blood pressure created by the pumping of the heart) is relatively low in this location. With increased exercise and the accompanying increase in blood pressure, the pulse is more easily felt. This is why you should check digital pulse (DP) before exercise. You are not attempting to identify pulse "rate" but rather "pressure."
The vasculature of the equine foot is unique in several ways: Firstly, the veins within the foot do not have valves in them. Valves within veins prevent back flow of blood through the vein. Secondly, there are no A.V.A.'s (Arterial Vascular Anatomsis) described as  bypasses that allow for blood to be shunted from an artery directly to a vein, bypassing the delicate capillaries. Lacking these features, the vasculature of the foot, lying between the internal foot and the hoof capsule is  readily influenced by changes in circulation.
Changes in circulation can be the result of an increase in blood flow, or by a restriction of flow within the vascular caused by inflammation. It is very important that you determine which of the two may be occurring.
Both cause an increase in pulse at the V.A.N. apparatus. Increased blood flow in most cases is a good thing, whereas inflammation resulting in the inability of the blood to enter the foot correctly is a bad thing. Restriction due to inflammation can result in blood being shunted by A.V.A.'s that are present in the vascular at the coronary band and above. With blood being shunted from the arteries to the veins before it enters the foot,  pressure felt at the V.A.N. is  increased.
It is safe to say that lameness usually accompanies inflammation in the foot. Also, heat will be felt when you rest your hand on the outer hoof wall. If you have an increase in pressure, but there is no heat, or lameness, it is likely that the increase in pressure is related to an increase in blood flow. You should be aware that there is a fine line between increased circulation and inflammation. The cause of vascular dilation and increased circulation can also result in inflammation.
My advice is that you learn how to take your horse Digital Pulse and take the time to observe the pulse each morning before you exercise your horse. Do this for at least a week. I rate DP on a scale of 0/3 with 0 being normal. If I have difficulty finding the pulse it rates a 0. If it is faint it is rated 1, if it is easily felt it rates a 2, and if it is bounding I rate it a 3. You should be checking the pulse when your horse is sound to establish a baseline. If after a week you have found it normal for your horse to have a faint pulse, then faint pulse for your horse would rate 0. This will allow for early detection of changes in the foot's circulation of "your" horse.
Here is how you use your baseline.

0   Normal, no concerns
1   Monitor daily for change, no real change in daily routine.  
2   Horse should not be exercised, and veterinarian should be consulted.    
3   Treat as an emergency; horse should be seen by your attending veterinarian at the earliest possible time.  

I do not always treat immediately for inflammation when I have a 2 or even 3. I first want to determine whether there might be an abscess brewing. Treating for inflammation will hinder the abscess process. Abscesses often have to run their course and anti-inflammatory can stop the process leading to complications down the road. If you are not sure, it is always best to consult your veterinarian.

About the Author: 
Keith "KC" La Pierre APF, RJF, CF, MIAEP has been a farrier for more than 30 years. KC is the co-founder of the Institute of Applied Equine Podiatry. KC teaches and lectures on Applied Equine Podiatry through out the world. KC has developed and introduced dozens of innovative theories, methods, and products that continue to improve the quality of life of the horse. 

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