READERS may be aware that earlier this year there was a debate within the BHA on whether wind operations should be publicly announced at race declaration stage. This issue has been raised in the past but the idea of declaring such procedures in the same way as headgear or tongue-ties was shelved. However, in light of some recent high-profile winners having had wind operations, the issue has arisen again.

Here I will discuss some of the different types of conditions affecting the horses’ upper airway system and the operations routinely performed in attempting to correct them.

For a racehorse to perform to its maximum capabilities, it is essential to deliver a huge volume of air to its lungs. This air oxygenates the blood which, in turn, is pumped around the body to supply the muscles. Any condition which reduces the diameter of the horse’s upper airway will in turn reduce the amount of air getting to the lungs and the end result is a racehorse which cannot perform to its maximum capacity.

The two most common structures in the upper airway system which malfunction and so reduce airflow to the lungs are the soft palate and the larynx. In a normal horse, these two structures work in unison to control breathing and swallowing. The soft palate is a long thin piece of tissue which divides the pharynx into the nasopharynx (part of the back of the nose) and the oropharynx (part of the mouth).

The larynx is made up of a number of cartilages. Of these cartilages, the arytenoid cartilages and epiglottis are important during swallowing as they coordinate to prevent food and water being inhaled instead of swallowed. During swallowing, the arytenoid cartilages close and the epiglottis flips upward to occlude the opening of the trachea while at the same time the soft palate moves upwards to allow feed material to move from the mouth to the oesophagus.

During strenuous exercise, the nasopharnynx dilates and the arytenoid cartilages open maximally to allow as much airflow as possible. During exercise, it is crucial that the soft palate remains under the epiglottis so that the air is directed into the trachea and lungs.

DISPLACEMENT OF THE SOFT PALATE

When the soft palate displaces above the epiglottis at racing speeds, it blocks off the opening to the trachea and in doing so dramatically reduces the amount of air getting to the lungs. The cause of soft palate displacement is not fully known but it is believed to be a result of numerous factors, some of these being inflammation of the airway, anatomical abnormalities, nerve dysfunction and backwards movement of the larynx.

A horse which is displacing its soft palate will make a classical gurgling noise when the palate displaces at high-speed exercise. Overground endoscopy is now the gold standard diagnostic tool in diagnosing displacement of the soft palate as the airway can be visualised at peak exercise.

A conservative approach should be taken initialling in treating soft palate displacement. Airway inflammation should be treated medically and modifications made to tack either with the introduction of a spoon bit or tongue-tie. In our experience, particularly in young horses, this is a condition which will often resolve itself with minor adjustments in tack and treatment of underlying inflammatory conditions. A lot of young horses simply mature and ‘grow out of it’. For those horses that don’t fit into this category, there are numerous surgical options available, which in itself may suggest that none of them are particularly effective.

The two most common procedures are cautery of the soft palate and a laryngeal tie-forward.

Soft palate cautery involves scarring the soft palate with a laser or heated iron. Scarring the soft palate causes fibrosis and the palate to stiffen. This then makes the soft palate less likely to flip up during exercise.

The second procedure which is commonly performed is a laryngeal tie-forward. This is quite an invasive procedure which requires the horse undergoing a general anaesthetic. The aim of the procedure is to permanently fix the larynx in a forward position, allowing more cover of the soft palate and in doing so making displacement less likely. A soft palate cautery is often performed in conjunction with the tie forward procedure.

The reported success rates of this surgery vary but my opinion, based on our experience of monitoring horses’ airways over the course of their training careers, is a lot of the reported surgical success stories may well have got better and improved without the need for surgical intervention.

LARYNGEAL HEMIPLAGIA

As mentioned above, the larynx consists of two arytenoid cartilages which open when the horse needs air and close when swallowing to protect the trachea. Laryngeal hemiplagia is a condition where the one of the arytenoid cartilages (most commonly the left side) and vocal fold lose nervous innervations resulting in impaired movement. This tends to be a progressive condition with the end result often being complete paralysis of one side of the larynx.

In affected horses, the arytenoid cartilage and vocal cord is pulled into the airway when the horses inhales and obstructs the airflow hence significantly reducing the volume of air to the lungs. These horses will make a very distinctive ‘whistling’ noise at strenuous exercise created by the obstruction in airflow through the larynx.

The chosen surgical treatment will depend on the degree of paralysis present. In moderately severe cases where the larynx is affected but not completely paralysed, it may help to do a ‘Hobday’ operation. In the ‘Hobday’ procedure, the laryngeal ventricles and vocal cord are removed surgically to encourage scarring. The scar tissue acts to stabilise the area and prevents the vibrations in the larynx hence reducing or removing the noise.

In more severe cases of complete laryngeal paralysis, then a ‘tie-back’ operation is performed. A ‘tie-back’ procedure involves placing sutures in the left arytenoid cartilage to permanently abduct it in a fixed position out of the airway. This surgery is a relatively invasive procedure requiring the horse to undergo a general anaesthetic. There are also postoperative considerations. With the artytenoid cartilage on the affected side being permanently open, it cannot protect the trachea from inhaling food so the horse must be fed from the ground indefinitely to minimise this risk.

Although this option may sound like an effective treatment by permanently abducting the artyenoid cartilage, the reality is the success rates of the surgery in racehorses is around 50% at best.

This is by no means an exhaustive list of the surgical procedures routinely performed on racehorses’ upper airways. However this short list highlights that the term wind operation is a very loose term which can refer to a multitude of procedures, some of which have relatively low success rates and questionable benefits to the horse’s athletic performance.

John Martin from Stradbally, Co Laois, graduated from University College Dublin and is in practice at Mark Johnston Racing. This article first appeared in the Kingsley Klarion, published by Mark Johnston Racing.

Hands On writer Liz O’Flynn

on leave

After five years of writing our weekly article on veterinary matters our popular columnist Liz O’Flynn is taking a temporary break from Hands On. Liz would like to thank her readers for all their letters and requests and notes of appreciation of her articles over this period and hopes to return in the not too distant future.