Op/Ed: Video Endoscopy Not All Black and White

[Wandering Eyes]

Piet Ramzan BVsc FRCVS, a partner at Rossdales in Newmarket, offers a veterinary perspective on the recent debate regarding scoping sales yearlings.

There has been considerable recent interest in the use of videoendoscopy of the upper airway at public auctions, and in particular expansion of this practice to the U.S. from Europe and Australia, where it has been available for some time. As with many aspects of vettings a broad range of opinions exists, however much of the current commentary would lead the casual observer to conclude that videoendoscopy is just a technological advance that irons out the main problem areas of the scoping process for all stakeholders. Unfortunately, as it is the equine throat we are dealing with, things are not quite so black and white. Given that we have now had quite a lot of experience with sales videoendoscopy in all its manifestations, how should we view the main points in the debate?

Convenience

Without doubt videoendoscopy can streamline the vetting process for examining vets and consignors alike if a repository system is mandated by the sales company (or is at least well supported by vendors), and if videos are of good quality. That convenience factor is readily lost if videos are held by the consignor on memory sticks instead of in the repository: it is often more expedient to physically scope an animal than to return to a viewing screen or wait for a missing stick.

Video Quality

A good video recording must allow observation of the throat through a full range of movements from total relaxation to full opening stimulated by swallowing or nasal occlusion. Assessing upper airway function can be complex as many throats go through transient periods of appearing to be reasonably symmetric, and other periods of relative weakness. The chances of arriving at a laryngeal grading that is fair to the horse are improved with longer observation, and appropriate levels of stimulation/occlusion. Although the general standard of videos has been improving over the years, there is still great variability in quality at any given auction; even the nostril used for passing the scope (something that can influence appearance of the larynx) can vary between veterinarians. In some parts of the world (notably Australia) it is not uncommon to be presented with extremely short videos (sometimes less than 10 seconds’ duration). Combined with suboptimal viewing conditions (ie. on a smartphone) it is difficult to imagine that opinions given on the suitability of such horses for purchase could be defended successfully in the event of any subsequent litigation. Although some loose guidelines exist for videoendoscopy standards, there is a great need for industry-wide protocols that set out clear benchmarks for horse identification, recording length, number of stimulated swallows and use of nasal occlusion to induce prolonged laryngeal opening.

Variability in Laryngeal Grade

The pet hate of consignors is the variation in laryngeal grading that can occur between vets for the same horse, and that a ‘bad’ scope grade from a single vet might get around the sales complex. How can the same horse pass for one vet and fail for another? As it turns out, very easily. Aside from the obvious (technique and human fallibility), a myriad of horse-related factors can be responsible for the appearance of a throat differing between examinations, including level of stimulation, upper airway inflammation, freshness/tiredness of yearling, and use of sedatives.

Videoendoscopy can eliminate many of these variables as everyone views the same ‘snapshot in time’ of a throat from a single, controlled recording. Consignors might then go on to presume that by putting a video into the public sphere they will have solved the problem of vets giving differing opinions on a throat to their clients. Unfortunately the inherent subjectivity that comes with human observation of a dynamic structure applies just as much to viewing of videos as it does to physically scoping a horse. Indeed, a couple of scientific studies have looked into variation in grade between different vets when viewing videos of the same horses (‘inter-observer’ variation), as well as variation in grade given by the same vets (‘intra-observer’ variation) when viewing the same videos on two different occasions. In both situations substantial individual subjectivity occurs: average agreement in grade between observers is only around 62-63%, with the ‘borderline’ laryngeal grades that we all agonise over (Havemeyer grade II.2/ Lane grade 3) showing some of the lowest concordance between vets. Based on the current evidence the odds of two different vets agreeing on the grade of one of these ‘borderline’ throats are only marginally better than tossing a coin. One suspects that if these studies were replicated in a Thoroughbred sales setting, agreement between vets would be better (because sales vets are much more closely ‘calibrated’ to each other) but the fact remains that videoendoscopy does not eliminate differences in opinions over individual throats.

It is not all bad news, however, as the majority (roughly 80%) of yearlings have throat grades that we consider to represent good function: for these horses it is not at all important whether vets agree on precise grading. It is the smaller (probably around 5-10% of yearlings) group of potentially borderline throats that cause the majority of headaches, as these are the horses that straddle the pass/fail red line. Every potential purchaser has a different perception of the risk posed by such throats: a pinhooker or Hong Kong buyer is likely to be much more risk-averse than someone with a large purchase order for training clients. Some buyers even seek advantage in a competitive marketplace by getting a trusted veterinary opinion on a weak throat that might have scared away others. Hence vets will always have a range of opinions on whether a video as standalone evidence gives them enough information to make a recommendation to their client/s. Many of us consider that videos are greatly inferior to physical scoping for assessing the less-than-perfect throat.

Does videoendoscopy always give a fair representation of true upper airway function?

A big concern of prospective purchasers in the video debate is whether the videoendoscopy process can be manipulated to be favourable to the vendor in the case of horses with poor/borderline upper airway function. The most obvious issue here is true identification of the animal, but whilever consignor and veterinary codes of ethical conduct hold sway this needn’t trouble anybody too much: if the video is an unbroken/unedited recording of the horse, microchip and passing of the endoscope up the nostril, there is little room for deception. On the broader topic of ‘showing a throat off in the best possible light’, however, there is no question that this can be, and is, done regularly; indeed if you are the consignor’s vet you could take the view that presenting the horse in the most saleable condition is part of your job. While it is fair to say that a paralysed larynx cannot be made to look ‘normal’, there are several tricks of the trade that can permit the borderline/weaker grades (that would normally scare off potential purchasers) to appear satisfactory on a video. These range from simply performing the videoendoscopy post-exercise or with some form of stimulation (eg twitching), recording short clips, to more nuanced refinements such as placement of the scope tip to get a ‘favourable’ field of view, or not permitting the arytenoid cartilage to relax fully (by repeatedly stimulating a swallow reflex). At every major auction, horses which have arrived with videos showing perfectly satisfactory throats are subsequently found after fall of hammer to be returnable under the conditions of sale pertaining to wind, and the only conclusion one can draw is that in most cases these animals had weak throats all along that were not truly represented (by design or otherwise) by their videos.

An aspect of this issue that may surprise many consignors is that we regularly encounter videos that show off a horse’s laryngeal function in a poorer light than should be the case. Normal throats can sometimes appear weak at rest or during certain periods of the video, and without the benefit of adequate occlusion of the nostrils it is possible to conclude that ‘without further evidence it is likely that the horse has a weak larynx’. If the examining vet has the time and inclination to go back to the consignor and perform a rescope (and is permitted to do so), often these horses are found to be entirely normal. Clearly the great danger to the consignor is that if vets are too busy or can’t be bothered to rescope (or if the consignor refuses permission), and just report to clients that they suspect a weak throat, that these horses get bypassed by buyers for no reason whatsoever other than a substandard video. A poorly acquired video can undersell a horse just as readily as a shrewdly acquired one can ‘upgrade’ a throat.

Does videoendoscopy eliminate the need for physical scoping at the sales?

As most horses have straightforward throats, and assuming that the quality of most videos is satisfactory, the use of videoendoscopy can greatly reduce the need for physical scoping at the sales complex. However the inherent variability in appearance of ‘borderline’ throats, lapses in video quality, and the different demands placed on vets by their respective clients make it inevitable that a proportion of horses will need to be physically scoped to allow the most accurate assessment of a throat. Anecdotally our team estimates that somewhere around 1 in every 10 to 15 videos needs a rescope.

Is repeated scoping of horses a welfare issue?

Consignors sometimes invoke repetitive scoping as a welfare issue (the term ‘inhumane’ has even been used irresponsibly by some) when making the case for videoendoscopy. In my view this needs a strident rebuttal, not least because of the implication that vets (whose entire vocation is the betterment of equine welfare) are actively undertaking procedures that harm horses. The yearling Thoroughbred is generally an incredibly well handled and compliant animal, and the vast majority tolerate endoscopy with no or minimal restraint. More resistance can be encountered palpating testicles than from running an endoscope up a nostril. In the UK it is common practice for endoscopy to be performed without using a nasal twitch, with no evidence that this is unsafe for either horse or handler/vet. Clearly as with blood sampling, shoeing etc a small number of horses are difficult to scope, however they typically make this known on the first or second attempt: it is simply not the case that repeated battles are fought with non-compliant horses at the sales, as consignors and vets would not tolerate the risk to horse or personnel. If a consignor warns that the horse is difficult, accepted practice is to either communicate with the vet who ‘successfully’ scoped the horse previously or undertake a wind test, rather than trying to repeat an unpleasant experience for horse and vet. There is no evidence that repeat scoping causes any harm to horses, and one suspects that the use of this argument actually has more to do with consignors’ general desire to have control over veterinary information about their horses.

To conclude, while videoendoscopy is a useful tool, it is not a flawless modality and certainly does not eliminate the problem of vets disagreeing on assessment of laryngeal function. Horses with apparently ‘good’ throats pre-sale continue to fail post-sale wind-tests, and horses with ‘bad’ throats continue to embarrass vets by going on to have notable racing careers. We should all respect the fact that pre-sale endoscopy has inherent flaws and while videoendoscopy offers some advantages of convenience it can also misrepresent the true upper airway function of some horses. Consignors should accept that regardless of the quality of videos that they put up for public view there will always be a proportion of horses that examining vets will wish to rescope, either because of concerns arising from the video recording or because of the specific demands of prospective purchasers: granting permission for these repeat scopes is almost always in their best interest.

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