RESPIRATORY ENDOSCOPY AT REST

Endoscopy is an examination which allows to visualise the inside of the airways: the nasal cavities, ethmoid, the pharynx and the larynx that make up the throat. Muscles support the walls of the horse’s throat: the contraction of these muscles is the only way to maintain the throat open and dilated during exercise.

Instability of the pharynx or larynx can lead to an obstruction of the airways and disrupt the horse's breathing. These dynamic obstructions may generate a respiratory noise or decreased performances. It is advisable to include a respiratory endoscopy during a prepurchase examination.

Horses have an anatomical peculiarity in their respiratory tract : guttural pouches. These are two air-filled pouches located on each site of the throat. They can be the site of bacterial or fungal proliferation. Large vessels (including carotid arteries) and important nerves run in the walls of these pouches. Thus any disorder of the guttural pouches can have serious consequences on the horse’s health. Guttural pouches can be explored by endoscopy.

Beyond the larynx, the trachea and the first bronchi may be seen. An endoscopic exam can help determine if locate if there is mucus in the trachea, a sign of inflammation, or traces of blood, a sign of pulmonary haemorrhage. 

When is an airway endoscopy indicated? 

It is recommended to perform a respiratory endoscopy whenever the horse presents symptoms like cough or nasal discharge, breathlessness or a respiratory noise at rest or during work, difficulties in breathing or bleeding from one or the two nostrils.

During the endoscopic exam, it is possible to sample secretions present in the trachea and submit them to analysis. 

How is a resting endoscopy done?

It is preferable to do this examination without sedation, as sedation can alter the function of the mobile structures in the pharynx or larynx.

The endoscope is introduced in one of the nasal passages and the anatomical structures, from the nostrils to the larynx (or beyond) are carefully and systematically inspected. 

This examination is generally well tolerated by horses; even it might induce a bit of coughing. 

ENDOSCOPY RESPIRATORY DURING EXERCISE

With overground endoscopy, a horse's airways can be examined during work, under normal conditions. This technique has revolutionised our way to diagnose and treat upper airway conditions!

Dynamic airway obstructions are impossible to detect at rest. Recreating normal working conditions is essential to establish an accurate diagnosis. 

When is an exercising endoscopy indicated? 

Overground dynamic endoscopy is recommended in horses that produce a respiratory noise during exercise. It can also be indicated in horses presenting with unexplained underperformance, cough, abnormal breathing or reluctance to work with head flexion. 

NEWS: Emmanuelle Van Erck has just published an article in the Equine Veterinary Journal(2011) mentioning 129 racehorses cases examined with a DRS. This study shows for the first time the significant influence that a horseman and his riding on the morphology and stability of the respiratory upper airways.

How is an exercising endoscopic examination done?

An appointment is taken at the stables. Ideally, the horse should be examined, ridden by his usual rider. For a racehorse or an eventer, the examination should be done on a safe track that allows reaching high speeds. For sport horses, an indoor or outdoor arena is sufficient.

The horse is prepared as usual; a special saddle pad holding the equipment replaces the usual saddle pad. The endoscope is introduced into the upper airways through a nostril and stays fixed during the exam. During the exercise, it is possible to visualise the upper airways live, by telemetric transmission. Even if the signal is temporarily interrupted, the whole exam sequence is systematically recorded on the horse.

The video sequence can be engraved on DVD or e-mailed to the owner or to the referring veterinarian or surgeon. 

RESPIRATORY FUNCTION TEST

A test of respiratory function allows to determine if the horse has disturbances of his breathing or respiratory capacity, if ventilation is impeded, if the horse presents bronchial spasm or hyper-reactivity or if the quality of the lung tissue is altered. 

After treatment of a respiratory disease, a respiratory function test allows to determine if the horse has correctly recovered, if the treatment should be continued or if there are irreversible lesions.

How is a respiratory function test done?

The technique used is called IOS or Impulse oscillometry system. The IOS is a non-invasive technique based on the propagation of short pressure impulses in the respiratory tree. 

A mask is placed on the horse's nose and an amplifier generates the impulses. The horse breathes totally normally during the examination, which lasts only about thirty seconds. 

THORACIC ULTRASONOGRAPHY 

In case a respiratory problem is suspected, lung ultrasonography is an easy exam than can be performed either in a clinic or at the stables. It enables us to explore the lung surface (pleura) in order to detect possible irregularities or abscesses. To complete this exam, thoracic radiographs are sometimes needed to explore the whole thickness of the lungs.

How is this exam performed? 

Hair is clipped if needed over the thorax and alcohol or water and coupling gel is applied for the contact. The horse does not need to be sedated. 

SAMPLING OF RESPIRATORY FLUIDS (TRACHEAL WASH AND BRONCHOALVEOLAR LAVAGE)

In case an inflammatory or infectious problem is suspected in the respiratory system, sampling of respiratory fluids helps confirm the diagnosis and identify the bacteria and which antibiotic to use. 

How is this exam performed? 

For the tracheal wash, the horse is sedated and an endoscope is inserted into the nostril to the trachea. A small catheter is introduced passed through the endoscope and a few millilitres of sterile saline in instilled into the trachea and then aspirated. The procedure is similar for the bronchoalveolar lavage except this time we use and long flexible tube that is inserted into the bronchi to sample alveolar cells. Samples are sent to the lab for analysis. P