Dynamic Respiratory Endoscopic Examination


Galloping-TB.jpgDynamic respiratory endoscopy (DRE) or dynamic overground endoscopy (DOE) is an exciting technology that has made substantial improvements in our ability to accurately diagnose, and subsequently treat, upper respiratory disorders in horses exercising under their normal environmental conditions.


DRE/DOE is indicated in horses with upper airway disorders, abnormal noise production during exercise, exercise intolerance, and poor performance.


Dynamic obstructions of the upper respiratory tract often times only occur during high-speed and intense exercise. As a result, these transient events are likely under diagnosed or misdiagnosed by resting endoscopic examination alone. Until recently, exercising endoscopic examination of the upper respiratory tract in horses was only available via high speed treadmill examination. However, with the advent of DRE/DOE, endoscopic examination of horses in their normal exercising conditions and in their natural environment is now possible.  DRE/DOE thus eliminates the need for treadmill examination, is safer, less expensive, and more convenient for both you and your horse.


How is a DRE/DOE examination performed? Once you call and schedule an appointment for your horse, we will travel with the DRE/OGE equipment to your horse’s normal training facility to conduct the examination. The dynamic endoscope is similar to a normal resting endoscope and is inserted into one of your horse’s nostrils. After ensuring correct positioning of the endoscope in the airway, the endoscope is secured to the horse via a special purpose noseband that fits over the horse’s bridle (Figure 1). The transmitting-recording devices are mounted within custom designed saddle pads for driving and riding disciplines (Figure 3). The video-endoscopic images are recorded continuously onto an SD card in the recording device while the horse performs its normal exercise routine under the conditions in which the abnormality in performance was noted. Real time visualization of the horse’s upper airway is also possible through a portable, wireless monitor (Figure 4). Once the horse finishes exercising and the examination is complete, the video-endoscopic recording is reviewed with a specialized software program which allows the videos to be played in slow motion and still images obtained (Figure 5). Images from the workout can then be emailed or recorded onto a CD/DVD for all interested parties to view.




Examples of Common Upper Airway Disorders in Horses:

RA=Right Arytenoid; LA=Left Arytenoid; RAEF=Right Aryepiglottic Fold, LAEF=Left Aryepiglottic Fold, VC=Vocal Cords; E=Epiglottis; SP=Soft Palate, T=Trachea/Windpipe


Normal: The upper airway maintains its normal appearance and function throughout the exam.
Normal at rest.   Normal at exercise.
Intermittent Dorsal Displacement of the Soft Palate (iDDSP): The soft palate becomes displaced dorsal to (above) the epiglottis, obscuring it from site, and results in partial airway obstruction.
Normal at rest.   iDDSP at exercise.
Left laryngeal hemiplegia (LLH)/Roarer: The left arytenoid (LA) is not fully abducted (opened) when compared to the right arytenoid, and progressively collapses into the airway during exercise resulting in partial airway obstruction.
Asymmetric at rest.   LLH at exercise.
Axial Deviation of the Aryepiglottic Folds (ADAEF): The right and left AEF collapse into the airway during exercise resulting in an hour glass appearance to the airway and obstruction of airflow.
Normal at rest.   ADAEF at exercise.
Vocal cord/Ventricle Collapse (VCVC), ADAEF, Ventroaxial Luxation of Arytenoid (VLA): The combination of airway disorders seen here (VCVC, ADAEF, and VLA) results in a markedly reduced airway size and substantial airway obstruction.
Normal at rest.   VCVC, ADAEF, VLA at exercise.

The following are recent publications about dynamic respiratory endoscopy in veterinary journals:


Kane, E.  Dynamic videoendoscopy: A new method for diagnosing equine upper airway disease.  DVM NEWSMAGAZINE. February 1, 2010.


Pollock PJ, Reardon RJM.  Dynamic respiratory endoscopy without a treadmill: Initial experiences.  Equine Veterinary Education, Volume 21, Number 7, July 2009, pp. 367-370.


Desmaizieres LM, Serraud N, Plainfosse B, et al.  Dynamic respiratory endoscopy without a treadmill in 68 performance Standardbred, Thoroughbred, and saddle horses under natural training conditions.  Equine Veterinary Journal, Volume 41, Number 4, April 2009, pp. 347-352.


Pollock PJ, Reardon RJ, Parkin TD, et al.  Dynamic respiratory endoscopy in 67 Thoroughbreds under normal ridden exercise conditions.  Equine Veterinary Journal, Volume 41, Number 4, April 2009, pp. 354-360.


Further information about the DRScope can also be found at http://www.optomed.fr/article.php?article=1057


If you have further questions regarding dynamic respiratory endoscopy, or to schedule a DRE/DOE examination for your horse, please contact Dr. Jennifer Smith at NJEC.