After sending out a previous newsletter about EIPH I received quite a bit of feedback suggesting additional causes of bleeding in race and performance horses. The most interesting was the possibility that bleeding from the lungs was the result of asphyxia, or lack of oxygen.
This theory was first advanced by Dr. James Rooney in 1970, and has been recently brought into the limelight again by Dr. Robert Cook, who has written a fascinating article about the subject.
In the article he lists upper airway obstruction as the cause of asphyxia in race and performance horses. Dr. Cook goes on to say that if a horse takes even three obstructed breaths he can damage his lungs enough to initiate bleeding. The causes he lists for upper airway obstruction include:
- Poll Flexion: Pressure on the larynx (voice box) and trachea (wind pipe) can interfere with air passage to the lungs.
- Recurrent Laryngeal Neuropathy: This condition is also known as laryngeal paralysis or roaring, and can cause full or partial paralysis of the flap-like opening to the larynx, thus narrowing the opening for air to pass through.
- Soft Palate Problems: Dorsal (or upward) displacement of the soft palate at the back of the throat partially blocks airflow into the larynx. Many experts believe that tongue movement can displace the soft palate, which explains the common practice of tying a race horse's tongue to his lower jaw during a race.
- Conformation: Horses with long narrow heads or small nostrils are prone to airway obstruction. Some horses are also born with deformed wind pipes-another causative factor.
- The Penalty of the Rider and Saddle: When carrying the extra weight of a rider, the horse's demand for oxygen increases while at the same time, a tight girth
holding the saddle in place restricts the horse from expanding his chest fully during deep breathing.
- Bit Interference: Traction or pulling on the bit can force the horse into poll flexion or cause the horse to open his mouth. Both of these factors can interfere with air flow. The bit can also stimulate the horse to swallow, which can lead to displacement of the soft palate.
To avoid bleeding from these causes, Dr. Cook makes the following suggestions:
- Ride without a bit (in a bitless bridle, for instance) or on a loose rein
- Avoid excessive poll flexion (rating) during training or racing
- Select the lightest and most skilled riders, especially riders with soft hands
- For severe bleeders, avoid running in intense heat and humidity, and give plenty of time between races to allow the lungs to recover from the irritation and inflammation caused by previous bleeding episodes
- Treat any known upper airway disease
- Select horses with conformations that maximize their ability to bring air into the lungs
- Avoid over-tightening the girth
- Forego Lasix
medication but reduce bulk feed and limit water intake on the day of racing
One of our readers also suggested that running horses barefoot may decrease the amount of concussion coming up through the legs and may possibly reduce the chances of bleeding.
This entire area of research is very new and very interesting, and I look forward to applying this information to future cases. As more riders compete their horses without bits and shoes I'll also be tracking their results closely to see if their horses have fewer health problems.
Contributed By:
Madalyn Ward, DVM
