Unsoundness of the Respiratory Tract Flashcards
what is the most common current name for heaves?
equine asthma
what was heaves first called? then what was it called? what is now the classic common cause/name other than equina asthma?
chronic obstructive pulmonary disease (COPD), then allergic airway disease; now called/due to recurrent airway obstruction
what is one of the most common respiratory disorders of the horse?
heaves
what horses are the classic candidates for heaves?
those that have been stabled for a long period of time; are fed and bedded cereal and or grass products (dry in poor ventilation)
what is the probable etiology for heaves?
repeated mucosal allergic challenge in the airyways leads to constriction of the airways and mucus production
what can be sources of hypersenstivity (or allergy) for horses; give 3 examples
inhaled environmental contaminants: fungal spores, plant pollen, or other protein sources
what is often reported, but not ALWAYS associated with heaves?
history of a preceding viral or bacterial infection
describe exercise tolerance of horses with heaves (2)
- often adversely affected
- coughing at onset of exercise due to increased respiratory rate
describe the respiratory rate of horses with heaves?
often high even at rest, with flared nostrils to take in more air
describe the normal resp rate of a horse, then compare to heaves
normal: 8-12 breaths per minute
with heaves: 25-30 breaths per minute
describe the cough of a horse with heaves
chronic, harsh, non-productive cough that is worse when the horse is stabled (re-exposed to contaminant/allergy)
describe characteristics of horses severely affected with heaves (2)
- may lose weight dramatically
- have a heave line, which is a result of marked hypertrophy of the muscles of the caudo-ventral thorax (flank)/abdominal oblique muscles as the horse is working so much harder to breathe
what is observed in severe cases of heaves, giving it its name?
an obvious extra expiratory push from the abdominal and thoracic muscles, possibly with an associated grunt
how is heaves prevented?
avoid dusty hay or atmosphere
what are 4 treatments for heaves?
- anti-inflammatory like prednisone or dexamethazone
- clenbuterol (ventipulman)
- apoquel tablet
- inhalers
describe clenbuterol as a treatment for heaves
an anabolic steroid that body builders use for muscle growth, but is also a bronchodilator
describe an apoquel tablet as treatment for heaves
not FDA approved yet, but a new treatment as of this summer
describe the issue with using inhalers for treating heaves
some horses won’t tolerate it, plus it involves physical labor by the owner
what happens physiologically with heaves?
air passages of the lungs constrict, making it more difficult for air to move in and out of the lungs
when horses with heaves are exposed to triggering factors, what happens? (3)
- airways become inflamed
- bronchi and broncioles constrict (inflammatory chemicals may be involved)
- mucus is produced as the body tries to prevent the invader from entering, yielding respiratory issues in the process
what are 8 important indications of heaves?
- horses older than 6 years (average onset at 9 years old)
- prolonged or repeated stabling (or exposure to other dusty environments)
- chronic cough and reduced exercise intolerance
- diificulty breathe in other wise healthy animal (Dyspnea)
- wheezing and crackling lung sounds
- labored breathing in horses at rest (as indicated by abdominal lift, flaring nostrils)
- worsening of clinical signs when horse exposed to poor quality feeds or environments
- improvement or remission of clinical signs when horse kept in pasture or in a near dust-free environment
why is the average onset of heaves at 9 years or over six years old?
horses are older and more likely ro stay in stalls
what is a bronchoalveolar lavage?
put saline into airways and then pull it back out, hoping to remove debris that can then be sent off to determine the irritating protein causes heaves
what is a drawback of bronchoalveolar lavage?
horses do not like it and will start coughing once the senstive carina is hit
what are two other names for recurrent laryngeal neuropathy?
- larygneal hemiplasia
- roaring (common name)
what is reccurent larygneal neuropathy?
- paralysis (or partial paralysis) of nerves that control the muscles of the vocal cords
- horse roars or whistles when air is inhaled into the lungs
- becomes obvious with exertion
what is the most common form of recurrent larygneal neuropathy? cause?
left reccurent laryngeal neuropathy, the left nerve becomes unmyelinated, losing integrity and function
although all horses may be affected, what type of horses are commonly affected by recurrent laryngeal neuropathy? (2)
- larger horses (over 16 hands)
- younger horses (2-6 years) will start showing signs as they begin to work
give 6 breeds commonly affected by recurrent laryngeal neuropathy
- shire
- dutch warmblood
- hanoverian
- TB
- standardbred
- QH
describe the prevalence of recurrent larygneal nueropathy in quarter horses
it is estimated that 80-90% are affected to some degree, but mild conditions may not show clinical effects
what is a physical characteristic that may indicate recurrent laryngeal neuropathy? compare normal to affected horses
a narrow madibular space (the width between the jaw bones within the throat latch)
normal: 4-5 fingers width
affected: less than 3 finger width
why does reccurent laryngeal neuropathy usually affect the left nerve?
it is the largest nerve in the body, and wraps around the aorta, subjecting it to damage
what do horses with recurrent laryngeal neuropathy usually present with?
for investigation of inspiratory noises and/or poor exercise tolerance
what is roaring, physiologically?
inspiratory dyspnea
what does recurrent laryngeal neuropathy cause?
resistance to air movement, which decreases oxygen intake capacity, causing a decrease of oxygen in the blood and tissue during exertion
describe the effort required to move air into and out of the lungs with recurrent larygneal neuropathy going from rest to exercise?
can take 3-10 times more effort, depending on severity
when does recurrent larygneal neuropathy present and what happens as time passes?
presents at an early age, effects increase with age
describe the majoity of great racehorses’ relationship to recurrent larygneal neuropathy
these great horses are reported to be among the 5% of racehorses that have little or no recurrent larygneal neuropathy and have exceptionally wide jaws
how did recurrent larygneal neuropathy used to be diagnosed? describe
the slap test:
scope the horse, then slap the back of the neck and watch the larygneal reflex and fluttering of the arytenoid cartilage; the greater the neuropathy, the longer the latency and greater impairment for respiratory exchance (latency measured using electrodes placed at larynx)
now, how is recurrent larygneal neuropathy diagnosed? (2)
via endoscopy either using
1. high-speed treadmill, but horses may not like or adapt so use
2. overground edoscopy
describe overground endoscopy to diagnose recurrent larygneal neuropathy
- camera inserted up the horse’s nose and secured to the bridle
- a pack on the riders back transmits a signal to a monitor allowing the larynx to be visualized while the horse undergoes its normal exercise
how is recurrent larygneal neuropathy treated?
surgically, via larygnoplasty, where the left arytenoid cartilage is tied back out of the way to improve airflow and return pressures back to normal
what is another name for horses with exercise induced pulmonary hemorrhage?
bleeders
when does exercise induced pulmonary hemorrhage occur?
when the fragile pulmonar blood vessels in the lungs rupture during exercise
what is the high pressure across capillary walls, associated with exercise induced pulmonary hemorrhage, caused by? (2)
- high blood pressure within the pulomonary capillaries, causes by large cardiac output during exercise
- negative pressures within the alveoli caused by inspiration of large amounts of air
in what two kinds of horses is exercise induced pulmonary hemorrhage common? name one other animal this was also seen in
thoroughbred racehorses and endurance arabian runners; was also seen in racing greyhounds
what allows the rupture of capillariy walls and the flow of blood into interstitial and alveolar spaces as seen in exercise induced pulmonary hemorrhage?
the extreme thinness of the blood gas barrier, which is more than 50 times thinner than a human hair
what happens during exercise in horses with exercise induced pulmonary hemorrhage? (2) is outward bleeding always observed?
- opposing forces are applied across the fragile capillary membrane
- the membrane can rupture and spill blood out of the blood vessels into the alveoli, which might not always result in outward bleeding
when and why is exercise induced pulmonary hemorrhage most often observed?
spontaneous physical disruption of the lung tissue, related to absolute intensity of exercise at the suggested threshold of horses cantering at speeds of 20mph or faster
what is the suggested threshold of speed that can cause damage to lungs as a result of broken blood vessels during exercise induced pulmonary hemorrhage? what does this mean for thoroughbreds
cantering at speeds of up to 20mph; TB can run 35-40 mph and the harder the horse works, the more likely this will happen, so TB predisposed
what causes a predisposition to exercise induced pulmonary hemorrhage and why?
chronic airway disorders (like heaves or recurrent larygneal neuropahty) that cause physical disruption of lung tissue and a concurrent loss of elasticty as a result of the other pulmonary pathology (scar tissue)
explain why TB are predisposed to exercise induced pulmonary hemorrhage other than their fast speeds
they are very susceptible to respiratory disorders due to being around so many other horses and in stalls, this causes scar tissue in lungs, and makes them more susceptible to exercise induced pulmonary hemorrhage
what is a suggested mechanical cause of exercise induced pulmonary hemorrhage?
impact-wave trauma, or the punding of hooves causing physical trauma to dorso-caudal aspect of lungs
what are the two, general contributing causes of exercise induced pulmonary hemorrhage
- the horse’s powerful heart is pumping blood at a hgh pressure combined with
- shock wave produced when the horse hits the ground when running
what will severely affected horses with exercise induced pulmonary hemorrhage show and for how long?
will show moderate or severe post-exercise bilateral epistaxis, that is bright red and occurs within 30 minutes of exercise
what happens in rare cases of exercise induced pulmonary hemorrhage?
- the chest and neck of the horse is splattered with bright red blood
- horses will die during or immediately after exercise
describe the lungs of horses damaged by exercise induced pulmonary hemorrhage
severely bruised
describe grades 0-4 of exercise induced pulmonary hemorrhage
grade 0: no blood detected
grade 1: one or more felcks of blood, and 2 or mroe streams of blood covering more than 10% of treacheal surface
grade 2: one long stream or more than 2 short streams occupying less than 33% of tracheal circumference
grade 3: multiple distinct streams of blood covering over 33% of tracheal circumference
grade 4: multiple, coalescing stream of blood covering more than 90% of the tracheal surface with blood pooling at the thoracic inlet
how are mild cases of exercise induced pulmonary hemorrhage detected? (2)
- endoscopically, for the cases without clinical effects
- by examining tracheal apsirates
what may happen to horses if the pulmonary hemorrhage is severe enough? (4)
- affected horse may have distressed expression
- cool out slowly
- cough occasionally
- swallow frequently when hemorrhage is occurring
what is often the first indicator or exercise induced pulmonary hemorrhage?
frequent swalloing after a race or exercise
describe treatment of exercise induced pulmonary hemorrhage
usually none given, not much available once blleeding starts
describe prevention of exercise induced pulmonary hemorrhage
many things have been tried with little success
describe how lasix (furosemide) is used with exercise induced pulmonary hemorrhage
- it is a diuretic that lowers blood pressure because it decreases body fluid (makes horses urinate more frequently), decreasing blood volume and therefore BP
- it is routinely given before exercise because good evidence suggests that it decreases the severity and incidence of exercise induced pulmonary hemorrhage
- it is linked to eprformance enhancement, and is controversial to use because it compromises lung and kidney integrity