Respiratory pathology

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Respiratory pathology

• AVS 435 Equine Exercise Physiology

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• Midterm next Wednesday, March 5
• Similar format as MT 1
• 100 points
• Must be present in class room
• Material covered since last MT
• Thermoregulation
• Respiratory (through tonights lecture)

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• Respiratory pathology
• Any reduction in diameter of airways has a
  profound effect on ventilation, and therefore
  performance

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• Respiratory and orthopedic diseases are the most
  common causes of poor performance in athletic
  horses
• Respiratory disease is found in 40-42 of
  racehorses (70 in sport horses) presented for
  poor performance
• More recent study up to 78

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• Upper airway disease
• Nostrils to trachea at thoracic inlet
• Lower airway disease
• Thoracic inlet through bronchi, bronchioles and
  alveoli
• Horses often affected by multiple concurrent
  respiratory problems

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• Both URT and LRT susceptible to
• Infectious disease
• Viral, bacterial, fungal, parasitic
• Inflammatory disease
• Heaves recurrent airway obstruction
• Trauma
• Neoplasia

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• Most common upper respiratory tract diseases
• Soft palate dorsal displacement (50)
• Laryngeal hemiplegia
• Pharyngeal collapse
• Epiglottic entrapment
• All obstructive airway diseases

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• Direct effect on performance
• Increase in obstruction gt decrease in functional
  radius gt increased resistance gt decreased
  ventilation gt decreased VO2max
• Airway noise
• Subjectively viewed as unsoundness in many
  showing disciplines

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• The ideal ventilation-perfusion ratio is 0.8 1
• Quantify by V Q
• Any decrease in ventilation is going to adversely
  affect V/Q ratio ltltlt 1
• Any decrease in perfusion is going to adversely
  affect V/Q ratio gtgtgt 1

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• V/Q mismatch adversely affects performance, may
  be mild to severe
• Falling off
• Horse in training is doing well, then performance
  drops off
• Onset can be chronic or acute, depending on
  etiology

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• Soft palate dorsal displacement palatal
  instability
• Most common pharyngeal disorder
• Affects 29 35 of racehorses dxed with resp dz
• Often a dynamic dz
• May only occur during exercise
• Diagnosis more difficult

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• Pharynx
• Located betweennasal/oral cavityand larynx
• Portion dorsal(above) softpalate isnasopharynx
• Muscle and membranous tissues

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• Normalfunction
• During breathing,the free edgeof the
  softpalate isventral (underneath) the
  epiglottis to provide uninterrupted air flow from
  nasal passages to trachea

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• Normalfunction
• During swallowing,soft palate elevatesto caudal
  wall ofpharynx epiglottisflips dorsal
  andcaudal to cover trachea tongueelevates and
  moves caudal to move food against roof of palate
  and into esophagus

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• SPDD
• Soft palateis displaceddorsal
  toepiglottisduringbreathing
• Narrows tracheal opening, turbulentair flow,
  decreased ventilation

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• SDPP
• Dramatic decrease in performance
• Displacement may be intermittent or persistent
• Persistent poorer prognosis
• Dynamic disorder gt occurs during high speed
  exercise, rarely at rest
• On the bit, fatigued may be factors

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• SDPP
• Gurgling, rattling or choking sound during
  expiration
• Airway sounds differentiate between SDPP and
  laryngeal hemiplegia (GTQ)
• Non-invasive microphones to record respiratory
  sounds during exercise to assist diagnosis
• Up to 30 of SDPP-affected horses may not make
  associated sounds

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• SDPP
• May or may not cough
• Repeated attempts to swallow during exercise

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• Diagnosis via endoscopy
• Manually occlude nostrils may cause palate to
  displace
• Poor correlation between function at rest and
  during exercise

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• May be ulcers on free edge of soft palate from
  chronic irritation
• SP can also temporarily displace during normal
  endoscopic exam
• Dont leap to SPDD diagnosis if no history of
  exercise intolerance

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• Goldstandardvideo-endoscopyevaluatedat
  speed,fatigued,bit in mouth, on high speed
  treadmill

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• SDPP
• Exact cause unknown
• Proposed malformation, hypoplasia, neuromuscular
  disease
• Soft palate innervated by vagus CN X
• Always evaluate guttural pouches for empyema,
  mycosis
• Lavage with caustic substances may irritate vagus
  nerves, cause symptoms

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• Multiplemuscular,cartilagenousand
  bonystructures to open andstabilize
  pharynxand larynx during respiration
• Damage to any of them reduces stability