EQUINE RESPIRATORY SYSTEM: OVERVIEW AND DIAGNOSTICS Flashcards
how can a horse modulate upper airway resistance?
- Dilation of external nares
- Vasoconstriction
- Dilation/ stabilization of pharynx
- Increase area of rima glottidis
- Extension of head
how can a horse modulate lower airway resistance?
- Inhalation → dilates airways
- Exhalation → narrows airways
- Airway smooth muscle
> Most important > Regulating resistance
pulmonary physiology review?
- resp rate
- tidal volume
- Respiratory rate= 8-24 brpm
- Resting tidal volume= 4-5 liters
- Exercising tidal volume= 13 liters
- Maximal exercise= 75L O2/min
horse lung field
epaxial muscles, scapula, curvilinear line to 16th ICS
where in the resp system does resistance occur?
50% in nose, 25% trachea, 25% bronchioles
locomotor respiratory coupling mechanism
- when they are in contracted phase, stomach contents move backwards, head goes up, they inhale
- then legs go out, stomach contents go forward, head goes down, they exhale
Normal respiratory rate for adults, foals, neonates
- Adults- 8-24 breaths/ minute
- Foals- 20-40 breaths/ minute
- Neonates- 60-80 breaths/ minute
Abnormal respiratory patterns to watch out for
- “Heave line” > expiratory distress, working hard to push air out
- Paradoxical respiration > inspiratory and expiratory distress, common with pleuropneumonia
- Synchronous diaphragmatic flutter > severe electrolyte abnormalities, diaphragm contracts in time with heart, rhythmic noise
Abnormal upper airway sounds
- Stridor > High pitched inspiratory noise
- Stertor > Low pitched, raspy inspiratory noise
- Tracheal rattle > Oscillation of mucus
normal airway/beath sounds
- origins, where are they loud vs quiet
- when are they easy vs hard to hear?
- Created by airway turbulence
- Loudest → base of lung and on inspiration
- Quietest → diaphragmatic lobes and on expiration
- Difficult to hear
> Noisy environments
> High body condition score - Easy to hear
> Foals
> Underweight horses
Abnormal lower airway sounds? when we heat them?
Crackles
* Short, popping sounds
* Sudden pressure equalization when collapsed airways open
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Wheezes
* High or low-pitched musical sounds
* Oscillation of airway walls
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Pleural friction rubs
* Rubbing or creaking sound
* End of inspiration and beginning of expiration
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Expiratory grunt
* Loud sound at end of expiration
* Indicates pain
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Absent or diminished sounds
* Most common ventrally
> something blocking, eg. consolidation, etc.
rebreathing exam procedure, utility? contraindications?
- Place bag over both nostrils
- Inhalation of increasing levels of CO2
> Increased respiratory rate and depth
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Utility - Enhance breath sounds
- Reveal abnormal sounds
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Contraindications - Respiratory distress/ unstable
- Severe or diffuse abnormalities
ultrasonography for thorax
- what is it good for?
- limitations?
- what is it bad for?
Ultrasonography utility
* Non-invasive
* Stall-side or in the field
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Sensitive for
* Pleural surface/ superficial abnormalities
* Pleural space disease
* Some diaphragmatic hernias
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Limitations
* Poor contact= poor image
* Aerated lung is not penetrated
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Not sensitive for
* Deep (axial) pulmonary disease
* Caudal mediastinal disease
* Axial diaphragmatic hernias
what do comet tails represent on ultrasound?
disruption of pleural surface
thoracic radiograph utility? indications and limitations?
- Portable units- foals and small ponies
- Evaluate lesion pattern
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Indications - Thoracic trauma
- Unresponsive or recurrent disease
- Extrapulmonary disease
- Deep lung disease
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Limitations - Portable units
> Not capable in most ponies and horses - Summation
- Lack of orthogonal views
- Low sensitivity for small lesions
- Pleural fluid obscures underlying structures