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
endoscopic exam for thorax - utility, indications, limitations
- Stall-side or in field
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Indications - Poor performance
- Abnormal respiratory noise
- Nasal discharge
- Epistaxis
- Coughing
- Facilitate sample acquisition
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Limitations - Size and maneuverability
- Sample collection
- May need sedation
- May induce respiratory distress
dynamic endoscopy use
poor performance at higher speed, or intermittent issues
- evaluate function of upper airway
upper airway sampling methods? one to watch out for?
Swab
* Nasal swabs
* Nasopharyngeal swabs
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Fluid collection
* Guttural pouch
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Biopsy
* Superficial lesions of URT
* Except fungal plaques on large arteries!
transtracheal wash indications? percutaneous technique and its pros and cons?
Indications
* Infectious lower respiratory disease
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Percutaneous technique
* Minimizes contamination
* More invasive
* Complications (are minimal and rare)
> Subcutaneous emphysema
> Abscess or cellulitis
tracheobronchial aspirate indications? endoscopic technique pros and cons?
Indications
* Infectious lower respiratory disease
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Endoscopic technique
* Minimally invasive
* Minimal complications
* Risk sample contamination (based on how you deploy your scope - don’t let it touch your sample!)
> Upper airway
> Endoscope
bronchoalveolar lavage
-indications, techniques, complications
For Diffuse or chronic disease > end up in some part of the lung, but you wont know where
- not a sterile sample! not something you should culture!
- for cytology
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Techniques
* Blind
* Endoscopic
> technique is the same either way - wedge into section of lung > then infuse fluid and rapidly draw back
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Complications (usually mild)
* Coughing
* Trauma
* Bronchospasm
* Fever
lower airway cytology
- what cells do we expect in tracheal aspirate?
- what about bronchoalveolar lavage?
TRACHEAL ASPIRATE
* 40-80% macrophages
* (1-50% epithelial cells)
* < 20% neutrophils
* < 10% lymphocytes
* < 1% eosinophils
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BRONCHOALVEOLAR LAVAGE
* TNCC- <530 cells/uL
* 40-70% macrophages
* 30-60% lymphocytes
* < 5% neutrophils
* < 2% mast cells
* < 0.5% eosinophils
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- note difference in neutrophils, lymphocytes
what tells us we have upper airway contamination
- squamous epithelial cells
> if we see bacteria with these, esp. outside cells, these bacteria are likely from upper airway and contamination > dont culture this sample
