General Evaluation of the Equine Lower Respiratory Tract Flashcards
How should the normal equine lung look? What lobes are found on each side?
lack deep interlobar fissures and distinct lung lobes
- LEFT = cranial, caudal
- RIGHT = cranial, intermediate, caudal
Where does the trachea bifurcate in horses? Which bronchus is more susceptible to disease?
5-6 intercostal space
right bronchus is more straight = right pulmonary disease more common
How does the respiratory epithelium differ down the airway?
becomes thinner and less ciliated
What are the 2 vascular supplies of the lung? What happens at each?
- PULMONARY - low pressure, low resistance; gas and nutrient exchange
- BRONCHIAL - nutrient supply to lymphatics, vascular and airway components
What are important aspects to an equine history to diagnose respiratory disease?
- age and breed (signalment)
- environment (housing, feeding)
- job (race vs. pasture)
- recent events
- endemic disease
- trauma
- vaccination history
- chief complaint
- prior medical problems
What are important aspects to inspection of a patient for diagnosing respiratory disease?
- demeanor
- posture
- mental status
- movement
- deformation
- nasal discharge
- cough
- respiratory effort (dyspnea)
- respiratory effort
(nostrils should be flat at rest, if they’re consistently abducted, there is an increased respiratory effort)
What landmarks should be palpated and percussed for diagnosing respiratory disease?
- nostrils (air flow, odor)
- area over sinus (should be hollow)
- lymph nodes
- larynx/pharynx
- trachea
- jugular
- neck
- chest
In what conditions should auscultation be done? What piece of equipment is commonly used?
quiet conditions (hard in the field and in barns)
rebreathing bags —> cover nostrils to obstruct breathing and listen to the first few breaths for accurate and quality sounds
What do wheezes and crackles upon auscultation indicate?
WHEEZE = inspiratory, bronchoconstriction
CRACKLES = moist, fluid
What is important to note about normal equine respiration?
there is a small abdominal component during expiration (active phase)
- however, a continuously pumping chest shows increased effort
What is dyspnea? Tachypnea? Hyperpnea? Apnea? Hyper/hypoventilation?
DYSPNEA = difficulty breathing
TACHYPNEA = rapid, shallow breathing
HYPERPNEA = increased frequency and depth of breathing
APNEA = no discernable breathing
HYPER/HYPOVENTILATION = alveolar ventilation (PaCO2)
What are the 2 major indications for respiratory endoscopy? How do horses typically react?
- visualization of internal anatomical strucures (see discharge or inflammation)
- determine additional exams
tend to be insensitive to scopes in trachea —> hyperresponsiveness is typically pathological
What does mucus in the trachea typically indicate?
non-specific sign of inflammation
What does blood in the trachea typically indicate?
sign of recent hemorrhage, especially when properly times after exercise (30-120 mins post, exercise-induced pulmonary hemorrhage)
How should the bronchial septum look in a healthy horse? What 3 things can change its appearance?
should be very thin
- age
- inflammation
- edema
What are 4 reasons that pulmonary radiographs are especially difficult in horses?
- only laterals are possible in adults
- four films are required to cover lung fields
- equipment is especially expensive
- chest movement restricts techniques
What are 3 indications for pulmonary radiographs?
- infectious/non-infectious lower respiratory disease
- pneumothorax
- diaphragmatic hernias
How are ultrasounds used for respiratory disease diagnosis in equine medicine?
can only observe surface of parenchyma, but are able to see fluid accumulation
- pleural effusion!
What are 2 indications for tracheal washes? What should be done for collection?
- collect secretions from the LRT
- culture and cytology
sedate with alpha 2 agonists, Detomidine or Xylazine
What are the 2 tracheal wash techniques?
- trans-endoscopic
- trans-tracheal
What are 3 pros and 2 cons to trans-endoscopic tracheal washes?
PROS = fast, no outside signs, visualization possible
CONS = costly equipment, LRT contamination
What are 2 pros and 3 cons to trans-tracheal washes?
PROS = cheap equipment, no contamination
CONS = sterile preparation required, hair must be clipped and a small incision is made, no visualization
What equipment is required for tracheal washes? What 2 collection tubes are used?
- commercial needle and catheters kit
- sterile, physiologic saline solution
- 20-60 mL syringe
- EDTA - cytology
- red top - culture
What are the 2 possible uses of tracheal wash fluids?
- CYTOLOGY - direct smear, centrifugation to cellular pellet
- CULTURE (sterile!)
What can cause variable results in tracheal wash cytology? What 4 cells are commonly seen?
rest, exercise, volume
- epithelial (tufts)
- neutrophils
- eosinophils
- erythrophages (macrophage that trapped a RBC)/hemosiderophages
Where should samples be taken for suspected viral respiratory disease in clinical and non-clinical horses?
- CLINICAL = nasal swab
- SUBCLINICAL = tracheal wash
(PCR)
How does endoscopy compare to bronchoalveolar lavage?
ENDOSCOPY = visualization, higher cost and maintenance
BAL = no visualization, low cost
How are bronchoalveolar lavages performed?
- sedation with Detomidine, Xylazine, Butorphanol, or nose twitch
- use a saline + lidocaine solution as a local anesthetic to diminish coughing and laryngospasm
- quickly pass the BAL tube past the larynx so that swallowing does not induce placement in the esophagus
- advance the BAL tube until it is in a wedged position and deploy the balloon
- instill about 250-300 mL of NaCl 0.9% and recover about 50% of the solution
What is BAL fluid used for? How can it be confirmed that the tube reached the correct position?
cytology more specific to lower respiratory disease
BAL fluid should be foamy, indicating that surfactant is present
What are the 3 major cells found on BAL fluid cytology? What should not be found in a healthy horse?
- macrophages (50%)
- lymphocytes (50%)
- neutrophils (<5%)
+/- eosinophils and mast cells
erythrophages/hemosiderophages
What are 5 indications for thoracocentesis?
- verify presence of pleural effusion
- collect fluid for cytological evaluation of infection, inflammation, trauma, or neoplasia by collecting different fractions of fluid
- collect fluid for bacterial cultures and antibiotic sensitivity
- treatment for pleural effusion, hemothorax, and pneumothorax
- local therapy
What is the normal color, protein concentration, and cell count of pleural fluid?
straw-colored, clear, odorless, small volume
< 3 gm/dL
< 10,000 cells/uL (non-degenerate neutrophils, mononuclear cells, mesothelium)
What are some indications of septic pleural fluid?
- cell count > 10,000 cells/uL
- degenerate neutrophils
- cloudy fluid with fibrin clots
- foul odor indicating anaerobic infection and poor prognosis
- protein concentration > 3 gm/dL (bacterial product)
- glucose < 40 mg/dL (bacterial energy source)
What does the presence of morphologically normal and abnormal lymphocytes in pleural fluid indicate?
NORMAL = chylous effustion
ABNORMAL = lymphosarcoma
What are 2 indications for pulmonary biopsies?
- diffuse lung disease
- abnormal massess seen on radiographs
(only used in combination with other techniques)
What are 4 contraindications for pulmonary biopsies?
- hemoptysis, hemorrhage
- pneumothorax
- infection
- horses in respiratory distress (increased risk of tearing more tissue)
What is the point of performing pulmonary function tests?
observe lung compliance and resistance
What is the classical site for arterial blood gas testing? What other site can be used? What is observed in this test?
common carotid at the base of the neck
common carotid at the mid-neck, behind the jugular vein
oxygen, carbon dioxide, pH
What equipment is required for arterial blood gas testing? Under what conditions is it taken?
heparinized syringe and properly sized needle
anaerobic
What is a normal PaO2 and PaCO2 in horses?
PaO2 = 95-100 mmHg
PaCO2 = 40-45 mmHg
What is the most common bloodwork done to diagnose respiratory disease in horses?
- hematology
- biochemistry
- serology (SAA quickly responds, fibrinogen takes longer to respond to inflammation/pneumonia)
Which respiratory sample should you submit for culture?
a.. tracheal lavage fluid
b. bronchoalveolar lavage fluid
A
BAL fluid is only used for lower respiratory tract cytology
True or false: It is easy to auscultate the equine lung.
FALSE —> hard to find a quiet space, must listen in multiple fields
True or false: It is best to perform endoscopy at a specific interval after exercise to determine if there is overt bleeding.
TRUE —> hemorrhage requires time to make it to the lower airways (30-120 mins)
True or false: Tracheal lavage fluid cytology is a good indicator for lower airway inflammation.
FALSE —> BAL fluid is best, tracheal lavage fluid is less sensitive
