Exam 2 - Equine Lower Respiratory Tract Flashcards
what are some important components of your general physical exam for a horse with lower respiratory tract disease?
TPR, MM, CRT, nasal discharge/cough, airway noise, respiratory rhythm/rate/character
what are some important components of your respiratory physical exam for a horse with lower respiratory tract disease?
note any distress/dyspnea, pleurodynia, thoracic excursion, abdominal effort, ventral edema, or exercise intolerance
does guttural pouch empyema usually cause a unilateral or bilateral nasal discharge?
it depends - even if it’s unilateral empyema, it can cross over & cause bilateral nasal discharge
what conditional changes should be considered in a horse with a cough?
indoors vs. outdoors
rest vs. exercise
what is pleurodynia?
pleural pain
what are the clinical signs of pleurodynia?
shallow guarded respiration
anxious facial expression
abducted elbows
stiff forelimb gait
decreased thoracic excursion
grunt/escape maneuver
reluctance to cough
what is required for cyanosis to be present?
at least 5mg deoxygenated hemoglobin per 100 ml of blood - blue mucus membranes
how would you characterize these mucus membranes? is it a sensitive indicator of hypoxemia?
cyanotic
no - not sensitive
what are the topographic boundaries for the lung fields in the horse?
7th ICS - tuber coxae
16th ICS - tuber ischii
13 ICS - middle of the thorax
11 ICS - point of the shoulder
what do you expect to hear over the lung fields of a normal horse at rest?
nothing
what are ‘normal’ lung sounds?
bronchovesicular
what are examples of abnormal lung sounds?
crackles, wheezes, pleural friction rubs, attenuated lung sounds, referred large airway sounds
what do crackles sound like?
short, explosive, discontinuous non-musical sounds
what do wheezes sound like?
continuous musical sounds
what does a pleural friction rub sound like?
continuous or discontinuous, low pitch, mirror-image sound
how are attenuated lung sounds characterized?
silent regions of the lung field
decreased bronchovesicular sounds
can’t be appreciated without a rebreathing bag
what are some differentials of thoracic pathology that result in attenuated lung sounds?
- pleural effusion
- pleural or pulmonary abscess
- pulmonary granuloma
- pleural or pulmonary tumor
- pericardial effusion
- diaphragmatic hernia
- pneumothorax
how are referred large airway sounds characterized?
tracheal and/or mainstem bronchial sounds heard within the lung fields
what are some examples of thoracic pathology that result in referred lung sounds?
- pulmonary consolidation
- pleural or pulmonary abscess
- pulmonary granuloma
- pleural or pulmonary tumor
- pulmonary atelectasis
- pleural effusion
what are some differentials for percussable dullness?
pleural effusion
pleural abscess
pulmonary abscess
pulmonary granuloma
pulmonary consolidation
pleural/pulmonary tumor
pericardial effusion
diaphragmatic hernia
what are some differentials for percussable hyper-resonance?
pneumothorax
emphysematous bullae
enlarged lung fields
diaphragmatic hernia
what is endoscopy used for?
diagnosis of URT abnormalities
look at turbinates
look at pharynx/larynx
arytenoids
what are some diseases that may be seen on pharyngoscopy/laryngoscopy of the pharynx?
- cicatrix
- dorsal displacement of the soft palate
what are some diseases that may be seen on pharyngoscopy/laryngoscopy of the guttural pouch?
- mycosis
- empyema
what are some diseases that may be seen on pharyngoscopy/laryngoscopy of the larynx?
- laryngeal hemiplegia
- arytenoid chondropathy
what are some diseases that may be seen on pharyngoscopy/laryngoscopy of the epiglottis?
- aryepiglottic fold entrapment
- sub-epiglottic cyst
- aryepiglottic flutter
what is the pathogenesis of this pictured pathology?
nasopharyngeal cicatrix - unknown etiology
common in east & central tx, may be environmental exposure
progressive disease
what disease is pictured?
cicatrix
what is the pathogenesis of this pictured pathology?
dorsal displacement of the soft palate - caused by the impairment of the pharyngeal branch of the vagus nerve
what clinical signs are seen with dorsal displacement of the soft palate?
exercise intolerance, noise at exercise, diagnosed on dynamic endoscopy
how is this disease process treated?
tie forward surgery
staphylectomy
tenectomy of the strap muscles
cornell collar
what is this?
dorsal displacement of the soft palate
what is this?
aryepiglottic fold entrapment
what is the pathogenesis of aryepiglottic fold entrapment?
epiglottis is caught in the redundant tissue surrounding it - can be intermittent or chronic
what are the clinical signs associated with aryepiglottic fold entrapment?
respiratory noise & may affect swallowing
what is this?
laryngeal hemiplegia
what is the pathogenesis of laryngeal hemiplegia?
progressive paralysis of the left arytenoid cartilage - caused by neuromotor function of the left recurrent laryngeal nerve
what abnormality is seen here?
cleft palate
what are the benefits of using dynamic video endoscopy?
real time upper airway exam during normal training or exercise with the head in the normal position while avoiding the risk of the treadmill
what 3 scopes are available for dynamic scoping?
dynamic respiratory scope, OPTOMED, & france
what pathology is seen on this radiograph of the thorax?
pulmonary abscess
what pathology is seen on this radiograph of the thorax?
pleural effusion & pulmonary abscess
what pathology is seen on this radiograph of the thorax?
pneumothorax
what pathology is seen on this radiograph of the thorax?
bronchial pattern - equine asthma
what pathology is seen on this radiograph of the thorax?
miliary interstitial pattern
what pathology is seen on this radiograph of the thorax?
interstitial pneumonia
why is thoracic ultrasound used for peripheral lungs in horses?
localize & characterize the disorders, such as:
atelectasis, consolidation, abscessation, necrosis, & neoplasia
why is thoracic ultrasound used for the pleural space in horses?
localize & characterize disorders of the pleural space, such as:
pleural effusion, ‘gas echoes’, pleural fibrin, loculations, abscessation, & pneumothorax
why is thoracic ultrasound used for the mediastinum in horses?
localize & characterize disorders, such as:
effusion, abscessation, & neoplasia
what artifact is seen on this ultrasound of equine lungs? what does it indicate?
comet tails
what pathological process is going on in this ultrasound? where is the lung?
pleural effusion
how would you likely characterize this effusion? why?
transudate - anechoic
how would you likely characterize this effusion? why?
exudate - mixed echo pattern
how would you likely characterize this effusion? why?
hemothorax - homogenous & echogenic
what pathology is seen on this ultrasound of equine lungs?
gas echoes in pleural fluid
what pathology is seen on this ultrasound of equine lungs?
pleural fibrin
what pathology is seen on this ultrasound of equine lungs?
pleural loculae
what diagnostics will you primarily use from tracheobronchial aspiration?
cytology, differential cell counts, & gram’s stain
what is the purpose of tracheobronchial aspiration?
retrieve diagnostic sample of airway secretions for cytology, gram’s stain, & cell differentials
what are the main 3 ways we obtain tracheobronchial aspiration?
percutaneous tracheal aspirate
trans-endoscopic tracheal aspiration with guarded catheters
BAL - blind BAL or trans-endoscopic
what are the advantages of percutaneous trans-tracheal aspiration? disadvantages?
advantages - aerobic sampling for microbiologic culture & samples pooled secretions from the entire lung
disadvantages - invasive, complications - SQ cellulitis/abscess/emphysema, & no visualization
what is the technique of doing a percutaneous trans-tracheal aspirate?
introduce catheter
infuse 30-60 ml of sterile saline
aspirate fluid
reposition catheter
re-aspirate
remove catheter
inject SQ amikacin
what are the advantages of trans-endoscopic tracheal aspiration? disadvantages?
advantages - less invasive, avoid complications, assess URT, & direct visualization of collection process
disadvantages - potential contamination from the endoscope or URT
what is the technique used for trans-endoscopic tracheal aspiration?
standing horse, +/- sedation
disinfect endoscope & channel - cidex solution for 20 minutes & rinse scope/biopsy channel
advance scope into pharynx, aseptic handling of catheter & insert, advance past end of the scope, advance internal catheters, plug comes out, remove stylet
infuse 30-60 ml of sterile saline & aspirate sample from tracheal puddle
what should you do with a sample from a trans-endoscopic tracheal aspiration?
cytology - edta tubes
aerobic bacterial culture & susceptibility
anaerobic bacterial culture & susceptibility
what would be seen on cytology from a trans-endoscopic tracheal aspiration supportive of sepsis?
predominance of neutrophils
degenerative neutrophils
bacteria - intracellular or extracellular
why is a positive culture of off a trans-endoscopic tracheal aspiration not necessarily indicative of a bacterial infection? how should you interpret it?
pathogenic & non-pathogenic bacteria can be isolated from TTW of normal horses!!
interpret the cultures in conjunction with: method of collection, cytologic findings, clinical signs, & other findings
T/F: BAL yields a more representative sample of lower airways than tracheal aspirates
true
what are BALs used for?
retrieve fluid & cells lining the distal airways & alveoli
excellent cell morphology
why is BAL only used for cytology?
contamination from the upper airway
T/F: there is a good correlation between BAL cytology & histological findings of distal airways & airway reactivity
true
what is a BAL suitable for when using it as a diagnostic test?
assessment of diffuse lower airway disorders such as:
recurrent airway obstruction, SPA-OPD, & inflammatory airway disease
what is a BAL NOT suitable for when using it as a diagnostic test?
localized lung disorders such as:
bacterial pneumonia/pleuropneumonia & lung abscesses
where are samples usually taken with BAL?
caudodorsal lung region - suitable for detecting exercise-induced pulmonary hemorrhage
T/F: BAL samples airway secretions from multiple lung segments
false - only one
what is the general technique used for BAL?
test inflate cuff on BAL tube
restrain horse, well sedated, clean 1 nostril, small amount of KY on tube
push tube up ventral meatus so the tube enters the pharynx
stretch horses head out & advance tube into trachea - most horses cough
infuse 30-60cc of epinephrine without lidocaine near tracheal bifurcation
advance tube until it wedges into bronchus & inflate cuff, hold tube securely against nostril
infuse 100ml of warmed sterile saline, use 3-way stop cock, aspirate fluid gently
repeat infusion & aspiration 2 more times for a total of 300 ml infused
% of fluid recovery increased with each infusion
how should you handle samples from BAL?
mix all 3 together & place into EDTA tubes & submit to lab for direct smears, gram stains, cytology, & differential cell counts
what are the benefits of trans-endoscopic BAL?
need endoscope > 160cm
allows visualization of lower airways
visual selection of BAL site
aseptic prep of endoscope - use biopsy channel
what should normal BAL fluid look like?
clear to mildly turbid with a thick layer of surface foam (surfactant)
what is the predominant cell type in normal BAL fluid?
macrophages > lymphocytes > neutrophils > mast cells > eosinophils
what percentage of neutrophils is normal in normal BAL fluid?
<5%
how does cytology of BAL compare to TA?
cytologic features & differential cell counts are different!! cytology is better preserved
BAL will have lower neutrophils, higher macrophages/lymphocytes, & fewer epithelial cells
what cell is seen on this cytology of normal BAL fluid?
alveolar macrophage
what cell is seen on this cytology of normal BAL fluid?
lymphocytes
what is a normal BAL cell differential?
macrophages: 40-70%
lymphocytes: 30-60%
neutrophils: < 5%
mast cells: < 2%
eosinophils: < 1%
BAL cytology is useful for what common disorders in horses?
equine asthma - inflammatory airway disease, recurrent airway obstruction, & summer-pasture associated obstructive pulmonary disease
exercise induced pulmonary hemorrhage
in what situation would you chose to perform a tracheal aspirate on a horse with respiratory disease?
when you suspect septic, focal, or multifocal pulmonary disease
in what situation would you chose to perform a BAL on a horse with respiratory disease?
when you suspect diffuse, non-septic, pulmonary disease
in what situation would you chose to perform both a tracheal aspirate & BAL on a horse with respiratory disease?
if you’re not sure
when one fails to provide adequate diagnostics
T/F: BAL may not detect focal or multifocal pulmonary disorders
true
what are the 2 most common causes of pleural effusion in horses?
- pleuropneumonia
- neoplasia
what are the classifications used for pleural effusion in horses?
- transudate
- modified transudate
- exudate - septic or non-septic
- hemorrhagic effusion
when is a lung biopsy used?
reserved for horses in which histologic examination of lung tissue is essential for diagnosis & treatment
performed after all other efforts have failed
not recommended for horses with increased respiratory rate & effort
what are potential complications of lung biopsies?
intrapulmonary hemorrhage, intrapleural hemorrhage, epistaxis, respiratory distress, pneumothorax, & death
what are some indications for pursuing a lung biopsy?
sonographically visible pulmonary mass
minimal risk of complications
diagnostic challenge - miliary rad pattern (fungal, EMPF, interstitial, neoplasia)
what is the technique used for lung biopsy?
ultrasound for site selection, aseptic prep, local anesthesia, stab incision in skin
12 gauge needle, advance through intercostal muscles, obtain biopsy quickly
submit sample in formalin to histopath lab
how should your patient be monitored after a lung biopsy?
monitor closely for 24 hours!!!!
look for: epistaxis, tachypnea, respiratory distress, & ultrasound of pleural space/peripheral lung
what are the clinical indications of pulmonary scintigraphy?
assess regional perfusion & ventilation
determine ventilation to perfusion ratios
detect occult sites of pulmonary infection
what are the research indications of pulmonary scintigraphy?
assess mucociliary clearance
detection of pulmonary bleed sites
study of deposition of aerosolized medications
what are pulmonary function tests?
tests that assess mechanical properties of lungs, lung volume, & gas exchange
usually require specialized equipment & personnel, so rare in private practice
what diagnostic test can be easily done in practice & yield useful lung function information?
arterial blood gases
what does PaO2 indicate on arterial blood gas analysis?
most sensitive measure of lungs ability to oxygenate blood
what does PaCO2 indicate on arterial blood gas analysis?
most sensitive measure of ventilation
where can you sample arterial blood from a horse?
carotid artery
transverse facial artery
facial artery under ventral mandible - under anesthesia
dorsal metatarsal artery in foals
brachial artery in foals
what is seen on this perfusion study using pulmonary scintigraphy?
cold spot associated with lung abscess
what is seen on a pulmonary scintigraphy study of normal horses?
ventilation evenly distributed throughout lung fields
what is seen on a pulmonary scintigraphy study of abnormal horses?
bronchoconstriction, airway edema, & inflammation
