General Evaluation of the Equine Lower Respiratory Tract

Lecture 39

What are the two vascular supplies to the normal lung?

pulmonary circulation

bronchial circulation

Which vascular supply to the normal lung is low pressure and low resistance and is the site for gas exchange and nutrients?

pulmonary circulation

Which vascular supply to the normal lung is the nutrient supply to lymphatics and serves vascular and airway components?

bronchial circulation

What history is important to obtain during an evaluation of the lower respiratory tract?

age and breed

environment (housing, feeding, etc)

“job”

recent events

endemic diseases

trauma

vaccination history

CHIEF COMPLAINT

prior medical problems

What are the steps of a physical exam for the lower respiratory tract?

inspection —> demeanor, posture, mental status, movement, deformation, nasal discharge, cough, dyspnea, respiratory rate

palpation and percussion —> nostrils (flow, odor), area over sinuses, lymph nodes, larynx/pharynx, trachea, jugular, neck, chest

auscultation —> quiet conditions, use rebreathing bag, trachea, bronchi, lung

What is the term for normal respiration?

eupnea

What is the term for difficulty breathing?

dyspnea

What is the term for rapid, shallow breathing?

tachypnea

What is the term for increased frequency and depth of breathing?

hyperpnea

What is the term for no discernable breathing?

apnea

What two terms are used in reference to alveolar ventilation (PaCO2) being too low or too high?

hyper / hypoventilation

What diagnostic tools can be used for evaluation of the lower respiratory tract?

imaging —> endoscopy, radiographs, ultrasound, thoracoscopy, scintigraphy

respiratory sample collection

pulmonary function testing

bloodwork

What are indications for respiratory endoscopy?

visualization of URT or LRT

determine need for additional exams

How many radiographic films are erquired to cover the entire equine lung field?

4

What are indications for pulmonary radiographs?

infectious LRT disease

non infectious LRT disease

pneumothorax

diaphragmatic hernias

What methods can be used for respiratory sample collection?

tracheal lavage

bronhoalveolar lavage

thoracocentesis

pulmonary biopsy

What techniques can be used for a tracheal wash to collect secretions from the LRT for culture and cytology?

trans-tracheal

trans-endoscopic

What are advantages for trans-endoscopic tracheal wash?

fast

no outside signs

visualzation

What are disadvantages for trans-endoscopic tracheal wash?

equipemtn costly

contamination LRT

What are advantages for trans-tracheal wash?

cheap equipment

no contamination

What are disadvantages for trans-tracheal wash?

sterile preparation

clip, small incision

no visualization

Elevated neutrophils, eosinophils, and mast cells on BALF cytology indicate what?

inflammation

Elevated RBCs, erythrophages, and hemosiderphages on BALF cytology indicate what?

bleeding

What is the normal cell population on BALF cytology?

50% macrophages, 50% lymphocytes, <5% neutrophils

What are indications to perform a thoracocentesis?

verify the presence of pleural effusion

collect fluid for cytological evaluation —> infection, inflammation, trauma, neoplasia

collect fluid for bacterial culture and antimicrobial sensitivity

treat pleural effusion, hemothorax, pneumothorax

for local therapy

Describe normal pleural fluid obtained by thoracocentesis.

straw colored, clear, and odorless

small volume <10mL

protein concentration < 3 gm/dL

cell count <10,000 cells/microliter and composed of nondegenerate neutrophils, mononuclear and mesothelial cells

What are indications that pleural fluid is septic?

cell count >10,000 cells/dL

presence of degenerative neutrophils

cloudy fluid that often contains fibrin clots

foul odor = anerobic infection

protein concentration > 3 gm/dL

glucose concentration <40mg/dL

preponderance of morphologically normal lymphocytes indicates chylous effusion

preponderance of morphologically abnormal lymphocytes indicates lymphosarcoma

What are indications to perform a pulmonary biopsy?

only in combinations with other techniques

diffuse lung disease

What are contraindications for pulmonary biopsy?

hemoptysis, hemorrhage

pneumothorax, infection

horses with respiratory distress

What are methods to perform pulmonary function testing?

classic test

oscillometry

plethysmography

forced expiration

What vessel should be used to obtain an arterial blood gas?

carotid artery

What is normal PaO2 for arterial blood gas?

95-100 mmHg

What is normal PaCO2 for arterial blood gas?

40-45 mmHg

Which respiratory sample should you submit for culture?

tracheal lavage fluid

It is easy to auscultate the equine lung.

False

It is best to perform endoscopy at a specific interval after exercise to determine if there is overt bleeding.

True

How long after exercise should you perform endoscopy for overt bleeding?

30-120 minutes post exercise

Tracheal lavage fluid cytology is a good indicator for lower airway inflammation.

False

Which is a better indicator for non-infectious lower airway inflammation?

bronchoalveolar lavage