Small Animal Pulmonary Diseases

Small Animal Pulmonary Parenchymal Diseases

• These diseases pertain to non-infectious conditions.
• A brief clinical signs/physical exam review is crucial in assessing pulmonary parenchymal disease.

Diseases Processes

• Non-cardiogenic pulmonary edema (NCPE): Characterized by fluid accumulation not due to heart issues.
• Pulmonary hemorrhage: Bleeding in the lungs.
• Pulmonary contusions: Injuries to the lung tissue caused by blunt force trauma.

What is the Pulmonary Parenchyma?

• The parenchyma is the functional part of an organ.
• It consists of alveoli, pulmonary microvasculature, and interstitial tissues.
• Oxygen and carbon dioxide are exchanged between the alveoli and capillaries.

Clinical Signs

• Cough
• Exercise intolerance
• Tachypnea
• Excessive panting
• Increased respiratory effort (leading to respiratory distress)

Physical Exam

• Inspiratory and/or expiratory effort assessment
• Evaluating bronchovesicular sounds (increased or decreased)
• Listening for crackles
• Looking for cyanosis

Helpful Information

• Clinical signs and physical exam findings can mimic airway, pleural space, and mediastinal diseases.
• Non-respiratory factors can also cause tachypnea.

Step 1: Stabilize the Patient First

• Administer oxygen
• Administer anxiolysis/sedation

Pulmonary Edema

• Edema is the abnormal accumulation of fluid in tissues.
• Pulmonary edema involves fluid buildup in the interstitial spaces and alveoli.
• Edema arises from problems in fluid flow through capillaries (due to pressure changes and permeability alterations).

Pulmonary Edema MOA - 3 Classifications

• High pressure PE: Due to cardiac issues (cardiogenic).
• Increased permeability PE: Due to inflammation (ARDS, TRALI).
• Mixed PE: High pressure and permeability issues combined.

Pulmonary Edema - Underlying Pathology

• Cardiogenic: Increased transcapillary pressure due to left atrial pressure increases.
• Non-cardiogenic: Increased transcapillary pressure without left atrial pressure increase, or increased vascular permeability.

Cardiogenic Pulmonary Edema

• Most common pulmonary edema type in veterinary medicine.
• Usually develops gradually.
• Treatment involves addressing the underlying cardiac condition and using diuretics.

Diagnosis

• Thoracic radiographs, echocardiogram, CT scans, and edema fluid protein levels are used.
• Differentiating between cardiogenic and non-cardiogenic edemas is critical.

Non-Cardiogenic Pulmonary Edema

• Acute respiratory distress syndrome (ARDS): Severe hypoxemic respiratory failure.
• Transfusion-related acute lung injury (TRALI): ARDS type connected to blood product transfusions.
• Negative pressure pulmonary edema (NPPE): Also called post-obstructive pulmonary edema (POPE). This edema is related to upper airway obstructions.
• Neurogenic: Post-traumatic brain injury or seizures can cause it.
• Electrocution: Extreme sympathetic stimulation causing edema.

Acute Respiratory Distress Syndrome (ARDS)

• A clinical syndrome characterized by severe hypoxemic respiratory failure.
• Severe pulmonary edema is due to increased capillary permeability.

Causes of ARDS

• Pulmonary: Aspiration pneumonia, pneumonia, pulmonary contusions, chest trauma, mechanical ventilation.
• Extra-pulmonary: Sepsis, systemic inflammatory response syndrome (SIRS), shock, pancreatitis, trauma, and acute kidney injury (AKI)

Pathophysiology of ARDS

• Injury to the lungs leads to fluid leakage which activates the immune system.
• Subsequent phases are exudative and proliferative.

Diagnostic Criteria for ARDS

• Acute onset, known risk factors, bilateral diffuse pulmonary infiltrates, high protein edema fluid, evidence of insufficient gas exchange.

Treatment and Prognosis of ARDS

• Treatment includes supportive care (oxygen therapy).
• Prognosis is poor (10-20% survival rate).

Transfusion-Related Acute Lung Injury (TRALI)

• Subset of ARDS linked to blood product transfusions.
• Blood product components cause neutrophils to accumulate in the lungs leading to inflammation.

Negative-Pressure Pulmonary Edema

• Develops from forcible inspiration against a closed glottis.
• The resulting low intrathoracic pressure causes fluid leakage.

Pulmonary Hemorrhage

• Bleeding from the airway or below larynx.
• Causes include infectious conditions (heartworm, leptospirosis), foreign bodies, neoplasia, and bleeding disorders.

Pulmonary Contusions

• Result from chest wall impacts.
• Damage leads to tissue hemorrhaging and fluid accumulation in the lung tissue.
• Symptoms worsen over 24-48 hours.

Diagnosing Pulmonary Disorders in Animals

• Important diagnostic tools include:
  • Thoracic radiographs
  • Lung ultrasound
  • CT scans
  • Transtracheal washes (TTW) or bronchoalveolar lavage (BAL)
  • Bloodwork (CBC, Coags)

Treatment and Prognosis for Various Pulmonary Conditions

• Treatment mainly involves supportive care, including oxygen supplementation and anxiolysis/sedation.
• Prognosis depends largely on the underlying condition.

Questions/Additional Points

• Identifying and distinguishing between different types of pulmonary edema through history, clinical signs, physical exam, and diagnostics
• Causes of upper airway obstructions

Neurogenic Pulmonary Edema (NPE)

• Associated with post-traumatic brain injuries or seizures.
• Pathophysiology involves fulminant sympathetic stimulation.
• Edema results from both systemic pressure increase and increased capillary permeability.

Electrocution

• Similar pathophysiology as NPE, involving extreme sympathetic stimulation.