Small Animal Pulmonary Diseases Quiz

Small Animal Pulmonary Parenchymal Diseases

• These diseases are non-infectious.
• A brief outline includes clinical signs and physical examination of the disease.
• Diseases processes include non-cardiogenic pulmonary edema (NCPE), pulmonary hemorrhage, and pulmonary contusions.

Pulmonary Parenchyma

• The pulmonary parenchyma is the functional tissue of the lung.
• It includes alveoli, pulmonary microvasculature, and interstitial tissues.
• The alveoli are involved in gas exchange, with oxygen entering and carbon dioxide exiting the bloodstream.

Clinical Signs

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

Physical Exam

• Difficulty breathing (inspiratory and/or expiratory effort)
• Changes in bronchovesicular sounds (increased or decreased)
• Crackles (abnormal lung sounds)
• Cyanosis (bluish discoloration of the mucous membranes)

Helpful Information

• Clinical signs and physical exam findings can mimic other conditions such as airway, pleural space, or mediastinal diseases.
• Non-respiratory causes of tachypnea should also be considered.

Stabilization

• The first step is to stabilize the patient.
• Oxygen administration is a key initial treatment.
• Anxiolysis (anxiety reduction) / sedation might be needed.

Pulmonary Edema

• Edema is abnormal fluid buildup in tissues.
• In pulmonary edema, serous or hemorrhagic fluid accumulates in the interstitial space and alveoli.
• Edema is caused by alterations in fluid flow across capillaries
• Changes in pressure (e.g., increased, decreased) and capillary permeability may occur.

Pulmonary Edema MOA - 3 Classifications

• High pressure PE: Can be cardiogenic. Fluid therapy may be needed.
• Increased permeability PE: Conditions such as ARDS and TRALI can lead to this type of PE.
• Mixed PE has both high pressure and permeability components; the causes often include negative pressure (e.g., neurogenic or electrocution).

Cardiogenic Pulmonary Edema

• This is the most common type in veterinary medicine.
• It usually develops gradually, and is often caused by left-sided heart failure which increases left atrial pressure.
• Increased pulmonary capillary pressure, caused by increased venous pressure, leads to fluid leaking into the lungs.

Non-Cardiogenic Pulmonary Edema

• This type includes ARDS, TRALI, and negative pressure pulmonary edema (NPPE; also called post-obstructive pulmonary edema or POPE).
• Other causes may include neurogenic and electrocution.

Acute Respiratory Distress Syndrome (ARDS)

• ARDS is a severe hypoxemic respiratory failure.
• It’s caused by capillary permeability issues resulting in fluid, protein, red blood cells and white blood cells leaking into the alveoli of the lungs.
• Inflammation plays a key role from injury to the lungs (including mechanical ventilation, systemic injury).

Causes of ARDS

• Pulmonary causes (e.g., aspiration pneumonia, pneumonia, pulmonary contusions, chest trauma, mechanical ventilation).
• Extra-pulmonary causes (e.g., sepsis, systemic inflammatory response syndrome (SIRS), shock, pancreatitis, trauma, acute kidney injury (AKI).

Pathophysiology of ARDS

• Damage to the lungs (local or systemic injury) results in inflammation, release of fluids and proteins into the alveoli, and further immune system activation.
• This may lead to a fibroproliferative phase with the proliferation of type II pneumocytes and interstitial fibrosis.

Diagnostic Criteria of ARDS

• Acute onset (< 72 hours)
• Known risk factors
• Thoracic radiographs show bilateral, diffuse pulmonary infiltrates.
• High protein edema fluid.
• Evidence of insufficient gas exchange on blood gas analysis.

Treatment and Prognosis (Pulmonary Diseases)

• Oxygen therapy; often mechanical ventilation is required.
• Treatment of the underlying condition using medications such as corticosteroids, bronchodilators, and pulmonary vasodilators.
• Prognosis is variable, often severe, with survival rates around 10–20% despite treatment.

Transfusion-related Acute Lung Injury (TRALI)

• A subset of ARDS associated with blood transfusions.
• Components in the blood products cause neutrophils to accumulate in the lungs, which triggers inflammation.
• Treatment includes oxygen therapy and supportive care.

Negative Pressure Pulmonary Edema

• Causes include strangulation, choking, near-hanging, and upper airway obstructions.
• Forcible inspiration against a closed glottis and dramatically decreased intrathoracic pressure lead to a decrease in pulmonary interstitial hydrostatic pressure.
• This change leads to increased venous return to the right heart and increased pressure gradient between pulmonary interstitium and vessels.
• This results in fluid leaking from capillaries to the interstitial space.

Neurogenic Pulmonary Edema (NPE)

• Post-traumatic brain injury and seizures are possible causes.
• Fulminant sympathetic stimulation results in an increase in systemic arterial and venous pressures causing the increase in capillary permeability.

Electrocution

• A subcategory of neurogenic pulmonary edema.
• Similar pathophysiology to NPE, characterized by extreme sympathetic stimulation.
• Radiographic findings are bilateral, diffuse interstitial to alveolar infiltrates.
• Treatment is supportive and includes oxygen therapy.
• Prognosis is usually good with supportive care.

Diagnosis Approaches

• History, clinical signs, and physical exam are essential for developing a preliminary diagnosis.
• Radiographs (thoracic), echocardiogram, CT scans, and fluid protein levels are diagnostic tools.
• A differential diagnosis using approaches outlined in the presentation may be required.

Pulmonary Hemorrhage

• Bleeding from any source in the respiratory tract is a possibility causing pulmonary hemorrhage.
• Infectious agents (e.g., heartworm, leptospirosis) and foreign bodies are possible causes.
• Diseases such as neoplasia or bleeding disorders can cause the hemorrhage.
• Blunt force trauma (contusions) in the chest region can cause bleeding issues.

Pulmonary Contusions

• Chest wall impact causes injury to the lungs and results in lung contusions.
• Hemorrhage and fluid leak into the lung parenchyma and can worsen over 24–48 hours.

Diagnostic approach

• Thoracic radiographs of variable and non-specific findings.
• Lung ultrasound is also a crucial diagnostic tool.
• Transtracheal washes (TTWs) or bronchoalveolar lavage (BALs)
• Bloodwork testing (CBC, coagulation profiles) are helpful for diagnostic purposes.

Treatment and Prognosis

• Oxygen therapy and treatment of underlying conditions are necessary to manage respiratory issues.
• Treatments depend on the specific disease and factors such as underlying cause.
• The presentation shows good prognosis for some conditions.
• Prognosis depends on the underlying condition.

Test your knowledge on non-infectious pulmonary parenchymal diseases in small animals. This quiz covers clinical signs, physical examination findings, and key disease processes such as non-cardiogenic pulmonary edema and pulmonary hemorrhage. Enhance your understanding of respiratory health in pets.