Pleural disease

• What are the 4 reasons for difficulty breathing?

  URT obstruction

  Loss of thoracic capacity

  Pulmonary parenchyma disease

  Non-CRS conditions

  metabolic/ physiologic
• Causes for the loss of the thoracic capacity

  Pleural effusion - blood, pus, chyle, true/modified transudate.

  Pneumothorax

  Neoplasia - pleural or mediastinal

  Ruptured diaphragm

  Abdominal abnormality - severe ascites/ mass.

  Gross cardiomegaly.
• What is the pluera?

  Inner wall of the body cavities lined by single layer of mesothelial cells. Pleura covering the surface of the lung is the visceral (pulmonary) pleura.
• What is the mediastinum?

  Left and right pleural sac around the lungs. Mediastinum is the space between them. More or less in the midline of the thorax. Mediastinum is continuous in most species. Thin in dogs and cats. Contains important structures: blood vessels, nerves, oesophagus, heart and trachea.
• What is pleural disease?

  Accumulation of:

  Fluid - pleural effusion

  Air - pneumothorax

  Soft tissue mass - abdominal organs.

  Severity of disease depends on the quantity of fluid or air, or size of the mass.

  In addition to direct compression of lungs can also lead to a loss of negative pressure causing the lungs to collapse.
• Clinical signs of pleural disease

  Restrictive breathing pattern; short, shallow breaths.

  Tachypnoea

  Open mouth breathing

  Dyspnoea, respiratory distress.

  Orthopnoea - elbow abduction, sternal recumbency, using theit bodies to open their lungs as much as possible, this is only normal in tortoises as they do not have diaphragms.

  Cyanosis.
• Pleural effusion

  Accumulation of fluid. On auscultation can hear muffling of lung and heart sounds especially ventrally when standing. On percussion there is increased dullness. A number of different fluid types can be present.
• What are the causes of pleural effusion?

  Leaky capillaries, increased intravascular pressure, increase in interstitial lung fluid, decrease in pleural pressure, increase in pleural fluid protein (increases oncotic pressure), disruption of the thoracic duct or blood vessels.
• What is hypoalbuminaemia?

  Less albumin in the blood than there should be, transudate will pool when you have less albumin. Occurs when have a condition causing you to loose protein from the gut, e.g. protein losing enteropathy.
• Modified transudate in pleural effusion causes?

  Most common cause is due to increased hydrostatic pressure secondary to right sided heart failure (e.g. pericardial disease, cardiomyopathy, pulmonary hypertension, pulmonary stenosis). Caused by diaphragmatic hernia or lung lobe torsion or neoplasia.
• Non-septic effusion (exudate)

  FIP, neoplasia, chronic chylothorax, chronic lung lobe torsion, fungal infection.
• Septic effusion (pyothorax) exudate

  Penetrating chest wound, foreign body inhalation (grass seed), ruptured oesophagus, ruptured pulmonary abscess/ tumour, Haematogenous bacterial spread.
• Chyle (chylothorax) exudate

  Disruption of the thoracic duct - Lymphangiectasia, cranial vena cava obstruction, neoplasia, heart disease, fungal infection, lung lobe torsion, diaphragmatic hernia, trauma of the thoracic duct.
• Blood (haemothorax) exudate

  Trauma, coagulopathy, neoplasia, lung lobe torsion.
• There is pleural effusion in the X-ray because the lung has been pushed away by the pleural fluid.

  
• Thoracocentesis

  Local anaesthetic rarely needed unless large bore catheter.

  Clip area - if possible use quiet clippers (minimise stress).

  Quickly surgically prepare the site.

  Butterfly needle or catheter at intercostal space 6-8.

  Ideally localise large pocket of fluid with the ultrasound first.

  Aseptic technique.
• Thoracostomy (chest drains)

  Use in animals that will require multiple thoracocentesis over a short period of time, if there are large volumes of effusion, pneumothorax, chest wall injuries (flail chest/ flail segment), bite wounds, most Pyothorax cases or following chest surgery.
• Management of effusion

  Heart failure - treatment of HF

  Pericardial effusion - treat effusion with drainage

  Pyothorax - antibiotics, systemic and local (broad spectrum and treat anaerobes), be aware that cultures will often come back as negative, Lavage, long course of treatment with guarded prognosis.

  Chylothorax - Diet and/or surgery.
• Pneumothorax

  Rupture of major airways/ lung parenchyma.

  Thoracic trauma (e.g. broken rib lacerates pleura, penetrating wound).

  Perforation of the oesophagus.

  Bullous, necrotic or neoplastic lung disease which leak air into the pleural space.

  Iatrogenic (e.g. prolonged ventilation under GA, bronchoscopy).

  Gas producing bacterial infection in pleural space.
• clinical findings with pneumothorax

  Restricitive breathing (slow-rapid breaths).

  Auscultation reveals dull lung sounds dorsally, increased sounds ventrally (bronchovesicular).

  Percussion - increased resonance (sounds like a drum).
• Diagnosing pneumothorax

  Physical examination. Assesment of respiratory status. Thoracic radiographs, if the animal is stable enough. Routine heamotology/ biochemistry. Blood gases and pulse oximetry - helps to asses severity.
• Pathophysiology of pneumothorax

  Loss of negative pressure in pleural space means that lungs are not effectively ’coupled’ to rib cage. As rib cage is raised lungs do not inflate. Lungs collapse and tidal volume is very low. Severity depends on degree of the pneumothorax and underlying disease.
• Treatment of traumatic pneumothorax

  Oxygen treatment, drain pneumothorax as necessary (avoid over drainage). Approximately 90% recovery with strict cage rest up to 2 weeks. Some will require chest drains and Heimlich valve. If no improvement then surgical exploration and correction will be required. If open wounds the sterile dressings and surgery as soon as patient is stable.
• Spontaneous pneumothorax

  History; dyspnoea, anorexia, vomiting, may present with rapid progression of respiratory distress.

  Most common cause is ruptures pulmonary bulla or sub-pleural bleb.

  Can occur with chronic asthma in cats.
• management of spontaneous pneumothorax

  Medical management to stabilise until diagnostic tests decide whether surgical intervention is required. Lobectomy as necessary. Prognosis is dependant on the underlying cause.
• Mediastinal lymphoma

  Most common in young cats, also seen in cats with multi centric or stage 3-5 lymphoma if so is considered a negative prognostic indicator. Tachypnoea, inspiratory hyper-Noel, dull heart sounds, pleural effusion. Non-compressible anterior mediastinum

  Check FeLV/FIV status (~50% positive for FeLV).

  treat with chemo +/- radiotherapy.
• Thymoma

  Rare, commonest in older dogs. From thymi’s epithelium, often infiltrated with lymphocytes. Benign or malignant, mets rare from both. 60% feline version cystic. Present with respiratory distress +/- cranial caval syndrome +/- myaesthenia gravis. Megaoesophagus also common if focal MG or disrupted due to presence of mass.
• Cranial caval syndrome

  Mass pressing on the cranial vena cava and causing problems where the restart of the blood is building up in the body and the only way it can go is leak out the valve and you get this effusion around the face.
• Pleural tumour

  Mesothelioma - RARE

  From epithelial lining cells - pleural, abdominal, pericardial. Major links with asbestos inhalation, complex mechanism. Causes large volume effusions and pain. Multifocal small masses, hard to image, ultrasound and CT most useful.