Disorders of Respiratory System Flashcards
Define the anatomy of the pleural space and what is a pleural effusion?
The (potential) pleural space lies between the parietal pleura (innermost layer of chest wall) and the visceral pleura (outer lung layer). The potential pleural space is a capillary gap that normally contains only a few drops of serous fluid. However, this space may be enlarged when fluid (pleural effusion) fills this cavity.
a) What is the basic aetiology of a pleural effusion?
b) What is the diagnostic approach to a pleural effusion?
c) Describe the 2 main categories of pleural fluid?
d) What are the leading causes of transudative and exudative fluid?
a) Excess pleural fluid formation (from the interstitial spaces of the lung, the parietal pleura, or the peritoneal cavity) or when there is decreased fluid removal by the lymphatics.
b) Usually first picked up on CXR >CT >US guided thoracentesis>Measure fluid Protein & LDH
c) Transudative fluid, commonly caused by systemic factors, and exudative fluid, commonly caused by local factors.
d) Transudative: Left ventricular failure/cirrhosis/Nephrosis
Exudative: Bacterial pneumonia, malignancy, viral infection, and pulmonary embolism
a) How are transudative and exudative fluid initially differentiated?
a) Exudative fluid meets one of the following criteria:
1-Pleural fluid protein/serum protein >0.5
2-Pleural fluid LDH/serum LDH >0.6
3-Pleural fluid LDH more than two-thirds the normal upper limit for serum
NB: If clinically the patient is thought to have a transudative effusion, protein levels in the serum and the pleural fluid should be measured. If this gradient is >31 g/L (3.1 g/dL), the exudative categorization by these criteria can be ignored because almost all such patients have a transudative pleural effusion.
a) If the patient has an exudative pleural effusion, what further tests need to be ordered?
b) What is the glucose cut off level and what are the DDx above and below this?
a) Description of the appearance of the pleural fluid (PF)
PF glucose level
PF differential cell count
PF MC&S
TB markers and
PF cytology.
b) If Glucose level is <60mg/dL, consider malignancy, bacterial infections or rheumatoid pleuritis. If above this, consider PE or TB
a) What is the most common cause of Pleural Effusion, what is the treatment and what is another test that can confirm diagnosis?
a) The must common cause of Pleural Effusion is left ventricular failure. Treatment is primarily around optimisation via medications. If required, a pleural fluid N-terminal pro-brain natriuretic peptide (NT-proBNP) >1500 pg/mL is virtually diagnostic that the effusion is secondary to congestive heart failure.
a) What are the 11 types of pleural effusion?
b) Give a short definition of each.
a) Left Ventricular HF, Hepatic Hydrothorax, Parapneumonic effusion, effusion secondary to malignancy, mesothelioma, effusion secondary to PE, TB Pleuritis, Effusion secondary to viral infection, Chylothorax, Haemothorax, Miscellaneous
b) LVF: Fluid in the lung interstitial space crosses the visceral pleura; overwhelming lymphatic capacity to remove it.
Hepatic Chylothorax: Movement of peritoneal fluid through small diaphragm openings into pleural space. Commonly R).
Parapneumonic Effusion: Assoc w bacterial pneumonia, lung abscess, or bronchiectasis. Likely most common cause of exudative pleural effusion.
Effusion secondary to malignancy: Likely due to disseminated metastatic disease not amenable to chemotherapy.
Mesothelioma: Primary tumors that arise from the mesothelial cells (cells that reduce friction) that line the pleural cavities; most are related to asbestos exposure.
Effusion secondary to PE: Exudative pleural fluid.
TB Pleuritis: Due primarily to a hypersensitivity reaction to tuberculous protein in the pleural space.
Effusion secondary to viral infection: These effusions resolve spontaneously with no long-term residua.
Chylothorax: Thoracic duct is disrupted and chyle accumulates in the pleural space. Usually due to trauma.
Haemothorax: Most result from trauma; other causes include rupture of a blood vessel or tumor.
Miscellaneous-e.g. oesophageal rupture, pancreatic disease, abdominal abscess.
a) If a patient has a suspected transudative pleural effusion, what clinical signs would indicate that a diagnostic Thoracentesis still needs to be performed?
b) What is the name for a grossly purulent effusion?
c) Describe the differences in presentation with anaerobic vs aerobic bacterial pneumonia
a) If effusions are not bilateral and comparable in size, if patient is febrile, or if patient has chest pain.
b) Empyema
c) Aerobic-acute febrile illness, chest pain, sputum & leukocytosis.
Anaerobic-Subacute illness with wt loss, brisk leucocytosis, mild anaemia & hx predisposing them to aspiration
a) What is an indication for therapeutic thoracentesis in terms of pleural effusion size?
b) What 5 factors indicate that a procedure more invasive than thoracentesis may need to be perfomed? e.g. chest tube
a) If the free fluid separates lung from chest wall by >10 mm, a therapeutic thoracentesis should be performed
b)
1-Loculated pleural fluid
2-Pleural fluid pH <7.20
3-Pleural fluid glocose <3.3mmol/L (<60mg/dL)
4-Positive Gram stain or culture of the pleural fluid
5-Presence of gross pus in the pleural space
a) What are the treatment options for loculated pleural fluid?
b) What are the treatment options if fluid cannot be completely removed with therapeutic thoracentesis?
c) What 3 malignancies most commonly cause malignant pleural effusions?
d) How is the diagnosis of malignant pleural effusion made and what procedure should then be performed to prevent furture effusions?
a) Thoracoscopy with the breakdown of adhesions
b) Thoracoscopy (view the pleural space) Decortication (removing inner fibrous capsule)
c) Lung carcinoma, breast carcinoma and lymphoma
d) Cytology of pleural fluid, then if negative thoracoscopy if malignancy is suspected. Pleural abrasion (pleural abrasion - scrub parietal pleura until a uniform aspect of bloody pleura is achieved [usually to prevent recurrent spont pneumothorax])
should be performed at the time of thoracoscopy to effect a pleurodesis (adherance of lung to the chest wall).
a) What the CXR signs in mesothelioma and how is definitive Dx acheived?
b) How is TB Pleuritis diagnosed?
c) How is Chylothorax diagnosed, and what is the initial mgmt?
d) How do you define a haemothorax with blood markers in pleural fluid?
e) What is it called when abdominal ascites produce a pleural effusion?
a) Pleural effusion, generalised pleural thickening, shrunken hemithorax. Image guided needle biopsy or thoracoscopy is neeed for Dx.
b) High levels of TB markers in pleural fluid (adenosine deaminase or interferon-y). Also Dx can be done via culture of pleural fluid, needle biopsy of the pleura, or thoracoscopy.
NB: Treatments of pleural and pulmonary TB are identical.
c) Milky pleural fluid, triglyceride level exceeding 1.2mmol/L. Initial rx is insertion of chest tube and administration of ocreotide (somatostatin analogue).
d) When haematocrit is more than one-half of tha tin peripheral blood.
e) Meigs’ syndrome
1-Desribe the Functional Residual Capacity (FRC)
2-Describe Vital Capacity (VC)
3-Describe air flow and pressure gradients in the airways during expiration. How is this related to FEV1?
1- Outward recoil of the chest wall is equal to the inward recoil of the lung, i.e lung is pulled both outward and inward simultaneously at FRC, and thus its pressure falls below atmospheric pressure (typically, −5 cmH2O).
2-Excursion between full and minimal lung inflation
3-During exhalation, gas leaving the alveoli must gain velocity as it proceeds toward the mouth. This reduces intraluminal gas pressure, airway size and flow, until there is not net increase in flow aka flow limit. FEV1 in spirometry can be used to measure this flow limit.
1) How does pulmonary fibrosis change maximal expiratory flow and why?
2-How does Emphysema change maximal expiratory flow and why?
3) How does Asthma or Chronic bronchitis change maximal expiratory flow and why?
1-Pulmonary fibrosis increases maximal expiratory flow in relation to lung volume, because lung recoil pressure is increased.
2-In emphysema, lung recoil pressure is reduced; this reduction is a principal mechanism by which maximal expiratory flows fall.
3-Diseases that narrow the airway lumen at any transmural pressure (e.g., asthma or chronic bronchitis) or that cause excessive airway collapsibility (e.g., tracheomalacia) also reduce maximal expiratory flow.
1-Describe these flow volume loops
2-Why does airflow limitation seldom occur during inspiration?
1-Flow-volume loops. A. Normal. B. Airflow obstruction.
C. Fixed central airway obstruction (either above or below the thoracic inlet).
D. Variable upper airway obstruction (above the thoracic inlet)
E. Variable lower airway obstruction (below the thoracic inlet).
2-The more negative pleural pressures during inspiration lower the pressure outside of the airways, thereby increasing transmural pressure and promoting airway expansion
Section-WOB
