Air and Liquid in Pleural Space - Scharf Flashcards
What are the pleural pressures?
Liquid pressure = hydrostatic pressure or weight of water column due to gravity (1cm/cm height)
Surface Pressure = pressure of two surfaces pushing together (depends mostly on shape of lungs and CW
Measured by:
esophageal balloon
pleural balloons (pericardial balloons)
liquid filled catheter
Causes of pleural effusion
• Increased fluid in lung (>5ml/g lung dry weight)
– CHF, pneumonia (parapneumonic), pulmonary embolus,
transplant (no lymph drainage from lung)
• Increased intravascular pressure in pleural
– RV or LV failure, SVC syndrome (obstruction 0f SVC by tumor)
• Increased pleural fluid protein (depends on Lp)
• Decreased pleural pressure
– atelectasis, stiff lung
• Increased fluid in peritoneal cavity: through direct
connections (defects) - ascitis, peritoneal dialysis
– pressure gradient favors movement to chest from abdomen
• Disruption of thoracic duct (chylous or white effusion
Decreased Fluid Absorption
• Obstruction of lymphatics draining parietal pleura
– tumor
• Increased systemic vascular pressure
– fluid overload, CHF, SVC syndrome
Exudate vs Transudate
Exudate associated with increased Lp
inflammation of pleura or lung,
shedding of cells or protein into pl. space
tumor
Transudate associated with increased hydrostatic
pressure - CHF, lymph obstruction
Criteria for effusion over transudate=Light criteria:
Ratio Protein Effusion/Serum >.5
Ratio LDH Effusion/Serum >.6
WBC > 500
1/3 is 67% chance, 2/3 is 95% of exudate
What should be analyzed in pathological pleural fluid?
Macroscopic description
Protein, LDH, Cell count
Cytology/microscopic
Cultures - routine, TB, Fungus
Glucose
• low glucose effusions: TB, empyema,
connective tissue diseases
Amylase - pancreatic disease (Left)
pH (production of CO2 by organisms)
Other - fibers, hyaluronidase, etc.
Physiologic effects of pleural effusion
Physiologic effects of pleural effusion
Restrictive ventilatory defect (loss of lung
volume)
• However: Only around 1/3 of the effusion volume is lost to
the vital capacity. Most goes into expanding the chest
wall
• Hypoxemia is secondary to closure of terminal airway
units - especially with obesity or lung disease
Dyspnea
– Inspiratory muscles are shortened (loss of force
generation)
– Related to underlying lung disease which just
exaggerated the effects of the effusion
Effects on venous return and diastolic filling
• hinders ability to increase CO in exercise
Why is there no gas in the pleural space?
Gradient drives it into the capillaries and out of the space. Even more so without nitrogen (with 100% O2 administration).
If present, can cause pneumothorax.
Physiologic consequences of pneumothorax
Increase pleural pressure causes decreased transpulmonary pressure in the lung. Chest wall pressure and volume increases. Leads to decrease in vital capacity.
Spontaneous pneumothorax
•Primary has incidence of 1.2/1000,000 per year
•Rupture of subpleural blebs (bubbles) usually in
apices
•Airway inflammation plays a role
• smoking, pollution
•Predisposition: broad swings in atmospheric
pressure
-DIVING (surfacing with breath hold or with closed airways - e.g. asthma)
•Tall, thin males especially predisposed, Marfan’s,
bronchial abnormalities
Complications: tension pneumothorax and contralateral recurrence cause death.
Signs and symptoms of spontaneous pneumothorax
Nothing,, Dyspnea, Sharp chest pain, develops at rest, Horner’s syndrome (rare), hyperresonance of chest, tracheal deviation away from side of PTX, Ribs more apart on side of PTX.
Therapy for spontaneous pneumothorax
•CT scan not necessarily indicated in first occurrence,
but
•should be used for most other cases
•Observe and O2 in mild cases
•Drain pleural space - aspirate, chest tube
•Instillation of sclerosing agents
-Talc, Tetracycline, Doxycycline
•Staple apical bullae - VATS, Open thoracotomy
•Predicting recurrence: Hard to do.
•Most clinicians will not do extensive work up for first
simple uncomplicated event - Diving should be
prohibited
