Session 6 Flashcards
(43 cards)
What is a pneumothorax
Presence of air in the pleural space
Why does air enter the pleural space
-Pleura have a hole
-Intrapleural pressure is lower than atmospheric pressure
-Air moves from an area of high to low pressure
-Pleural seal is broken
-Lungs disconnected from chest wall and collapse due to inward elastic recoil
When does primary spontaneous pneumothorax occur
Usually young, tall, thin males
Rupture of an underlying sub pleural blew or bulla can be responsible
What are blebs and bullas
Bleb = small thin walled air containing spaces
Bulla = permanent, air filled space at least 1cm
How does bleb or bulla rupture cause pneumothorax
Creates an opening on visceral pleura
Consequent loss of negative intrapleural pressure
Loss of seal
Partial or complete lung collapse
Smoking and pneumothorax
Increases risk of primary spontaneous pneumothorax by 10-20 fold
Secondary spontaneous pneumothorax causes
COPD, CF, lung malignancy or asthma
Traumatic pneumothorax cause
Iatrogenic- invasive medical procedures e.g. central vein cannulation, pleural tap or biopsy, transbronchial biopsy, fine needle aspiration
Accidental = penetrating chest injury lacerating parietal pleura and/or visceral pleura, laceration due to fractures rib
What is a tension pneumothorax
Can occur due to any aetiology and is defined as any size of pneumothorax causing mediastinal shift and cardiovascular collapse
How does a tension pneumothorax develop
Due to a one-way valve system at site of breach in pleural membrane
Air enters pleural cavity during inspiration but doesn’t leave during expiration
Increase in intrapleural pressure that exceeds atmospheric pressure for much of respiratory cycle
Result of tension pneumothorax
Impaired gas exchange from loss of lung volume
Impaired venous return and reduced cardiac output
Typical features of hypoxaemia and haemodynamic Compromise
How does mediastinal shift occur
Tension pneumothorax
Mediastinum shifts towards Contralateral side
Impinges on and compresses Contralateral lung
impairs cardiac venous return
Why does pneumothorax cause impaired cardiac venous return
Veins of the body rely on low intrathoracic pressure to return blood to the heart
Course of the veins returning to heart is distorted due to mediastinal shift
Decreased preload and decreased cardiac output = decreased blood pressure (unless compensatory mechanisms)
Reason for tachycardia in tension pneumothorax
Cardiac output = Stroke volume x HR
Increased intrathoracic pressure and hypoxaemia may directly impact heart
What do to when tension pneumothorax is suspected
Immediate decompression of thorax - not delayed for radiographer confirmation
Needle thoracocentesis: wide bore cannula into second intercostal space mid clavicular line (2ICS MCL), just above the third rib
Clinical features and radiology of pneumothorax
Sudden onset of pleuritic chest pain and dyspnea
Reduced chest movements and breath sounds on affected side,
percussion hyper resonant on affected side, vocal resonance reduced
Clinical features that suggest tension pneumothorax
Severe respiratory distress, tachypnoea, tracheal shift, elevated JVP, tachycardia, hypotension
By what route is the air getting into the pleural space when a visceral bleb bursts (as in primary spontaneous pneumothorax)
Air enters through lung parenchyma across visceral pleura and into space during inspiration
Pleural seal broken, part or all of lung collapses
Not a one way valve as each expiration of air can get out of pleural space
What maintains pleural fluid
Secreted by parietal pleura and drained through lymphatics of parietal pleura
Balance of hydrostatic and oncotic pressures and lymphatic drainage
Purpose of pleural fluid
Maintains pleural seal that keeps visceral and parietal pleura connected
Lubricant to facilitate sliding motion of both pleural surfaces during inspiration and expiration
Pleural effusions may result from
Disruption of the balance between hydrostatic and oncotic pressures, or disrupted lymphatic drainage
What is pleural effusion
Collection of extra fluid in the pleural space
Types of pleural effusion
Blood = haemothorax
Chyle = chylothorax (lymph)
Pus = empyema
Characterisation of effusions
Removal and analysis of fluid = diagnostic pleural aspiration
Simple effusions= transudates or exudates
