Acute respiratory medicine Flashcards
(20 cards)
Define the two types of respiratory failure.
Type 1 - hypoxaemia and normal/low CO2
(i.e. the lung retains its ability to blow off CO2)
Type 2 - hypoxaemia AND hypercapnia
What is the aetiology of type 1 respiratory failure?
Type 1 - ventilation/perfusion (V/Q) mismatch to certain PARTS of the lung
Reduced ventilation (adequate perfusion) - problem with alveoli:
- acute asthma
- atelectasis (collapsed lung)
- pneumothorax
- pulmonary oedema
- pneumonia
- ARDS
Reduced perfusion:
- PE
What is the aetiology of type 2 respiratory failure?
Type 2 - affects lung as a WHOLE → inadequate ventilation (affects concentration gradients of CO2 and O2)
- acute severe asthma
- COPD
- upper airway obstruction
- neuropathies (GBS, MND)
- drugs (opiates)
Asthma, COPD → obstructive lung diseases → can’t expel air properly → impairs ventilation
How can respiratory failure be managed?
Type 1 - CPAP
Type 2 - BiPAP
What is a pneumothorax?
Air in the pleural space (between visceral and parietal pleura)
What are the different types of pneumothorax?
Spontaneous (primary and secondary)
Traumatic
Tension
What is the aetiology and risk factors for a spontaneous pneumothorax?
PRIMARY:
Aetiology - rupture of a subpleural bleb
Risk factors:
- male
- tall and thin
- smoker
SECONDARY:
Aetiology - pre-existing lung disease which affects alveoli (so air is more likely to leak out and collect under the visceral pleura → more prone to rupture)
Examples:
- COPD
- cystic fibrosis
- TB
- pneumonia
- lung carcinoma
What is a tension pneumothorax?
When a one-way valve is created so air can enter into the pleural space but cannot escape
Air builds up and pneumothorax gets larger → MEDICAL EMERGENCY
What are the complications and symptoms/signs of a tension pneumothorax?
Complications:
- lung compression
- mediastinal shift
Symptoms/signs of lung compression;
- severe dyspnoea
- tracheal deviation (away from lesion)
- silent chest (i.e. no breath sounds in that region)
- hyperresonance
- reduced expansion (on lesioned side)
Symptoms of mediastinal shift:
- hypotension
- tachycardia
How would you treat a pneumothorax?
Tension pneumothorax:
- needle aspiration (2nd ICS MCL)
Primary pneumothorax:
- If no SOB or <2cm: discharge
- > 2cm/SOB: needle aspiration + O2
- Otherwise: chest drain (+ O2)
Secondary pneumothorax (lung disease or 50 y/o smoker):
- If no SoB or <1cm: Observe + O2
- 1-2cm: needle aspiration
- > 2cm/SoB: chest drain (+ O2)
What are the different types of PE?
Acute massive PE - sudden complete occlusion of pulmonary artery
Acute submassive PE - sudden incomplete occlusion of pulmonary artery
Chronic PE - acute PE treated but clot does not fully dissolve → gets lodged in pulmonary microvasculature
What are the symptoms of the different types of PE?
Acute massive PE:
- collapse
- central crushing pain
- severe dyspnoea
Acute submassive PE:
- pleuritic chest pain
- haemoptysis
- dyspnoea
Chronic PE:
- exertional dyspnoea
What are the signs of PE on investigation?
ECG:
S1Q3T3 pattern (indicative of RV strain and therefore suggestive of PE):
- a prominent S wave in lead I
- a Q wave (i.e. like deep) and inverted T wave in lead III
- Sinus tachycardia
- RBBB (marrow)
- Right axis deviation
CXR:
- Westermark sign
(area of increased translucency of lung distal to occlusion caused by ischaemia and infarction)
How do you prevent a venous thromboembolism?
Mechanical - anti-embolic (compression) stockings
Pharmacological - LMWH
How would you investigate a PE?
Calculate a Well’s score to determine the patient’s risk of having a PE
If score is:
- 4 or more - high risk of PE → CTPA
- less than 4 - low risk of PE → D dimer
(negative D dimer = no PE, positive doesn’t necessarily mean PE - could be something else)
Positive D-dimer:
- immediate CTPA to rule out PE
- if not possible, prescribe LMWH or Fondaparinux in the meantime (↑ antithrombin action)
What does the Well’s score take into account?
PE SCORE:
- Previous DVT/PE
- Evidence of DVT
- Stasis
- Cancer
- Opinion is PE
- Rate Raised (>100)
- Exsanguination (haemoptysis)
How would you manage a PE?
Are they haemodynamically stable? (unstable = SBP < 90 mm Hg)
YES (submassive PE):
- respiratory support
- anticoagulation (fondaparinux/heparin for 5 days, warfarin for 3 months)
NO (massive PE):
- respiratory support
- 1st line: thrombolysis (alteplase, streptokinase - fibrinolytics)
- 2nd line: embolectomy
What is ARDS?
Acute hypoxaemic lung injury:
- diffuse inflammatory response in alveoli
→ pulmonary oedema and alveolar collapse
→ reduced ventilation
→ V/Q mismatch
→ type 1 respiratory failure
What are some causes of ARDS?
Things that cause systemic inflammation:
- drugs
- severe burns
- transfusion reactions
- sepsis
Things that cause primary alveolar inflammation:
- pneumonia
- nearly drowning
- COVID
How do you define ARDS?
Using the Berlin criteria
Simplified version - ARDS:
Alternative cause (i.e. there isn’t one - like cardiogenic pulmonary oedema)
Rapid onset (i.e. < 1 week)
Dyspnoea
Similar to cardiogenic pulmonary oedema on CXR
