Respiratory Flashcards
What is type 1 respiratory failure?
Low PaO2 with normal/low PaCO2
What is type 2 respiratory failure?
Low PaO2 with raised PaCO2
What 3 things can cause a raised alveolar-arterial gradient?
- V/Q (ventilation/perfusion) mismatch
- Diffusion limitation
- Shunt (right to left)
What causes a normal alveolar-arterial gradient but low PaO2?
Low oxygen tension, caused by hypoventilation or reduced FiO2 e.g. at high altitudes
What acute adaptations to high altitude does the body make?
Increased heart rate
Hyperventilation
Give an example of an adaption to chronic high altitude
Increase haemoglobin concentration
What is high altitude pulmonary oedema?
Pulmonary oedema caused by exaggerated hypoxic pulmonary vasoconstriction that can happen to some individuals 2-3 days after ascent.
What is the treatment for high altitude pulmonary oedema?
Descent, oxygen and pulmonary vasodilators
What is the most common monogenic recessive disorder?
Cystic fibrosis
What are the features of cystic fibrosis?
- Abnormal ion transport
- Impaired mucociliary clearance
- Recurrent and chronic infections
- Impaired digestion
- Fertility problems
- Liver disease and diabetes
How is obstructive lung disease classified?
Low FEV1 (i.e. <80% predicted) FEV1/FVC ratio <0.7
How is restrictive lung disease classified?
Low FVC (i.e. <80% predicted) FEV1/FVC ratio normal
Which type of lung disease affects the airways?
Obstructive
Which type of lung disease can affect the lung parenchyma and chest wall/pleura?
Restrictive
What is TLCO?
A measurement of the lung’s diffusing capacity (by measuring uptake of CO)
What causes low TLCO?
- Thickening of the alveolar-capillary membrane
- Reduced lung volumes
What causes raised TLCO?
- Bronchiectasis
- Pulmonary vasculitis
- Obstructive sleep apnoea
In healthy individuals, how much fluid is present in the pleural space?
5-10ml
What is pneumothorax?
Collapse of the lung, caused by the presence of air in the pleural space
What are the four categories of pneumothorax?
- Primary spontaneous pneumothorax
- Secondary spontaneous pneumothorax
- Traumatic pneumothorax
- Iatrogenic pneumothorax
What causes primary spontaneous pneumothorax?
Rupture of an apical pleural bleb, which forms a pin-prick size hole. (No underlying lung disease)
What are the risk factors for primary spontaneous pneumothorax?
Male, smoker, tall and thin, age 20-40
High risk of recurrence
What causes secondary spontaneous pneumothorax?
- Known lung disease, usually COPD but can also be caused by asthma, ILD, cancer, cystic lung disease.
- Infection (anything that causes cysts in the lungs)
- Genetic predisposition e.g. from Marfan’s syndrome
Give some examples of procedures that could lead to iatrogenic pneumothorax
Pacemakers, CT lung biopsies, central line insertion, mechanical ventilation, pleural aspiration
How can pneumothorax present?
Can be asymptomatic, but can also cause sudden breathlessness, pleuritic chest pain and a cough. Rarely presents with life threatening respiratory failure/cardiac arrest.
What are the signs of pneumothorax?
- Small pneumothorax may have no clinical signs
- Tachypnoea
- Hypoxia
- Unilateral chest wall expansion
- Reduced breath sounds
- Hyper-resonant percussion note
What potentially life-threatening condition can cause tracheal deviation, surgical emphysema, distended neck veins and cardiovascular compromise?
Tension pneumothorax
What causes tension pneumothorax?
A valve-like mechanism forms and air enters the pleural space, increasing pressure in the chest and causing compression and reduced blood flow back to the heart.
How is tension pneumothorax managed?
Urgent decompression by inserting cannula then removing the needle, followed by chest drain insertion as longer term measure.
What is surgical emphysema?
When air leaks out of the pneumothorax via a breach in the parietal pleura and finds its way under the skin, causing the skin to feel like bubble wrap. Auscultation reveals a crepitus type noise.
How is surgical emphysema treated?
By making little cuts in the skin to let the air out
What is pleural effusion?
Collection of fluid in the pleural space (will collect at the bottom if patient is sitting up so will show up better on x-ray if patient is upright)
What causes pleural effusion?
Imbalance in hydrostatic and oncotic pressure differences, therefore caused by anything that affect oncotic pressures e.g. inflammation.
What are the two categories of pleural effusion?
Transudates
Exudates
What is transudative pleural effusion?
Pleural effusion caused by increased hydrostatic pressure or reduced osmotic pressure in microvascular circulation
–> pleural fluid protein <50% of serum protein
Give some examples of conditions that can cause transudative pleural effusion
Heart failure Cirrhotic liver disease Renal failure Hypoalbuminaemia Myxoedema (thyroid failure) Ascites/peritoneal dialysis Meig's syndrome
What is exudative pleural effusion?
Pleural effusion caused by increased capillary permeability and impaired reabsorption
–> pleural fluid protein is > 50% of serum protein
Give some examples of conditions that can cause exudative pleural effusion
Pneumonia Cancer TB Autoimmune conditions e.g. rheumatoid arthritis, SLE Pulmonary embolism Asbestos Post cardiac surgery Drug induced e.g. amiodarone, beta blockers, methotrexate, phenytoin
What are the symptoms of pleural effusion?
Breathlessness Cough Fever Pain Others dependent on underlying cause
What are the signs of pleural effusion?
Reduced chest wall expansion
Quiet breath sounds
‘Stony’ dull percussion
Reduced tactile/vocal fremitus
Shows up on x-ray once about 250ml of fluid is present
How is pleural effusion investigated?
Initial chest x-ray
Thoracic USS with pleural aspiration
CT chest for cysts
Pleural aspirate can be sent for microscopy, culture and cytology.
What does turbid/foul smelling pleural aspirate indicate?
Empyema/parapneumonic effusion
What does bloodstained pleural aspirate indicate?
Haemothorax/trauma/PE
What do food particles in pleural aspirate indicate?
Oesophageal fistula
What procedures can be carried out during a medical thoracoscopy for pleural effusion?
Pleural fluid drainage
Biopsies for diagnosis
Talc poudrage for pleurodesis
How is pleural effusion managed?
Depends on size, symptoms and underlying cause
- Small –> treat conservatively
- Infection –> antibiotics, chest drain if pus present
- Malignant effusion –> consider chest drain +/- talc
- Treat underlying cause
What features of pleural aspirate would suggest infection?
Low pH <7.2 Glucose <3.4mmol/L PF LDH > 1000IU/L Bacterial growth on culture Macroscopic appearance of pus (also smell)
What is empyema?
Pus in the pleural space
What organisms are usually responsible for community acquired empyema?
Streptococcus milleri
Streptococcus pneumoniae
Staphylococcus aureus
Anaerobes
What organisms are usually responsible for hospital acquired empyema?
MRSA
Staphylococcus aureus
Enterococcus
What are the symptoms of empyema?
- Patient feels unwell, not improving
- Swinging fevers/rigor
- Cough/chest pain
How is empyema treated?
- Prolonged course of antibiotics
- Chest drain
- Surgery (pleurodesis with talc, indwelling pleural catheter)
What is haemothorax?
Blood in the pleural cavity with a haematocrit ratio >50% of that of serum
What are some of the possible causes of haemothorax?
Trauma Post-op Bleeding disorders Lung cancer PE Aortic rupture Thoracic endometriosis
How is haemothorax managed?
Large bore chest drain
Possible vascular intervention
?Surgery
What is hydropneumothorax?
Fluid and air in the pleural space
What are the causes of hydropneumothorax?
Iatrogenic (e.g. introduction of air during pleural aspiration)
Gas forming organisms
Thoracic trauma
What causes pleural thickening?
Asbestos
Cancer
Post infection
What are the symptoms of oesophageal rupture?
Severe chest pain after vomiting
Dyspnoea
Fever
What are the signs of oesophageal rupture?
Surgical emphysema
Pneumothorax
Pleural effusion
How is oesophageal rupture managed?
Antibiotics, surgery
What are the features of the asthmatic bronchus?
Chronic inflammation
Mucous secretion
Narrowing of airway
Constriction
What is atopy?
The tendency to develop IgE mediated reactions to common aeroallergens
What are the two types of asthma?
Eosinophilic
Non-eosinophilic
What is eosinophilic asthma?
Severe, more rare type of asthma where TH2 cells activate B cells, resulting in an inflammatory response with mast cell migration and degranulation. Can be atopic or non-atopic.
What is non-eosinophilic asthma?
TH1 cells (which normally appear to help fight infection), activates monocytes and macrophages. Triggered by cigarette smoke and pollutants.
What other conditions are associated with asthma?
Eczema Hayfever Nasal disease Allergies Reflux disease (irritates airway, can trigger asthma)
How can asthma be distinguished from COPD?
- COPD tends to occur later in life
- COPD usually caused by smoking
- COPD less variable day to day and diurnally
- COPD more problematic in winter
What sort of wheeze might be heard in a patient with asthma (if not well controlled)?
Polyphonic
Expiratory and inspiratory
Widespread
No crackles
Asthma may increase responsiveness to which challenge agents?
Mannitol
Methacholine
What might lung function tests show in a person with asthma?
Spirometry may show airway obstruction - reduced FEV1, reduced FEV1/FVC ratio
Bronchodilator reversibility should be present
What other conditions can often complicate co-existing asthma?
Bronchiectasis
Breathing pattern disorders
Vocal cord dysfunction
What kind of asthma treatments are available?
Bronchodilators (SABA, LABA, leukotriene receptor antagonists, theophyllines)
Anti-inflammatory drugs (steroids)
New biologics (omalizumab, mepolizumab)
What is the role of steroids in asthma?
Reduce airway inflammation and decrease mortality risks
What kind of asthma are new biologic treatments useful for?
Severe eosinophilic asthma, e.g. omalizumab is anti-IgE injection therapy
What is classified as moderate asthma?
PEF 50-75% of best/predicted
SpO2 > 92%
What is classified as acute/severe asthma?
PEF 33-50% of best/predicted
SpO2 > 92%
Respiration > 25
Pulse > 110
Unable to complete sentence in one breath
What is classified as life threatening asthma?
PEF < 33% best or predicted SpO2 < 92% Silent chest, cyanosis, poor respiratory effort Arrythmia, hypotension Exhaustion, altered consciousness
How is a moderate asthma attack managed?
- Give b2 bronchodilator via spacer (one puff every 60s up to 10 puffs) to see if PEF > 75%
- -> monitor for 2 hours, consider discharge
- If not, follow acute severe asthma protocol