Respiratory Medicine Flashcards
What reduces pulmonary compliance? (2)
Pulmonary venous engorgement + alveolar oedema
Atelectasis
Which cells release pulmonary surfactant?
Type 2 alveolar epithelial cells -> This lowers surface tension of the fluid lining the alveoli increasing lung compliance
What causes respiratory distress syndrome?
Lack of surfactant
Where does the greatest resistance to flow occur in the airways?
Medium-sized bronchi
What can happen to small airways at low lung volumes? Where is most susceptible to this?
They can close completely which can lead to areas of atelectasis
This particularly occurs at the lung bases
What is hypoxic vasoconstriction?
This is when vasoconstriction occurs in small arterioles of a hypoxic region of the lung
This helps divert blood away from areas of poor ventilation to ensure ventilation and perfusion is matched
Where are central and peripheral chemoreceptors found? what do they respond to?
Central - Medulla (Increases in H+ in the CSF secondary to increased pCO2 in blood)
Peripheral - Carotid + aortic bodies (Low O2, High CO2 and pH changes)
What is Cheyne-Strokes breathing?
Periods of apnoea followed by hyperventilation
When does Cheyne-Strokes breathing occur? (3)
Severe heart failure
Severe brain damage
High altitudes
What is the normal FEV1 : FVC ratio?
70-80%
What conditions show reduced FEV1 with normal FVC (reduced ratio)?
Occurs in airway obstruction eg asthma and COPD
What conditions show reduction in FVC with preserved FEV1 : FVC ratio?
Restrictive disease eg. pulmonary fibrosis, neuromuscular disease, obesity and pleural disease
How can TLC, RV and FRC be measured? (3)
Helium dilution
Nitrogren washout
Body box
What are the different causes of hypoxaemia? (7)
Hypoventilation (Opiate overdose, Respiratory muscle paralysis)
V / Q mismatch (PE)
Low inspired pO2 (High altitudes)
Impaired diffusion (Pulmonary oedema, interstitial lung disease)
Bronchiolar-alveolar cell carcinoma
Shunts (Pulmonary AV malformations, cardiac right to left)
Breathing in hypoxic mixtures
What does right shift of the oxygen dissociation curve represent? What can trigger this? (4)
Right shift increases how easily O2 offloads in the tissues
Caused by high temp, acidosis, increase in pCO2 and increased 2,3-diphosphoglycerate (2,3-DPG)
What does left shift of the oxygen dissociation curve represent? What can trigger this? (6)
O2 held on more closely by the Hb
Caused by low temp, alkalosis, decrease in pCO2, decrease in 2,3-diphosphoglycerate (2,3-DPG), COHb and fetal Hb
What are some early responses to altitude of the body? (2)
Hyperventilation due to hypoxic stimulation of peripheral chemoreceptors
The subsequent resp alkalosis is corrected via renal excretion of bicarb
What are some later changes in response to high altitude? (3)
Hypoxaemia -> EPO via kidneys -> polycythaemia thus incerased O2 carriage by blood
Increased 2,3-DPG production -> right shift of O2 dissocation curve -> better offloading to tissues
Hypoxic vasoconstriction -> increased pulmonary artery pressure -> RVH (nb. pulmonary HTN can be associated w/ pulmonary oedema - altitude sickness)
Most important allergens responsible for asthma? (5)
House dust mite
Dog allergen
Cat allergen
Pollen
Grasses
Moulds
Which drugs can trigger asthma attacks?
B-blockers
NSAIDs inc aspirin
What are the features of early stages of asthma? (3)
Airways narrowed by a combination of:
1. Bronchiolar smooth muscle contraction
2. Mucosal oedema
3. Mucus plugging
In early stages, these changes are reversible
What are the features of chronic asthma? (3)
Same features as early asthma however stuctural changes develop and lead to irreverisble fibrosis of airways
Structural changes:
1. Thickening of basement membrane
2. Goblet cell hyperplasia
3. Smooth muscle hypertrophy
What causes sputum to be yellow / green in asthma?
Presence of eosinophils
What are some features that suggest someone’s asthma may respond to steroids?
Sputum eosinophils >2 %
FENO >50 parts/billion
What are some lung function tests that support asthma? (4)
Significant diurnal PEFR variability (>20%) for 3 or more days / week for 2 weeks
Significant improvement in PEFR (>15%)+ FEV1 (400ml+) with bronchodilator / steroids
Reduced FEV1 (Decreased FEV1:FVC ratio)
Raised exhaled nitric oxide concentration (FENO)
When should patient with acute asthma be referred to ICU? (7)
Worsening PEFR
Persistent / worsening hypoxia
Rising pCO2
Decreasing pH
Exhaustion
Altered conciousness
Respiratory arrest
Features of life threatening asthma? (10)
- Hypoxaemia
- PEFR <33% of predicted
- Exhaustion
- Bradycardia (pulse <60 beats/min) or arrhythmmia
- Hypotension
- A silent chest
- Altered consciousness
- Poor respiratory effort
- Cyanosis
- A normal or raised PCO2.
Discharge criteria for patient with asthma? (5)
- PEFR should be at least 75% of the patient’s best or predicted value
- PEFR diurnal variability on monitoring should be <25%
- The patient should have required no nebulised bronchodilators for at least 24 hours
- The patient should have a written asthma action plan
- The patient should have follow-up in primary or secondary care within 30 days of discharge
What other respiratory condition do most patients with allergic bronchopulmonary aspergillosis have?
Asthma but can also occur in those without asthma
What feature determines long term prognosis in those with COPD? What is a better way?
Post-bronchodilator FEV1 however this is poor in isolation
BODE index (BMI, airflow obstruction, dyspnoea, exercise) - 7 or more is 31% 2y mortality
Can COPD progress if the person stops smoking?
Yes
Causes of COPD? (5)
- Smoking (usually a history of at least 20 pack-years)
- Air pollution
- Low birthweight and low socio economic status
- Dust exposure
- α1-Antitrypsin deficiency
What is chronic bronchitis?
Chronic cough + sputum production for at least 3 months in 2 consecutive years in the absence of other causes
What is emphysema?
Abnormal, permenant enlargement of airpaces distal to terminal bronchioles
It is accompanied with destruction of their walls without obvious fibrosis
What are the different types of emphysema? (4)
Centriacinar (affects upper lobes, associated w/ smoking)
Panacinar (more common in a1-antitrypsin deficiency - whole acinus affected: alveoli, bronchioles + blood vessels)
Paraseptal
Scar emphysema (Localised around scars)
What happens to DLCO in emphysema?
Reduced - which means reduced gas transfer
How is COPD severity measured using FEV1? (4)
- Mild: FEV1 ≥80% predicted
- Moderate: FEV1 50–79% predicted
- Severe: FEV1 30–49% predicted
- Very severe: FEV1 <30% predicted
What are the signs of Cor pulmonale?
Raised JVP
R Ventricular heave
Loud P2
Tricuspid regurg
Peripheral oedema
Hepatomegaly
Does adding inhaled steroids in addition to LA bronchodilators in COPD impact disease progression?
No
Why are inhaled steroids used in COPD management alongside long-acting bronchodilators?
They reduce frequent of exacerbations and improve QoL in patients w/ severe or v. severe COPD
Which patients with COPD can be considered for lung transplants?
Under 65 with FEV1 and DLCO <20% of predicted
History of hospitalisation with exaccerbation associated with pulmonary hypertension +- cor pulmonale despite O2 therapy
Which patients with COPD should be referred for pulmonary rehab? Why?
All motivated patients regardless of severity
Increases exercise tolerance + improve QoL
When are abx indicated in COPD exacerbations?
If 2 of the following are present:
* Increased breathlessness
* Increased sputum volume
* Increased sputum purulence.
What needs to be done in COPD exacerbation if hypercapnia and acidosis is present on inital ABG?
Treated as normal for hour
Repeat ABG
If acidosis with hypercapnia persists non-invasive positive pressure ventilation should be started via face mask
