S6: asthma, COPD, bronchiectasis & cystic fibrosis Flashcards
What is asthma?
Chronic inflammatory disorder of the airways
Inflammatory symptoms are usually associated with widespread but variable airflow obstruction and an increase in airway responsiveness to a variety of stimuli
Characterised by a triad of bronchial smooth muscle contraction, airway inflammation & increased secretions
Describe the difference in reversibility after bronchodilator use in asthma and COPD
Asthma: airway obstruction in asthma is often reversible – improvement in FEV1 of 12% or more after bronchodilators
COPD: airways obstruction is not fully reversible - < 12% improvement FEV1 on spirometry after bronchodilators
Describe the pathophysiology of asthma
Initially a type 1 hypersensitivity reaction (immediate response)
Allergen -> dendritic cell -> CD4+ cells -> Th2 cell
Th2 cells activate B-lymphocytes (also activated by re-exposure of allergen) & eosinophils
B-lymphocytes -> plasma cells -> IgE -> mast cells have receptor (Fc)
Mast cell degranulation – histamine, cytokines, leukotrienes & eosinophils secrete leukotrienes & cytokines -> these both cause inflammation and bronchoconstriction
List asthma triggers
Allergens – pollen, animals Cold air GORD Exercise Fumes – car exhaust Cigarette smoke
Describe what long term poorly controlled asthma can lead to
Airway remodelling, some of which may not be fully reversible
Changes include:
-hypertrophy & hyperplasia of smooth muscle
-hypertrophy of mucus glands
-thickening of basement membrane
Describe the effect of airways narrowing in asthma
Causes wheezing & other clinical features of asthma
Results in an obstructive pattern on spirometry & typical flow volume loops
Air trapping with increased residual volume & hence increased functional reserve capacity
Describe the effect on gas exchange in asthma
Airway narrowing -> reduced ventilation of the affected alveoli -> V/P mismatch
In unmanaged mild to moderate asthma: decreased pCO2 & pO2 = type 1 respiratory failure
Severe attacks: extensive involvement of airways with complete blockage of some airways & exhaustion (limits respiratory effort) -> limits the amount of CO2 which can be breathed out
Increasing pCO2 is a sign of LIFE-THREATENING ASTHMA
Describe signs and symptoms of asthma
Dry, nocturnal cough Wheeze Breathlessness Chest tightness Atopy
Describe the management of asthma
Step 1: short acting beta-2 agonist (finger tremor is a side effect), bronchial smooth muscle relaxation (blue inhaler)
Inhaled corticosteroid – anti-inflammatory (brown inhaler)
Step 2: combination inhaler – long acting beta-2 agonist & anti-inflammatory
Step 3: can increase dose of inhaled corticosteroid or add leukotriene receptor antagonist
Step 4: specialist care
Describe the emergency management of asthma
Oxygen
Short acting beta-2 agonist
Steroids
ADMIT
What is COPD?
A disease characterised by persistent respiratory symptoms & airflow limitation
Due to airways and/or alveolar abnormalities
Caused by significant exposure to noxious particles or gases
Describe the pathophysiology of COPD
Small airways disease – airway inflammation, airway fibrosis, luminal plugs
Parenchymal destruction – loss of alveolar attachments, decrease of elastic recoil
Both lead to airflow limitation
Describe emphysema and chronic bronchitis
Emphysema – elastin breakdown & subsequent loss of alveolar integrity leading to permanent destructive enlargement of the airspaces distal to the terminal bronchioles
Chronic bronchitis – excessive mucous secretion and impaired removal of the secretions
Describe the diagnosis of COPD
Symptoms: shortness of breath, chronic cough & sputum
Risk factors: host factors, tobacco, occupation & indoor/outdoor pollution
Spirometry: required to establish diagnosis
List the signs of COPD
Often few or none especially at rest Purse lip breathing Hyperinflation/barrel-shaped chest Prolonged expiratory phase Wheeze on auscultation Late features include cyanosis & right-sided heart failure
Describe the investigations for COPD
Spirometry shows an obstructive pattern with FEV1/FVC ratio <70% & limited reversibility following treatment with bronchodilators
Decreased diffusing capacity of the lung for CO is a feature of emphysema
Describe management/treatment for COPD
Smoking cessation Vaccinations Pulmonary rehabilitation Long term oxygen treatment Surgical interventions
List complications of COPD
Recurrent pneumonia
Pneumothorax
Respiratory failure
Cor pulmonale
What is bronchiectasis?
Chronic, irreversible dilatation of one of more bronchi due to destruction of the elastic and muscular components of the bronchial wall
Bronchi exhibit poor mucous clearance and there is predisposition to recurrent or chronic bacterial infections
List the causes of bronchiectasis
Post-infection Immune deficiency Genetic/mucociliary clearance defects – cystic fibrosis Obstruction May co-exist with COPD
Describe the symptoms and signs of bronchiectasis
Cough Sputum production Crackles, high-pitched inspiratory squeaks & rhonchi Dyspnoea Fever
Differentiate COPD from bronchiectasis
Diminished breath sounds in COPD
Bronchiectasis – rhonchi may be auscultated, but with additional inspiratory squeaks and crackles
Chest CT – normal/show emphysema in COPD, thickened, dilated airways with/without air fluid levels in bronchiectasis
Differentiate bronchiectasis from asthma
Inspiratory squeaks and crackles are not present in asthma & wheezing not present in bronchiectasis
Chest CT – signet ring sign in bronchiectasis
Bronchiectasis will not be fully reversible with bronchodilator treatment
What is the signet ring sign?
Seen in bronchiectasis
Dilated bronchus & accompanying pulmonary artery are seen in cross section
Bronchus is markedly dilated and larger than the artery
Describe the management of bronchiectasis
Treat underlying cause to prevent disease progression
Physiotherapy
Antibiotics
Vaccinations
What is cystic fibrosis?
Autosomal recessive disorder
Caused by gene mutation on chromosome 7
Abnormal function of the epithelial chloride channel – cystic fibrosis transmembrane conductance regulator (CFTR) – key role in maintaining lung epithelial function
Describe the role of CFTR in lungs
Transports chloride out of the cell & regulates ENaC
Critical role in hydration of surface mucous airways – defective ion transport reduces airway surface liquid hydration & leads to thick and sticky mucous (impairs muco-ciliary clearance)
Describe how CF is diagnosed
Positive newborn screening test result/history of CF in a sibling/one or more characteristic phenotypic features
AND increased sweat chloride concentration (sweat test) or identification of two CF mutations (genotyping)
List the main CF clinical presentations
1) Meconium ileus – infants bowel blocked by sticky secretions
2) Intestinal malabsorption
3) Recurrent chest infections
4) Newborn screening
5) Atypical presentation – mutations that cause faulty, but not entirely misfunctioning, CFTR protein
List the clinical features of CF
Chronic sinusitis Repeated lower respiratory tract infection Nasal polyps Pancreatic insufficiency Male infertility Finger clubbing Osteoporosis
Describe CF lifestyle advice
No smoking Avoid other CF patients Avoids friends with infections Vaccination Ensure optimal nutrition
List the common CF complications
Respiratory infections
Low body weight
Distal intestinal obstruction syndrome – faecal obstruction in ileo-caecum
