Respiratory COPY Flashcards
what is FEV1? what is it like in healthy people?
- forced expiratory volume in 1 second
- in which a person takes a maximal inspiration and then exhales maximally as fast as possible. the important value is the fraction of the total “forced” vital capacity expired in 1 second
- healthy individuals can expire approximately 80% of the vital capacity in one second
what is the procedure for measuring FEV1?
- breath in to total lung capacity (TVC)
- exhale as fast as possible until lungs emptied
- total volume produced is the forced vital capacity (FVC)
how does flow change with expiration?
flow is greatest at the start of expiration, it declines linearly with volume. FEF25 = flow at point when 25% of total volume to be exhaled has been exhaled
what does FEV1 show AND
what are normal and abnormal values for FEV1?
- it’s a good overall assessment of lung health
- The result is compared with the predicted values,
- if the FEV1 is 80% or greater than the predicted value = normal
- if the FEV1 is less than 80% of the predicted value = low i.e abnormal
what are the normal and abnormal values for FVC?
AND
What does a low FVC indicate
- less reproducible than FEV1
- the result is compared with the predicted values,
- if the FVC is 80% or greater than the predicted value = normal
- FVC is less than 80% of the predicted value = low i.e abnormal
- a low FVC = airway restriction
what are features of type 1 respiratory failure? what is a common cause?
- pO2 (partial O2 pressure) is low
- pCO2 (partial CO2 pressure) is low or normal
- with type 1 = 1 change = low pO2 then normal/low CO2
- pulmonary embolism (form of ventilation-perfusion mismatch) most commonly causes Type 1
- also pulmonary oedema, pneumothorax + pneumonia
what are features of type 2 respiratory failure? what is a common cause?
- pO2 is low
- pCO2 is high
- with type 2 = 2 changes = low pO2 + high pCO2
- alveolar hypoventilation causes Type 2
- e.g. COPD, asthma, motor neurone disease
what are causes of respiratory failure?
- impaired ventilation (neural and mechanical problems)
- impaired perfusion, if extensive (cardiac failure or multiple PE)
- impaired gas exchange defects, if severe (emphysema or diffuse pulmonary fibrosis)
- hypoventilation (COPD, neuromuscular weakness, obesity, chest wall deformity, reduced drive)
- obstruction (asthma, COPD, OSA, pneumonia)
- diffusion (IPF, other ILDs, emphysema)
- perfusion (PE, cardiac failure, shunt, pulmonary hypertension)
what are neural and mechanical problems which can lead to impaired ventilation which can cause respiratory failure?
- neural: narcotics, encephalitis, a cerebral space-occupying lesion, motor neurone disease (resulting in neuromuscular weakness)
- mechanical: airway obstruction, trauma, muscle disease and pleural effusion
what are signs of hypercapnoea?
- bounding pulse
- flapping tremor
- confusion
- drowsiness
- reduced consciousness
what is the FEV1/FVC and FEV1 and FVC like in obstructive respiratory disease?
- FEV1/FVC below 0.7
* FEV1 lower than FVC
what are examples of obstructive respiratory disease? what are features of them?
- asthma: variable airflow obstruction and reversible
- COPD: relatively fixed airflow obstruction and may be a mixture of restrictive and obstructive disease
- bronchiectasis
what is the FEV1/FVC and FEV1 and FVC like in restrictive respiratory disease?
- FEV1/FVC above 0.7
- FVC and FEV1 below 80% predicted value
- due to restriction, lung volumes are small and most of breath is out in first second
what are examples of restrictive respiratory disease?
- sarcoidosis
- interstitial lung diseases
- obesity (OHS)
- scoliosis
- muscular dystrophy/ALS
what is the transfer coefficient? how is it calculated?
- measure of ability of oxygen to diffuse across the alveolar membrane
- can calculate by inspiring a small amount of carbon monoxide, then hold breath for 10 seconds at total lung capacity, then the gas transferred is measured
in what diseases is the transfer coefficient low?
- severe emphysema
- fibrosing alveolitis
- anaemia
- pulmonary hypertension
- idiopathic pulmonary fibrosis
- COPD
in what diseases is the transfer coefficient high?
pulmonary haemorrhage
what is COPD?
chronic obstructive pulmonary disease
• a disease state characterised by airflow limitation that is not fully reversible
• the airflow limitation is usually both progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases
what is COPD associated with the development of?
- chronic bronchitis: cough with sputum for 3 months for 2 or more years
- emphysema: histologically enlarged airspaces distal to terminal bronchioles, with destruction of alveolar walls
what is the epidemiology of COPD?
- cigarette smoking is the major cause of COPD and is related to the daily average of cigarettes smoked and years spent smoking
- chronic exposure to substances
- alpha-1 antitrypsin deficiency
- patients are rarely symptomatic before middle-age
chronic exposure to what things can lead to COPD?
- cigarette smoke
- occupational pollution
- outdoor air pollution
- inhalation of smoke from biomass fuels used in heating and cooking in poorly ventilated areas
what is alpha-1 antitrypsin deficiency? what respiratory disease can it cause?
- causes early onset COPD (due to proteolytic lung damage)
- a rare cause of cirrhosis (due to accumulation of the abnormal protein in the liver)
- mutations in the alpha-1 antitrypsin gene on chromosome 14 lead to reduced hepatic production of alpha-1 antitrypsin which normally inhibits the proteolytic enzyme, neutrophil elastase
what is the pathophysiology of COPD?
- there are increased mucus-secreting goblet cells within the bronchial mucosa, especially in the larger bronchi
- in more advanced cases the bronchi become inflamed and pus is seen in the lumen
- chronic bronchitis
- emphysema
what are features of chronic bronchitis in COPD?
- Chronic cough with sputum production
- Inflammation -> ciliary dysfunction, airway thickening and ↑ goblet cell size and number.
- ↑ goblet cell count -> mucous plugs -> narrowing of airways
- Must be present for most days for at least 3 months in 2 consecutive years.
what are microscopic features of chronic bronchitis in COPD?
- microscopically there is infiltration of the bronchi and bronchioles with acute and chronic inflammatory cells
- the epithelial becomes ulcerated and the squamous epithelium replaces the columnar cells (squamous metaplasia) when the ulcer heals
what are features of inflammation in chronic bronchitis in COPD? what happens in early/late stages?
- the inflammation is followed by scarring and thickening of walls, narrowing the small airways
- the small airways are affected early on, initially without breathlessness
- the initial inflammation is reversible and accounts for the improvement if smoking is stopped early
- in the later stages, the inflammation continues, even if smoking is stopped
what are features of emphysema in COPD? what does it lead to?
- dilatation and destruction of the lung tissue distal to the terminal bronchioles
- results in loss of elastic recoil, which normally keeps the airways open in expiration
- leads to expiratory airflow limitation and air trapping
- premature closure of airways limits expiratory flow while loss of alveoli decreases capacity for gas transfer
what are features of centriacinar emphysema?
- distension and damage is concentrated around the respiratory bronchioles, whilst the more distal alveolar ducts and alveoli tend are well preserved
- extremely common
what are features of panacinar emphysema?
- less common
- distension and destruction affect the whole acinus and in severe cases the lung is just a collection of bullae
- associated with alpha-1 antitrypsin deficiency
what are features of irregular emphysema?
scarring and damage that affects the lung parenchyma
patchily, independent of acinar structure
what is V/Q (ventilation perfusion) and PaCO2 like in COPD?
- partly due to damage and mucus plugging of smaller airways from the chronic inflammation and rapid closure of smaller airways in expiration leading to loss of elastic support; this leads to a fall in PaO2 and increased work or respiration
- CO2 excretion is less affected by V/Q mismatch and many patients have low-normal PaCO2 values due to increasing alveolar ventilation in an attempt to correct their hypoxia
- other patients fail to maintain their respiratory effort and then their PaCO2 levels increase
- in the short term, this rise in CO2 leads to stimulation of respiration, but in the longer term, these patients become insensitive to CO2 and come to depend on the hypoxaemia to drive ventilation
what is the pathogenesis of cigarette smoke causing COPD?
- causes mucus gland hypertrophy in the larger airways and increased neutrophils, macrophages and lymphocytes in the airways, bronchi and bronchioles
- inflammatory mediators (elastases, proteases, IL-1,-8 and TNF-alpha) are released and attract inflammatory cells, induce structural changes and break down connective tissue (protease-antiprotease imbalance) in the lung resulting in emphysema
- inactivates alpha-1 antitrypsin
what are symptoms of COPD?
- characteristic symptoms are productive cough with white or clear sputum, wheeze and breathlessness, usually following many years of a smokers cough
- colds seem to settle on the chest and frequent infective exacerbations occur, with purulent sputum
- symptoms can be worsened by cold or damp weather and atmospheric pollution
what are systemic effects of COPD?
- hypertension
- osteoporosis
- depression
- weight loss
- reduced muscle mass with general weakness
what is the seen on examination of COPD?
- breathless at rest, prolonged expiration, poor chest expansion, hyperinflated lungs (barrel chest)
- pursed lips on expiration help to prevent alveolar and airway collapse
what are complications of COPD?
- later stages are characterised by the development of respiratory failure:
• PaO2 less than 8kPa (60mmHg) or
• PaCO2 greater than 7kPa (53mmHg) - those with advanced disease may develop pulmonary hypertension (fluid retention, peripheral oedema, central cyanosis, breathlessness)
what are differential diagnoses of COPD?
asthma, congestive heart failure, bronchiectasis, allergic fibrosing alveolitis, pneumoconiosis and asbestosis
what is used to diagnose COPD?
- based on a history of breathlessness and sputum production in a chronic smoker
- in the absence of a history of cigarette smoking then asthma is a more likely explanation, unless there is a family history suggesting alpha-1 antitrypsin deficiency
- lung function test
- CXR
- high resolution CT scans used to show emphysematous bullae
- haemoglobin and packed cell volume may be high due to persistent hypoxaemia and secondary polycythaemia
- arterial blood gases may be normal or show hypoxia with/without hypercapnia in advanced cases
- ECG is often normal
- alpha-1 antitrypsin levels and genotypes
what does a lung function test show in COPD? what is the FEV1/FVC and FEV like?
- shows progressive airflow limitation with increasing severity and breathlessness
- FEV less than 80% predicted value
- FEV1/FVC less than 0.7 - airway obstruction
- multiple peak flow measurements may be necessary to exclude asthma
what is stage 1 COPD?
FEV1 less than 80% of predicted value
what is stage 2 COPD?
FEV1 50-79%
what is stage 3 COPD?
FEV1 30-49%
what is stage 4 COPD?
FEV1 less than 30% of predicted value
what can be seen on a CXR in COPD?
- may be normal or show evidence of hyper-inflated lungs indicated by low, flattened diaphragms and a long narrow heart shadow
- there may be reduced peripheral lung markings and bullae (complete destruction of lung tissue producing an airspace greater than 1cm)
what is treatment of COPD?
- smoking cessation
- bronchodilators
- corticosteroids
- prevention of infection (pneumococcal vaccination, influenza vaccine, antibiotics for exacerbations)
- oxygen therapy
- antimucolytic agents reduce sputum viscosity
- diuretics to treat oedema
- pulmonary rehabilitation
- good diet to reduce weight
- alpha-1 antitrypsin replacement
how are bronchodilators used to treat COPD?
- inhaled (with spacer device if necessary) tiotropium bromide (a LAMA) used as an initial therapy with a rescue SABA e.g. salbutamol or terbutaline to prevent/reduce acute symptoms
- a LABA e.g. formoterol or salmeterol is added in patients with persistent dyspnoea (difficulty breathing)
how are corticosteroids used to treat COPD?
- prednisolone daily for two weeks should be given with measurements of lung function before and after the treatment
- if there is an increase in FEV by more than 15% then discontinue prednisolone and move to inhaled corticosteroid e.g. beclometasone twice daily
how is oxygen therapy used to treat COPD? how much is given?
- long term domiciliary oxygen therapy has survival benefits
- prescribed to patients who no longer smoke
- oxygen is given 19 hours per day every day via nasal prongs to increase arterial oxygen saturations to more than 90%
what is the epidemiology of asthma?
- commonly starts in childhood between the ages 3-5 years and may either worsen or improve during adolescence
- peak prevalence between 5-15 years
- more common in developed countries
what are the three characteristics of asthma?
- airflow limitation; usually reversible spontaneously or with treatment
- airway hyper-responsivenes
- bronchial inflammation with T lymphocytes, mast cells, eosinophils with associated plasma exudation, oedema, smooth muscle hypertrophy, mucus plugging and epithelial damage
what are the two main types of asthma? what are causes of them?
• allergic/eosinophilic asthma (70%): - allergens and atopy - childhood asthma often accompanied by eczema • non-allergic/non-eosinophilic (30%): - exercise, cold air and stress - smoking and non-smoking associated - obesity associated - starts in middle-age
what are genetic factors that may lead to asthma?
- genes controlling the production of cytokines IL-3,-4,-5,-9,-13
- ADAM33 is associated with airway hyper-responsiveness and tissue remodelling
what are environmental factors that may lead to asthma?
- early childhood exposure to allergens and maternal smoking
- growing up in a ‘clean’ environment may predispose towards an IgE response to allergens whereas growing up in a ‘dirtier’ environment may allow the immune system to avoid developing allergic responses
what are risk factors for asthma?
- personal history of atopy
- family history of asthma or atopy
- obesity
- inner-city environment
- premature birth
- socio-economic deprivation
what are precipitating factors for asthma?
- occupational sensitisers such as wood dust, bleaches and dyes, isocyanates (industrial coating and spray painting) and latex
- cold air and exercise
- atmospheric pollution and irritant dusts
- diet; more fruit and veg is protective
- emotion
- drugs such as NSAIDs can trigger attacks, also beta-blockers result in bronchoconstriction, leading to airflow limitation and potential attack
- allergen-induced asthma
what is the primary abnormality in asthma?
primary abnormality in asthma is narrowing of the airway which is due to smooth muscle contraction, thickening of the airway wall by cellular infiltration and inflammation and the presence of secretions within the airway lumen
what do mast cells release in asthma?
• histamine results in bronchoconstriction (via H1
receptor) and inflammation
• tryptase
• prostaglandin2
• cysteine leukotrienes result in bronchoconstriction and inflammation
• TNF-alpha, IL-3 (increases number of mast cells), -4 (causes IgE synthesis) and -5; result in inflammation and airway remodelling
• all act on smooth muscle, small blood vessels,
mucus-secreting cells and sensory nerves cause the
immediate asthmatic reaction
what do eosinophils do in asthma?
- found in large numbers in the bronchial wall and secretions
- attracted to the airway by IL-3 and IL-5, they also prime eosinophils for enhance mediator secretion
- when activated, eosinophils release LTC4 and major basic protein, eosinophilic cationic protein and eosinophilic peroxidase these are toxic to epithelial cells
- both the number and activation of eosinophils are rapidly decreased by corticosteroids
what do dendritic cells and lymphocytes do in asthma?
- abundant in mucous membranes of the airways and the alveoli
- dendritic cells play a role in the initial uptake and presentation of allergens to lymphocytes
- T helper lymphocytes activate and release cytokines
what are the changes in the lung 30 minutes after allergen challenge in asthma?
there is bronchoconstriction
what are the changes in the lung 3 hours after allergen challenge in asthma?
the initial bronchoconstriction decreases, then inflammation occurs due to the vasodilation which decreases blood flow and leads to a build up of
white blood cells, increased vascular permeability and
unregulated adhesion molecules
what are the changes in the lung 6 hours after allergen challenge in asthma?
there is worsening inflammation resulting in eosinophils (attracted to site by IL-5) releasing their mediators that result in a second wave of bronchoconstriction
what is the pathophysiology of remodelling in asthma?
- airway smooth muscle undergoes hypertrophy and hyperplasia leading to a larger fraction of the wall being occupied by smooth muscle tissue
- the airway wall is thickened by the deposition of repair collagens and matrix proteins below the basement membrane
- deposition of matrix proteins, swelling and cellular infiltration expand the submucosa beneath the epithelium so that, for a given degree of smooth muscle shortening there is excess airway narrowing
- swelling outside the smooth muscle layer reduces the retractile forces exerted by the surrounding alveoli so the airways close more easily
- the epithelium is stressed and damaged with loss of ciliated columnar cells
- increase in number of mucus-secreting goblet cells
- damage to the epithelium makes it more vulnerable to infection by common respiratory viruses and pollution
what is the clinical presentation of asthma?
- intermittent dysponea
- wheeze
- cough (especially nocturnal); frequent symptom in children
- sputum
- symptoms worse at night
- episodic shortness of breath
- provoking factors: allergens, infections, menstrual cycle, exercise, cold air
what is the clinical presentation of asthma during an attack?
- there is reduced chest expansion
- prolonged expiratory time
- bilateral expiratory polyphonic wheezes
- tachypnoea
what is the clinical presentation of uncontrolled asthma?
- PEFR less than 50%
- respiratory rate less than 25
- pulse less than 110
- normal speech
what is the clinical presentation of a severe asthma attack?
- inability to complete sentences
- pulse greater than 110bpm
- respiratory rate greater than 25/min
what is the clinical presentation of a life threatening asthma attack?
- silent chest
- confusion and exhaustion
- cyanosis (PaO2 less than 8kPa)
- bradycardia
- PEFR less than 33%
what is the immediate treatment of an asthma attack?
- oxygen therapy to maintain O2 sat (94%-98%)
- nebulised 5mg salbutamol (+ ipratropium if life threatening)
- prednisolone (with/without hydrocortisone IV)
- take ABGs and repeat within 2 hours if severe attack or patient deteriorating
- CXR if no response to treatment
- check PEFR within 15-30 mins/regularly
- oximetry to ensure SaO2 is greater than 92%
what are differential diagnoses of asthma?
pulmonary oedema, COPD (may co-exist), large airway obstruction caused by foreign body/tumour, pneumothorax, bronchiectasis
what is used to diagnose asthma?
- RCP3 questions (nocturnal waking, usual symptoms, interference with ADLs)
- asthma control test
- lung function tests (PEFR, spirometry, CO test)
- exercise tests
- trial of corticosteroids
- exhaled nitric oxide (measures eosinophilic inflammation and corticosteroid response)
- blood and sputum tests (eosinophilia)
- skin prick tests to help identify allergic trigger factors
- history
how is asthma control test used to diagnose asthma? what are the results?
- 25: well controlled
- 20-24: on target
- less than 20: off target
how is peak expiratory flow rate used to diagnose asthma?
measurement on waking, prior to taking a bronchodilator and before bed, after a bronchodilator
- asthma is diagnosed by demonstrating a greater than 15% improvement in FEV1 or PEFR following the inhalation of a bronchodilator
how is asthma distinguished from COPD?
- COPD is a later disease more dominantly of smokers
- more of a relentless progressive dyspnoea with wheeze
- less day-day variation
- winter symptoms and sputum production in COPD
- overlap can occur
what are the aims of treatment of asthma?
- abolish symptoms
- restore normal or best possible lung function
- reduce risk of severe attacks
- enable normal growth to occur in children
- minimise absence from school or employment
- avoidance of identified causes if possible
- use of lowest effective doses of medication to minimise side effects
what is used to treat asthma?
- control of extrinsic factors when specific allergen triggers are identified
- bronchodilators
- anti-inflammatory steroids
- other agents with bronchodilator activity
- steroid-sparing agents
what are some types of bronchodilators used to treat asthma?
- beta2-agonists
- muscarinic antagonists
- methylxanthines
what are features of beta2-agonists used to treat asthma?
- are beta-2 selective i.e. work only in lungs, however in high doses the B2-agonists are not selective and will act on other receptors
- lead to bronchodilation
- beta-agonists also inhibit mast cell activity thereby reducing inflammatory response
- at high concentrations e.g. in badly controlled asthmatics a tolerance may develop due to B2-receptor desensitisation
what short acting beta agonists are used to treat asthma? how long do they act for?
- salbutamol (partial agonist)
- terbutaline
- 4 hours
- prescribed as two puffs as required
what long acting beta agonists are used to treat asthma? how long do they act for?
- salmeterol
- formoterol (full agonist)
- 12 hours
- longer acting since there are more lipophilic so they remain in the tissue for longer
what short and long acting muscarinic antagonists are used to treat asthma?
- short-acting e.g. ipratropium
- long acting e.g. tiotropium - has high affinity and disassociates slowly from muscarinic receptors
what is the mechanism of action of muscarinic antagonists? how are they used to treat asthma?
- act on airway M3 receptors
- normally ACh (parasympathetic) binds to M3 receptor bound to Gq protein resulting in phospholipase C converting phosphate to DAG resulting in protein kinase C production resulting in smooth muscle contraction
- muscarinic antagonists prevent ACh from binding since they bind to the M3 receptor thereby blocking ACh action
what is the mechanism of action of methylxanthines? how are they used to treat asthma?
these are phosphodiesterase inhibitors; prevent the conversion of cyclic-AMP to 5’-AMP resulting in a build up of cyclic-AMP and thus increased smooth muscle relaxation
what are examples of methylxanthines used to treat asthma?
theophylline (non-selective so has wide range of side effects e.g. CVS, CNS and GI tract) and aminophylline
what are features of inhaled corticosteroids used to treat asthma? what are the different types of corticosteroids?
- all patients who have regular persistent symptoms need regular treatment with inhaled corticosteroids
- there are two types of corticosteroids; mineralocorticoids and glucocorticoids
- hydrocortisone has anti-inflammatory properties but also has significant mineralocorticoid action so is not suitable as a treatment
- instead, semi-synthetic glucocorticoids that have reduced or no mineralocorticoid action and improved anti-inflammatory effects are used
what are examples of inhaled corticosteroids used in asthma?
- prednisolone
- beclomatasone
- budesonide
what is the effect of glucocorticoids on genes?
- glucocorticoids interfere with gene transcription
- glucocorticoid receptor is found on the promoter region of DNA and has zinc fingers that anchor receptor to DNA and recognise discrete sequences
- there is either a + glucocorticoid response element which increases transcription or -GRE response, which decreases transcription
what is a +GRE response?
+GRE results in increased lipocortin which inhibits PLA2 meaning there is a decrease in arachidonic acid and thus a decrease in prostaglandins and leukotrienes resulting in reduced inflammation and thus reducing symptoms
what is a -GRE response?
-GRE results in the suppression of cytokines e.g. TNF, IL-5 and IL-3 thereby reducing inflammation and thus reducing symptoms
what are side effects of inhaled corticosteroids in asthma?
- susceptibility to infection due to cytokine suppression
* metabolic such as osteoporosis and muscle wasting
what are other agents with bronchodilator activity that are used to treat asthma? what are some examples?
- leukotriene receptor antagonist e.g. montelukast
* oral corticosteroids needed for those not controlled on inhaled corticosteroids
what are examples of steroid-sparing agents that are used to treat asthma?
- methotrexate
- ciclosporin
- IV immunoglobulin
- anti-IgE monoclonal antibody (omalizumab)
what is the guideline medication regime for asthma?
- SABA
- SABA + ICS
- SABA + LABA + ICS
- SABA + LABA + ICS + 4th drug e.g. anti-IgE monoclonal etc. (severe)
what is the PEFR and treatment of step 1 (occasional symptoms, less frequent than daily) asthma?
- 100% predicted
- as-required SABAs
- if used more than once daily, move to step 2
what is the PEFR and treatment of step 2 (daily symptoms) asthma?
- <80% predicted
regular inhaled preventer therapy:
- anti-inflammatory drugs; inhaled low-dose corticosteroids up to 800ug daily
- leukotriene receptor antagonists, theophylline and sodium cromoglycate are less effective
- if not controlled, move to step 3
what is the PEFR and treatment of step 3 (severe symptoms) asthma?
- 50-80% predicted
inhaled corticosteroids and long-acting inhaled beta-2 agonist:
- continue inhaled corticosteroid
- add regular inhaled LABA
- if still not controlled, add either LTBA, modified release oral theophylline or beta-2 agonist
- if not controlled, move to step 4
what is the PEFR and treatment of step 4 (severe symptoms uncontrolled with high-dose inhaled corticosteroids)?
- 50-80% predicted
high dose inhaled corticosteroids and regular bronchodilators:
- increase high-dose inhaled corticosteroids up to 2000ug daily
- plus regular LABAs
- plus either LTRA or modified release theophylline or beta2-agonist
what is the PEFR and treatment of step 5 (severe symptoms deteriorating) asthma?
<50% predicted
regular oral corticosteroids
- add prednisolone 40mg daily to step 4
what is the PEFR and treatment of step 6 (severe symptoms deteriorating in spite of prednisolone) asthma?
<30% predicted
hospital admission
what is hypersensitivity pneumonitis/extrinsic allergic alveolitis?
- previously called extrinsic allergic alveolitis
- type of ILD; distinct cellular infiltrates and extracellular matrix deposition in lung distal to the terminal bronchiole i.e. diseases of the alveolar/capillary interface
what are interstitial lung diseases?
ILDs are a group of lung diseases affecting the lung interstitium (the tissue and space around the air sacs of the lungs)
what is the epidemiology of hypersensitivity pneumonitis?
- usually a disease of adults
- caused by an allergic reaction affecting the small airways and alveoli in response to an inhaled antigen or the ingestion of a causative drug
- there is diffuse, granulomatous inflammation of the lung parenchyma and airways in people who have been sensitised by repeated inhalation of organic antigens in dust
- there are acute, subacute and chronic forms
- acute and subacute forms cause a recurrent pneumonitis
- chronic disease can cause fibrosis, emphysema and permanent lung damage
- one of the most common causes worldwide is farmer’s lung
- associated with many jobs and hobbies
what jobs and hobbies is hypersensitivity pneumonia associated with?
- farmers lung; due to exposure to mouldy hay, Micropolyspora faeni and Aspergillus umbrosus
- bird/pigeon fanciers lung; due to exposure to avian proteins in droppings
- cheese-workers lung; due to exposure to mouldy cheese, Penicillium casei
- malt-workers lung; due to exposure to mould malt, Aspergillus clavatus
- humidifier fever; due to contaminated humidifying systems in air conditioners or humidifier in factories (especially in printing works), variety of bacteria
what are risk factors for hypersensitivity pneumonitis?
- pre-existing lung disease
- specific occupations including farmers, cattle workers, ventilation system workers, vets and those jobs that involve working with chemicals
- bird keeping
- regular use of hot tubs
what is the pathophysiology of hypersensitivity pneumonitis?
- the allergic response to the inhaled antigen involves both cellular immunity and the deposition of immune complexes (type 3 hypersensitivity reaction) resulting in inflammation through the activation of complement via the classical pathway
- some of the inhaled antigen may lead to inflammation by directly activating the alternate complement pathway
- these mechanisms attract and activate alveolar and interstitial macrophages so that continued exposure results in pulmonary fibrosis
what happens in the acute phase of hypersensitivity pneumonitis?
the alveoli are infiltrated with acute inflammatory cells
what happens in the chronic phase of hypersensitivity pneumonitis?
granuloma formation and obliterative bronchiolitis
what is the pathophsyiology of farmers lung in hypersensitivity pneumonitis?
• fungus in mouldy hay is inhaled
• if individual is already sensitised to the organism, a type III immune complex hypersensitivity reaction follows
• clinically there is acute dyspnoea and cough a few
hours after inhalation of the antigen
• one of the earliest features is bronchiolitis
• later, chronic inflammatory cells are seen in the interstitium together with non-caseating granulomas
• may resolve on antigen withdrawal but if there is chronic exposure then pulmonary fibrosis develops
what is the clinical presentation of acute (4-6hours post exposure) hypersensitivity pneumonitis?
- fever
- rigors
- myalgia
- dry cough
- dyspnoea
- crackles (no wheeze)
- chest-tightness
- patients may be mistakenly diagnosed with a chest infection
- symptoms related to level of exposure
what is the clinical presentation of subacute hypersensitivity pneumonitis?
- occurs with intermittent or lower-level exposure
- history or repeated acute attacks
- signs same as acute, symptoms less severe and more gradual onset
- can be present as recurrent pneumonia
- improvement is seen in weeks to months following removal from exposure
what is the clinical presentation of chronic hypersensitivity pneumonitis?
- usually no history of preceding acute symptoms
- if the source of antigen is removed only partial improvement of symptoms
- cyanosis and clubbing may develop
- weight loss
- increasing dyspnoea
- type 1 respiratory failure
what are differential diagnoses of hypersensitivity pneumonitis?
infection, connective tissue disorders causing ILDs, pulmonary fibrosis, asthma, drug-induced ILD
what is used to diagnose hypersensitivity pneumonitis?
- CXR
- FBC (raised WCC, increased ESR)
- lung function test (reversible restrictive defect, reduced gas transfer during acute attacks)
- bronchoalveolar lavage (analysis of lymphocyte cound and CD4/CD8 ratio)
what is seen on CXR in hypersensitivity pneumonitis?
- fibrotic shadow in upper zone of lung (upper zone mottling/consolidation)
- diffuse small nodules and increased reticular shadowing may be present but not specific
what is the treatment of acute hypersensitivity pneumonitis?
- remove allergen
- give O2 (35-60%)
- oral prednisolone followed by reducing dose
what is the treatment of chronic hypersensitivity pneumonitis?
- avoid exposure to allergen
- long term steroids can achieve chest x-ray and physiological improvement
- corticosteroids
what are types of occupational lung disorders? what can they each be caused by?
- acute bronchitis and oedema from irritants such as sulphur dioxide, chlorine, ammonia or nitrogen oxides
- pulmonary fibrosis from inhalation of inorganic dust e.g. coal, silica, asbestos, iron and tin
- occupational asthma
- hypersensitivity pneumonitis
- bronchial carcinoma due to asbestos, polycyclic hydrocarbons and radon in mines
what is pneumoconiosis?
pneumoconiosis means the accumulation of dust in the lungs and the reaction of the tissue to its presence
what is the epidemiology of coal-workers pneumoconiosis? what is the pathophysiology?
- common dust disease in countries that have or have had coal-mines
- caused by the inhalation of coal dust particles over 15-20yrs
- these particles are ingested by alveolar macrophages in the small airways and alveoli which then die, releasing enzymes and causing fibrosis
what is the diagnosis of simple pneumoconiosis?
- produces fine micro nodular shadowing in the chest x-ray
- graded on CXR
what can simple pneumoconiosis progress to?
- can progress to the development of progressive massive fibrosis
- this almost never occurs in mild pneumoconiosis but risk increases with more severe simple pneumoconiosis
what is the pathophysiology of progressive massive fibrosis?
- patients develop round fibrotic masses mostly situated in the upper lobes sometimes with necrotic central cavities
- rheumatoid factor and anti-nuclear antibodies are both often present in the serum of patients with PMF and also in those suffering from asbestosis or silicosis
- there is apical destruction and disruption of the lung resulting in emphysema and airway damage
what is the clinical presentation of progressive massive fibrosis?
- due to progression of coal workers pneumoconiosis
- sufferers have considerable effort dyspnoea and fibrosis
- sputum may be black
what is the diagnosis of progressive massive fibrosis?
- seen on CXR with upper-zone fibrotic masses
- rheumatoid factor and anti-nuclear antibodies are both often present in the serum of patients with PMF and also in those suffering from asbestosis or silicosis
- lung function tests show a mixed restrictive and obstructive ventilatory defect with loss of lung volume, irreversible airflow limitation and reduced gas transfer
what is the treatment/progression of progressive massive fibrosis?
- manage by avoiding coal dust exposure and claim compensation
- disease can progress or develop even after coal exposure has ceased and may lead to respiratory failure
where is silicosis seen? what is it caused by? what is its pathogenesis?
- uncommon but seen in stonemasons, sand-blasters, pottery and ceramic workers and foundry workers involved in fettling
- caused by the inhalation of silica dioxide which is very fibrogenic
- silica is particularly toxic to alveolar macrophages and readily initiates fibrogenesis
what is seen on CXR and spirometry in silicosis?
- CXR appearance show diffuse nodular pattern in upper and mid-zone and thin streaks of calcification (egg-shell calcification) of the hilar nodes
- spirometry shows a restrictive ventilatory defect
what is the clinical presentation of silicosis?
patients have progressive dyspnoea and an increased incidence of TB
what is the treatment of silicosis?
manage by avoiding exposure to silica and claim compensation
where has asbestos been used? why?
has widely been used in roofing, insulation and fireproofing due to its resistance to heat, acid and alkali
what are types of asbestos?
- chrysolite (white asbestos, 90%; least fibrogenic)
- crocidolite (blue asbestos, 6%; most fibrogenic and most likely to cause asbestosis and mesothelioma)
- amosite (brown asbestos, 4%; least common, intermediate fibrogenicity)
is crocidolite (white asbestos) easily inhaled or not? why/why not? what are features of it?
crocidolite is easily inhaled due to its thin long shape but also easily trapped in the lungs, its also resistant to macrophage and neutrophil enzymatic destruction
what is asbestosis? what is its pathophysiology?
- type of ILD; distinct cellular infiltrates and extracellular matrix deposition in lung distal to the terminal bronchiole
- fibrosis of the lungs caused by asbestos dust, which may or may not be associated with fibrosis of the parietal or visceral layers of the pleura
- significant time lag between exposure and development of disease, particularly mesothelioma (20-40 years)
what is the clinical presentation of asbestosis?
- progressive disease characterised by breathlessness and progressive dyspnoea and accompanied by finger clubbing and bilateral basal end-inspiratory crackles
- also causes pleural plaques and increases risk of mesothelioma and bronchial adenocarcinoma
what is the treatment of asbestosis?
only symptomatic management is known e.g. corticosteroids
what is byssinosis?
- an occupational lung disease caused by exposure to cotton dust in inadequately ventilated working environments
- commonly occurs in workers who are employed in yarn and fabric manufacture industries
- occurs worldwide but is declining particularly in areas where the number of people employed in cotton mills is falling
what is the clinical presentation of byssinosis?
- symptoms occur on the first day back at work after a break with improvement as the week progresses
- chest tightness, cough and breathlessness occur within the first hour in dusty areas of the cotton mill
- those with asthma are affected badly by the cotton dust
what is the diagnosis of byssinosis?
there are no changes on CXR and aetiology/nature of disease is unknown
what is berylliosis?
chronic allergic-type lung response and chronic lung disease caused by exposure to beryllium and its compounds; a form of beryllium poisoning
what is beryllium? where is it used?
- beryllium is a copper alloy with high tensile strengths and resistance to high temperature and corrosion
- widely used in the aerospace industry, atomic reactors and many electrical devices
what is the clinical presentation of berylliosis?
- when beryllium is inhaled it can cause a systemic illness with a clinical picture similar to sarcoidosis
- progressive dyspnoea with pulmonary fibrosis
- rare
what is bronchiectasis? what does it result from?
• chronic infection of the bronchi and bronchioles leading to permanent dilatation of these airways
• results from pulmonary inflammation and scarring due to infection, bronchial obstruction or lung fibrosis
- the resulting scarring causes airway distortion and dilatation with further inflammation in the wall of the damaged airway due to secondary infection
what is the epidemiology of bronchiectasis? what triggers it?
- more common in women than men
- may develop after lung infections
- it is the pathological end point of many diseases
- present at any age but increases with age
what lung insults can cause bronchiectasis?
- post infection (most common)
- congenital
- mechanical bronchial wall obstruction (foreign body, post-TB stenosis, lymphnodes/tumour)
- allergic bronchopulmonary aspergillosis
- HIV
- ulcerative colitis
- hypogammaglobulinaemia
- rheumatoid arthritis
what can cause post infection bronchiectasis?
- previous pneumonia
- granulomatous disease e.g. TB
- measles, whooping cough
- allergic bronchopulmonary aspergillosis
- pertussis
- bronchiolitis
what can cause congenital bronchiectasis?
- cystic fibrosis
- deficiency of bronchial was elements
- primary ciliary dyskinesia (Kartagener’s syndrome)
what is the pathophysiology of bronchiectasis?
- failure of mucociliary clearance and impaired immune function contribute to continued insult to bronchial wall, through the recruitment of inflammatory cells and uncontrolled neutrophilic inflammation; bronchitis → bronchiectasis → fibrosis
- airways dilate due to pulmonary inflammation and scarring, as fibrosis contracts
- secondary inflammation changes lead to further destruction of airways
what is the clinical presentation of bronchiectasis?
- usually the lower lobes are affected
- chronic cough with production of copious amounts of foul smelling purulent sputum (khaki coloured) with intermittent haemoptysis
- dyspnoea
- finger clubbing especially in cystic fibrosis
- wheeze
- infection usually characterised by increased sputum volume and increased purulence
- chest pain
- recurrent exacerbations with long recovery time
what are differential diagnoses of bronchiectasis?
COPD, asthma, TB, chronic sinusitis, cough due to acid reflux, pneumonia, pulmonary fibrosis, cancer, inhalation of foreign body
what is used to diagnose bronchiectasis?
- CXR
- sputum culture (bacterial colonisation)
- high resolution CT
- spirometry (obstructive pattern)
- sinus X-rays (may have rhinosinusitis)
- sweat test for all patients under 40, if cystic fibrosis suspected (will see high chloride concentration if CF)
- bronchoscopy to locate site of haemoptysis, exclude obstruction and obtain culture samples
- immunology e.g. total IgE to exclude bronchopulmonary aspergillosis
what is seen on CXR in bronchiectasis?
- dilated bronchi with thickened walls (tramline and ring shadows)
- multiple cysts containing fluid showing up as cystic shadows
what major pathogens are seen in bronchiectasis?
- Haemophilus influenza
- Streptococcus pneumoniae
- Staphylococcus aureus
- Pseudomonas aeruginosa
what is seen on high resolution CT in bronchiectasis?
- thickened, dilated bronchi with cysts at the end of bronchioles
- airways larger than associated blood vessels
what is used to treat bronchiectasis?
- improved mucus clearance (postural drainage, chest physio, mucolytics)
- antibiotics
- bronchodilators such as nebulised salbutamol is useful for asthma or COPD sufferers
- anti-inflammatory agents e.g. long term azithromycin can reduce exacerbation frequency
- surgery in localised disease or to control severe haemoptysis
what antibiotics are used to treat bronchiectasis?
- treatment of exacerbations usually lasts 2 weeks
- if pseudomonas aeruginosa then high dose oral ciprofloxacin twice daily
- Haemophilus influenzae responds to oral amoxicillin, co-amoxiclav or doxycycline; some multi-resistant species need IV cephalosporin
- if Staphylococcus aureus then give flucloxacillin
what is cystic fibrosis?
- genetic disorder affecting mostly the lungs, pancreas, liver, kidneys and intestines
- inherited in autosomal recessive manner
- caused by mutations in both copies of the gene for the CFTR protein
- one of the most common lethal autosomal recessive conditions in caucasians
- 25% condition and 50% carrier risk
what is the epidemiology of cystic fibrosis?
- much less common in Afro-Caribbean and Asian people
- multi-system disease although respiratory problems are usually the most prominent
- most people with CF also have pancreatic insufficiency
what are risk factors for cystic fibrosis?
- family history
- caucasians
where is the CF gene located? what protein does it code for?
CF gene is located on the long arm of chromosome 7 coding for the cystic fibrosis transmembrane regulator (CFTR) protein
• transport protein on membrane of epithelial cells that acts as a chloride channel
• transports chloride ions
• normally it actively exports negative ions especially Cl-, and Na+ passively follows causing an osmotic gradient and movement of water out of the cell and into the mucus
what is the commonest mutation that causes cystic fibrosis?
commonest mutation is the F508 deletion mutation and accounts for 70% of cases
what is the pathophysiology of cystic fibrosis in the lung?
- in the lungs, CFTR dysfunction leads to dehydrated airway surface liquid, mucus stasis, airway inflammation and recurrent infection
- the changes in the composition of airway surface liquid predispose the lung to chronic pulmonary
infections - this process originates in the small airways, leading to progressive airway obstruction and bronchiectasis
what is the clinical presentation of cystic fibrosis in neonates?
- failure to thrive
- meconium ileus - bowel obstruction due to thick meconium (earliest stool)
- rectal prolapse
- whilst the lungs of babies born with CF are structurally normal at birth, frequent respiratory infections soon develop and are the presenting feature
what is the clinical presentation of cystic fibrosis in the upper and lower respiratory tract?
- cough
- thick mucus
- wheeze
- recurrent infections
- bronchiectasis and airflow limitation
- sinusitis
- nasal polyps
- spontaneous pneumothorax
- haemoptysis and breathlessness (late)
- the resultant inflammatory response damages the airways and results in progressive bronchiectasis, airflow limitation and eventually respiratory failure
what is the clinical presentation of cystic fibrosis in the alimentary system?
- thick secretions
- reduced pancreatic enzymes (due to mucus blocking pancreatic duct)
- pancreatic insufficiency diabetes and steatorrhoea
- distal intestinal obstruction syndrome
- reduced bicarbonate
- maldigestion and malabsorption thus poor nutrition (associated with pulmonary sepsis)
- cholesterol gallstones and cirrhosis
- increased incidence of peptic ulcers and malignancy
what are other clinical presentations of cystic fibrosis?
- males infertile due to atrophy of vas deferens and epididymis
- females able to conceive but often develop secondary amenorrhea as disease progresses
- salty sweat
- clubbing
- osteoporosis
what is used to diagnose cystic fibrosis?
- clinical history
- family history of disease
- one or more of these:
• sweat test: will show high sodium and chloride concentrations greater than 60mmol/L (Cl- will be higher)
• absent vas deferens and epididymis
• GI and nutritional disorders - genetic screening for CF mutations
- faecal elastase test; good at excluding exocrine pancreas disease (protease is produced by pancreas and found in faeces) - in CF patient there will be low or no levels of elastase due to mucus blocking release
- microbiology
what microbiological species are looked for in cystic fibrosis diagnosis?
- Pseudomonas aeruginosa
- Mycobacterium abscessus
- Enterobacter spp.
- Klebsiella
- Prevotella spp. (anaerobe)
what is the treatment of cystic fibrosis?
- lung function (FEV1) and BMI should be recorded at every appointment
- education to improve QoL and good nutrition and prompt treatment of exacerbations
- stop smoking
- prophylactic antibiotics (flucloxacillin for S. aureus and amoxicillin for H. influenzae)
- pseudomonal and flu vaccine
- if MRSA present then treat with rifampicin and fucidin
- if Pseudomonas aeruginosa present then treat with ciprofloxacillin and nebulised colomycin
- regular chest physiotherapy (postural drainage, forced expiratory techniques)
- B2 agonists and inhaled corticosteroids for symptomatic relief
- mucolytics such as dornase alfa (nebulised) or inhaled DNAse to clear airways of mucus
- pancreatic enzyme replacement
- fat soluble vitamin supplements (ADEK)
- screening and treatment for osteoporosis
- amiloride inhibits Na+ transport thus less thick mucus
- bilateral lung transplant
how is bilateral lung transplant used to treat cystic fibrosis?
- patient needs to be on maximal therapy and fully compliant, psychologically well
- needs to be sick but not too sick
- HLA compatibility
- reasonable bone health
- if M abscessus bacteria present then cannot receive transplant since it can be associated with a rapid decline and active infection may preclude transplantation
- post transplant; major immunosuppressants
what is sarcoidosis? what does it affect? what does it typically present with?
- type of ILD
- a multi-system granulomatous disorder of unknown cause
- affects any organ system, but commonly involves the mediastinal lymph nodes and lung
- typically presents with bilateral hilar lymphadenopathy, pulmonary infiltration and skin or eye lesions
what is the epidemiology of sarcoidosis?
- usually affects adults aged 20-40 years
- more common in women
- prevalence highest in Northern Europe
- African-Caribbeans are affected more frequently and more severely than Caucasians, particularly by extra-thoracic disease
- often detected on routine X-ray
- first degree relatives have an increased risk of developing sarcoidosis (particularly in Caucasians)
what is the pathophysiology of sarcoidosis?
- typical sarcoid granulomas consist of focal accumulations of epithelioid cells, macrophages and lymphocytes (mainly T cells)
- generally unknown
what is the clinical presentation of sarcoidosis? what does acute sarcoidosis commonly present with?
- in 20-40% the disease is discovered incidentally, after a routine CXR and is thus asymptomatic
- sarcoidosis can affect any organ but has a predilection to the lung
- acute sarcoidosis commonly presents with erythema nodusum (red lumps form on the shins and less commonly thighs and forearms) with/without polyarthralgia; it usually resolves spontaneously
- constitutional symptoms (fever, weight loss, fatigue)
- respiratory symptoms
- other symptoms
what are respiratory symptoms of sarcoidosis?
- 90% have abnormal CXRs with bilateral lymphadenopathy with/without pulmonary infiltrates/fibrosis
- dry cough
- progressive dyspnoea
- reduced exercise tolerance
- chest pain
what are other symptoms of sarcoidosis?
- lymphadenopathy
- hepatomegaly
- deranged LFTs
- splenomegaly
- conjunctivitis
- glaucoma
- anterior uveitis
- hypercalciuria
- enlargement of lacrimal and parotid glands
- Bell’s palsy; lesion of facial nerve (CN7)
- facial numbness, dysphagia and visual field defects
- lupus pernio - blueish-red/purple nodules and plaques over nose, cheek and ears
- renal stones
- cardiac arrhthmias
- heart block
what are differential diagnoses of sarcoidosis?
rheumatoid arthritis, lymphoma, metastatic malignancy, TB, lung cancer, SLE, idiopathic pulmonary fibrosis and multiple myeloma
what is used to diagnose sarcoidosis?
- CXR (used for staging)
- blood tests
- bronchoscopy
- ECG (arrythmias/BBB)
- lung function tests (normal/reduced lung volumes, impaired gas transfer and restrictive ventilatory defect)
- tissue biopsy (diagnostic; non-caseating granuloma)
- broncheolar lavage (increased lymphocytes and neutrophils)
what is stage 0 sarcoidosis?
normal
what is stage 1 sarcoidosis?
bilateral hilar lymphadenopathy
what is stage 2 sarcoidosis?
pulmonary infiltrates with BHL
what is stage 3 sarcoidosis?
pulmonary infiltrates without BHL
what is stage 4 sarcoidosis?
progressive pulmonary fibrosis, bulla formation
(honeycombing - confluence of two or more elements of the bronchial tree) and bronchiectasis
what blood tests are done in diagnosis of sarcoidosis?
- raised ESR
- lymphopenia
- raised LFT
- raised Ca2+
- raised immunoglobulins
- serum ACE
- 24 hour urinary calcium if blood serum normal
what is the treatment of sarcoidosis?
- worse outcomes in patients with Afro-Caribbean and Asian descent those with extrathoracic disease
- patients with bilateral hilar lymphadenopathy don’t need treatment since most will recover spontaneously
- do not treat symptomatic patients at Stage 1
- do not treat asymptomatic patients at Stage 2 or 3
- corticosteroids
- transplantation in severe cases
- treat extra-organ complications
- acute: bed rest and NSAIDs
how are corticosteroids used to treat sarcoidosis?
- prednisolone orally then gradually reduce dose
- in severe illness give IV methylprednisolone
- if steroid-resistant then methotrexate, but close monitoring required
what is idiopathic pulmonary fibrosis?
- type of chronic scarring ILD characterised by a progressive and irreversible decline in lung function; distinct cellular infiltrates and extracellular matrix deposition in lung distal to the terminal bronchiole i.e. diseases of the alveolar/capillary interface
- there is patchy fibrosis or the interstitium and minimal or absent inflammation, acute fibroblastic proliferation and collagen deposition
- also known as cryptogenic organising pneumonia
what is the epidemiology of idiopathic pulmonary pneumonia?
- a progressive chronic pulmonary fibrosis of unknown aetiology although 20% of patient give history of occupational exposure to metals and wood dusts
- mean onset is in the sixties and presentation is very uncommon under the age of 50
- males are twice as likely to be affected
what is the pathophysiology of idiopathic pulmonary pneumonia?
- the pathogenesis of IPF is unknown
- repetitive injury to the alveolar epithelium, caused by
currently unidentified environmental stimuli leads to repair of the damaged tissue - in IPF, the wound healing mechanisms become uncontrolled, leading to the over-production of fibroblasts and deposition of increased extracellular matrix in the interstitium with little inflammation
- structural integrity of the lung parenchyma is disrupted; there is loss of elasticity and impaired gas exchange, leading to progressive respiratory failure
what are risk factors that are implicated in triggering the aberrant wound healing in idiopathic pulmonary fibrosis?
- cigarette smoking
- infectious agents (CMV, Hep C, EBV)
- occupational dust exposure (metals, woods)
- drugs; methotrexate, imipramine
- chronic GORD
- genetic predisposition
what is the pattern of lung disease of idiopathic pulmonary fibrosis?
- most patients with IPF show a pattern of lung disease described as usual interstitial pneumonitis
- this pattern of disease is characteristically patchy with the sub-pleural regions of the lower lobes predominantly affected
- there is variable interstitial inflammatory infiltrate in the affected areas of the lung with collapse of the lung architecture and the development of mystically dilated spaces within the fibrotic areas of the lung
(honeycombing) - a characteristic feature is the presence of areas of immature fibrous tissue or ‘fibroblastic foci’ in the less severely affected areas
what is clinical presentation of idiopathic pulmonary fibrosis?
- dry cough with/without sputum
- exertional dyspnoea
- malaise
- weight loss
- arthralgia
- cyanosis
- finger clubbing
- fine bi-basal end-inspiratory crackles
when can deterioration and acute exacerbations occur in idiopathic pulmonary fibrosis?
- step-wise deterioration can occur due to pneumothorax, pulmonary embolism or intercurrent infection
- but acute exacerbations with no identifiable cause are well recognised and are associated with increased mortality
what are the differential diagnoses of idiopathic pulmonary fibrosis?
COPD, asthma, bronchiectasis, congestive heart failure, atypical pneumonia, lung cancer, asbestosis and hypersensitivity pneumonitis
what are the characteristics of type 2 resp. failure?
- low blood [O2] = hypoxemia
- high [CO2] = hypercapnia
think broadly
causes of Type 1 resp. failure
- airway disorders
- congential
- infection
- vasculature problems
- neoplasm
Causes of type 2 resp. failure
- airway disorders - COPD, asthma
- drugs
- neurological - loss of resp. drive
- metabolic
what are the characteristics of type 2 resp. failure?
- low blood [O2] = hypoxemia
- high [CO2] = hypercapnia
think broadly
causes of Type 1 resp. failure
- airway disorders
- congential
- infection
- vasculature problems
- neoplasm
Causes of type 2 resp. failure
- airway disorders - COPD, asthma
- drugs
- neurological - loss of resp. drive
- metabolic
