Obstructive Lung Disease Flashcards
What is the diagnostic test for obstructive airway diseases?
- spirometry
- quantitative, objective measurement of lung function
- can be used to monitor the course of disease
Describe the relationship between radius and resistance according to respiratory illness
if radius of airway narrows (decreases) resistance to airflow increases and work of breathing increases
Describe how the physiology of airways change due to asthma and COPD
Asthma:
- inflammation
- swelling
- fibrosis
- increased mucus production
COPD:
- breakdown in elastic fibres holding airway opening
- not present in asthma
Describe what values you would see in a spirometry if the patient had an obstructive/restrictive respiratory illness
Obstructive disorder:
- FEV1 reduced <80% normal
- FVC reduced but to lower extent that FEV1
- FEV1/FVC ratio less than 0.7
Restrictive disorder:
- FEV1 reduced <80% normal
- FVC reduced <80% than normal
- FEV1/FVC ration normal >0.7
What is forced vital capacity and how must the patient breathe to measure this?
- total volume in the lungs minus the residual volume
- after slow maximal inspiration, patient exhales as hard and as long as possible
What is FEV1/FVC ratio a measure of?
airflow obstruction
What are examples of obstructive lung disease?
- asthma
- COPD
- bronchiectasis
- cystic fibrosis
Describe the contrasting features of asthma and COPD
Asthma / COPD:
non smoking / smoking
allergic / non-allergic
younger / over 50s
intermittent / chronic
non-progressive / progressive
eosinophil infiltration / neutrophils
diurnal variation / no diurnal variation
good corticosteroid response / poor corticosteroid response
good bronchodilator response / poor bronchodilator response
preserved FVC and TLCO/ reduced FVC and TLCO
normal gas exchange / impaired gas exchange
What are the symptoms to consider for asthma?
- wheeze
- breathlessness
- chest tightness
- cough
- especially if diurnal variation in symptoms and history of atopy
- symptoms in response to allergen, exercise and cold air
Describe the pathophysiology of asthma
3 components:
- airway narrowing/obstruction (reversible)
- airway hyper-responsiveness
- airway inflammation (eosinophils)
Important mediators:
- leukotriene B4 and cysteinyl-leukotrienes (C4 and D4)
- IL-4, IL-5, IL-13
- tissue damaging eosiniphil proteins
What things that worsen the symptoms of asthma?
- virus
- allergens (animal dander, dust mites, pollens, fungi)
- cold
- food/nutrition
- chemicals (smoke)
- exercise
What is the non-pharmacological treatment of asthma?
- achieve and maintain a normal BMI if overweight
- breathing exercise programmes
- stop smoking (patient and household members)
What are the features of moderate acute asthma?
- increasing symptoms
- PEF >50-75% (peak expiratory flow)
- no features of acute severe asthma
What is the criteria for acute severe asthma?
any one of:
- PEF 33-50%
- respiratory rate of 25 breaths per minute or more
- heart rate of 110 or more
- inability to complete sentences in one breath
What is the criteria for life-threatening asthma?
any one of the following in a patient with severe asthma:
- altered consciousness
- exhaustion
- arrythmia
- hypertension
- cyanosis
- silent chest
- poor effort
- PEF < 33%
- SpO2 < 8kPa
- normal PaCO2
What is the criteria for near fatal asthma?
- raised PaCO2
- requires ventilation
What is the management of acute severe asthma?
immediate treatment:
- oxygen SpO2 94-98%
- SABA via nebuliser
- IV steroid (hydrocortisone) then switch to oral steroid (prednisolone)
if patient it still not improving:
- IV magnesium sulphate
- switch from nebulised to IV salbutamol or methylxanthine
monitor blood gases and patient exhaustion/alertness
What is COPD?
- common, preventable, treatable disease
- characterised by persistent airflow limitation that is usually progressive and associated with an enhanced chronic inflammatory response in the airways and the lung to noxious particles or gases
- exacerbations and comorbidities contribute to overall severity in individual patients
What things affect COPD?
- tobacco smoking
- individual susceptibility
- host factors
- genetic abnormalities (eg. a1 antitrypsin deficiency)
- abnormal lung development
- age and sex (females)
What is a1 antitrypsin deficiency?
- enzyme in liver that counteracts proteinases
- early onset COPD (<45 years)
- Z-At gene
- autosomal codominance
- emphysema most marked in lower lobe of CXR
Describe the pathophysiology of a1 antitrypsin deficiency in COPD
- inflammation and fibrosis of bronchial wall
- hypertrophy of submucosal glands and hypersecretion of mucous
- loss of elastic, parenchymal lung fibres
- consider diagnosis if presents with breathlessness, chronic cough/sputum production and exposure to risk factors
What is the clinical presentation of COPD?
- insidious onset
- usually 50/60s
- chronic cough
- sputum production (typically worse in morning)
- increasing shortness of breath
- diminishing exercise tolerance
- history of exposure to risk factors
Describe the presentation of the pink puffer
- pink
- increasing SOB but little cough
- pursed lips
- barrel chest due to air trapping (inc in anteroposterior diameter)
- use of accessory muscle
- decreased breath sounds
Describe the presentation of a blue bloater
- cyanosed
- bloated: signs of right heart failure
- productive cough
- crackles and wheezes
