Obstructive and Restrictive Lung disease Flashcards
What are the main kinds of obstructive lung disease ?
Asthma
COPD
Bronchiesctasis (possibly due to CF)
What are the main kinds of restrictive lung disease ?
Idiopathic pulmonary fibrosis (IPF)
Sarcoidosis
How are obstructive and restrictive lung diseases distinguished from one another in diagnosis ?
Through spirometry measurements (repeatable measurement of lung function), which include FEV1.0 and FVC
State Poiseuille’s law, explaining its relevance to obstructive and/or restrictive lung disease.
R = 8ηL/πr^4
R being the resistance to flow when flow is laminar. This shows that resistance to flow is inversely proportional to radius, so small decrease in radius will have significant impact in resistance of flow and work of breathing, which is a major problem in some lung diseases.
What are the pathological changes in the airway causing reduced airflow in obstructive lung disease ? Compare these with the normal physiology of the airways.
Changes in airways, especially middle-sized bronchioles.
1) inflammation and fibrosis of the bronchial wall
2) hypersecretion of mucus (normally no mucus)
3) destruction of the elastic fibers that hold the airway open (normally present)
These results in reduced airflow in airways. These apply to COPD as well as asthma except for 3) which only applies to COPD.
Distinguish between spirometry results in normal conditions, in obstructive lung disease, and in restrictive lung disease (explaining the changes occurring). Graph the results of both obstructive and restrictive lung disease compared to a normal lung, in a spirometry test.
Spirometry indicates an abnormality if any of the following is present:
- FEV1 < 80% predicted normal
- FVC < 80% predicted normal
- FEV1:FVC ratio reduced (< 0.7)
1) OBSTRUCTIVE LUNG DISEASE
-FEV1 reduced (< 80% predicted normal)
-FVC usually reduced but to a lower extent than FEV1
-FEV1:FVC ratio reduced (< 0.7)
Because air is trapped in the lungs rather than lost, so it mainly just takes more time to get it out (although FVC does decrease a little bit).
2) RESTRICTIVE LUNG DISEASE
-FEV1 reduced (< 80% predicted normal)
-FVC reduced (< 80% predicted normal)
-FEV1:FVC ratio maintained (> 0.7)
Because smaller size of lungs means lungs cannot expand more, so FVC must also decrease considerably.
Refer to slide 7 of lecture on “Obstructive Lung Disease”
Briefly explain the procedure of spirometry.
- Clip on nose
- Maximum breath in and blow out as hard and fast as possible and keep blowing
- Normal, majority of air comes out in first second
Explain the change of air during spirometry in terms of lung volumes and capacities.
From total lung capacity to residual V
What volume/capacity is left in the lungs after a slow, maximal expiration ? (e.g. in spirometry) What volumes/capacities make this V/capacity ?
Forced Vital Capacity = inspiratory reserve volume \+ tidal volume \+expiratory reserve volume
I.E.
total lung capacity
-residual volume
Define FEV1.0 and FVC.
What is FEV1.0 /FVC ratio a measure of ? What’s a normal FEV1.0 /FVC ratio ?
Graph spirometry of a normal lung, showing FEV1.0.
FEV1.0 = forced expiratory volume in 1 sec. FVC = forced vital capacity, the maximal volume of gas that can be exhaled from full inhalation by exhaling as forcefully and rapidly as possible.
FEV1.0 /FVC ratio is a measure of airflow obstruction
FEV1.0 /FVC > 0.7 is normal
Refer to slide 9 in lecture on “Obstructive Lung Disease”
Identify the changes in lung volumes and capacities in obstructive, and restrictive lung diseases.
OBSTRUCTIVE
TLC normal or increased
Tidal Volume increased
FVC decreased (but to a lower extent than FEV1)
FEV1.0 decreased
FRC increased
RV increased (because air trapping so bronchioles close and alveoli cannot empty)
RESTRICTIVE TLC decreased FVC decreased FEV1.0 decreased FRC decreased Residual V decreased Tidal Volume decreased
Give an example of physiological V/Q mismatching. What happens in lung disease wrt this ?
Top of lungs ventilated more than bottom.
Perfusion of lungs greater at bottom than at the top.
Mismatch.
In lung disease, increased mismatch so some alveoli ventilated but no blood supply so blood cannot pick up O2.
In both obstructive and restrictive lung disease, the cause of hypoxia is increase in V/Q mismatching
Define bronchiectasis.
Chronic pus in bronchioles.
Distinguish between asthma and COPD wrt:
- Smoking patterns
- Allergic ?
- Age groups affected
- Timeline
- Rate of decline
- Immune cells involved
- Diurnal variations
- Corticoid response
- Bronchodilator response
- Change in FVC and TLCO
- Quality of gas exchange
COPD:
- Smokers
- Non-allergic
- Over 50s
- Chronic
- Progressively decline (but through treatment can reduce slope of decline)
- Neutrophils
- No diurnal variations
- Poor corticosteroid response
- Poor bronchodilator response (measure spirometry both before inhaled bronchodilators, and after that)
- Reduced FVC and TLCO
- Impaired gas exchange
ASTHMA:
- Non-smoking related (but can trigger asthma)
- Allergic (patients tend to have history of allergic rhinitis, eczema)
- Tends to be younger patients
- Intermittent
- Non-progressive (spirometry can be perfectly normal)
- Eosinophil infiltration
- Diurnal variation (nocturnal cough and wheeze)
- Good corticosteroid response
- Good bronchodilator response (measure spirometry both before inhaled bronchodilators, and after that )
- Preserved FVC and TLCO (i.e. thicker walls)
- Normal gas exchange
How is asthma diagnosed ?
♦ Clinical diagnosis, based on symptoms of:
• Wheeze
• Breathlessness
• Chest tightness
• Cough
♦ Especially if:
-Diurnal variations on symptoms and history of atopy
-Symptoms arise in response to allergen, exercise, cold air
-PEFR shows abnormalities
Define asthma.
Chronic inflammatory disorder of the airways…in susceptible individuals, inflammatory symptoms are usually associated with widespread but variable airflow obstruction and an increase in airway response to a variety of stimuli. Obstruction is often reversible, either spontaneously or with treatment.
Describe the pathophysiology of asthma.
Three components:
1) Airway narrowing / obstruction (reversible)
2) Airway hyper-responsiveness in response to trigger (e.g. allergen, infection) (and edema secondary to histamine release)
3) Airway inflammation
• Eosinophilic inflammation
Identify important mediators of asthma.
- Leukotriene B4 and cysteinyl-leukotrienes
- (C4 and D4) interleukins IL-4, IL-5, IL-1
- Tissue damaging eosinophil proteins
Describe a hypothesis which has been presented to explain why there has been an increase in asthma diagnoses over the past few years.
Hygiene hypothesis: houses are becoming too clean, leading to under-exposure to allergens to trigger T-lymphocytes (moderators of asthma) which would mediate a response.
Identify possible exacerbators/triggers of asthma.
- Virus
- Allergens - animal dander, dust mites, pollens, fungi
- Cold
- Foods / nutrition – vitamin D, A , E levels? • Chemicals – smoke
- Exercise