Pathology of Restrictive lung disease Flashcards
Where does restrictive lung diseases affect the lungs
In the Interstitium lying within the alveoli of the lungs
What is the interstinum of the lung
potential space between alveolar epithelium and alveolar capillary endothelium, which sit on basement membranes
What is the outcome of restrictive lung disease
reduces the lungs compliance - creates a stiff lung
reduced total lung capacity
reduced gas transfer
ventilation/perfusion imbalance
What is the result of restrictive lung disease on the FEV1 FVC and their ratio
FEV1 AND FVC are reduced,
but the FEV1/FVC ratio remains the same
What causes the reduction of the total lung capacity in restrictive lung disease
altering of lung parenchyma - portion of the lung involved in gas transfer
In normal alveolar wall what is the relationship between e alveolar epithelial and intersitial capillary endothelial cell basement membranes, what does this allow
direct contact allowing efficient gas exchange
What is the pathological process of restrictive lung disease and what does it result in
interstitial inflammation
alveolar wall thickening due to interstital filtrate
potentially resulting in scaring and fibrosis
What is the clinical presentations of restrictive lung disease
Dyspnoea:
shortness of breath during exercise followed by at rest
Respiratory failure type 1 (reduced oxygen in the blood)
Heart failure
Abnormal Chest X-ray
What is the overall aetiology of restrictive lung disease
Something damages the lung tissue parenchymal and the lung injury leads to an inflammatory process
What is the two responses to Parenchymal (Interstitial) Lung Injury
either chronic or acute
What are the the further responses of the chronic response to parenchymal lung injury
interstitial pneumonitis response
granulomatous response
or other patterns
What is the acute response to Parenchymal (Interstitial) Lung Injury
Diffuse alveolar damage
What is the potential causes of Diffuse alveolar damage
Major trauma Chemical injury / toxic inhalation Circulatory shock Drugs Infection Auto(immune) disease Radiation idiopathic
What is the two stages in the pathology of Diffuse alveolar damage
Exudative stage
proliferation stage
What steps occur in the exudative stage of diffuse alveolar damage
- Damage and destruction to the endothelia cells results in the capillary cells becoming very leak
- The leads to a massive pulmonary oedema - much more than acute inflammatory response
- alveolar spaces fill with protein rich fluid
- The massive outpour of macromolecule and proteins form a layer on the degraded basement membrane
- Form hyaline membrane
What does the body want to achieve in proliferation stage of diffuse alveolar damage
The body wants to repair the damage to the alveoli
What is the outcome of the proliferation stage of diffuse alveolar damage
alveolar proliferation leads to a mixture of fibril and inflammatory cells, these then attempt to repair the damage by laying down rapid fibrosis tissue, thus creating a solid mass in the lungs
What is the outcome of most patients with Diffuse alveolar damage
Its a fatal disease as may patients die from respiratory distress ARDS, shocked lung etc, as lung loses all compliance
What is the histological features of DAD
Protein rich oedema Fibrin Hyaline membranes - Epithelial proliferation Fibroblast proliferation Scarring - interstitium and airspaces
What are the two Granulomatous responses in Parenchymal (Interstitial) Lung Injury
sarcoidosis
Hypersensitivity pneumonitis
What is sarcoidosis
is a mulit granulomatous disorder
Do sarcoidosis granulomas cause necrosis
no
How can you differentiate between sarcoidosis and TB
caseations are very unusual in sarcoidosis, but necrosis occur in TB, causing these caseation cheese like appearance
What is the most key feature of sarcoidosis
The alveoli around the granulomas are normal
How does scarring occur in sarcoidosis
fibrosis of the granuloma
sarcoidosis is a multi system disorder but what is the most common sites of infection
Skin, Lungs and lymph nodes
eyes - sometimes
What is the symptoms of sarcoidosis
Tender reddish bumps or patches on the skin (Erythema nodosum)
Red and teary eyes or blurred vision.
Swollen and painful joints (acute arthralgia)
Bilateral hilar lymphadenopathy - enlarged lymph
shortness of breath
cough
abnormal CXR
What specific cell types are present in Lymph node
Sarcoidosis
Non-caseating Epithelioid Granulomas
What are the investigation need for the diagnosis of Sarcoidosis
Clinical findings Imaging findings - CXR Serum calcium levels angiotensin converting enzyme levels (high levels present in Sarcoidosis) Biopsy Pulmonary function test Spirometry
What is Hypersensitivity Pneumonitis
an inflammation of the alveoli within the lung caused by hypersensitivity to inhaled organic microorganism
What is examples of organisms that trigger Hypersensitivity Pneumonitis
Thermophilic actinomycetes - bacterium
Bird / Animal proteins - faeces, bloom
Fungi - Aspergillus spp
Chemicals
Examples of Thermophilic actinomycetes are:
- Micropolyspora faeni
- Thermoactinomyces vulgaris
What type of hypersensitivity pneumonitis does this cause
Farmers lung
Where would you find
- Micropolyspora faeni
- Thermoactinomyces vulgaris
Mouldy hay
What is the pathology of hypersensitivity pneumonitis that leads to disruption of diffusion and then respiratory failure
Inhalation of particle, which then deposits in the interstitium, disrupting the diffusion by creating an inflammatory reaction and lowering gas transfer
What is the signs and symptoms for acute hypersensitivity pneumonitis
Fever, dry cough, myalgia,
Chills 4-9 hours after Ag exposure
Crackles, tachyopnoea, wheeze
Precipitating antibody
What is the main aetiology of hypersensitivity pneumonitis
causative antigens
What is the signs and symptoms of chronic hypersensitivity pneumonitis
Malaise, SOB, cough
Crackles and some wheeze
hypersensitivity pneumonitis is immune complex mediated by what hypersensitivity reactions
Type III and Type IV Hypersensitivity reaction
What cells are present in hypersensitivity pneumonitis
epithelioid granulomas Foamy histiocytes (macrophages laden with lipid)
Where is hypersensitivity pneumonitis located in the lungs
Upper zones - centriacinar
what can chronic hypersensitivity pneumonitis lead on to cause
Bronchiolitis obliterans - fixed airway obstruction
Why is hypersensitivity pneumonitis more likely to be an upper zone disease
as corresponds to inhalation of antigens as thats where the are more likely to deposit
interstitial pneumonitis UIP is a lung diseases characterised by
progressive scarring of both lungs (no granulomas)
What is the potential causes of interstitial pneumonitis UIP
Connective tissue diseases ; esp scleroderma and rheumatoid disease
Drug reaction
Post infection
Industrial exposure - asbestos
What is the morphology of interstitial pneumonitis UIP
Patchy interstitial chronic inflammation
proliferating fibroblastic foci
Type 2 pneumocyte enlarge
What gives you the evidence if its an old or a recent injury
whether interstitial pneumonitis UIP is temporal or spatial
What is the general demographic of interstitial pneumonitis
Ages 50 above
More likely to be male >female
What is the clinical signs of interstitial pneumonitis
Dyspnoea, Cough,
Basal Crackles, Cyanosis, Clubbing
Progressive disease
What is used to investigate interstitial pneumonitis
Chest X ray
Pulmonary function test - reduced gas transfer
spirometry
What is the outcome of end stage interstitial pneumonitis
The lung tries to repair itself with cystic fibrosis but fails creating the appearance of a honeycomb lung
When is V/Q imbalance the lowest
In hypoxemia conditions
due to local alveolar hypoventilation due to some focal disease
What increases the V/Q ratio imbalance
increase even the slightest amount of oxygen breathed in (FIO2)
Restrictive disease affects diffusion in what two ways
Increase thickness and surface areas of membrane, increasing gas transfer time
increase equilibration time above 0.25 seconds
What is the normal equilibration time?
0.25 seconds
What is the normal capillary transit time
0.75seconds
If restrictive lung diseases increases equilibration time, how does this create hypoxia
as equilibration time increases to the same time or more as capillary transit time, meaning there is not enough time to fully saturate RBC,
When can an increased equilibrium time cause problems
Its fine at rest,
when excise results in a decrease in PaO2
When Pa o2 falls it causes hypoxemia, what corrects hypoxemia and restores diffusion
corrected by increasing FIO2, which increase PA O2 again thus increasing the rate of diffusion
Why does a large shunt respond badly to increase in FI O2
Blood leaving normal lung is already 98% saturated
Why does CO2 levels increase in alveolar hypoventilation
lack of air moving in and out of the lungs leading to an imbalance in the alveolar CO2 levels – leads to retention of CO2 in arterial blood
