Interstitial Lung Disease

Question 1

What is the interstium?

Answer 1

The Interstitium – space in between two cells

Question 2

what is the function of the interstitium?

Answer 2

Function of the interstitium are: generating cells, motorway for diffusion, regulates immune function and structural mechanism for collagen i.e. scaffolding.

Question 3

What happens to the interstitium in interstitial lung disease and how does this effect lung function?

Answer 3

• The development of fibrous tissue in the Interstitium, making lungs less compliant, producing a restrictive Ventilatory defect.
• Airway resistance is NOT increased. In fact, the FEV1/FVC ratio can be > 70%, due to the increased radial traction on the airway, which keeps the airway open.
• Lengthening of the diffusion path between alveolar air and blood impairs gas exchange, with oxygen uptake being affected selectively, as CO2 diffuses much more readily.

Question 4

What are the histological features of the interstium in ILD?

Answer 4

Histologically there are increase activated Alveolar Macrophages which attract Neutrophils and Eosinophils, local lung damage due to ROS and proteases and tissue destruction and fibrosis.

Question 5

Why is ventilation and diffusion impaired?

Answer 5

Ventilation is impaired as they become stiff unable to expand and deflate, diffusion is impaired because there is a thick viscous liquid for materials to diffuse between and perfusion as capillaries are destroyed or damaged.

Question 6

How do patients with interstitial lung disease present?

Answer 6

Shortness of breath, cough (both chronic). On examination (may be asymptomatic) signs of underlying disease, clubbing, cyanosis, tachycardia, signs of right heart failure, tachypnoea, decreased chest movement and course crackles.

Question 7

What happens to oxygen and carbon dioxide?

Answer 7

Overall decrease in oxygenation and increase in carbon dioxide in the body. Oxygenation is effected first because it is much less soluble.

Question 8

What is a restrictive deficit?

Answer 8

Interstitial disease creates a restrictive deficit – reduction in how quickly it leaves and the total that is breathed out.

Question 9

What can be seen on CT scans in interstitial lung disease?

Answer 9

Round cystic areas – honeycombing. Don’t go away when turned over and CT scan taken again. Bottom of lung does most of gas exchange.

Question 10

What are the different types of interstitial lung disease?

Answer 10

• Occupational – asbestosis, silicosis and coal worker’s pneumoconiosis
• Treatment related – radiation, methotrexate, nitrofurantoin, amiodarone and chemotherapy
• Connective tissue disease – Rheumatoid Arthritis, SLE (systemic lupus erythematosus – systemic autoimmune inflammatory disease), polymyositis (autoimmune disease of the muscle), scleroderma (immune attach o the connective tissues) and sjogren’s (autoimmune disease of the moisture producing glands of the body)
• Immunological – sarcoidosis (formation of granulomas all over the bodies organs) and hypersensitivity pneumonitis (hypersensitivity of alveoli to organic dusts leading to granuloma formation)
• Idiopathic – CFA/IPF (idiopathic pulmonary fibrosis)

Question 11

What are pigeon fancier’s likely to get?

Answer 11

Pigeon fancier very likely to get hypersensitivity pneumonitis

Question 12

What is IPF?

Answer 12

IPF (idiopathic pulmonary fibrosis). Most common form of idiopathic interstitial disease. Presents at 60-80 years of age, median survival 3 years. Drugs used to treat – pirfenidone and nintedanib – slows decline in FVC but lots of drug toxicity.

Question 13

How does asbestos effect the lungs? in the EXAM!!!

Answer 13

Asbestos plaques – isolated thickening of the pleura

Diffuse pleural thickening – chronic thickening of the pleura

Benign asbestos pleural effusion (BAPE) – build-up of exudate in the pleural cavity

Asbestosis – interstitial lung disease caused by asbestos

Mesothelioma – cancer of the pleura

Bronchogenic lung cancer – cancer of the epithelium of the bronchus or bronchiole

Rounded atelectasis – rounded and folding of the lungs and the lobes collapse.

Question 14

What drugs can cause ILD?

Answer 14

Methotrexate (RA and weirdly ILD), bleomycin (lymphoma), amiodarone (arrhythmias) and nitrofurantoin (recurrent UTIs). Treatment is to stop the drug and give steroids.

Question 15

What is sarcoidosis?

Answer 15

Age of onset 20-80. Often asymptomatic cough or rash. PFT (pulmonary function tests) – normal, restrictive, obstructive and mixed. Biopsy – non-caseating granuloma, differential diagnosis is lymphoma and TB, treatment is none, steroids or methotrexate.

Question 16

What is pleural fluid circulation, what secreted pleural fluid and where is it absorbed?

Answer 16

Pleural fluid circulation – constant circulation as we produce it then reabsorb it.

Pleural fluid turnover – 15mil per day (but can increase to 300ml)
Produced by capillary filtration (starling’s forces) parietal pleura only.
Absorption – lymphatic drainage, parietal pleural lymphatics – via stomata on parietal surface (mainly on the mediastinal diaphragmatic regions.

Question 17

How are the parietal and visceral pleura innervated?

Answer 17

Parietal Pleura – somatic sympathetic and parasympathetic innervation by phrenic and intercostal nerves.

Visceral pleura – devoid of somatic innervation. So we only get pain when parietal pleura is inflamed.

Question 18

How can you get a pleural effusion?

Answer 18

The stomata can be blocked up by infection, elevated systemic venous pressure or other diseases of the lymphatic system such as lymphoma. Can have increase in production of fluid such as in heart failure, liver failure, peritoneal fluid, changes in permeability.

Question 19

What is a transudate?

Answer 19

Transudate=watery – usually due to decreased oncotic pressure or increased venous pressure.

Question 20

What is an exudate?

Answer 20

Exudate=proteins – pleural fluid protein divided by serum proteins > 0.5 or the pleural fluid lactate dehydrogenase (LDH) divided by serum LDH is > 0.6.

Question 21

How do we analyse pleural effusions?

Answer 21

Get fluid sample guided by ultrasound or CT guided. Once we have a sample it is analysed for appearance, cell count, protein, LDH, pH, Glucose and cytology.

Question 22

Describe the different reasons for the formation of different types of effusions

Answer 22

• Transudate – heart failure, hypoalbuminaemia, atelectasis, nephrotic syndrome, constrictive pericarditis and Meigs syndrome.
• Exudate – infection, TB, Malignancy, Rheumatoid arthritis, pulmonary embolism, asbestos related and pancreatitis.
• Empyema – (pH<7.2, glucose < 3.4mmol) – when the fluid is infected
• Haemothorax – usually traumatic or iatrogenic (due to medical treatment) may need chest drain or surgical drainage
• Chylothorax – milky appearance due to lymphatic interruption, lymphoma or iatrogenic.

Question 23

What are the common causes of metastatic malignancies in the pleura and what is the most common primary malignancy of the pleura

Answer 23

Metastatic – most common from lung and breast cancer
Primary – mesothelioma form asbestos exposure, Chest pain always present, breathlessness, X-rays: effusion and mediastinal pleural enhancement.

Question 24

Discuss the epidemiology of pneumothorax

Answer 24

Around 20 cases per 100’000 per year in males but more like 2-6 in females. Common in tall thin males.

Question 25

Who do primary pneumothraces occur in?

Answer 25

Primary – otherwise healthy people

Question 26

Who do secondary pneumothraces otherwise occur in?

Answer 26

Underlying lung disease e.g. cancer, COPD etc.

Iatrogenic Pneumothorax – procedures such as due to a clinical line.

Question 27

What is the common cause of primary spontaneous pneumothraces, how do they present and what is the risk of re-occurrence?

Answer 27

Primary Spontaneous pneumothorax – smoking is important (especially cannabis). Risk of recurrence is 54% within the first 4 years. Present with pleuritic chest pain, dyspnoea (difficult or laboured breathing). Investigations done by CXR (or CT scan if needs be). Small is < 2cm from chest wall and large is > 2cm.

Question 28

How are pneumothoraces treated?

Answer 28

No treatment for small apart from to return if worsening shortness of breath. Treatment for large via aspiration or chest drain. If recurrent then can glue pleura together – chemical pleurodesis and if this doesn’t work, then can surgically stick the pleura together – open thoracotomy and pleurectomy.

Question 29

What is a tension pneumothorax?

Answer 29

In tension pneumothorax – pressure of air in pleural cavity is increasing causing cardiovascular compromise (tachycardia, hypotension), shift of apex beat, hypoxaemia and expansion with hyper resonance and absent breath sounds on side of collapse.

Medical emergency – no CXR required – cannula into affected side in the 2nd intercostal space at the sternal angle. Should hear a hisss. Add chest drain and give oxygen.

Question 30

What precautions must be taken after a pneumothorax?

Answer 30

Can’t fly for at least week after confirmed resolution, permanently no diving allowed unless bilateral surgical pleurectomy.

Question 31

Discuss some chest wall diseases and their symotoms

Answer 31

Congenital – pectus deformities, scoliosis, kyphosis and muscular dystrophy

Acquired – trauma, iatrogenic, ankylosing spondylitis (spinal arthritis in young males) and motor neurone disease.

Ventilation failure, sleep disordered breathing, inability to clear secretions as they can’t cough properly, atelectasis and pneumonia.