Year 1 Peer Based Learning 2019Respiratory System

Please note – this learning resource has been produced by the GUMS Academic Team. It is possible that there are some minor errors in the questions/answers, and other possible answers that are not included below. Make sure to check with other resources.

Scenario 1:

Stem 1: Toby Acco is a 54 year old male. He has a 20 pack year history of smoking. His flow volume loop is shown below; normal is shown for reference.

Question 1: Define pack year

Number of packs of cigarettes smoked per day by the number of years the person has smoked

Question 2: What is the difference between a lung ‘capacity’ and ‘volume’

A capacity = 2 or more lung volumes totaled together

Question 3: Define the lung volumes/capacity shown on the graph at the right

VC = vital capacity = maximum volume of gas that can be expired after a maximal inspirationRV = residual volume = air remaining in lung after a maximal expirationTLC = sum of all volumes - volume of gas in lung after a maximal inspiration (IRV + TV + ERV + RV)

Year 1 Peer Based Learning 2019Respiratory System

Question 4: State the pattern of lung disease Toby has and how RV and TLC from question 3 have changed. State the underlying mechanism for this (in two words). Obstructive disease. RV and TLC have both increased (RV goes from 0 to about 4 now; TLC goes from 0 to 8). The mechanism for this is air trapping.

Question 5: Summarise the main spirometry/lung volume/capacity findings in obstructive disease and restrictive disease by completing the below table:

Obstructive Disease Restrictive Disease

RV increased Decreased

TLC Increased Decreased

FRC Increased Decreased

FEV1:FVC Decreased Normal or increased

(discuss how this ratio is changed with the students: in obstructive FEV1 drops more than FVC —> decreases ratio; in restrictive there is low FEV1 and low to very low FVC —> normal or increased ratio)

Year 1 Peer Based Learning 2019Respiratory System

Question 6: What is the most likely diagnosis? Define this disease

COPD - broad term for chronic bronchitis and emphysema. Explain that even though these are two different diseases, because the major risk factor for both is smoking, they commonly occur together - this is why the blanket term ‘COPD’ is given

Question 7: Contrast the pathophysiology mechanism of obstruction in chronic bronchitis and emphysema

Both are caused by smoking (which acts as an irritant).

Chronic bronchitis. It results mainly from hypertrophy and hyperplasia of bronchial mucinous glands (mainly) and also goblet cells. This leads to increased mucous production leading to mucous plugging – this is an obstruction. Smoking also causes shortened and immotile cilia, which further decreases ability to clear mucus.

Emphysema. Smoking causes inflammation in the airways, leading to production of proteases via inflammatory cells such as macrophages and neutrophils. These proteases (eg, collagenases, elastases) cause destruction of elastin and collagen, which are responsible for elastic recoil of the lung. Normally, when air leaves the lungs, there is negative pressure which acts to collapse the airways, however the elastic recoil of the lungs prevents this from occurring. In emphysema, the loss of elastin leads to:

● Collapsing airway walls on expiration (due to negative pressure) leading to air-trapping

● More compliant (stretchy) alveoli on inspiration, increasing lung volumes

There is also degradation of fibrous septa in the lungs, leading to alveoli collapsing into larger alveoli, decreasing the surface area for gas exchange to occur.

Question 8: for the following signs/symptoms, state which is more characteristic of chronic bronchitis vs emphysema and explain why:

- cyanosis - chronic bronchitis: mucus plugging causes a low V/Q ratio (decreased ventilation across the entire lungs) 🡪 hypercapnia and hypoxaemia. This is not as much of an issue in emphysema, because the V/Q ratio is more normal or even high (increased ventilation due to increased lung compliance, and ‘decreased blood flow’ due to reduced surface area with the alveoli)

- prolonged expiration with pursed lips - emphysema: breathing with pursed lips forces a ‘back pressure’ into the airways —> ensures smaller airways remain patent

- productive cough - chronic bronchitis: huge mucus production results in coughing; no where near as much mucus in emphysema (it does occur, just not as much)

- wheezing - chronic bronchitis: this is the sound of air ossicilating within narrowed airways - the intense mucus plugging causes this. also ask students: name another disease where wheezing is seen and state the mechanism for this: answer = asthma; mechanism = bronchoconstriction AND mucus plugging

Year 1 Peer Based Learning 2019Respiratory System

Year 1 Peer Based Learning 2019Respiratory System

Question 9: What if a patient also presented with liver cirrhosis? Which one of the diseases (chronic bronchitis or emphysema) is more likely to also occur concurrently? State what protein is defective and the mechanism for developing the disease it causes

Alpha-1-antitrypsin deficiency. Causes emphysema. Alpha-1-antitrypsin is an anti-protease. Explain that emphysema is caused by an imbalance of proteases and anti-proteases. In smoking, there is increased inflammation —> more proteases released —> number of anti-proteases cannot counteract this. In alpha-1-antitrypsin deficiency, even if the person doesn’t smoke, the fact that there are no anti-proteases can’t counteract the inflammation that will naturally occur as life goes on —> emphysema

Question 10: Which disease is more likely to have the following x-ray? Explain

increased AP diameter = barrel chest = emphysema, for expansion of the thorax, it is a battle between the chest wall and lung tissue. lung recoil has a tendency to collapse inwards, and the chest wall has a tendency to pull the thorax outwards. because of loss of elastic recoil, the chest wall wins this war —> barrel chest

● Ask what other features might be seen on X-ray: increased lung field lucency and

flattened diaphragm – both due to hyperinflation

Year 1 Peer Based Learning 2019Respiratory System

Q11. Which disease is more likely to cause infection as a complication? Explain

Infection is more likely in chronic bronchitis. a general principle in pathology is that if there is an obstruction, you get infection down-stream e.g. give a faecolith causing appendicitis as an example

Question 12: What is the effect of hypoxia on the pulmonary vasculature? Explain in ONE sentence the impact of long-term COPD on the heart and name this condition

Hypoxia causes vasoconstriction. Give the example of an upper lobar bronchus obstruction. Here, it is advantageous to constrict the pulmonary vasculature, because you divert the blood to the other lobes of the lung and can still get sufficiency gas exchange. Now, nowhere is getting enough oxygen in COPD, so everywhere constricts.

One sentence: hypoxic vasoconstriction —> increases afterload —> RVH and heart failure - cor pulmonale

Question 13: You administer ipratropium. State the MOA

muscarinic antagonist —> bronchodilation

Stem 2: 10 years later, he presents to the UQ student with clubbing and haemoptysis.

Question 14: What are the differentials for clubbing? How about haemoptysis?

Clubbing (many mechanisms; postulated to be related to hypoxaemia. in saying this, COPD is NOT a cause of clubbing!)Cardiac: cyanotic congenital heart lesionsResp: lung cancer (most common cause), bronchiectasis, NOT COPD!GI: cirrhosis many others, but these are the main ones. lung cancer is the main DDx

Haemoptysislung cancerbronchiectasisTB PE for any bleeding - coagulopathy other rarer ones

Stem 3: The UQ physician who originally found the clubbing and haemoptysis attributed both of these findings to being complications of COPD, given the patient had bad hypoxaemia and long standing disease. He fails to order the appropriate investigations (CT scan, PET scan, bronchoscopy) and the patient is discharged. The patient eventually

Year 1 Peer Based Learning 2019Respiratory System

presents with distended neck and arm veins, a droopy eyelid and blurred vision. Blood tests show elevated LFTs

Question 15: What disease (don’t need to be specific) has he most likely developed now? List all the structures that could be affected here.

lung cancer. upper lobe = pancoast tumour = compresses sympathetic chain (e.g. stellate ganglion) and SVC or brachiocephalic veins. also should check for: - recurrent laryngeal nerve (hoarseness of voice)- thoracic outlet syndrome: compression of lower trunk or T1 of brachial plexus plus subclavian

vessels - intrinsic hand muscle wasting (e.g. thenar, hypothenar wasting - get a picture from google images and show them), ischaemia, pain and oedema in upper limb from vessel compression

- need to stage this cancer - elevated LFTs especially raise concern for metastases!

Question 16: The doctor explains to the patient that they have developed serious complications from their lung cancer - they have SVC obstruction and likely metastases. The doctor also explains that these complications would have occurred a few years later in life if this was diagnosed earlier. The patient wishes to sue the UQ physician for negligence. Would he be successful in his claim?

● To succeed in negligence four elements need to be satisfied.

● A duty of care must exist (1/2 mark)

● The doctor/patient relationship incorporates a duty of care (1/2 mark).

● The doctor must breach that duty of care with reference to the standard of care (1/2 mark).

● Given that this is a case of failed diagnosis (1/2 mark),

● The standard is that of a reasonable and competent doctor in the same circumstances (1/2 mark)

● In considering the standard, it was highly probable that serious harm would occur if a doctor were to miss a diagnosis of lung cancer at the earliest possible point, particularly given the patient’s history of smoking and other lung diseases (1/2 mark)

● The burden of taking precautions in this case would be fairly low when weighed against the probability and likely seriousness of harm (1/2 mark)

● The symptoms being spoken of (clubbing and haemoptypsis) are clearly not related to COPD and a reasonable and competent doctor would have recognized this and investigated further (1/2 mark)

● The doctor may raise a defence (s22 of the Civil Liability Act) that at the time their actions would have been widely accepted by peer professional opinion (1/2 mark)

● This defence will not succeed because it is well known that clubbing with haemoptysis is most commonly caused by lung cancer, particularly in a patient with this patient’s history of smoking – this would be the peer professional opinion warranting further testing (that wasn’t done) (1/2 mark)

Year 1 Peer Based Learning 2019Respiratory System

● Therefore the doctor here breached their duty of care (1/2 mark)

● The patient must have suffered reasonably foreseeable harm (1/2 mark)

● It is foreseebale that a failure to diagnose lung cancer would lead to more serious disease and a shortening of life (1/2 mark)

● The harm must have been caused by the breach (1/2 mark)

● But for the failure to investigate and diagnose lung cancer when symptoms presented, the patient may not have developed more serious disease (metastases) and may have had a longer and higher quality of life (1/2 mark)

● There is nothing on the facts that would suggest limiting the scope of liability (ie. no clear indication of contributory negligence or anything that would limit the doctor’s liability)

● Damages must be foreseeable and quantifiable (1/2 mark)

● The cost of ongoing care and treatment is quantifiable, as is any loss of income the patient incurred as a result of this more serious diagnosis (the latter could be difficult to quantify if he was already sick) (1/2 mark)

● It is foreseeable that someone with this level of disease incurs substantial costs of ongoing care and treatment that they otherwise would not have accrued (1/2 mark)

● Given, that all four elements of negligence have been satisfied, the UQ physician would be found negligent (1/2 mark).

Stem 4 : The patient complains of altered mental state.

Question 17: If these were caused by his lung cancer, elucidate TWO possible mechanisms for this

prompt students with: think about paraneoplastic syndromes

small cell lung cancer —> releases ADH, causing SIADH —> hyponatraemia —> altered mental statesquamous cell clung cancer —> releases PTHrP (Parathyroid hormone-related protein), causing hypercalcaemia —> altered mental state

Question 18: complete the following table, comparing the main features of lung cancers:

also explain that small cell lung cancer is its own category - the others (squamous cell, adenocarcinoma etc.) are all types of non-small cell lung cancer. small cell treated by chemo/radiotherapy; non-small treated by surgery

give them the following mnemonic to help them remember: squamous cell and small cell lung cancer are ’s’entral, caused by smoking, have paraneoplastic syndromes and are more common in males. the one thing that is different is treatment. then, adenocarcinoma, is mostly the opposite!

Year 1 Peer Based Learning 2019Respiratory System

location in lung risk factors paraneoplastic syndromes

histological features

treatment

small cell lung cancer

central male smoke SIADH, Lambert-Eaton syndrome, ACTH

neuroendocrine tumour, poorly differentiated

chemotherapy/radiotherapy

adenocarcinoma

peripheral non-smokers and female smokers

nil back to back glands, mucin

surgery

squamous cell central male smokers hypercalcaemia keratin pearls, intercellular bridges

surgery

Stem 5 : The patient goes onto develop a fever and the following x-ray whilst in hospital:

Question 19: State the diagnosis. What predisposed him to this infection? What is the most common causative organism? What is the treatment for this? What is this patient’s prognosis?

Year 1 Peer Based Learning 2019Respiratory System

Lobar pneumonia

COPD (esp. chronic bronchitis)

S. pneumoniae

Penicillin (State strep has no resistance to penicllins)

Poor (state pneumonia is a common cause of death of the elderly in the hospital

Wrap up: state other important topics for them to study: pleural effusion, pneumothorax other types of pneumonia etc.