Smoking the Dog and Lead OSCE by Adam

You have 4 minutes reading time. This OSCE will run for a maximum of 7 minutes.


A 29M presents with left sided chest pain and SOB after smoking marijuana at a friends house two evenings prior.

He self presented to ED and is sat comfortable in the acute assessment area watching youtube videos.

Vitals: RR 18, Sats 99% RA, PR 80 Sinus, BP 115/75.

Tall slim, reduced left sided BS

Pathology results:
Unremarkable FBE, U&E, LFT and initial High Sens Troponin

Instructions for the candidate

1. Take a focussed history from the patient
2. Please interpret his Xray pointing out the relevant positives and negatives.
3. Please provide a differential for the Xray changes observed.
4. Discuss an appropriate management plan with the patient.

Domains being examined

  • Medical Expertise
  • Prioritisation And Decision Making
The candidate has 4 minutes reading time. This OSCE is expected to run for a maximum of 7 minutes.

For the actor

-You smoking marijuana with a bong 2 nights ago and developed sudden onset sharp pain worse on inspiration.
-You've been to work since thinking the pain would simply subside, but it never did, pain remains constant, doesnt radiate, left side of chest.
-You feel SOB, but are able to do your everyday things though exercising to intensity would be an issue.
- You've taken paracetamol only
-No prior episodes
-No Cough, fevers, weight loss.
-No syncope, collapse.
-No trauma
-No immobilisation/recent surgery
-No prior VTE
-No vomiting
- Last ate a meatball subway an hour prior to arrival

- Nil
- No known connective tissue diseases, though is hypermobile

- Nil
-No allergies

- Father MI aged 65
- Mother T2DM

- Smoke marijuana 2-3x week, nil other recreational drugs
- 2-3 Stubbies per day
- Work as diesel mechanic
- Live near to the hospital with a flatmate

For the examiner

1. Has structured approach to interpreting the CXR
2. Ask to differentiate between a primary and secondary pneumothorax and provide a differential of 5 causes of secondary pneumothorax when prompted.
3. Enquires about life threatening causes of CP in history: PE, Aortic Dissection, Infective origin, MI, oesophageal rupture
4. Provides a safe sensible plan based on established guidelines or recent research ( BTS guidelines, PSP NEJM study)

Domains Assessment Objectives

Medical Expertise
Pneumothorax classification:
1. Primary- Otherwise healthy lungs in the absence of trauma or iatrogenic insult. (generally ruptured apical alveolus in tall thin smoker) Primary 25% yearly recurrence rate without pleurodesis. 6:1 male predominance
- Bong smoker raises incidence 4 x fold
2. Secondary - Pneumothorax complicated by underlying lung disease, often more severe presentation, due to already compromised resp physiology.
DDx: Airway disease (COPD, ASTHMA), ILD (sarcoid, IPF, Catamenial), Infectious (esp HIV/PCP, TB), Supperative LD (CF, Bronchiectasis) Malignant,
3. Traumatic and Tension
4. Iatrogenic.

Prioritisation And Decision Making
- BTS Guidance for estimating PTx size:
1.When following the BTS guidelines, pneumothorax size should be determined (on a PA chest radiograph) by measuring the distance from the lung edge to the thoracic wall at the level of the hilum and not at the apex. <2cm defined as small and aproximately = 50% collapse. The PA radiograph has a sensitivity of ~80-85% at identifying small pneumothoraces. US achieves a sens of 98%
- American society of chest physicians:
1. 3cm from apex of lung to cupola of chest <3cm defined as small

1. For small primary Ptx: Repeat xray in 24hrs time, if not worsening. discharge. expect 3-4 for complete recovery. refer to resp for urgent F/U. refer to CTS if recurrent ( VATS, resection of pleural blebs). safety when and how to return. Advocate for smoking cessation. No Flying for at least a week after a follow up xray has confirmed complete resolution, or > 6weeks.
The British Thoracic Society Fitness to Dive Group39 recommends that underwater diving should be permanently avoided after a pneumothorax, unless the patient has had bilateral open surgical pleurectomy.

Key Points:
Smoking is strongly associated with pneumothorax recurrence [B]
Breathless patients require intervention regardless of pneumothorax size [C]
All patients with secondary pneumothoraces require admission [C]
Oxygen should be applied to all patients with a pneumothorax if they are breathless or require admission [B]
Simple (needle) aspiration should be considered the first-line treatment for primary spontaneous pneumothoraces that require intervention [A]
Simple (needle) aspiration should be only be used for secondary pneumothoraces when the pneumothroax is small (1-2cm) and the patient is not breathless [B]
Small drains are as effective as large drains in treating spontaneous pneumothoraces and their use is preferred [B]

Key Pitfalls:
Failure to identify the pneumothorax as secondary and thus following the wrong BTS management algorithm
Discharging a patient with a secondary pneumothorax from the ED
Belief that the absence of a hiss on attempted needle decompression excludes a tension pneumothorax
Use of excessive force when inserting track dilators and chest drains
Insertion of chest drains outside of the safe triangle
Failure to give patients advice on smoking cessation
Failure to advise patients against flying and diving
Failure to organise review of discharged patients

Nb. Landmark study PSP Trial NEJM 2020:
- (316 patients) Compared pig drain for large primaries (>32%) vs conservative.
- Radiology resolution at 8 weeks similar 98 vs 94%
- However less serious complications, shorter stay in hospital , shorter recovery.
- Advocate for treating large PSPs as small.

Recognised complications of chest drain

False passage (subcutaneous)
Intra-peritoneal placement with liver or splenic injury
Surgical Emphysema
Haemothorax (intercostal or lateral thoracic artery injury)
Intercostal nerve injury
Long thoracic nerve injury
Lung laceration
Tube blockage
Myocardial injury

Other Assessment Notes

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