Thoracic POCUS allows us to evaluate the dyspnoeic patient by checking for the presence of a pleural effusion
In this clip
- there is a large volume of (anechoic) fluid above the diaphragm
- the lung edge is seen moving into the field with each respiration
- can you also see the small amount of free fluid below the diaphraghm?
In this patient, a drain was successfully sited for a recurrent pleural effusion and the patient was moved to the ED short stay unit
Tips for visualising a pleural effusion
- Depth – set the depth to 18cm to see beyond the posterior pleural surface
- Focus – set the focus beyond the area of interest
- Gain – turn up the gain to see all structures present (eg. septations that may be present in the effusion)
- Probe/ preset – if looking for a pleural effusion consider using a curvilinear probe. If a lung preset is chosen, this is often optimised for shallow anterior pleural surface. You may need to to increase the depth to 18cm and/or adjust the gain
- Artefact – can you see the spine sign? If you see vertebral bodies on lung US above the diaphragm, this is because fluid (pleural effusion) allows sound waves to propagate back towards the transducer. If you do not see the spine sign above the diaphragm it is usually because air ‘blocks’ the passage. Therefore ‘spine sign +’ indicates pleural effusion, ‘spine sign negative’ means air in the lung (no effusion).
*Novice users should make every attempt to adjust the machine settings to optimise your image. The user should be reminded ‘work your left hand (machine controls) before you work your right hand (US transducer)‘
Pitfalls to avoid
- Is this fluid below or above the diaphragm? Do not mistake a pleural effusion for sub-diaphragmatic strutures
- Is it a simple effusion or is it septated or loculated? A simple effusion is generally easier and safer to drain using POCUS
- Choose your drainage site carefully – avoid the 10cm either side of the midline on the patient’s back. In this area, blood vessels are more likely to be tortuous and prone to inadvertent instrumentation and injury. It is generally safer to choose a drainage site somewhere along the posterior axillary line
- Avoid pulmonary vessels – visualise these with colour doppler
- Size – a large (>1cm) pleural effusion is more easily drained than a smaller one. Even a large effusion may not be the cause of your patient’s symptoms – is it necessary to drain this effusion in the ED?
- Check for post procedural pneumothorax – look for the presence of A lines and lung sliding or try turn on power doppler
Once you have chosen the site for your drain – it is more practical to insert the needle without real time ultrasound guidance. Put down the probe, site the drain and watch the fluid flow…
Want to check for re-expansion pulmonary oedema? Look for B lines as they develop – it is quicker than a portable CXR