Viva 6

You are asked to see a 60-year-old male who has been trampled by a bull. He has a history of previous right sided pneumonia complicated by empyaema 10 years ago but is otherwise well

CT shows a significant right sided pneumothorax, but nil other injuries. He currently has a respiratory rate of 30, Saturations 94% 15L NRBM, HR 100, BP 140/90.

 

What technique would you use to decompress this patient’s chest and why?.

(This viva dealt with the insertion and complications of thoracostomy tubes.)

The original college viva had a haemopneumothorax, but I removed the haemo.

The trainee should be directed to discuss large bore ICCs

What are the features of this case that might make you cautious? 

• Need for immediate thoracotomy
• Lung densely adherent to the chest wall throughout the hemithorax (eg. following empyema)

What size of drain would you choose?

1. Small bore pleural catheters (8-14 Fr) inserted by Seldinger technique: spontaneous pneumothorax, free flowing (transudative) pleural effusions 

2. Middle-size pleural catheters (14-20Fr), using Seldinger technique or blunt dissection: spontaneous pneumothorax, free flowing (transudative) pleural effusions, pyothorax or empyema 

3. Large bore pleural catheters (20-24 Fr), using blunt dissection only: haemothorax, acute trauma, open thoracostomy, post cardiothoracic surgery oesophageal or spinal surgery, acute traumatic pneumothorax

What are the essential features of a safe environment for this procedure?

The following features need to be arranged before ICC insertion:

• Appropriate sterile and nonsterile equipment, including a tray to prepare it. 
• Skilled assistant 
• Monitoring equipment - minimum cardiac and SpO2 monitoring
• Adjustable bed and/or something for the patient to lean on 
• Drugs including pre-medication, local anaesthetic, sedation, etc
• An ultrasound machine 
• Facilities to confirm placement radiologically (i.e mobile radiography or similar)

Can you demonstrate how you would position the patient?

Can you demonstrate how you would drape the patient? Only fabric drapes are available

Correct draping technique:

• Drape widely
• Place the drape nearest to you first 
• Place drapes to cover the patient to witin your arm's reach 
• Drape all of the patient's un-prepped skin with a fenestrated drape

How do you pick the most appropriate site of insertion?

The marking of a site using thoracic ultrasound for subsequent remote aspiration or pleural drain insertion is not recommended.

Real time bedside ultrasound imaging, wherever available, should be used to select the appropriate site for pleural drain placement. 

Typical site of insertion: mid-axillary line, between 4th and 5th ribs, usually on a line lateral to the nipple. 

The "triangle of safety" is bordered by:

• the anterior edge of the latissimus dorsi,
• the lateral border of the pectoralis major muscle, 
• a line superior to the horizontal level of the nipple, 
• base of the axilla.

Insertion of a pleural drain should be made within the “triangle of safety” with the following potential exceptions:

• where breast tissue covers the triangle of safety and insertion would require the drain to pass through breast tissue
• when an ultrasound assessment has defined a better position for access to a pleural effusion
  When the mid clavicular line is considered more appropriate for management of pneumothorax

Where is the liver here, in relation to the ribs?

The surface anatomy related to the liver:

• In the midaxillary line, it is at the right 7th intercostal space (or 5th at full expiration)

The surface anatomy related to the spleen:

• The spleen spans the 9th-11th intercostal spaces in the left midaxillary line (from upper border of the 9th rib to the lower border of the 11th rib

How much local anaesthetic would you use?

 Lignocaine 1 % without adrenaline: maximum dose is 3mg/kg 

 Lignocaine 1 % with adrenaline (1:100 000): maximum dose is 7mg/kg

Can you demonstrate your technique of dissecting down to the pleural space?

This should be a safe demonstration of using the Kelly clamp

Can you demonstrate how you would place the ICC?

How do you know it is at the correct depth?

How would you confirm that it is in the right position?

Clinically: 

•  Aspiration of the expected pleural content 
• Visualised condensation on the inside of the tube (due to the warm humid air from the chest cavity) 
• By percussion and auscultation of the affected hemithorax 
• By the auscultated sound of suction (when this drain is placed on suction) 
• By improvement of gas exchange and/or haemodynamics 
• By the oscillation of the fluid in the drain 
• By bubbling in the underwater seal 

By imaging: 

•  Chest Xray and ultrasound

A satisfactory drain position is:

• Tip nearer the apex of the lung, for pneumothorax drainage
• Tip nearer the base of the lung, for pleural effusion drainage

AND

• All side-holes inside the chest cavity 

A standard large-bore ICC has numbers on the surface which indicate depth of insertion from the most distal side-hole. Allowing a normal chest wall thickness of 3cm, the ICC would therefore need to be inserted to a depth marker of 5 or 6 cm to give a satisfactory margin of error.

Why might a patient need multiple ICCs?

Indications for multiple ICCs include:

• Loculated effusion
• An existing drain which is poorly positioned but still somewhat functional (in which case you may wish to leave it in situ until the new drain's position is confirmed 
• High-flow bronchopleural fistula (insufficient flow from a single catheter) 
• Following cardiothoracic surgery

Can you explain to me the features of this underwater seal system?

How does it work?

• One would need to mention that it is a dry suction underwater seal drain

"What are the safety features of this device?"

• Underwater seal (of course)
• Transparent collection chamber
• Positive pressure release valve
• Manual high negative pressure vent
• Suction control
• Air leak monitor
• Retractable stand and bedside hanging arms to prevent accidental spills.

"What is the purpose of the underwater seal?"

• The underwater seal prevents the inward movement of air. It excludes air from re-entering the chest cavity via the chest tube.

What routine surveillance would you expect your ward staff to perform?

The following regular observations should be made on every patient after ICC insertion:

• Presence of bubbling 
• Presence of oscillation 
• Drained volume of fluid

The drained volume of fluid is an important parameter for draining pleural fluid:

• 1.0-1.5L per hour is the maximum rate of pleural fluid drainage which should be permitted
• If the drain produces more fluid than this, it should be clamped for 1 hour
• This reduces the risk of re-expansion pulmonary oedema.
• In haemothoraces, an excess of 100ml/hr output is concerning, as it may represent an injured intrathoracic vessel or ongoing arterial blood loss

In addition to drain obs, the appearance of the insertion site needs to be documented during every ICU round.

Additionally, the patient should have a minimum of 4-hourly observations recorded, consisting of: 

• Resp rate 
• SpO2 
• Heart rate 
• Blood pressure 
• Temperature 
• Pain assessment

Does this drain need to be on suction? Why, or why not?

What does it mean when the drain is swinging, but not bubbling?

Can you talk me through how you would safely remove the ICC in a conscious cooperative patient?

When removing the chest drain, maintaining a positive intrathoracic pressure is important so that air is not entrained into the chest cavity while a breach in the chest wall exists.

• In the spontaneously breathing patient, pleural pressure is negative during inspiration and positive during expiration.
• In the mechanically ventilated patient, pressure is positive during both inspiration and expiration, but it is most positive during inspiration.

The BTS guidelines had previously recommended removing the chest drain during expiration or Valsalva, but this is no longer the case. Instead,  the patient should be asked to take a deep breath in, and to hold it. This maximises positive intrathoracic pressure, which prevents entrainment of air through the chest wall defect. The objective is to ensure that there is no negative intrathoracic pressure during the chest drain removal procedure, and to ensure the lung is closely apposed to the pleura.

Disclaimer: the viva stem above may be an original CICM stem, acquired from their publicly available past papers. Or, perhaps it is a slightly altered version of the original CICM stem. Or, it is a completely original viva stem, concocted by the monstrously amoral author of Deranged Physiology for nothing more than his own personal amusement. In either case, because the college do not make the main viva text or marking criteria available, almost everything here has been confabulated. It might sound like a plausible viva and it could be used for the purpose of practice, but all should be aware that it does not represent the "true" canonical CICM viva station.