Bronchoscopy in critical care is not an uncommon procedure, and is an important tool for investigation and treatment of certain groups of patients. Flexible bronchoscopy is almost exclusively the form used, and is generally to form meant when the term bronchoscopy is used. Bronchoscopy refers to imaging of the tracheobronchial tree, hence the name. It was first performed in 1897, and has been progressively developed since.
Types of Bronchoscope
There are 2 main types of bronchoscope for undertaking this procedure:
This is rarely used in critical care but is used in other settings sometimes. As the name suggests, the scope is rigid in its structure, producing notable limitations on access to the bronchial tree. However, this also provides several advantages in function and thus can be useful for more complicated airway procedures e.g. removal of a foreign body, airway stenting, control of massive haemoptysis.
This is the more common form of scope found in critical care. Again the name gives the clue that this scopes can be controlled and bent to allow greater access to the bronchial tree. There are a couple of different types.
Traditional scopes used a fibreoptic design A light source (usually a xenon lamp) will provide light for illuminating the bronchial tree. This is usually part of the ‘stacker’ system, and the light is transmitted down to the tip of the scope via the fibreoptic cables. This light is reflected off the tissues and transmitted back up the fibreoptic cables, of which there are between 5000 and 40,000. As the cables are aligned in a coherent fashion, the image is preserved and can be viewed at the end of the scope or displayed on a monitor. This uses the principle of total internal reflection which is a popular topic for anaesthesia exams This is a good video from Khan Academy on the topic (here) and Wikipedia page (here)
Unfortunately these scope can be fairly vulnerable to damage, and trauma or excessive bending can result in damage to the fibers and subsequent loss of image transmission through that fibre. After each use, these scopes need full cleaning and sterilisation.
The features of a bronchoscope will commonly include:
The handle will contain:
an adaptor for video screen monitoring,
a control lever,
a suction port,
a working channel.
The control lever allows movement of the tip of the scope in one plane of movement only. The working channel can be used for instilling fluid (local anaesthetic or saline for lavage and sampling) or oxygen.
The insertion cord contains the bundle of fibreoptic fibres. These are a mix of the light transmitting fibres and the image transmitting ones, encased in a sealed plastic case.
This video talks through setting up a scope systems:
Newer scopes are more disposable in nature. These use a very small camera at the tip, with the bronchial tree illuminated by a light emitting diode (LED). The image data from the camera is transmitted by a cable up the scope to be displayed on a monitor (the monitor is usually reusable). These have the advantage of being more portable, less/no downtime (for cleaning) and some theoretical benefits of reduced cross-infection risks. The low manufacturing costs also mean that the cost is fairly comparable. They are perhaps less useful for therapeutic interventions in some scenarios, when comparing the suction port and working channel.
Can be defined as diagnostic or therapeutic, which may be combined at the same time.
Inspection of tracheo-bronchial tree - visualisation of pathology e.g. tumours, burns
Sampling e.g. sputum sample
Suctioning of secretions/blood
Difficult airway management e.g. awake fibreoptic intubation
Guiding placement of advanced airway device e.g. tracheostomy, bronchial blocker
Advanced intervention of airways pathology e.g. control of bleeding point
There’s no escaping the fact that you need to know a bit of anatomy for performing a bronchoscopy. This is primarily the anatomy of the bronchial tree, but a few other bits of information are useful to know. There is a very useful bronchoscope simulator available here.
The Tracheobronchial Tree This is the branching network of passages that connects the alveoli to the larynx, and therefore subsequently to the air outside our body. It’s primary function is conduction of gas. It is ordered as a series of tubes in decreasing diameter. Starting at the larynx:
Trachea The trachea is the single tube connecting the larynx to the start of each lung. It starts at the cricoid ring and runs infero-posteriorly into the thoracic cavity, finishing at the carina (approximately at the level of T4/5). It is about 12cm in length, with roughly half extra-thoracic, and the other half intra-thoracic. It’s structure is comprised of 12-20, C-shaped cartilaginous rings anteriorly that support it’s shape. The posterior part is made up of the trachealis muscle. It is 1.6 - 2cm in diameter, and wider in men. There is a change in both its diameter and length with respiration. Where it finishes at the carina, the trachea splits into the two main bronchi; left and right.
It’s internal surface is made up of pseudostratified columnar epithelium, which are ciliated and mucous producing, helping to humidify inspired air, and catch and remove inhaled particles. Sensation within the trachea is provided by the Vagus Nerve (CN X) which provides the afferent limb of the cough reflex.
Main Bronchi These are direct continuations of the tracheobronchial tree from the carina. They conduct air to and from the left and right lungs.
The Right Main Bronchus is larger, shorter and more vertically orientated than the left. These features mean that it is the most likely route that an aspirated foreign body or an ETT of excessive length will go. It is 25mm long, ending with the branching off of the Right Upper Lobe Bronchus.# It is around 21mm in diameter. It does effectively continue inferiorly beyond this point, but is now named the Bronchus Intermedius. This is around 30mm in length.
The Left Main Bronchus is 50mm in length, ending with division into the lobar bronchi. It is about 18mm in diameter.
Lobar and Segmental Bronchi The lobar bronchi transmit air to each individual lobe of the lungs. They divide into segmental bronchi. These transmit air to each bronchopulmonary segment. These are anatomically and functionally distinct units of lung with an individual blood supply and ventilation - this allows them to be individually resected without impact on the surrounding lung.
Right Lung This has 3 lobes:
These subsequently result in 10 bronchopulmonary segments:
As you can note, when you consider the lower against the upper and middle lobes combined, the names of the segments are the same. The order is based on how they arise from the bronchi.
Of note, an anatomical variant is where the right upper main bronchus arises from the trachea. This is know as a pig bronchus, or bronchi sui, as it is the normal anatomy in a pig.
Left Lung This has 2 lobes:
Upper (which includes the lingular)
I think it is easier to consider the lingular as the Left Middle Lobe for purposes of remembering the bronchopulmonary segments. There can be some variation in the number of bronchopulmonary segments in the left lung (quoted at 8-10) but the common variation is 9:
My mnemonic (pretty rubbish): “The left lung is superior so doesn’t like being in the middle’ The ‘middle lobe’ (lingula) on the left is divided into superior/inferior rather than medial/lateral segments, and the left lower lobe is missing the medial segment compared to the right.
Identify need for procedure
Consent the patient - may not be possible in ITU. A very good explanation of the procedure is needed for awake fibreoptic intubation.
Ensure appropriate monitoring
Ensure optimal sedation and analgesia
Optimise ventilation -
High airway pressure alarms,
Volume controlled ventilation
Stop enteral feed. Aspirate NG tube
Have emergency equipment and drugs available e.g. reintubation
Set up bronchoscope.
Have flushes prepared if planning sampling
Switched catheter mount to one with an access port
Try to minimise intervention time
Maintain situational awareness e.g. patients observations
Take samples as needed
Label and send any samples
Disinfect scope by the bedside - will require further sterilisation
Observe for complications/deterioration
Optimise ventilation in light of procedure
There are some very useful videos on the Bronchoscopy International Youtube channel (here)
Respiratory There are significant changes to ventilation, primarily due to the effect of partial airway obstruction and increased resistance to flow:
Reduced tidal volumes
Elevated inspiratory pressures
Increased intrinsic PEEP
Suctioning through the procedure can also result in alveolar collapse, alongside the reduced ventilation mechanisms described. Bronchospasm may also occur from prolonged suctioning. These features mean that there can be a transient deterioration in respiratory function after bronchoscopy, even though it may have been therapeutic in intention e.g. to remove mucous plugging. Hypoxia during the procedure is relatively common and warrants cessation of the procedure to allow optimal ventilation to resume.
Cardiovascular Increased intrathoracic pressure can reduce preload and therefore cardiac output in some patients. Similarly, the hypoxia and hypercapnia from impaired ventilation can increase pulmonary vascular resistance. However, the procedure can also be particularly stimulating, and there may be a significant sympathetic response, raising heart rate and blood pressure. This may put strain on patients with ischaemic heart disease, and performing bronchoscopy in the period following a recent MI has a higher risk associated with it.
Other The stimulation of bronchoscopy can raise ICP, so adequate sedation must be ensured. Bleeding from airway trauma is also a possible complication, and coagulation abnormalities should be considered beforehand. There is a risk of accidental extubation if due care isn’t taken.