Fibreoptic bronchoscope: structure and function

What it is used for (link structure → function)

Flexible endoscope used to visualise upper airway, larynx and tracheobronchial tree and to facilitate airway interventions.
Common anaesthetic uses: awake intubation, difficult intubation, confirmation of tube position, bronchial toilet, guidance for DLT/bronchial blocker placement, assessment of airway pathology/trauma.
Key performance requirements: adequate image quality, steerability, suction/oxygen insufflation, compatibility with ETT sizes, robust decontamination pathway.

How it is built (high-yield anatomy of the scope)

Main components: control section (handle), insertion tube, distal bending section with tip, umbilical (light/processor connector), working channel and valves.
Optics: either fibreoptic (coherent fibre bundle) or video (chip-in-tip CMOS/CCD).
- Fibreoptic: image transmitted via coherent fibre bundle; illumination via separate non-coherent light fibres.
- Video: distal sensor converts image to electrical signal; typically improved resolution and less fibre breakage artefact.
Steering: angulation lever(s) tension control wires running to distal bending section; typically 2-way (up/down), some 4-way (up/down/left/right).
Working channel: allows suction, oxygen insufflation, topicalisation (LA), and passage of instruments (biopsy forceps/brush) depending on scope type.
External diameter and channel diameter determine which ETT can be railroaded and how effective suction is.

How it functions in practice (what each part does)

Illumination: light source (xenon/LED) transmitted via light guide to distal tip; adequate illumination is essential for mucosal detail and orientation.
Image formation: objective lens at tip focuses image onto fibre bundle or sensor; eyepiece/processor displays image; focus is usually fixed with depth of field.
Tip control: lever deflects distal tip; rotation of insertion tube provides left/right orientation; avoid excessive force to prevent mucosal trauma and scope damage.
Suction/insufflation: suction port connected to wall suction; insufflation via oxygen/air source (if available) helps clear secretions and maintain view but can cause gastric insufflation if misused.
Railroading an ETT: scope acts as a steerable stylet; ETT advanced over insertion tube; bevel orientation and tube size affect hang-up at arytenoids/epiglottis.
- Common mitigation: rotate ETT 90° anticlockwise, use Parker Flex-Tip, use smaller tube, use an Aintree intubation catheter via supraglottic device.

Typical specifications (numbers to know)

Adult FOB outer diameter commonly ~5.0–6.0 mm; paediatric ~2.2–4.0 mm (varies by manufacturer).
Working channel commonly ~2.0–3.0 mm (adult); smaller in paediatric scopes → reduced suction capability.
Minimum ETT internal diameter to railroad: typically ETT ID ≥ (scope OD + ~1.0–1.5 mm) to allow smooth passage and some gas egress.
- Example: 5.5 mm OD scope usually fits through ≥6.5–7.0 mm ID ETT (depends on tube design).
Angulation range (typical): up ~160–180°, down ~90–130° (model-dependent).

Ports/controls on the handle (what each does)

Angulation lever(s): deflect distal tip; may have a friction lock to hold position.
Suction valve/button: occlusion applies suction to working channel; release stops suction.
Instrument/working channel port: entry for suction tubing connector, syringes for saline/LA, or instruments (if compatible).
Light guide/processor connector: connects to light source and video processor (video scopes) or eyepiece (older fibreoptic).

Advantages and limitations (structure-driven)

Advantages: dynamic airway assessment; ability to navigate around anatomy; can be used awake with topical anaesthesia; can pass through supraglottic devices; allows suction and targeted topicalisation.
Limitations: view easily obscured by blood/secretions; small working channel limits suction; requires training; fragile and expensive; infection control burden; oxygenation may be limited during prolonged attempts.

Care, handling and decontamination (exam-relevant)

Damage risks: fibre breakage (black dots), lens scratching, kinking insertion tube, over-angulation with force, crushing in drawers, chemical damage from inappropriate agents.
Immediate post-use: bedside wipe-down, suction detergent/water through channel, leak test (if reusable), then send for reprocessing per local policy.
Reprocessing: manual cleaning (critical step) followed by high-level disinfection or sterilisation as per manufacturer; drying and correct storage reduce biofilm risk.
Single-use video bronchoscopes: reduce cross-infection and repair costs; may have different handling, image quality, and environmental/cost considerations.

Safety considerations

Hypoxia risk during prolonged attempts: preoxygenate, apnoeic oxygenation, consider nasal oxygen, limit attempt time, and have a failed plan.
Airway trauma: gentle advancement, avoid levering on teeth/arytenoids, use adequate topicalisation and sedation strategy.
Local anaesthetic toxicity: track total dose (including sprays/nebules/gel); consider patient factors (low weight, hepatic impairment).
Infection control: treat as semi-critical device contacting mucous membranes; strict adherence to decontamination and traceability.

Describe the structure of a fibreoptic bronchoscope.

Break it into handle, insertion tube, distal tip, optics, and channels.

Control section/handle with angulation lever(s), suction valve, working channel port, and connector to light source/processor.
Insertion tube containing optical system (fibre bundle or video wiring), illumination fibres, working channel, and control wires.
Distal bending section and tip with objective lens, light outlets, channel exit port, and sometimes chip-in-tip sensor.

How does a fibreoptic bronchoscope transmit an image?

Contrast fibreoptic vs video systems.

Fibreoptic: objective lens forms an image onto a coherent fibre bundle; each fibre maintains spatial orientation to reconstruct the image at the eyepiece/processor.
Illumination is delivered separately via a non-coherent bundle from an external light source.
Video: distal CMOS/CCD sensor converts image to an electrical signal transmitted to a processor/monitor.

What is the working channel for, and what are its limitations?

Functions: suction of secretions, instillation of saline/anti-fog, topical local anaesthetic, oxygen insufflation (if set up), and passage of instruments in appropriate scopes.
Limitations: small diameter reduces suction efficiency; easily blocked by thick secretions/blood; increases resistance to gas flow if attempting to ventilate through the scope.

Explain how the tip is steered and why scopes get damaged.

Steering via tension control wires attached to the distal bending section; angulation lever increases/decreases wire tension to deflect the tip.
Damage mechanisms: forcing the scope when tip is maximally flexed, kinking the insertion tube, crushing, excessive torque, and chemical damage from inappropriate cleaning agents.

You see multiple black dots in the image. What does this indicate and what are the implications?

Suggests broken fibres in a fibreoptic image bundle (fibre breakage).
Implications: reduced image quality and navigation; scope may still function but may be unsuitable for difficult cases; requires repair/replacement and reporting per local policy.

How do you choose an appropriate tracheal tube size for fibreoptic intubation?

Ensure ETT internal diameter is sufficiently larger than scope outer diameter to allow railroading without excessive friction.
As a rule: ETT ID ≥ scope OD + ~1.0–1.5 mm (check manufacturer guidance).
Consider tube design (reinforced, Parker, nasal RAE) and the need for suction/oxygenation during the attempt.

During railroading, the tube hangs up at the larynx. What manoeuvres help and why?

Rotate ETT 90° anticlockwise to redirect bevel away from arytenoids and reduce impingement.
Withdraw slightly and re-advance under vision; optimise head/neck position and jaw thrust; ensure scope is midline and not tenting anteriorly.
Use a smaller ETT or a different tip design (e.g., Parker Flex-Tip) to reduce snagging.

What pre-use checks would you perform on a reusable fibreoptic bronchoscope?

Visual inspection: insertion tube integrity, distal tip, lens cleanliness, no cracks, no kinks.
Image/illumination: connect to light source/processor; confirm bright, clear image; check for excessive black spots or flicker.
Angulation: full range up/down (and left/right if present), smooth movement, lock function if present.
Working channel patency: suction works; flush with saline; ensure valves present and functioning.
Leak test (if part of local pre-use process) to detect damage to internal sheaths before use/reprocessing.

Describe how illumination is delivered and what can cause a dim image.

Light source (often LED) transmits light via a light guide to the distal tip.
Dim image causes: low light source output, poor connection, damaged illumination fibres, dirty lens, secretions/blood on tip, or incorrect white balance/settings on video processor.

What are the main differences between fibreoptic and video bronchoscopes relevant to function and failure modes?

Fibreoptic: image degradation with fibre breakage (black dots); may be more sensitive to bending/handling; can be used with eyepiece (older systems).
Video: chip-in-tip gives high resolution; failure tends to be electronic (no image) rather than progressive black-dot artefact; often easier teaching via shared screen.
Both: view obscured by secretions/blood; working channel limitations persist.

Outline infection control requirements for bronchoscopes and why they matter.

Bronchoscopes contact mucous membranes and potentially sterile lower airway; require meticulous cleaning then high-level disinfection/sterilisation per manufacturer and local policy.
Manual cleaning is crucial to remove bioburden; inadequate cleaning increases risk of cross-infection and biofilm formation in channels.
Traceability/documentation and correct storage/drying reduce infection risk.

You are shown a flexible bronchoscope. Talk me through it: identify parts, describe how it works, and how you would check it before use.

A common equipment viva: systematic description + function + checks + safety.

Identify: handle (angulation lever, suction valve, channel port), insertion tube, distal bending section/tip, connector to light/processor.
Function: illumination to tip; image via coherent fibre bundle or distal sensor; steering via control wires; suction/instillation via working channel.
Checks: integrity, image quality/brightness, angulation smoothness, suction/channel patency, appropriate ETT compatibility, and (where applicable) leak test and decontamination status.
Safety: avoid hypoxia (preoxygenation, time-limited attempts), avoid trauma, manage LA dosing, ensure infection control compliance.

Why is suction often ineffective during fibreoptic intubation and what can you do about it?

Reason: small working channel diameter and long narrow lumen → high resistance; thick secretions/blood obstruct channel and obscure lens.
Mitigation: pre-suction with Yankauer; antisialagogue; topical vasoconstrictor for nasal route; use saline flush/anti-fog; consider a larger scope if available; consider alternative technique if heavy bleeding.

Discuss how the bronchoscope’s design influences oxygenation/ventilation during an intubation attempt.

Scope occupies airway lumen and may impede gas flow around it; railroading an ETT further reduces airflow until intubation complete.
Working channel can be used for limited insufflation but is not a reliable ventilation route; risk of gastric insufflation and inadequate alveolar ventilation.
Practical steps: preoxygenate, nasal oxygen/HFNO if appropriate, maintain spontaneous ventilation for awake techniques, and time-limit attempts with reoxygenation breaks.