Spontaneous Ventilation (SV) in GA for Paediatric Airway Foreign Body Removal

Rationale - Why SV Is the Traditional Standard

• Keeps the FB in its current position (negative pressure "sucks" toward the FB rather than pushing past it)
• Prevents progressive distal migration that positive pressure can cause
• Avoids the risk of converting a partial obstruction into a complete one
• Maintains ventilation if the FB slips off forceps during retrieval, since the child can still move air
• Barash Clinical Anesthesia, 9e, p. 4110: "Spontaneous ventilation may potentially minimize the risk of distal translocation of the foreign body and pressure accumulation due to a ball/valve effect."
• Cummings Otolaryngology, p. 3981: "Debate centers around the method of ventilation and the risk of converting a partial obstruction into a more complete obstruction when using any form of positive pressure ventilation."

Induction Technique with SV

Advantages of SV

1. Prevents distal FB migration - the most important theoretical advantage
2. Maintains ventilation safety net - if FB dislodges off forceps, the child continues breathing
3. Real-time feedback - respiratory effort alerts the endoscopist to desaturation or obstruction
4. Avoids muscle relaxant complications - no risk of succinylcholine-associated complications (hyperkalaemia, masseter spasm) or residual neuromuscular block
5. Reduced haemodynamic disturbance - no PPV-related venous return reduction in an already compromised child

Disadvantages and Challenges of SV

1. Narrow therapeutic window - anaesthetic depth must balance between apnoea (too deep) and laryngospasm/movement (too light)
2. Bucking and laryngospasm - inadequate depth during bronchoscope passage is a real risk; SV has a significantly higher rate of intraoperative laryngospasm and bucking
3. Hypoxaemia - inadequate SV leads to hypoventilation; this is compounded by gas leak around an open bronchoscope
4. Hypotension - deeper anaesthesia needed to maintain SV without movement can cause cardiovascular depression
5. Higher CO₂ - permissive hypercapnia often accepted; paediatric anaesthetists must balance this against respiratory drive

SV Technique: Practical Conduct

• Sevoflurane is the gold standard for inhalational induction and maintenance - rapid titration, pleasant smell, preserves airway reflexes at lower depths
• Propofol TIVA (often with dexmedetomidine) is an alternative/adjunct gaining popularity for SV - propofol infusion can maintain SV at lighter depth with less respiratory depression than high concentrations of volatiles
• Dexmedetomidine - alpha-2 agonist; produces sedation and analgesia with preserved SV; useful adjunct to reduce volatile/propofol requirements
• Remifentanil - short-acting opioid occasionally used but carries high apnoea risk; requires careful titration

• Ventilation is achieved via the side-port of the rigid ventilating bronchoscope
• Frequent telescope removal to allow ventilation through the bronchoscope barrel
• Intermittent withdrawal to mid-trachea if hypoxia develops
• Capnography and SpO₂ mandatory throughout

SV vs Controlled Ventilation (CV): The Evidence

• Barash, p. 4110: "A study that retrospectively analysed complications for rigid bronchoscopy cases for foreign-body removal comparing spontaneous with controlled ventilation did not find a more significant association with a complication with either technique."

• Laryngospasm was significantly more frequent in the SV group (p = 0.004)
• Bucking was significantly more frequent in the SV group (p = 0.017)
• Minimum SpO₂ differed significantly across groups (p = 0.013), with SV trending toward more hypoxaemia
• Pulmonologist satisfaction was highest in the rocuronium group
• Agitation in recovery was lowest in the propofol-SV group
• No significant difference in anesthesia or bronchoscopy duration

When SV is Particularly Favoured

• Ball-valve/check-valve FB - organic material (peanuts, seeds) in main bronchi where PPV risk of distal migration is highest
• Tracheal FB - most dangerous location; SV avoids complete obstruction from PPV
• Incomplete/partial obstruction where any PPV might tip into complete obstruction
• Centres with less CV experience for paediatric shared-airway cases
• Unstable child where muscle relaxant reversal capability is limited

When CV May Be Preferred

• Complete obstruction already present (SV already not moving air effectively)
• Full stomach / aspiration risk where RSI with muscle relaxant is needed
• Surgically challenging cases - complete immobility improves extraction success rate and pulmonologist satisfaction
• Experienced teams comfortable with jet ventilation or high-frequency ventilation through the bronchoscope
• Prolonged procedures - maintaining SV depth for >30 min is technically demanding

Ventilation Through the Bronchoscope

• Gas leak is always present when the proximal end of the bronchoscope is open for instrumentation
• The surgeon and anaesthetist must communicate closely - ventilation pauses during FB grasping
• Hypoxia from inadequate ventilation is remedied by removing the telescope and withdrawing to mid-trachea
• Bronchospasm during instrumentation: treat with deepened anaesthesia, nebulised salbutamol, or IV bronchodilators
• Pneumothorax should be suspected if acute deterioration occurs - especially with distal ball-valve FBs

Summary Table

Key Takeaway

• Barash Clinical Anesthesia, 9e - Foreign-Body Aspiration section
• Cummings Otolaryngology Head and Neck Surgery - Anesthetic Considerations / Aerodigestive Foreign Bodies
• Chavoshi T et al. (2024). Pediatric Rigid Bronchoscopy Complication with Three Different Anesthesia Regimes. Anesth Pain Med, PMID 40078474