Jet Ventilation

Introduction

• Jet ventilation, first described by Douglas Sanders in 1967, delivers high-pressure gas through a narrow orifice to maintain oxygenation and ventilation, providing a motionless surgical field while preserving access to the airway.
• Low-frequency jet ventilation (LFJV) delivers breaths at 10-30 breaths/minute using hand-triggered devices like the Sanders injector or Manujet III.^1,2
  • Gas exchange occurs primarily through bulk convective flow, similar to conventional ventilation.
  • LFJV is typically applied via short, rigid catheters through laryngoscopes or bronchoscopes, or emergently via transtracheal jet ventilation (TTJV) in “can’t intubate, can’t ventilate” scenarios.^1,3
• High-frequency jet ventilation (HFJV) uses frequencies of 60-600 breaths/minute with tidal volumes smaller than anatomic dead space.^1,3
  • Heated, humidified jets at adjustable frequencies are delivered by modern automated ventilators such as the Monsoon III and TwinStream.^2,3
  • Some ventilators (e.g., TwinStream) provide superimposed HFJV (SHFJV), combining high- and low-frequency jets simultaneously through separate lumens to enhance carbon dioxide elimination.⁴
• Regardless of frequency, jet ventilation has evolved to include various delivery methods, such as supraglottic, subglottic, and transtracheal approaches.

Physical Principles and Mechanisms of Jet Ventilation

• High-pressure gas is delivered through a narrow orifice to generate tidal volumes. Additional ambient gas is entrained by the jet of oxygen or air-oxygen mixture as it exits the nozzle via the Venturi effect, effectively increasing the delivered tidal volume.²
• Expiration during jet ventilation is entirely passive, relying on lung and chest wall recoil, requiring an open airway to prevent barotrauma. Some devices (e.g., the Ventrain system) can apply suction during expiration, allowing for active exhalation.³
• During LFJV, gas is exchanged via bulk flow, like standard ventilators, although delivered through a narrow-bore cannula.
• In HFJV, tidal volumes may be smaller than anatomic dead space, so conventional ventilation alone is insufficient for gas exchange.¹
• Gas exchange in HFJV occurs via several mechanisms (Figure 2):
  • Laminar flow: Fast-moving air travels along the central axis of the airway while air exits along the peripheral airway (Figure 1).^1,3
  • Taylor dispersion: Radial diffusion of high-velocity gases from the airway spreads to the alveoli, facilitating oxygenation and carbon dioxide removal.^1,3
  • Pendelluft: Also known as collateral ventilation, gas is redistributed between adjacent lung tissue with different compliance and resistance.^1,3
  • Cardiogenic mixing: Cardiac contractions agitate lung tissue, contributing modestly to gas exchange but still facilitating some ventilation.¹
  • Molecular diffusion: Air moves along a concentration gradient, which plays a minor role at the macroscopic level but contributes to overall exchange.¹
• SHFJV delivers low-frequency (12-20/minute) breaths during HFJV through separate lumens, allowing improved carbon dioxide elimination in longer cases.⁴

Clinical Applications

• Airway surgery
  • Jet ventilation provides a nearly motionless surgical field, aiding visualization and minimizing tissue disruption during these procedures.^1,3
  • Common procedures include laser surgery, vocal cord lesion excision, tracheal resections, and foreign body removal.
• Rigid bronchoscopy
  • Jet ventilation maintains oxygenation and ventilation while allowing unobstructed access to the airway for instruments and visualization.⁴
• Cardiac electrophysiology
  • HFJV produces near-immobility of the thoracic structures, offering several advantages during interventional cardiac procedures (e.g., atrial fibrillation ablation).⁵
  • In one prospective crossover study, HFJV reduced median coronary sinus movement by approximately 5-fold (2.0 mm vs 10.5 mm), improving catheter stability and reducing procedural time.⁵
• Other applications
  • HFJV has been employed to minimize organ motion during hepatic and renal tumor ablations and during extracorporeal lithotripsy.^2,5
  • The use of transtracheal jet ventilation in “can’t intubate, can’t oxygenate” scenarios has declined due to the high risk of barotrauma and the widespread availability of supraglottic devices.³

Anesthetic Management

• Preoperative assessment
  • Review the patient’s airway anatomy, prior anesthetic records, and pulmonary function tests.
  • Relative contraindications of jet ventilation include morbid obesity, severe chronic obstructive pulmonary disease (COPD), restrictive lung disease, or upper airway obstruction greater than 50%.^1–3
• Anesthetic technique
  • Total intravenous anesthesia is required during jet ventilation; volatile anesthetics cannot be delivered through jet ventilators. Propofol, remifentanil, and short-acting agents are commonly used.^1,3
  • Neuromuscular blockade is typically necessary to prevent coughing, movement, and laryngospasm.
• Monitoring considerations
  • Standard American Society of Anesthesiologists monitors plus arterial line for cases >30 minutes or when frequent blood gas monitoring is anticipated.
  • End-tidal CO_₂ is unreliable; use intermittent conventional breaths for capnography or percutaneous CO_₂ monitoring.
  • Continuous observation of chest rise, auscultation, and airway pressure is essential.
• Ventilator management
  • Permissive hypercapnia (PaCO_₂ 45-60 mmHg, pH >7.20) is generally well-tolerated if hemodynamics remain stable.
  • Adjust driving pressure, frequency, and inspiratory time based on oxygenation and ventilation needs (Table 2)

Complications and Safety Considerations

• Barotrauma: Pneumothorax, pneumomediastinum, and subcutaneous emphysema result from high airway pressures and insufficient exhalation. Prevention requires continuous airway pressure monitoring, ensuring a patent upper airway, and avoiding jet ventilation if upper airway obstruction exceeds 50%.^2,3
• Hypercapnia: More common in patients with obesity, COPD, and restrictive lung disease. Management includes increasing driving pressure, decreasing frequency or inspiratory time to prolong expiration, and measuring arterial blood every 30 minutes. End-tidal CO₂ measurement requires either intermittent standard tidal-volume breaths or side-stream sampling.^1–3
• Hypoxia: Can be corrected by increasing the FiO₂, driving pressure, or inspiratory time. High-flow nasal cannula can also be used simultaneously.^2,3
• Catheter malposition: This requires clinicians to continuously visualize the catheter position, perform regular position checks during manipulation, and initially place the catheter under direct laryngoscopy. Misalignment or esophageal placement can result in gastric distention or even rupture.^1,2
• Other complications include dysrhythmias, inadequate humidification, aspiration, necrotizing tracheobronchitis, laryngospasm, and airway fire.