Is flow control ventilation a mode of ventilation available on ventilators?

Flow-Controlled Ventilation: An Emerging Ventilation Mode

Yes, flow-controlled ventilation (FCV) is a real and available ventilation mode on specialized ventilators, though it is not yet widely adopted in standard clinical practice. 1, 2

What is Flow-Controlled Ventilation?

FCV represents a fundamentally different approach to mechanical ventilation that maintains constant flow during both inspiration and expiration, distinguishing it from traditional volume-controlled or pressure-controlled modes. 1, 2

Key Characteristics:

• Constant bidirectional flow: Unlike conventional modes where flow varies throughout the respiratory cycle, FCV maintains steady flow rates during both phases of breathing 1
• Automatic flow control: The ventilator automatically controls airway flow while monitoring intratracheal pressure and regulating peak inspiratory pressure and end-expiratory pressure 1
• Typically uses 1:1 I:E ratio: FCV is designed to operate with equal inspiratory and expiratory times, which differs from conventional ventilation strategies 3
• Compatible with narrow-bore tubes: FCV has been successfully used with specialized narrow-lumen endotracheal tubes (such as the Tritube), expanding airway management options 1

Clinical Evidence and Performance

Gas Exchange Efficiency:

• Improved oxygenation: FCV achieves higher PaO2 levels compared to volume-controlled ventilation with identical tidal volumes and plateau pressures [FCV: 38.2 kPa vs VCV: 35.2 kPa, p<0.001] 3
• Enhanced CO2 elimination: FCV produces lower PaCO2 levels while maintaining adequate minute ventilation [FCV: 4.8 kPa vs VCV: 5.1 kPa, p<0.001] 3
• Normal pressure amplitudes: FCV achieves adequate ventilation with intratidal pressure amplitudes in the normal range [10 cmH2O] and minute volumes of approximately 5.0 L/min 1

COVID-19 ARDS Experience:

• In moderate COVID-19 ARDS patients, FCV maintained similar oxygenation to conventional ventilation (PaO2/FiO2 ratio 169 mmHg vs 168 mmHg) but achieved this with lower tidal volumes and minute ventilation 4
• FCV was feasible in all studied patients with no adverse events during 30-minute ventilation periods 4

Current Availability and Equipment

FCV is currently available through specialized ventilators, most notably the Evone ventilator system, which was specifically designed to deliver this mode. 1 This is not a mode found on standard ICU ventilators like those offering traditional volume control, pressure control, or pressure support modes. 5, 6

Comparison to Established Modes

Traditional ventilation modes recognized in clinical guidelines include:

• Volume-controlled ventilation: Delivers preset tidal volume with variable pressure 6
• Pressure-controlled ventilation: Delivers preset pressure with variable tidal volume 6
• Pressure support ventilation: Patient-triggered, pressure-limited mode 7
• SIMV and Assist-Control: Hybrid modes combining mandatory and spontaneous breaths 6

FCV represents a distinct departure from these established modes by controlling flow as the primary variable rather than volume or pressure. 2

Critical Limitations and Caveats

Equipment-Specific Risks:

• Tube obstruction risk: The narrow-bore tubes used with FCV systems have high flow resistance, increasing susceptibility to obstruction from airway secretions 1
• Dislocation risk: Four out of 16 patients experienced tube dislocations in one study, with two attributed to coughing during FCV 1
• Limited availability: FCV requires specialized equipment not present in most ICUs, limiting its accessibility 1, 2

Evidence Limitations:

• Short-term data only: Most studies evaluate FCV for 30-60 minutes; long-term safety and efficacy data are lacking 1, 3, 4
• Small sample sizes: Published studies involve fewer than 20 patients, limiting generalizability 1, 3, 4
• No mortality or morbidity data: Current evidence focuses on physiologic parameters rather than patient-centered outcomes 1, 3, 4

Clinical Bottom Line

While FCV is a legitimate ventilation mode available on specialized equipment, it remains investigational and is not part of standard ventilatory practice. 2 The established modes recommended by major societies—including volume-controlled assist/control for initial ventilation and pressure support for weaning—remain the standard of care. 6 FCV may offer theoretical advantages in gas exchange efficiency and could expand options for difficult airway management, but clinicians should not consider it a replacement for conventional modes until larger trials demonstrate improved patient outcomes. 1, 2, 3