Evaluation: Maquet FLOW-i C20 General-Purpose Anesthesia Unit

February 22, 2017 | Evaluations & Guidance


  • The FLOW-i is used for general anesthesia during surgery for the entire range of patients (neonates through adults).
  • It can also be used to provide supplemental oxygen (O2) (typically via a nasal cannula or loose-fitting mask) and capnography during monitored anesthesia care (MAC).
  • In addition to the C20, which we evaluated, there are two other FLOW-i models:
    • C30: adjustable height
    • C40: boom-mounted
  • Major components and features
    • Minimum dimensions: 31 in (D) × 43 in (W)
    • Ventilator and breathing system:
      • The FLOW-i has a unique reservoir called the volume reflector, which acts as a virtual bellows.
      • The volume reflector acts similarly to a mechanical bellows, with a drive gas (O2) controlling the patient gas (a mixture of exhaled and fresh gases that intermingle between breaths).
      • Unlike a traditional bellows, there is no physical mechanism in the volume reflector separating the drive and patient gases. Instead, the volume reflector is designed to minimize mixing between the two.
      • Because there is no physical barrier separating the drive gas from the patient gas, in the event of a leak that exceeds the fresh gas flow—which would eventually cause a traditional bellows to collapse and make mechanical ventilation impossible—the volume reflector will use the drive gas (O2) to ventilate.
      • The volume reflector has no moving parts, and the entire assembly can be autoclaved.
      • The unit uses fresh gas compensation to prevent changes in fresh gas flow from affecting delivered tidal volumes.
      • It automatically compensates for breathing circuit compliance (breathing circuit compliance must be measured at the start of each case or if the circuit is changed during a case).
      • The volume reflector is located under the main work area.
      • Volume during automatic ventilation: 2.9 L (including absorber canister and volume reflector).
    • Fresh gas controls
      • Electronic controls on main display for balance gas (air or nitrous oxide N2O; O2 is always the primary gas), total fresh gas flow rate, and O2 concentration.
      • Fresh gas flow settings are off (when unit is in standby) or 0.3-20 L/min.
      • Fresh gas controls do not work when device experiences a total electrical failure. Emergency O2 controls (see below) allow delivery of O2 in such circumstances.
    • Emergency ventilation system
      • Since this unit has an electronic mixer, a mechanical control for O2 is needed in the event of a total electrical failure.
      • Emergency ventilation system controls are behind a door below the main power button, and consist of:
        • Mechanical flow control and flow tube that provides 0-10 L/min O2.
        • Mechanical adjustable pressure-limiting (APL) valve (primary APL valve is electronically controlled).
        • Switch that activates emergency ventilation system (and shuts down unit, although the unit would typically not be operating when emergency ventilation system is activated).
    • Vaporizers
      • The FLOW-i can only work with Maquet electronic injector vaporizers.
      • The FLOW-i has two active mounts.
      • Because the vaporizers are electronic, the anesthesia provider selects the agent and concentration on the main display. Also, the fill level of the active vaporizer is shown graphically on the main display and the unit alarms for low vaporizer fill level.
      • Vaporizers mainly deliver agent during the inspiratory phase.
      • Vaporizer can be filled while in use. Agent delivery is paused when filling and resumes at set concentration when filling is complete and lid is closed.
    • Gas analyzer
      • An integral component of the ventilator.
      • Takes a side-stream sample from the patient wye at 200 mL/min and analyzes the inspired and expired concentration of O2, carbon dioxide (CO2), and anesthetic gases.
      • Sampled gas is returned to the breathing system.
      • Sample line enters water trap on left side of unit.
    • Absorber
      • Maquet disposable canister.
      • Bypass valve allows changing absorbent during case without introducing a leak into the breathing system.

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