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Critical Care Medicine

Answer 2
  1. PRVC ventilation. This patient’ baseline ventilator graphics (Figure) demonstrate a pressure-controlled mode. When lung compliance decreases after mucous plugging, VT drops and airway pressure increases gradually to restore the delivered VT, which is typical of PRVC ventilation (a newer dual-control mode). Pressure-control and pressure-support modes are pressure-targeted; when lung compliance decreases, VT goes down but pressures remain constant. Assist/control mode is volume-targeted; when lung compliance decreases, pressure goes up, maintaining the set VT. Dual-control modes combine the advantages of volume control ventilation (constant VT) and pressure-control ventilation (rapid variable flow). PRVC is a pressure-targeted, time-cycled mode that uses VT as a feedback control for continuously adjusting the pressure target, which limits airway pressure while maintaining a constant VT and automatically reduces pressure once lung mechanics improve or patient effort increases. When lung or chest wall compliance is reduced, a reduction in VT occurs only transiently with PRVC (versus pressure-control mode) as the pressure is increased in response to the reduction in VT.3

    3. Branson RD, Johannigman JA. The role of ventilator graphics when setting dual-control modes. Respir Care 2005;50:187-201.

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