VOLUME-LIMITED VENTILATION
Clinician sets the peak flow rate, flow pattern, VT, RR, PEEP, and FiO2; inspiration ends once the set inspiratory time has elapsed. |
| Controlled mechanical ventilation (CMV) |
- VE is determined entirely by the set RR and VT.
- No patient effort required.
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| Assist control (AC) |
- Minimal VE is determined by setting the RR and VT.
- Patient can increase the VE by triggering additional breaths.
- Each patient-initiated breath receives the set VT from the ventilator.
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| Pressure regulated volume control (PRVC) (also called volume control plus [VC+]) |
- VT is set and the applied airway pressure changes to attain the target VT.
- The initial applied inspiratory pressure is determined by the change in pressure required by the previous breath to attain the VT.
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| Intermittent mandatory ventilation (IMV) |
- Minimal VE is determined by setting the RR and VT; patient can increase the VE by spontaneous breathing, rather than patient-initiated ventilator breaths.
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| Synchronized intermittent mandatory ventilation (SIMV) |
- A variation of IMV; ventilator breaths are synchronized with patient inspiratory effort; can be used to titrate the level of ventilatory support.
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PRESSURE-LIMITED VENTILATION
Clinician sets the inspiratory pressure level, I:E ratio, RR, PEEP, and FiO2; inspiration ends after delivery of the set inspiratory pressure. |
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Pressure-limited CMV (also called pressure control ventilation)
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- VE is determined entirely by the set RR and inspiratory pressure.
- Patient does not initiate additional VE above that set on the ventilator.
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Pressure-limited AC
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- Set RR and inspiratory pressure determine the minimum VE.
- The patient can increase the VE by triggering additional ventilator-assisted, pressure-limited breaths.
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Pressure-limited IMV or pressure-limited SIMV
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- The set RR and inspiratory pressure determine the minimum VE.
- The patient can increase the VE by initiating spontaneous breaths.
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Pressure support
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- Flow-limited mode that delivers inspiratory pressure until the inspiratory flow decreases to a predetermined percentage of its peak value.
- Clinician sets the pressure support (inspiratory pressure), applied PEEP, and FiO2. The patient must trigger each breath because there is no set RR. The VT, RR, and VE are dependent on multiple factors, including ventilator settings and patient-related variables.
- The work of breathing is inversely proportional to the pressure support level and the inspiratory flow rate.
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Continuous positive airway pressure (CPAP)
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- Delivery of a continuous level of positive airway pressure.
- Functionally similar to PEEP.
- The ventilator does not cycle during CPAP and no additional pressure above the level of CPAP is provided; patients must initiate all breaths.
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Bilevel positive airway pressure (BiPAP)
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- Noninvasive positive pressure ventilation (NPPV) that delivers a preset inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP).
- The VT correlates with the difference between the IPAP and the EPAP.
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Airway pressure release ventilation (APRV)
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- High continuous positive airway pressure (P high) is delivered for a long duration (T high) and then falls to a lower pressure (P low) for a shorter duration (T low).
- Alveolar recruitment is maximized by the high continuous positive airway pressure.
- VT is related to both the driving pressure and the compliance.
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Inverse ratio ventilation (IRV)
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- The inspiratory time exceeds the expiratory time.
- Strategy employed during volume-limited or pressure-limited mechanical ventilation to increase the mean airway pressure and potentially improve oxygenation.
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