The Mechanical Ventilator Model is a generic representation of a positive-pressure ventilation device and
inhaled gas/agent administration. It models a semi-closed circuit breathing system. The current implementation is limited, but the data model is designed for future expansion.
The results of this system were evaluated for pressure control-continuous mandatory ventilation (PC-CMV) ventilation mode. The results show excellent correlation with the expected values.
The results of this system were evaluated for pressure control - continuous mandatory ventilation (PC-CMV) and volume control - assist control (VC-AC) ventilation modes. The results show excellent correlation with the expected values.
Future work will add more ventilation modes, including assisted breathing functionality.
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<i>Figure 1. Circuit diagram of the Mechanical Ventilator. The circuit employs the a driver pressure source, resistance, and valves.</i>
<i>Figure 1. Circuit diagram of the Mechanical Ventilator. The circuit employs a driver source (either pressure or flow, depending on the mode and settings), resistances, and valves.</i>
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### Connecting to the %Respiratory Circuit
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- Connection (Off, Mask, Tube): Connection type to the %Respiratory System
- Inspiration Phase
- Trigger: Transition to inspiration
- Time: Total length of expiration phase to trigger inspiration phase
- Pressure: Ventilator sensor pressure value to trigger inspiration phase
- Flow: Ventilator sensor flow value to trigger inspiration phase
- Machine Trigger: Control triggers
- Time: Total length of expiration phase to trigger inspiration phase
- Patient Trigger: Assisted triggers
- Volume: Ventilator sensor volume change value to trigger inspiration phase
- Pressure: Ventilator sensor pressure value to trigger inspiration phase
- Waveform (square, exponential, ramp, sinusoidal, sigmoidal): Pattern of driver function
- Pause: Time of plateau (i.e., constant driver pressure) between inspiration and expiration
- Target (PIP, TV, EtCO2, etc.): Value to set/achieve
- Flow: Ventilator sensor flow value to trigger expiration phase
- Waveform (square, exponential, ramp, sinusoidal, sigmoidal): Pattern of driver function
- Baseline (PEEP or FRC): Value to set/achieve
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## Assumptions and Limitations
Currently, the Mechanical Ventilator uses ideal pressure sources and one-way valves. Only setting appropriate for a PC-CMV mode are allowed and tested. However, the system is defined and implemented to allow for future mode expansion without data model changes.
Currently, the Mechanical Ventilator uses ideal pressure sources and one-way valves. Only setting appropriate for a PC-CMV or VC-AC modes are allowed and tested. However, the system is defined and implemented to allow for future mode expansion without data model changes.
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# Results and Conclusions
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## Validation - Settings
The Mechanical ventilator settings are fully dynamic and do not have any bounds enforced. A scenario that varies these settings in several different combinations is included with the code base and produces the outputs shown in Figure 2.
The Mechanical ventilator settings are fully dynamic and do not have any bounds enforced. A scenario that varies the PC-CMV settings in several different combinations is included with the code base and produces the outputs shown in Figure 2.
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<center><i>Figure 2. These plots show the successful implementation of varying Mechanical Ventilator settings without patient spontaneous breathing.</i></center><br>
A scenario that varies the VC-AC settings for assisted breathing for a patient with moderate ARDS produces the outputs shown in Figure 3.
<center><i>Figure 3. These plots show the successful implementation of varying Mechanical Ventilator settings without patient spontaneous breathing.</i></center><br>
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## Validation - ARDS
The %Respiratory ARDS model with mild, moderate, and severe severities is extensively tested in this scenario. The patient is administered a neuromuscular blockade to prevent spontaneous breathing and ideal PIP, PEEP, and FiO2 values are set in the ventilator to maintain adequate SpO2 values. Results successfully match expected empirical data and trends, as shown in table 1. Example outputs are shown in Figure 3.
The %Respiratory ARDS model with mild, moderate, and severe severities is extensively tested in this scenario. The patient is administered a neuromuscular blockade to prevent spontaneous breathing and ideal PIP, PEEP, and FiO2 values are set in the ventilator to maintain adequate SpO2 values. Results successfully match expected empirical data and trends, as shown in table 1. Example outputs are shown in Figure 4.
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<center><i>Figure 3. These plots show the successful implementation of a ventilated patient with varying ARDS severities.</i></center><br>
<center><i>Figure 4. These plots show the successful implementation of a ventilated patient with varying ARDS severities.</i></center><br>
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Table 1. Cumulative validation results for Anesthesia Machine specific conditions and actions scenarios.
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## Coming Soon
Logic and results for handling more ventilation modes, including assisted breathing.
Logic and results for handling more ventilation modes.
