Overview
In early May of 2020, the project reached its 1st phase, providing a “CMV-VC Time Triggered” prototype whose technical information is currently provided by this website. Now, a "Patient Triggered" version is in development for Phase 1b. Figure 2 shows the classification of these two types in the scheme of ventilation modes.
Figure 2 - Classification of CMV-VC Time Triggered and Patient Triggered in the Scheme of Ventilation modes
The idea of proceeding to a Phase 2 with a "PSV Patient Triggered" prototype, represented in Figure 3, has already been analyzed. As mentioned in the Fundamentals session, PSV is a non-invasive mode where a face mask is used instead of an endotracheal tube.
The utilization of portable PSV ventilators may be useful for patients in the early stages of COVID-19 as they can be used outside the ICU (since they do not use intubation). Thus, many ICU ventilators would free up to be used for patients with advanced COVID and with a more pressing need for intubation (CMV/SIMV).
Figure 3 - Classification of PSV in the Scheme of Ventilation modes
The following are the requirements for Phase 1a, which were already met in May 2020, and the requirements for Phase 1b, which are in progress. The requirements for Phase 2 will be added if the project continues.
Although not part of any of these requirements, a web interface was made to add value to the prototype. Viewing information in a web application is comfortable and especially useful for monitoring pressure and flow. In addition, the prototype ended up looking more like professional ventilators!
High-Level Requirements for Phase 1a
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The device shall use 120VAC as voltage input.
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The device shall have a power backup able to keep the system working during, at least, 5 minutes without interruption.
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The power backup shall provide periodic audible alarm while its battery is being used.
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The device shall have a push button to initiate the actuator (which is responsible for the ventilatory cycles).
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The device shall have a push button to stop the actuator.
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The device shall have a green LED to indicate whether the actuator is performing the ventilatory cycles or not.
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Before starting to perform ventilatory cycles, the actuator shall move to its reference point automatically.
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The device shall have a yellow LED to indicate that the actuator is moving to its reference point.
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The device shall be able to periodically provide a specific Tidal Volume (TV) of air in a specific Respiratory Rate (RR) in a specific Inspiratory Time (IT).
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The device shall provide a knob for users to configure the Tidal Volume (TV) to be delivered.
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The device shall offer the following Tidal Volumes (TV) for configuration: (200 – 800) ml range with steps of 100 ml.
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While being selected by the knob, Tidal Volumes (TV) shall be visualized on a display.
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The device shall provide a knob for users to configure the Respiratory Rate (RR) in which the Tidal Volume (TV) that is to be delivered.
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The device shall offer the following Respiratory Rates (RR) for configuration: (10 – 40) bpm range with steps of 1 bpm.
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While being selected by the knob, Respiratory Rates (RR) shall be visualized on a display.
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The device shall provide a knob for users to configure the Inspiratory Time (IT) in which the Tidal Volume will be delivered.
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The device shall offer the following Inspiratory Time (IT) for configuration: (0.50 – 4.00) s range with steps of 0.25 s.
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While being selected by the knob, Inspiratory Times (IT) shall be visualized on a display.
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In the case of choosing a Inspiratory Time (IT) too high to guarantee the Respiratory Rate (RR) already chosen, a "(-)" sign shall be added next to the value corresponding to the RR on the display in order to inform that this RR cannot be met with this configuration (will be lower).
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In case the IT is too low and the tidal volume is relatively too high, it is possible that the actuator does not have enough speed to satisfy this configuration during the inspiration phase. In this case, the Tidal Volume shall be automatically adjusted to the maximum possible allowed in this configuration, and shall be shown it on the display.
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Configurations shall not be allowed while the device is performing ventilation cycles.
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During a ventilation cycle, a pop-of-valve shall release air in case the air pressure in the line is equal to or greater than 60 cm H2O.
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The device shall have a PEEP valve configurable in the range 5-20 cm H2O.
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The device shall have a HEPA filter connected to the line in a position where the exhaled air passes.
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Exhaled air shall not be delivered to the environment without passing through the HEPA filter.
High-Level Requirements for Phase 1b
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All high-level requirements for Phase 1a shall be kept.
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The device shall provide the means for users to switch between the “time-trigger” to “patient-trigger” modes and vice-versa.
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Whenever the device is turned on, “time-trigger” mode shall be automatically selected (default).
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In “patient-trigger” mode, a breath cycle shall be triggered whenever a patient trigger signal is detected.
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The device shall have at least one method to detect a “patient-trigger” signal: by pressure or by flow.
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A patient trigger signal by pressure shall be inferred if pressure in the line drops 5 cm H2O without having a ventilation cycle.
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A patient trigger signal shall be inferred if flow in the line drops 4 L/m without having a ventilation cycle.
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In a “patient-trigger” mode configuration, if no patient trigger signal is detected 5 seconds after the last exhalation, a ventilation cycle shall be automatically triggered.