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A rapidly deployable individualized system for augmenting ventilator capacity

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Science Translational Medicine  24 Jun 2020:
Vol. 12, Issue 549, eabb9401
DOI: 10.1126/scitranslmed.abb9401
  • Fig. 1 Design of the individualized system for augmenting ventilation efficacy.

    (A) Schematic of iSAVE setup on a closed-circuit ventilator for simultaneous ventilation of two patients. (B) Circuit diagram of iSAVE for closed-circuit ventilation. (C) Photograph of iSAVE connected to a Puritan Bennet 840 ICU ventilator and two test lungs.

  • Fig. 2 Individualized ventilation and management of patient interdependence using artificial test lungs.

    (A) Pressure, flow, and tidal volume waveforms illustrating three settings of differential tidal volume (VT) for two test lungs (blue and black) using closed-circuit ventilation. The ratio (50:50, 35:65, and 15:85) refers to the VT of the black:blue lungs. Pressure, volume, and flow in both lungs upon (B) decreased compliance in one lung (black) and (C) increased compliance in the other lung (blue). The orange dotted line indicates decrease or increase in compliance. The green dotted line indicates return of baseline ventilation parameters upon titration of the valves. Pressure, volume, and flow in both lungs upon (D) increased resistance in one lung (black) and (E) decreased resistance in the other lung (blue). Orange dotted line indicates increase or decrease in resistance. Green dotted line indicates return of baseline ventilation parameters upon titration of the valves. Waveforms from each lung are slightly offset to enable visualization.

  • Fig. 3 Ventilation of two pigs on the iSAVE.

    (A) Experimental setup for stages 2 and 3 of shared ventilation of pig A (74 kg) and pig B (88 kg) with iSAVE using closed-circuit ventilation. (B) Photograph of the experimental setup. Pressure, flow, and volume waveforms for (C) pig A ventilated individually (stage 1), (D) pig B ventilated individually (stage 1), and (E) pigs A and B ventilated together on the iSAVE (stage 3). (F) Table summarizing ventilatory and respiratory parameters and arterial blood gasses for (C) to (E). Means ± SD were calculated from 300 breathing cycles. No significant differences were found between the individual and shared ventilation approaches (homoscedastic two-tailed t test, P > 0.05).

  • Fig. 4 Differential tidal volume and PEEP during ventilation of two pigs on the iSAVE with closed-circuit ventilation.

    (A) Summary of ventilatory and respiratory parameters. Means ± SD were calculated from 300 breathing cycles. No significant differences were found between ventilation with and without differential PEEP (homoscedastic two-tailed t test, P > 0.05). (B) Pressure, flow, and volume waveforms for the two animals. Pig A (blue) and pig B (black) were ventilated with PEEP of 5 and 10 cm H2O, respectively.

  • Table 1 Key challenges in splitting ventilation.

    A comparison of the capabilities of existing splitting mechanisms and iSAVE. PEEP, positive end-expiratory pressure; FiO2, fraction of inspired oxygen; ΔC, change in compliance; ΔR, change in resistance; Pplat, plateau pressure.

    ConcernUniform splitting (pressure control mode)iSAVE (volume control mode)
    Individualized management of ventilation
    -PEEPx Shared between patientso Individualized to each patient
    -Tidal volumex Shared between patientso Individualized to each patient
    -FiO2, respiratory ratex Shared between patientsx Shared between patients
    -Alarmsx Changes to one patient’s status may not
    result in main ventilator alarm.
    o Changes to one patient’s status will cause main
    ventilator to alarm. Mechanical components
    to provide auditory alarms can be
    incorporated.
    Sudden changes to patient status can cause
    damaging rebalancing of airflow to other
    patient(s) toward most compliant lungs.
    x Ventilation cannot be quickly adjusted.o Can be managed by titrating flow control
    valves. One-way valves prevent backflow.
    Pressure release valves prevent excess
    pressure delivery.
    Improvement or deterioration of one
    patient (ΔC, ΔR) will automatically
    rebalance airflow, potentially harming
    other patient(s).
    x Ventilation cannot be individually
    rebalanced. Patients would need to be
    rematched as they improve/deteriorate.
    o Desired ventilation for each patient can be
    achieved through valve adjustment,
    allowing patients to improve/deteriorate
    while remaining on the same system.
    Abruptly removing patients requires
    breaking the circuit, causing
    aerosolization of the virus, exposing
    health care personnel.
    x Individual patient circuits cannot be quickly
    removed from circuit.
    o Individual patients can be quickly shunted/
    removed from the circuit. Inline filters limit
    aerosolization risk.
    Monitoringx Additional respiratory monitors and
    heightened clinical vigilance required
    x Additional respiratory monitors and
    heightened clinical vigilance required
    Measurement of pulmonary mechanicsx Shared between patientso Pplat can be measured using expiratory hold
    button. C and R can be computed for each
    patient.
    Ventilator calibration/self-testx Added circuit volume defeats the operational
    self-test.
    o Can be executed with modifications to circuit*
    Triggeringx Disabled. Patients will require sedation.x Disabled. Patients will require sedation.

    *See fig. S9 for details regarding the rerouting of standard sensing devices required for ventilator calibration and self-tests.

    Supplementary Materials

    • stm.sciencemag.org/cgi/content/full/scitranslmed.abb9401/DC1

      Fig. S1. Photographs of the iSAVE setup.

      Fig. S2. Differential tidal volume and PEEP delivery on the iSAVE using an open-circuit ventilator and test lungs.

      Fig. S3. Accommodation to changes in compliance of one test lung using the iSAVE and an open-circuit ventilator.

      Fig. S4. Ventilation at high lung resistances.

      Fig. S5. Ventilator alarm response to occlusion.

      Fig. S6. Adding a test lung to the circuit.

      Fig. S7. Cross-contamination validation using artificial lungs on a closed-circuit ventilator.

      Fig. S8. Individualized management of ventilation using the iSAVE on a pig lung and a test lung.

      Fig. S9. Modification of sensing circuit for a Hamilton G5 ventilator.

      Fig. S10. Whistle ring designs for two types of common pressure release (PEEP) valves.

      Table S1. List of components required for the assembly of the iSAVE.

      Table S2. Mechanical components used in the iSAVE and their readily available medical industry equivalents.

      Table S3. Measurement of respiratory mechanics for iSAVE system using test lungs.

      Table S4. Blood electrolytes and chemistry during ventilation in pigs.

      Table S5. Stratification for patient matching.

    • This PDF file includes:

      • Fig. S1. Photographs of the iSAVE setup.
      • Fig. S2. Differential tidal volume and PEEP delivery on the iSAVE using an open-circuit ventilator and test lungs.
      • Fig. S3. Accommodation to changes in compliance of one test lung using the iSAVE and an open-circuit ventilator.
      • Fig. S4. Ventilation at high lung resistances.
      • Fig. S5. Ventilator alarm response to occlusion.
      • Fig. S6. Adding a test lung to the circuit.
      • Fig. S7. Cross-contamination validation using artificial lungs on a closed-circuit ventilator.
      • Fig. S8. Individualized management of ventilation using the iSAVE on a pig lung and a test lung.
      • Fig. S9. Modification of sensing circuit for a Hamilton G5 ventilator.
      • Fig. S10. Whistle ring designs for two types of common pressure release (PEEP) valves.
      • Table S1. List of components required for the assembly of the iSAVE.
      • Table S2. Mechanical components used in the iSAVE and their readily available medical industry equivalents.
      • Table S3. Measurement of respiratory mechanics for iSAVE system using test lungs.
      • Table S4. Blood electrolytes and chemistry during ventilation in pigs.
      • Table S5. Stratification for patient matching.

      [Download PDF]

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