Differential Ventilation Using Flow Control Valves as a Potential Bridge to Full Ventilatory Support during the COVID-19 Crisis

  1. Matthew A. Levin
  2. Anjan Shah
  3. Ronak Shah
  4. Erica Kane
  5. George Zhou
  6. James B. Eisenkraft
  7. Martin D. Chen
  8. for the Mount Sinai HELPS Innovate Group

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Abstract

During the COVID-19 pandemic, ventilator sharing was suggested to increase availability of mechanical ventilation. The safety and feasibility of ventilator sharing is unknown.

Methods

A single ventilator in pressure control mode was used with flow control valves to simultaneously ventilate two patients with different lung compliances. The system was first evaluated using high-fidelity human patient simulator mannequins and then tested for 1 h in two pairs of COVID-19 patients with acute respiratory failure. Patients were matched on positive end-expiratory pressure, fractional inspired oxygen tension, and respiratory rate. Tidal volume and peak airway pressure (PMAX) were recorded from each patient using separate independent spirometers and arterial blood gas samples drawn at 0, 30, and 60 min. The authors assessed acid-base status, oxygenation, tidal volume, and PMAX for each patient. Stability was assessed by calculating the coefficient of variation.

Results

The valves performed as expected in simulation, providing a stable tidal volume of 400 ml each to two mannequins with compliance ratios varying from 20:20 to 20:90 ml/cm H2O. The system was then tested in two pairs of patients. Pair 1 was a 49-yr-old woman, ideal body weight 46 kg, and a 55-yr-old man, ideal body weight 64 kg, with lung compliance 27 ml/cm H2O versus 35 ml/cm H2O. The coefficient of variation for tidal volume was 0.2 to 1.7%, and for PMAX 0 to 1.1%. Pair 2 was a 32-yr-old man, ideal body weight 62 kg, and a 56-yr-old woman, ideal body weight 46 kg, with lung compliance 12 ml/cm H2O versus 21 ml/cm H2O. The coefficient of variation for tidal volume was 0.4 to 5.6%, and for PMAX 0 to 2.1%.

Conclusions

Differential ventilation using a single ventilator is feasible. Flow control valves enable delivery of stable tidal volume and PMAX similar to those provided by individual ventilators.

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  1. Version published to 10.1097/aln.0000000000003473
  2. ScreenIT

    SciScore for 10.1101/2020.04.14.20053587: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    Simulation Protocol: Two high-fidelity Human Patient Simulator mannequins (HPS Anesthesia Simulator Mannequin Systems, CAE Healthcare, Sarasota, FL) were used for simulation.
    CAE Healthcare
    suggested: None
    We tested the system under a variety of simulated patient physiologies likely to be encountered in patients with acute respiratory failure due to COVID-19, using both a GE-Datex-Ohmeda S5 anesthesia machine and a Puritan Bennett 840 ventilator (Medtronic, Minneapolis, MN).
    Medtronic
    suggested: (Medtronic, RRID:SCR_003988)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    At least one recently published protocol provides guidance on shared ventilation, but it has limitations.6 Differential ventilation using one ventilator and a split circuit with flow control valves adequately addresses all of the concerns expressed in the consensus statement that recommends against shared ventilation (see Appendix) and has advantages over previous protocols. The adjustable flow valves allow the pressure and volume delivered to each patient to be continuously individualized and titrated to changes in compliance. Appropriately-placed spirometry sensors enable accurate measurement of the delivered tidal volume, airway pressure, compliance, and end-tidal CO2 for each patient individually. These data can be displayed on a wall-mounted or portable monitor. The unidirectional valves in both the inspiratory and expiratory limbs prevent reverse gas flow in the circuits or mixing of breathing gas between patients. Limitations: Our current design has several limitations. First it does not allow for individualized control of respiratory rate, PEEP, or FiO2. In our limited clinical experience, this did not prove to be a significant issue in critically ill COVID-19 patients in the acute phase of their disease. Second, it requires prolonged sedation and paralysis, although many COVID patients require paralysis for optimal ventilation. Third, if one patient in the pair decompensates there may be a significant increase in ventilatory requirement requiring them to be separated...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

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  3. Version published to 10.1101/2020.04.14.20053587v1 on medRxiv