Differential Ventilation Using Flow Control Valves as a Potential Bridge to Full Ventilatory Support during the COVID-19 Crisis
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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 (P MAX ) 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 P MAX 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 H 2 O. 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 H 2 O versus 35 ml/cm H 2 O. The coefficient of variation for tidal volume was 0.2 to 1.7%, and for P MAX 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 H 2 O versus 21 ml/cm H 2 O. The coefficient of variation for tidal volume was 0.4 to 5.6%, and for P MAX 0 to 2.1%.
Conclusions
Differential ventilation using a single ventilator is feasible. Flow control valves enable delivery of stable tidal volume and P MAX similar to those provided by individual ventilators.
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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 Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
Software and Algorithms Sentences Resources Simulation Protocol: Two high-fidelity Human Patient Simulator mannequins (HPS Anesthesia Simulator Mannequin Systems, CAE Healthcare, Sarasota, FL) were used for simulation. CAE Healthcaresuggested: NoneWe 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). Medtro…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 Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
Software and Algorithms Sentences Resources Simulation Protocol: Two high-fidelity Human Patient Simulator mannequins (HPS Anesthesia Simulator Mannequin Systems, CAE Healthcare, Sarasota, FL) were used for simulation. CAE Healthcaresuggested: NoneWe 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). Medtronicsuggested: (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.
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