A rapidly deployable individualized system for augmenting ventilator capacity

Abstract

Strategies to split ventilators to support multiple patients requiring ventilatory support have been proposed and used in emergency cases in which shortages of ventilators cannot otherwise be remedied by production or procurement strategies. However, the current approaches to ventilator sharing lack the ability to individualize ventilation to each patient, measure pulmonary mechanics, and accommodate rebalancing of the airflow when one patient improves or deteriorates, posing safety concerns to patients. Potential cross-contamination, lack of alarms, insufficient monitoring, and inability to adapt to sudden changes in patient status have prevented widespread acceptance of ventilator sharing. We have developed an individualized system for augmenting ventilator efficacy (iSAVE) as a rapidly deployable platform that uses a single ventilator to simultaneously and more safely support two individuals. The iSAVE enables individual-specific volume and pressure control and the rebalancing of ventilation in response to improvement or deterioration in an individual's respiratory status. The iSAVE incorporates mechanisms to measure pulmonary mechanics, mitigate cross-contamination and backflow, and accommodate sudden flow changes due to individual interdependencies within the respiratory circuit. We demonstrate these capacities through validation using closed- and open-circuit ventilators on linear test lungs. We show that the iSAVE can temporarily ventilate two pigs on one ventilator as efficaciously as each pig on its own ventilator. By leveraging off-the-shelf medical components, the iSAVE could rapidly expand the ventilation capacity of health care facilities during emergency situations such as pandemics.

Fig. 1. Design of the individualized system for augmenting ventilation efficacy (iSAVE).

(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 (V_T) for two test lungs (blue, black) using closed-circuit ventilation. The ratio (50:50, 35:65, 15:85) refers to the V_T 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 stage 2 and stage 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-E). Mean ± SD was 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. Mean ± SD was 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 cmH₂O, respectively.