Model-based Patient Matching for in-parallel Multiplexing Mechanical Ventilation Support

An identifiable model of lung mechanics to diagnose and monitor COPD

BACKGROUND

Current methods to diagnose and monitor COPD employ spirometry as the gold standard to identify lung function reduction with reduced forced expiratory volume (FEV₁)/vital capacity (VC) ratio. Current methods utilise linear assumptions regarding airway resistance, where nonlinear resistance modelling may provide rapid insight into patient specific condition and disease progression. This study examines model-based expiratory resistance in healthy lungs and those with progressively more severe COPD.

METHODS

Healthy and COPD pressure (P)[cmH₂O] and flow (Q)[L/s] data is obtained from the literature, and 5 intermediate levels of COPD and responses are created to simulate COPD progression and assess model-based metric resolution. Linear and nonlinear single compartment models are used to identify changes in inspiratory (R_1,insp) and linear (R_1,exp)/nonlinear (R₂Φ) expiratory resistance with disease severity and over the course of expiration.

RESULTS

R_1,insp increases from 2.1 to 7.3 cmH₂O/L/s, R_1,exp increases from 2.4 to 10.0 cmH₂O/L/s with COPD severity. Nonlinear R₂Φ increases (mean R₂Φ: 2.5 cmH₂O/L/s (healthy) to 24.4 cmH₂O/L/s (COPD)), with increasing end-expiratory nonlinearity as COPD severity increases.

CONCLUSION

Expiratory resistance is increasingly highly nonlinear with COPD severity. These results show a simple, nonlinear model can capture fundamental COPD dynamics and progression from regular breathing data, and such an approach may be useful for patient-specific diagnosis and monitoring.

Translational design for limited resource settings as demonstrated by Vent-Lock, a 3D-printed ventilator multiplexer

Background

Mechanical ventilators are essential to patients who become critically ill with acute respiratory distress syndrome (ARDS), and shortages have been reported due to the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Methods

We utilized 3D printing (3DP) technology to rapidly prototype and test critical components for a novel ventilator multiplexer system, Vent-Lock, to split one ventilator or anesthesia gas machine between two patients. FloRest, a novel 3DP flow restrictor, provides clinicians control of tidal volumes and positive end expiratory pressure (PEEP), using the 3DP manometer adaptor to monitor pressures. We tested the ventilator splitter circuit in simulation centers between artificial lungs and used an anesthesia gas machine to successfully ventilate two swine.

Results

As one of the first studies to demonstrate splitting one anesthesia gas machine between two swine, we present proof-of-concept of a de novo, closed, multiplexing system, with flow restriction for potential individualized patient therapy.

Conclusions

While possible, due to the complexity, need for experienced operators, and associated risks, ventilator multiplexing should only be reserved for urgent situations with no other alternatives. Our report underscores the initial design and engineering considerations required for rapid medical device prototyping via 3D printing in limited resource environments, including considerations for design, material selection, production, and distribution. We note that optimization of engineering may minimize 3D printing production risks but may not address the inherent risks of the device or change its indications. Thus, our case report provides insights to inform future rapid prototyping of medical devices.