Sharing Mechanical Ventilator: In Vitro Evaluation of Circuit Cross-Flows and Patient Interactions

Abstract

During the COVID-19 pandemic, a shortage of mechanical ventilators was reported and ventilator sharing between patients was proposed as an ultimate solution. Two lung simulators were ventilated by one anesthesia machine connected through two respiratory circuits and T-pieces. Five different combinations of compliances (30–50 mL × cmH2O−1) and resistances (5–20 cmH2O × L−1 × s−1) were tested. The ventilation setting was: pressure-controlled ventilation, positive end-expiratory pressure 15 cmH2O, inspiratory pressure 10 cmH2O, respiratory rate 20 bpm. Pressures and flows from all the circuit sections have been recorded and analyzed. Simulated patients with equal compliance and resistance received similar ventilation. Compliance reduction from 50 to 30 mL × cmH2O−1 decreased the tidal volume (VT) by 32% (418 ± 49 vs. 285 ± 17 mL). The resistance increase from 5 to 20 cmH2O × L−1 × s−1 decreased VT by 22% (425 ± 69 vs. 331 ± 51 mL). The maximal alveolar pressure was lower at higher compliance and resistance values and decreased linearly with the time constant (r² = 0.80, p < 0.001). The minimum alveolar pressure ranged from 15.5 ± 0.04 to 16.57 ± 0.04 cmH2O. Cross-flows between the simulated patients have been recorded in all the tested combinations, during both the inspiratory and expiratory phases. The simultaneous ventilation of two patients with one ventilator may be unable to match individual patient’s needs and has a high risk of cross-interference.

Design of a flow modulation device to facilitate individualized ventilation in a shared ventilator setup

“…1 ) This allows to adapt ventilation to the patient, and not the other way around, as in the naive system. Additionally, two heat and moisture exchange filters (HMEFs) and four one-way valves should be provided to prevent cross contamination and pendelluft [ 30 , 31 ]. The ventilator must be used in a pressure-controlled mode.…”

Challenges in the Extracorporeal Membrane Oxygenation Era

“…Furthermore, as discussed by Shah and colleagues [13], intensivists had to face new clinical challenges. The shortage of mechanical ventilators pushed clinicians to investigate the possibility of sharing a ventilator, which raised a number of physiological questions such as circuit cross-flows and patient interactions, as discussed by Colombo et al [14]. In order to minimize the exposure of health care personnel, even routine clinical procedures such as percutaneous tracheostomy were modified [15].…”