Coping with COVID-19: ventilator splitting with differential driving pressures using standard hospital equipment

The global COVID-19 pandemic has led to a worldwide shortage of ventilators. This shortage has initiated discussions on how to support multiple patients with a single ventilator (ventilator splitting). Ventilator splitting is incompletely tested, experimental and the effects have not been fully characterised. This study investigated the effect of ventilator splitting on system variables (inspiratory pressure, flow and volume) and the possibility of different ventilation targets for each limb using only standard hospital equipment. Experiments were conducted on two test lungs with different compliances (0.02 l.cmH₂ O^-1 and 0.04 l.cmH₂ O^-1 ). The ventilator was used in both pressure and volume control modes and was set to ventilate the low compliance lungs at end-tidal volumes of 500 ± 20 ml. A flow restrictor apparatus consisting of a Hoffman clamp and tracheal tube was connected in series to the inspiratory limb of the high compliance test lungs and the resistance modified to achieve end-tidal volumes of 500 ± 20 ml. The restriction apparatus successfully modified the inspiratory pressure, minute ventilation and volume delivered to the high compliance test lungs in both pressure control (27.3-17.8 cmH₂ O, 15.2-8.0 l.min^-1 and 980-499 ml, respectively) and volume control (21.0-16.7 cmH₂ O, 10.7-7.9 l.min^-1 and 659-498 ml, respectively) ventilation modes. Ventilator splitting is not condoned by the authors. However, these experiments demonstrate the capacity to simultaneously ventilate two test lungs of different compliances, and using only standard hospital equipment, modify the delivered pressure, flow and volume in each test lung.