For the past 50 years, positive pressure ventilation has been a cornerstone of treatment for respiratory failure. Consensus surrounding the epidemiology of respiratory failure has permitted a relatively good fit between the supply of ventilators and the demand. However, the current COVID-19 pandemic has increased demand for mechanical ventilators well beyond supply. Respiratory failure complicates most critically ill patients with COVID-19 and is characterized by highly heterogeneous pulmonary parenchymal involvement, profound hypoxemia and pulmonary vascular injury. The profound increase in the incidence of respiratory failure has exposed critical shortages in the supply of mechanical ventilators, and those with the necessary skills to treat. While most traditional ventilators rely on an internal compressor and mixer to moderate and control the gas mixture delivered to a patient, the current emergency climate has catalyzed alternative designs that might enable greater flexibility in terms of supply chain, manufacturing, storage and maintenance. Design considerations of these 'emergency response' ventilators have generally fallen into two categories: those that rely on mechanical compression of a known volume of gas and those powered by an internal compressor to deliver time cycled pressure- or volume-limited gas to the patient. The present work introduces a low-cost, ventilator designed and built in accordance with the Emergence Use guidance provided by the US Food and Drug Administration (FDA) wherein an external gas supply feeds into the ventilator and time limited flow interruption guarantees tidal volume. The goal of this device is to allow a patient to be treated by a single ventilator platform, capable of supporting the various treatment paradigms during a potential COVID-19 related hospitalization. This is a unique aspect of this design as it attempts to become a one-device-one-visit solution to the problem. The device is designed as a single use ventilator that is sufficiently robust to treat a patient being mechanically ventilated. The overall design philosophy and its applicability in this new crisis-laden world view is first described, followed by both bench top and animal testing results used to confirm the precision, capability, safety and reliability of this low cost and novel approach to mechanical ventilation during the COVID-19 pandemic. The ventilator is shown to perform in a range of critical requirements listed in the FDA emergency regulations and can safely and effectively ventilate a porcine subject. As of August 2020, only 13 emergency ventilators have been authorized by the FDA, and this work represents the first to publish animal data using the ventilator. This proof-of-concept provides support for this cost-effective, readily mass-produced ventilator that can be used to support patients when the demand for ventilators outstrips supply in hospital settings worldwide. More details for this project can be found at https://ventilator.stanford.edu/
Investigating the effect of materials and structures for negative pressure ventilators suitable for pandemic situation