![]() The device has two Pitot tubes, one upstream of a flow constriction and facing upstream, and the other downstream of the flow constriction and facing downstream, and a third port for gas sensing. Although this part is available online, we developed a similar model that can be 3D printed (see Suplementary information). We envision such a device could be crucial in future pandemics and may also serve an important role in current low-resource settings.įor the passive spirometer, we selected the General Electric D-Lite ++ spirometer, which transduces flow velocity into a pressure difference. ![]() The advent of accessible microcontrollers and the rapidly falling cost of silicon electronics enable a low-cost, high-accuracy tidal volume measurement system to be built with interchangable parts which could supplement the functionality of existing minimal-feature ventilators or alternative respiratory devices, such as BiPAP machines. ![]() In this work, we present a middle ground to these two approaches: a guide to designing a cheap and accurate flow sensor for measurement of tidal volume, based around an easy-to-manufacture plastic spirometer which has been around for several decades. Most existing efforts to this end are focused on ventilators which are very cheap and but only provide pressure measurements, or on designs that rely on external and expensive flow meters. These events have made clear the importance of developing a low-cost, accurate, and easily deployed system that can supplement the existing IMV supply chain in future catastrophes. The shortage was so severe governmental agencies released emergency guidelines, including an FDA guidance allowing clinicians to repurpose BiPAP (bilevel positive airway pressure) machines commonly used as a treatment for sleep apnea, anesthesia machines, and simpler ventilators for emergency use if needed. president invoking the Defense Production act, as well as a number of emergency ventilator design efforts to bypass supply chain issues. This led to some companies re-purposing facilities to participate in ventilator production, the U.S. From the onset of the pandemic, there were concerns about equipment shortages, including intensive care unit (ICU) ventilators. Insufficient volume can lead to hypoventilation and CO2 buildup, or atelectasis (lung collapse). Typically, this is done by delivering a set volume of air to the patient in a given breath (tidal volume) based on their body weight. Monitoring of mechanical ventilation is critically important to ensure patients are receiving enough air. The majority of these patients (69%) require invasive mechanical ventilation (IMV) for a mean duration of 10 days. In the United States, of those who are admitted to the hospital for COVID-19, over 20% are subsequently admitted to the intensive care unit (ICU), although this number is decreasing as we learn how to better treat this disease. We envision this system being used to increase the ventilator supply in resource-constrained settings.Īs of August 25, 2020, there have been over 23 million cases and 815,000 deaths from the COVID-19 disease caused by the SARS-CoV-2 virus, with hospitals across the world shouldering the burden for treatment in most severe cases. We validate this system and show that the tidal volume accuracy for flows above 10 L /min was within 10%. We also provide a model to predict the error in tidal volume measurements based on the pressure sensor used and the flow during ventilation. In this paper, we present a standalone tidal volume measurement system consisting of a D-Lite spirometer, pressure sensor, microcontroller, and tubing with a cost of parts less than $50 USD. ![]() Solutions which could augment the ventilator supply rapidly and at low cost in the United States and elsewhere would be valuable. However, ventilators are complex and expensive devices, typically in the range of tens of thousands of US dollars, and are challenging to manufacture, typically requiring months. Close monitoring of patients is critical, with total volume per breath (tidal volume) being one of the most important data points. COVID-19 has become a significant burden on the healthcare systems in the United States and around the world, with many patients requiring invasive mechanical ventilation (IMV) to survive. ![]()
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