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Preventing Disease Transmission in Hospitals

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An inexpensive ventilator. Photo credit: Mohamed Amine Abassi

Researchers are developing simple and inexpensive tools – like a DIY ventilator – to treat patients more effectively and prevent disease transmission in hospitals.

The rapid spread of COVID-19 overwhelmed hospitals unable to cope with the increasing numbers of patients, many of whom required ventilators and other critical care. Such conditions can endanger medical personnel. Researchers are now investigating ways to increase the safety and effectiveness of hospitals during the pandemic.

A shortage of life-saving ventilators, typically costing around $ 30,000 each, hit hospitals particularly hard.

“By building a simple and cheap ventilator, we can help reduce this burden on medical staff,” said Mohamed Amine Abassi, a graduate student in fluid mechanics.

Based on a prototype designed by his advisor, engineering professor Xiaofeng Liu, Abassi, along with colleagues from San Diego State University and the University of California at San Diego, led efforts to build such a device from readily available parts – – Plastic tubing, pressure valves, humidifiers – – and an air supply. Then they tested it.

Preliminary results, released at the 73rd Annual Meeting of the Fluid Dynamics Division of the American Physical Society, suggest that the ventilator meets the basic requirements of the Food and Drug Administration. It is fully controllable on three parameters – – Air pressure, inspiratory time and positive end expiratory pressure (PEEP) – – with plans for further controls in progress.

Administer albuterol using a ventilator

A group from Lehigh University and the University of Arkansas for Medical Sciences searched for the most effective ways to administer albuterol through a ventilator. Photo credit: Rahul Rajendran

Abassi and Liu provide the ventilators that not only support overwhelmed hospitals in the US, but also in developing countries and rural areas with limited medical infrastructure. “If you can build it at home, you can use it,” Abassi said. “And you can build many of these fans in a very short time.”

Patients on ventilators with some lung diseases relevant to COVID-19 with underlying chronic lung conditions are often given drugs such as albuterol through an endotracheal tube. This treatment relaxes the bronchial muscles and improves airflow to the narrowed pulmonary airways.

A group out Lehigh University and the University of Arkansas for Medical Sciences were looking for the most effective ways to administer albuterol through a ventilator.

Ariel Berlinski and his group performed aerosol characterization experiments at the University of Arkansas. Rahul Rajendran of Lehigh used the results to study drug delivery through calculations.

“The aim of the research was to assess the efficiency of drug delivery when the type of nebulizer and its placement in the ventilation circuit were varied,” said Arindam Banerjee, member of the group and Lehigh professor of engineering.

The researchers found that a nebulizer with a vibrating mesh (instead of a jet) on the dry side of the humidifier delivers the highest dose to the lungs. Administration of albuterol by intubation works most effectively with smaller particles, while oral administration is more efficient with larger particles.

“Our results are critical to ventilator treatment,” said Banerjee.

Even under the best of circumstances, healthcare workers still risk getting COVID-19. A new breathing apparatus could reduce exhaled aerosols, which are known to carry the virus that causes the disease.

Researchers at Liberty University and Vapotherm wondered how frequent breathing treatments would affect aerosol emissions. So they decided to test a proposed design for a suction-connected PVC face mask and add a high speed nasal insufflation cannula – – the type of tube device that delivers oxygen to the nose.

With the help of medical experts, they then modeled a hospital room with two patients and four carers using sophisticated computer techniques. According to their model, fewer particles reach healthcare workers when patients wear the new device.

“It’s an inexpensive way to reduce the spread of airborne contamination by using supplies that are already in hospital rooms,” said Reid Prichard, an engineering graduate student. “This will remain an important tool after the pandemic ends.”

Another group from the University of South Florida, led by graduate mechanical engineer Anthony Perez, is studying what happens to aerosol contaminants that patients drop into a hospital isolation room – – and how quickly the contaminants leave the room.

“As many hospitals are reaching their capacity, it can be ensured that a hospital room can be safely entered after an aerosol generation process – – or after removing a previous patient so that hygienists can prepare the room – – requires significant downtime, ”said Perez.

According to the researchers, the ventilation recommendations from the Centers for Disease Control and Prevention assume that aerosols containing pathogens are perfectly mixed in a room. Using numerical simulations, the group found that incomplete mixing conditions had a significant impact on how quickly ventilation removes pathogens from a room.

“It’s both surprising and a little worrying that the air purification standard is based on what many believe is a calculation on the back of an envelope,” said Perez.

The simulations suggest that aerosol contaminants can linger in “dead zones” for around 10 minutes in a typical hospital isolation room. In the meantime, “short circuits” cause some packages of pollutants to be quickly expelled before they can disperse.

“Our research shows the need for a more accurate, yet cost-effective framework for predicting aerosol concentrations in any hospital room, particularly when assessing exposure of healthcare workers,” said Perez.

References:

Design, build and test a homemade ventilation system

Albuterol delivery via an adult ventilation circuit to a patient-specific tracheobronchial airway model

Novel Use of Joint Airway Treatment: Reducing COVID-19 Transmission

Numerical study of the role of ventilation rate in reducing exposure of health care workers to infectious aerosols in a hospital isolation room

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