IIT makes prototype to reduce O2 wastage
A team of alumni and researchers at the Indian Institute of Technology-bombay (IIT-B) have built a breathing device that can reduce wastage of oxygen when a Covid-19 patient is put on assisted breathing support such as ventilators.
The prototype, called ‘rebreather’, is a semi-closed circular breathing system that will allow patients to breathe in unused exhaled oxygen. Covid-19 patients with severe breathing trouble are put on ventilators that can supply oxygen through a combination of nasal cannula and mask at a flow rate of up to 50 litres per minute. However, the lung can only absorb one litre of oxygen in a minute. The rest of the 49 litres (L) are wasted. The researchers have used an existing technology of reusing exhaled oxygen— commonly used in diving and mountaineering systems — to cut down on this wastage.
“At a time when oxygen is in short supply across the country, this mode of recirculating oxygen can help save lives,” said Santosh Noronha, assistant professor, department of chemical engineering, IIT-B, who is one of the 15 members of the team behind rebreather. The prototype has been designed by the staff, students and alumni affiliated with Tata Centre for Technology and Design, department of chemical engineering, and Nex Robotics—a start-up by alumni of the institute.
According to the calculations by the team, this re-circulation of oxygen can reduce the number of cylinders required by a critical patient from nine to almost one per day. “It is a good system on paper and we [doctors] are quite excited about it. However, it has to be put into use in a hospital set up before we can be sure of its working,” said infectious diseases specialist Om Shrivastav, who was not part of the project. rebreather is a semiclosed circular breathing system with an inlet section which pumps in fresh oxygen from an oxygen cylinder or a centralised oxygen system in hospitals. The oxygen flow rate is set on the cylinder with a flow meter. An adjustable venturi valve is given at the input to allow for external air to be automatically pulled in based on the desired oxygen flow rate. A one port mask is attached to the patient. The exhaled air is fed to a container which has medical-grade soda lime. This soda lime selectively absorbs carbon dioxide from the exhaled output and allows the rest of the air to pass through to the inlet section of the system. The soda lime changes colour once it has exhausted its capability to absorb carbon dioxide and can be replaced.
The technical details of the system have been made public under Creative Commons to grant access to healthcare workers. A single unit of rebreather cost the team around ₹50,000. “The unit can be sanitised and reused. So it is mostly a one-time expense,” Noronha said. MUMBAI: