Oxygen Conserving Devices

 

Oxygen Conserving Devices

Richard G. Lanzara

 

Since the rise of the COVID-19 pandemic, many countries have been suffering from reduced oxygen supplies that have led to critical shortages. There is an acute need for oxygen-sparing devices that allow patients to get a controlled oxygen percentage without wasting oxygen.

A common post-op, set-up for patients recovering from surgery were oxygen delivery systems that were called Nebulizers or Humid-high bottles (see Picture 1) with an adjustable venturi that could be turned to deliver the desired oxygen concentration.

 

Picture 1 Examples of Nebulizers or Humid-High bottles

 

This was a common post-op, set-up for patients recovering from surgery, but one drawback was that large amounts of oxygen were being wasted by simply mixing with the room air.

Years ago, I had done some very preliminary research that suggested such oxygen conserving devices could be easily made from existing supplies of large bore tubing, non-rebreathing masks and reservoir bags (see Picture 2 for an example of a closed, non-rebreathing system with large bore tubing).

 

Picture 2 An example of a non-rebreathing system with large bore tubing. In my configuration, the blender and humidifier in the above picture are replaced by the Nebulizer or Humid-High bottle with an adjustable venturi (as shown in Picture 1).

 

At the time, the concern was that using venturi devices with non-rebreathing masks would significantly change the desired oxygen concentrations due to the back pressures on the venturi. I studied this system with three different venturi settings (30%, 50% and 80% oxygen) and found, using a suitable oxygen detector, that the selected oxygen concentrations did not change over a period of an hour. This showed that such closed systems might provide accurate oxygen concentrations and conserve oxygen consumption at the same time.

Therefore, oxygen can be delivered from a variable venturi device to a reservoir bag that the patient can then breath from using a non-rebreathing mask. The oxygen flows can be dramatically reduced to just maintain the inflation of the reservoir bag.

These materials are often readily available and easy to assemble. The use of one or more reservoir bags allows the provider to determine if the patient has sufficient volumes of oxygen to inhale (that is the oxygen flow is sufficient so that the bag does not fully collapse on inhalation). If necessary, more than one reservoir bag can be connected in tandem to increase the size of the reservoir. This allows for reduced flows of oxygen without compromising patient safety.

This may be a helpful configuration to consider when oxygen supplies are low.