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.
