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SUMMER 2012
How might PFCs be used to treat DCS?
Spiess:
Today, we envision that PFCs would be used by first responders at the
dive site and medical personnel in hospitals to treat DCS symptoms. The data
consistently show that treatment with PFCs at the surface decreases mortality
and, uniquely, seems to greatly reduce neurologic complications. (Research
administering PFCs at depth was also conducted, but tremendous logistical
difficulties limit the practicality of such an approach.)
To achieve the greatest benefit from the PFCs, it is important that patients
also breathe a high concentration of oxygen. There are several reasons for
this. First, it takes advantage of the extra oxygen-carrying capacity of the
PFCs, promoting oxygen delivery to tissues that might not be getting enough.
Second, PFC particles are so small they can get to parts of the body where
circulation is blocked by the air emboli of DCS, preventing red blood cells
from getting in. Third, PFCs speed up the offloading of nitrogen and the
shrinkage of bubbles. Finally, PFCs act as surfactants to speed up bubble
dissolution and stop them from lodging in small blood vessels.
PFCs are administered as IV fluids in emulsions resembling milk. An
emergency medical technician (EMT) could start an IV, administer PFCs,
have the patient breathe 100 percent oxygen and transport to definitive
care. Many sport-diving accidents occur in remote parts of the world where
recompression chambers are not immediately available. We think starting
treatment during evacuation could reduce complications and even be life
saving. We also think using PFCs might improve safety of medical evacuations
that require exposure to altitude during air transport.
What has the research taught us about these compounds?
Hill:
We know what they can’t do, and we have a pretty good sense of what
they can do. The right clinical scenario for their application is a transient
problem that resolves soon. They’re novel compounds that do what they’re
supposed to do, which is increase the oxygen dissolved in the fluid phase of the
blood. The oxygen that gets to your cells has to be released from hemoglobin
and red cells to diffuse through the fluid phase of the blood to get to the tissues.
So increasing the solubility of oxygen in the fluid phase of the blood enhances
tissue-oxygen delivery. Medicine hasn’t figured out the right way to use PFCs
yet, but there will likely be an application for them eventually.
How has research and development progressed toward the use of PFCs
for treating DCS?
Spiess:
PFC research has made great progress. It has been about 30 years
from the development of the first-generation compounds to today’s third- and
fourth-generation compounds. Fluosol-DA 20% was approved by the Federal
Drug Administration (FDA) and used in about 15,000 humans in the late
1980s and early 1990s. It was used as a treatment for acute blood loss and, to
my knowledge, never used to treat acute DCS. That being said, I have used
it experimentally for treating DCS and found it to be highly effective. Fluosol
was eventually withdrawn from the market because it was cumbersome to use.
It was supplied frozen, needed to be thawed and then sonicated (treated with
ultrasound) to get it back into a usable emulsion. While 15,000 usages sounds
like a good number, it is a failure if you are manufacturing and selling a drug, so
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