3
44 NAUI Nitrox Diver
Avoiding CNS Toxicity
Central Nervous System (CNS) toxicity is avoided by
abiding by easily managed limits. Avoid excessive oxygen
partial pressures. Remember that the recommended
maximum PO2 for recreational nitrox diving is 1.4
atmospheres, with a PO2 of 1.6 atmospheres as a
contingency amount. Plan your dives and choose a nitrox
mix that is appropriate to the dive. In the next chapter
you will learn how to find the maximum operating depth
for any given enriched air nitrox mixture as well as
how to determine the optimal mix when you know the
planned depth of the dive.
Verify What You Have Learned
Review the following questions about
The Physiology of Diving and Nitrox:
1. What is the condition characterized by impaired
mental and physical performance and changes in
mood and behavior?
2. The mechanisms of nitrogen narcosis are thought to
be similar to what?
3. What are the terms for absorption and elimination of
nitrogen during a dive?
4. List the signs and symptoms of decompression
sickness.
5. What is the primary waste product in metabolism?
6. When do symptoms of hypoxia appear?
7. Central nervous system toxicity can result from
what? Pulmonary toxicity?
8. What is the generally accepted PO2 exposure limit
for recreational nitrox diving?
9. What are some of the many factors that can increase
your susceptibility to CNS oxygen toxicity?
10. What does the mnemonic acronym “ConVENTID”
stand for?
For answers, see Appendix.
Professionals Leading the Way
As a scuba diver, each dive is predicated on
who leads and who follows. Diving knowledge,
skill and ability are what set leaders apart from
their dive buddies, groups or affiliations. NAUI
is where diving professionals are made and
scuba is defined. NAUI professionals enhance
diving’s definition by turning their certifications
into careers.
Ann H. Kristovich (1951-present)
Ann H. Kristovich, D.D.S., is the co-leader of
the Proyecto De Buceo Espeleologico Mexico
Y America Central and has been involved in
cave exploration since 1988 in Mexico, Belize,
and Central America. She is a cave diver, scuba
instructor, author, and record holder.
In 1993, she set a women’s cave diving depth
record of 554 feet (169 meters). Kristovich is an
instructor for IANTD, NSS-CDS, NACD, NAUI,
and TDI and teaches technical, deep, cave,
and mixed-gas diving. Kristovich’s articles and
photos have been published internationally.
In addition, she is an oral and maxillofacial
surgeon. Kristovich was inducted into the
Women Divers Hall of Fame in 2000.