DIVING

Appendix F. Glossary
typically in a monoplace chamber. The protocol employs
a maximum pressure equivalent to a depth of 60 fsw (18
msw). Decompression travel is at 1 ft·min-1 (2 ft·min-1 if
all symptoms were mild and cleared within the first 10 min
of reaching 60 fsw).
Hazard
A condition, event or circumstance that could lead to or
contribute to an unplanned or undesirable event and cause
injury or material damage.
Health Insurance Portability and Accountability Act
(HIPAA)
US Federal legislation designed to protect the privacy and
interests of individuals and their families. DAN collects dive
injury and fatality information in compliance with HIPAA.
Heliox
See “Mixed-Gas.”
Hematocrit
A measure of red blood cell volume in a sample volume of
blood. Normal ranges are 40-53% for males and 35-46%
for females.
Hemoptysis
The coughing up of blood or bloody sputum from the lungs
or airway.
Hyperbaric Oxygen (HBO)
The therapeutic administration of oxygen under conditions
of substantially increased atmospheric pressure. See also
“Hart-Kindwall Oxygen Recompression Treatment Table”
and “US Navy Treatment Table.”
Hypercapnia
Condition in which the level of carbon dioxide in the blood
is higher than normal.
Hyperglycemia
Condition in which blood glucose (sugar) is higher than
normal.
Hyperoxia
Condition of higher-than-normal partial pressure of oxygen.
In medicine, it refers to excess oxygen in the lungs or
other body tissues, which can be caused by breathing air
or oxygen at pressures greater than normal atmospheric
pressure.
Hyperreflexia
A condition in which the deep tendon reflexes are exaggerated.
Hypertension
High blood pressure. A medical condition associated with
the development of heart disease and stroke.
Hyperventilation
Voluntary ventilation of the lungs in excess of metabolic
need (achieved by increasing depth of breaths and/or rate
of breathing). Often used to lower carbon dioxide content of
the bloodstream and increase breath-hold time. Excessive
hyperventilation will increase the risk of loss of consciousness
due to hypoxia. See “Hypoxia of Ascent.”
Hypocapnia
Condition in which the level of carbon dioxide of the blood
is lower than normal. This state is typically produced by
hyperventilation.
Hypoglycemia
Condition in which blood glucose (sugar) is lower than
normal.
Hypoventilation
Ventilation of the lungs at an abnormally slow rate, not
meeting metabolic needs, resulting in a net accumulation
of carbon dioxide in the blood, which will drive the urge to
breathe in a healthy person.
Hypoxemia
Condition of lower-than-normal partial pressure of oxygen
in the blood. See “Hypoxia of Ascent.”
Hypoxia
Condition of lower-than-normal partial pressure of oxygen.
May be experienced by breathing a gas mixture at the
surface that was intended for a deep bottom. See “Hypoxemia”
and “Hypoxia of Ascent.”
Hypoxia of Ascent
Unconsciousness resulting from hypoxia compounded by
surfacing at the end of a breath-hold dive. The reduction in
pressure associated with returning to the surface causes
the oxygen partial pressure to fall faster than through metabolism
of the gas alone. This condition is commonly
called shallow water blackout in North America, but this
term was previously used in the UK to describe a different
problem. See also “Hyperventilation,” “Hypoxia,” and
“Hypoxic Loss of Consciousness.”
Hypoxic Loss of Consciousness (HLOC)
Loss of consciousness resulting from an acute state of
hypoxia.
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