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Safety and Health Information Bulletin

The purpose of this Safety and Health Information Bulletin
provides employees and employers with important information
about the hazards of orthostatic intolerance and suspension
trauma when using fall arrest systems. This bulletin describes
the signs and symptoms of orthostatic intolerance; discusses
how orthostatic intolerance can occur while workers are suspended
following a fall; and outlines recommendations for preventing
orthostatic intolerance, as well as recommendations for
worker training and rescue.

Orthostatic intolerance may be defined as “the development
of symptoms such as light-headedness, palpitations, tremu-lousness,
poor concentration, fatigue, nausea, dizziness,
headache, sweating, weakness and occasionally fainting during
upright standing”1,2. While in a sedentary position, blood can accumulate in the veins, which is commonly called “venous
pooling,” and cause orthostatic intolerance3. Orthostatic intolerance also can occur when an individual moves suddenly after
being sedentary for a long time. For example, a person may
experience orthostatic intolerance when they stand up quickly
after sitting still for a long time.

A well-known example of orthostatic intolerance is that of a soldier
who faints while standing at attention for a long period of
time. The moment the soldier loses consciousness, he or she
collapses into a horizontal position. With the legs, heart and
brain on the same level, blood is returned to the heart. Assuming
no injuries are caused during the collapse, the individual
will quickly regain consciousness, and recovery is likely to be

Venous pooling typically occurs in the legs due to the force of
gravity and a lack of movement. Some venous pooling occurs
naturally when a person is standing. In the veins, blood normally
is moved back to the heart through one-way valves using
the normal muscular action associated with limb movement. If
the legs are immobile, then these “muscle pumps” do not operate
effectively, and blood can accumulate. Since veins can
expand, a large volume of blood may accumulate in the veins.

An accumulation of blood in the legs reduces the amount of
blood in circulation. The body reacts to this reduction by speeding
up the heart rate and in an attempt to maintain sufficient
blood flow to the brain. If the blood supply is significantly
reduced, this reaction will not be effective. The body will
abruptly slow the heart rate and blood pressure will diminish
in the arteries. During severe venous pooling, the reduction in
quantity and/or quality (oxygen content) of blood flowing to
the brain causes fainting. This reduction
also can have an effect on other vital
organs, such as the kidney3. The kidneys
are very sensitive to blood oxygen,
and renal failure can occur with excessive
venous pooling. If these conditions
continue, they potentially may be fatal.3

Description of Hazard

Orthostatic intolerance may be experienced
by workers using fall arrest systems.
Following a fall, a worker may
remain suspended in a harness. The sustained
immobility may lead to a state of
unconsciousness. Depending on the
length of time the suspended worker is
unconscious/immobile and the level of
venous pooling, the resulting orthostatic
intolerance may lead to death. While
not common, such fatalities often are
referred to as “harness-induced pathology”
or “suspension trauma.”

Unconscious/immobile workers suspended
in their harness will not be able
to move their legs and will not fall into
a horizontal position, as they would if
they fainted while standing. During the
static upright position, venous pooling
is likely to occur and cause orthostatic
intolerance, especially if the suspended
worker is left in place for some time.
Venous pooling and orthostatic intolerance
can be exacerbated by other circumstances
related to the fall. For example,
shock or the experience of the event
that caused the fall, other injuries, the
fit/positioning of the harness, the environmental
conditions and the worker’s
psychological state all may increase the
onset and severity of the pooling and
orthostatic intolerance3,5. Unless the
worker is rescued promptly using established
safe procedures, venous pooling and orthostatic intolerance could result in serious or fatal injury, as the brain,
kidneys and other organs are deprived of

The amount of time spent in this position,
with the legs below the heart, affects
the manner in which the worker should be rescued3. Moving the worker quickly into a horizontal position—a
natural reaction—is likely to cause a
large volume of deoxygenated blood to
move to the heart, if the worker had
been suspended for an extended period.
The heart may be unable to cope with
the abrupt increase in blood flow, causing cardiac arrest3,5.

Rescue procedures must take this into
account. Recommended rescue procedures
are outlined below in the next section.

Conclusions and Recommendations

Prolonged suspension from fall arrest
systems can cause orthostatic intolerance,
which, in turn, can result in serious
physical injury, or potentially, death.
Research indicates that suspension in a
fall arrest device can result in unconsciousness,
followed by death, in less than 30 minutes4.

To reduce the risk associated with prolonged
suspension in fall arrest systems,
employers should implement plans to
prevent prolonged suspension in fall
protection devices. The plan should
include procedures for preventing prolonged
suspension, identifying orthostatic
intolerance signs and symptoms,
and performing rescue and treatment as
quickly as possible.

OSHA recommends the following general

Rescue suspended workers as quickly
as possible.

Be aware that suspended workers are
at risk of orthostatic intolerance and suspension

Be aware of the signs and syptoms of orthostatic intolerance.

Be aware that orthostatic intolerance is potentially life threatening. Suspended
workers with head injuries or who are
unconscious are particularly at risk.

Be aware of factors that can increase
the risk of suspension trauma.

Be aware that some authorities advise
against moving the rescued workers to
a horizontal position too quickly.


OSHA requires employers to train workers
to use fall arrest systems and other
personal protective equipment correctly
while performing their jobs, in accordance with standards 29 CFR 1910.132 (Personal Protective Equipment) 29
CFR 1915.159 (Personal Fall Arrest Systems)
and 29 CFR 1926.503 (Training
Requirements for Fall Protection).

Workers who wear fall arrest devices
while working, and those who may perform
rescue activities, should also be
trained in the following:

How to ascertain whether their
personal protective equipment is
properly fitted and worn, so that it
performs as intended.

How orthostatic intolerance/
suspension trauma may occur.

The factors that may increase a worker’s

How to recognize the signs and
symptoms identified in this Safety and
Health Information Bulletin.

The appropriate rescue procedures
and methods to diminish risk while suspended.

Rescue Procedures

Under 29 CFR 1926.502 (d) (Fall Protection
Systems Criteria and Practices),
OSHA requires that employers provide
for “prompt rescue of employees in the
event of a fall or shall assure that
employees are able to rescue themselves.”
This should include identifying
rescue procedures that address the
potential for orthostatic intolerance and
suspension trauma. Rescue procedures
also should address how the rescued
worker will be handled to avoid any
post-rescue injuries.

Rescue procedures should include the
following contingency based actions:

If self-rescue is impossible, or if rescue
cannot be performed promptly, the
worker should be trained to “pump”
his/her legs frequently to activate the
muscles and reduce the risk of venous
pooling. Footholds can be used to alleviate
pressure, delay symptoms, and provide
support for “muscle pumping.”

Continuous monitoring of the suspended
worker for signs and symptoms of orthostatic intolerance and suspension trauma.

Ensuring that a worker receives standard
trauma resuscitation6
once rescued.
Some authorities recommend that the
patient be transported with the upper
body raised.

If the worker is unconscious, keeping
the worker’s air passages open and
obtain first aid.

Monitoring the worker after rescue,
and ensuring that the worker is evaluated
by a health-care professional. The
worker should be hospitalized when
appropriate. Possible delayed effects,
such as kidney failure, which is not
unusual in these cases, are difficult to
assess on the scene.


1Robertson, David. Orthostatic Intolerance.
Vanderbilt University, Nashville, Tennessee.

2New York Medical College. Orthostatic
Intolerance. Vahalla, New York.

3Seddon, Paul. Harness Suspension:
Review and evaluation of existing information.
Health and Safety Executive. Research Report 451/2002. 104 pp.

4Sheehan, Alan. Suspension Trauma.
Training handout.

5Weems, Bill and Bishop, Phil. Will
Your Safety Harness Kill You? Occupational
Health & Safety. 72(3): 86-88, 90, March, 2003.

6National Association of Emergency
Medical Technicians. Provider Textbook
section in PHTLS Basic and Advanced
Prehospital Trauma Life Support Fifth
, St. Louis, MO: Mosby; 2003:
Section 1.

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