Flight Physiology
Patient Impact and Considerations
Understand complications to us
and patients
Relate how flight physiology
changes how we care for
patients.
Discuss stressors of flight, and
how to control their impact
78% nitrogen, 21% oxygen, 1% carbon dioxide
We don’t use nitrogen to live, but some of it is
in our bodies within our blood and body fluids
The higher the altitude, the less oxygen
available
Blood carries oxygen, and the heart makes it go
around and around (profound, I know)
Physiological Divisions
• Physiological zone
Extends from sea level to 10,000 feet
• Physiological-deficient zone
Extends from 10,000 to 50,000 feet
• Space-equivalent zone
Extends from 50,000 feet to 120 miles above Earth
• Total space-equivalent zone
Beyond 120 miles above Earth
Physical Laws of Gases
• Boyle’s Law
The volume of a gas is inversely proportional to its
pressure if the temperature remains constant.
• Dalton’s Law
The total pressure of a mixture of gases is equal to
the sum of the partial pressure of each gas in that
mixture.
• Henry’s Law
The amount of a gas in a solution varies directly with
the partial pressure that gas exerts on the solution.
Video
A scuba diver ascending will create larger
bubbles the closer to the surface they are,
because there is less water pressure which
allows the volume of air to expand.
Deep sea fish die when brought to surface
because the lack of pressure allows volume to
grow and they rupture their bladders, cells, and
membranes.
Squeezing a balloon mimics Boyle’s Law by
attempting to decrease the volume and
increase the pressure, resulting in a popped
balloon
Trapped Gases-Ear Block
Trapped Gases-Sinus Block
Trapped Gases-Tooth Pain
• Untreated cavities where pulp is exposed may be
the cause of tooth pain at altitude.
• The toothache often disappears at the same
altitude that if was first observed on ascent.
• Gases may be trapped in the teeth at altitude in
abscesses.
ET tube balloons
Air filled balloons in other body
areas
Chest tube pressure changes
The amount of carbon dioxide in the blood
has an important effect on the action of the
heart.
As carbon dioxide in the blood increases,
the heart rate speeds up so the heart can
send more oxygenated blood to the
tissues.
When carbon dioxide in the blood
decreases, the heart rate slows because
tissues need less oxygen.
What can this do to our cardiac pts?
Hypoxia - a deficiency of oxygen in
the body cells or tissue.
• Most frequently the result of
decreased pressure on an
unprotected body.
• In flight is usually caused by an
insufficient amount of oxygen in
the inhaled air, or a patient with
poor lung or cardiac function
Video
Hyperventilation
• A person affected by hypoxia
tends to increase breathing
rate in an attempt to take in
more oxygen.
• Results in increased emotional
tension or anxiety. (how would
it affect a COPD or MI
Videopatient?)
Dalton’s law of partial
pressures states that the
total pressure (Pt) of a gas
mixture is equal to the sum
of the partial pressures of
the individual gases in the
mixture.
While the pressure of C02 is fairly negligible in
the atmosphere, its concentrations are far
higher within the lungs, as it is a product of
respiration.
By increasing the percentage of any gas in air’s
mixture, a higher partial pressure of that gas
can be achieved, which is the basis of oxygen
therapy, and why giving a patient oxygen can
raise their saturations.
A diver subjects their body to increased pressure, which allows body tissues
to absorb more gasses. The oxygen is used up by cellular processes, but the
nitrogen is inert and just packs into the tissues. The deeper the diver goes
and the longer he stays, the more nitrogen packs into the tissues. The
nitrogen itself is not a problem. Eventually, it would reach a state of
equilibrium and stop on-gassing (packing in). The problem begins when the
diver ascends and reduces the pressure his body is under, making the
nitrogen less soluble in his tissues. If the diver comes up too fast (releases
the pressure too fast), the nitrogen comes out in the form of bubbles, just
like the soda. This condition is known as decompression sickness (DCS),
sometimes called the “bends”. To avoid DCS, a diver must monitor his depth
and time to limit the amount of nitrogen on-gassing and then ascend slowly
enough that the pressure is released slow enough to allow the nitrogen to
leave the tissues without forming bubbles.
The second part of Henry’s Law comes into play when diving in cold
water. Cold water makes the body on-gas faster, allowing shorter dive times
or shallower depth than would be possible in warm water. In addition,
working hard or jumping in a hot tub right after a dive can heat up the tissues
and make the nitrogen less soluble in the tissues which can result in DCS.
Not much unless we are caring for a patient
with a diving injury, then it may be to the
patients benefit to transfer by ground, and not
further decompress their body with elevation
A decompression chamber re-pressurizes the
body and allows decompression to happen in a
controlled manner.
Cause flyers more inconvenience than any
other factor in flight.
Sound intensity or loudness is measured in
decibels.
Vibrations are measured in frequency.
One effect of vibration is blurred vision.
For every 500' the temperature changes by ~1
degree Celsius, or a little more than 2 degree’s
per 1,000 feet, but not quite 2.5 degree’s.
Temperature changes for us, as we get hot or
cold in the environment so does our patient.
Remember, our patients are wearing only a
gown.
Creates a drying sensation at
altitude
Increased need for hydration
for us, especially with multiple
flights in a day
Loss of spatial orientation,
proprioception
Sitting or laying backwards
Vibration and turbulence
Ear problems, visual issues
Contributing medical and trauma
factors (CHI, chemo etc.)
This is why we medicate our patients