# Flight Physiology Patient Impact and Considerations.

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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 patient?) Video

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