Middle Ear and Sinus Problems in Flying

Middle Ear and Sinus Problems in Flying

During climbs and descents, the air in our closed cavities expands or contracts due to a difference between the pressure of the air outside the body and that of the air inside the body. 

If the air expands pressure builds up within the cavity and pain is experienced if it can't escape. Trapped gas expansion accounts for ear and sinus pain, as well as a temporary reduction in the ability to hear.

The physical ear consists of an outer conical shaped structure called external pinna. A middle chamber, that connects to the outside atmosphere, and the inner ear. 

The middle and inner ear are located in a small cavity in the bone of the skull. The tympanic membrane separates the outer ear and middle ear. The Eustachian tube connects the middle ear to the outside atmosphere. Pressure differences between the middle ear and the outside atmosphere are equalized by the Eustachian tube.There is a right and left Eustachian tube. They are normally shut but they open during chewing, yawning or swallowing to equalize the pressure.

A slight difference in external pressure and middle ear pressure can cause discomfort.

During a climb, middle ear air pressure may exceed the pressure of the air in the external ear canal, causing the eardrum to bulge outward. Pilots become aware of this pressure change when they experience alternate sensations of “fullness” and “clearing.”

 During descent, the reverse happens. While the pressure of the air in the external ear canal increases, the middle ear cavity, which equalized with the lower pressure at altitude, is at a lower pressure than the external ear canal. This results in the higher outside pressure, causing the eardrum to bulge inward.

This condition can be more difficult to relieve where the partial vacuum tends to constrict the walls of the Eustachian tube. To remedy this often painful condition, which also causes a temporary reduction in hearing sensitivity, pinch the nostrils shut, close the mouth and lips, and blow slowly and gently in the mouth and nose.

This procedure forces air through the Eustachian tube into the middle ear. It may not be possible to equalize the pressure in the ears if a pilot has a cold, an ear infection, or sore throat. A flight in this condition can be extremely painful, as well as damaging to the eardrums.

If experiencing minor congestion, nose drops or nasal sprays may reduce the risk of a painful ear blockage. Before using any medication, check with an AME to ensure that it will not affect the ability to fly.

In a similar way, air pressure in the sinuses equalizes with the pressure in the flight deck through small openings that connect the sinuses to the nasal passages. An upper respiratory infection, such as a cold or sinusitis, or a nasal allergic condition can produce enough congestion around an opening to slow equalization. As the difference in pressure between the sinuses and the flight deck increases, congestion may plug the opening. This “sinus block” occurs most frequently during descent. Slow descent rates can reduce the associated pain. A sinus block can occur in the frontal sinuses, located above each eyebrow, or in the maxillary sinuses, located in each upper cheek. It will usually produce excruciating pain over the sinus area. A maxillary sinus block can also make the upper teeth ache. Bloody mucus may discharge from the nasal passages.

Sinus block can be avoided by not flying with an upper respiratory infection or nasal allergic condition. Adequate protection is usually not provided by decongestant sprays or drops to reduce congestion around the sinus openings. Oral decongestants have side effects that can impair pilot performance. If a sinus block does not clear shortly after landing, a physician should be consulted.

Travelers on commercial planes, where pressurization is set at 6,000 feet, may experience pain if the passageways are blocked before takeoff.  Techniques described above, if not illegal, can alleviate the expected difficulty before takeoff.

Hyperventilation

Hyperventilation in Flying

When you breath too rapidly you blow off too much carbon dioxide. Basically, it affects the amount of free hydrogen ions (that determine acidity - too little pH above 7.0 (alkaline) - too much pH below 7.0 (Acidic).

The increased pH causes symptoms that alarms pilots when it occurs. When your frightened you breathe even faster and more deeply that increases the symptoms.

Hyperventilation can lead to unconsciousness when your respiratory system tries to regain control of your breathing.

Two instances where hyperventilation can occur is scuba diving and flying at higher altitudes. In both these situations a pilot may breathe faster than normal.

A little gruesome is the panic one feels when terminally ill with lung disease and breathing is difficult. You attempt to breathe faster and the pain becomes severe.

Many of these symptoms are similar to hypoxia. It is important to recognize the differences and diagnose what is really happening.

If you are using oxygen check the equipment and flow rate to ensure the symptoms are not hypoxia related.

Common symptoms of hyperventilation include:

• Visual impairment
• Unconsciousness
• Lightheaded or dizzy sensation
• Tingling sensations
• Hot and cold sensations
• Muscle spasms

Breathing normally is the best treatment for hyperventilation.
It restores the proper carbon dioxide level in the blood stream of your body. Sensors pick up on the lowered levels and restores normal breathing.

Another device is breathing into a paper bag (mixture begins to build up the amount of carbon dioxide which you inhale. This increases the concentration of carbon dioxide in your blood. (restores normal breathing). Talking aloud does the same thing. It prevents the release of carbon dioxide. Since, if you're still alive :):) , your cells continue to form carbon dioxide from normal respiration and the symptoms of hyperventilation disappear. The concentration of carbon dioxide rises in the blood. The pH of your blood lowers to the normal value of 7.42. (blood pH is slightly alkaline)

These methods of reversing the effects of hyperventilation will help after you recognize the symptoms.

Histotoxic Hypoxia

Histotoxic Hypoxia

In histotoxic hypoxia cells cannot use oxygen effectively. In this type of hypoxia the supply of oxygen is normal. Compromised is  the ability to use the oxygen.

Cellular respiration is the process where nutrients, after digestion into membrane selectable molecules, proceed into a series of chemical changes to produce ATP that provides the energy for the body to function.

There are both physical and chemical means to limit the ability of a cell's use of oxygen.

The beauty of the human body is the creation of energy at normal body temperature. (98.6 degrees Fahrenheit) Factors that may effect metabolism and cellular respiration is changes in the enzymes that catalyze the chemical reactions. Since these enzymes are located in a living human or lower animal they are called bio-enzymes. They need a perfect environment to operate and allow chemical reactions to proceed at body temperature. 

The practice of Medicine is the care of the body Systems that help, in normal conditions, to maintain this perfect environment for all the enzymes in the body. Oxygen is the final reactant, in this whole process that forms the ATP, that each and every cell in the body uses to produce its specific function.

Temperature changes, pH(Acidic Measurement), Concentrations of  liquid solutes, Trauma to the body (Shaking, automobile accident), Inorganic co-enzymes, and the concentration of enzymes themselves may change the enzyme or stop its production to prevent it from catalyzing its particular function. When that happens the entire reaction chain stops. Oxygen isn't utilized until the body can return itself to a perfect operating environment.

If this is serious the body may need a physician to help in the recovery.

There are substances that can affect the ability of an enzyme to attach to a chemical that is necessary for a reaction to take place. When the physical shape, of an enzyme changes, it is denatured and is no longer effective.
Chemicals that bring about change are drugs that can affect the perfect environment of the enzyme. Alcohol, poisons, narcotics, drinks that are too acidic or alkaline are a few examples.

Physical factors could be trauma, changes in membrane thickness (cellular) and, of course, the altitude which controls air pressure.

Histotoxic hypoxia is a very important form of hypoxia because substances that we eat, smell or absorb can interfere with the physiology of cells.

Stagnant Hypoxia

Stagnant Hypoxia

Stagnant means “not flowing,” and stagnant hypoxia, or ischemia, results when the oxygen-rich blood in the lungs is not moving, for one reason or another, to the tissues that need it. 

An arm or leg “going to sleep” because the blood flow has accidentally been shut off is one form of stagnant hypoxia.

On a more serious note, this kind of hypoxia can also result from shock, the heart failing to pump blood effectively, or a constricted artery. 

A rapid pull up from a steep dive causes a Grey Out due to excessive g-forces that occur during the recovery. This is due to the inability to move oxygen-rich blood to the brain. A Black Out is more pronounced.

Cold temperatures also can reduce circulation and decrease the blood supplied to extremities.

The illustrations with stagnant hypoxia are important but the underlying physiology is simpler.

Hypemic Hypoxia

Hypemic Hypoxia

When blood cannot supply enough oxygen to all the cells in our body it is called hypemic hypoxia. 

The oxygen deficiency is not caused by a lack of inhaled oxygen from the atmosphere. Severe bleeding (reduced blood volume), certain blood diseases (anemias), smoking (carbon monoxide ), altitude and whole blood donations (lack of red blood cells in sufficient numbers) are conditions that may occur to cause the lack of oxygen for normal functioning. Carbon monoxide presence is the most common and affects a blood molecule called hemoglobin.

Hypemic hypoxia is the result of hemoglobin that can't  chemically bind oxygen molecules. Why can't they bind the oxygen?

Engines produce a colorless, odorless  gas named carbon monoxide (CO). It provides the competition for the oxygen binding sites on the hemoglobin molecule when it is present in the air you breath inside the cockpit. In automobiles, an additive is added to the gasoline they burn that warns the occupants that exhaust fumes exist inside the car that contains carbon monoxide molecules. If you ignore the warnings, and fail to open windows for proper ventilation, your blood hemoglobin binding sites are occupied by carbon monoxide rather than oxygen. Remember carbon monoxide has a much greater attraction for hemoglobin than oxygen.

The affinity of carbon monoxide for hemoglobin binding sites is twenty times that of oxygen. It creates an unfair disadvantage for oxygen. Oxygen loses the binding site competition and you can lose you life if you don't respond to the warnings that carbon monoxide is present in your car or planes passenger compartment.

Your plane engine, through the mixture control, is adjustable to eliminate most of the unburned fuel. When you back off on the mixture control by 25 to 50 degrees, the presence of carbon dioxide is there, but virtually undetectable by your sense of smell.

Since the carbon monoxide is twenty times more likely to bind to oxygen the net result of the exhaust leak into a planes interior is you become unconscious before you detect the exhaust leak. If you can't respond the plane will crash.

You may read stories, periodically, about young couples found dead in "Lovers Lanes" because of carbon monoxide poisoning. It is unmistakeable,  because the skin is bright red from carbon monoxide  when the couple is found.

There is a fix. There are carbon monoxide detectors, on the market, that provide visual indications or beep a loud, distinctive sound, or both, that carbon monoxide is present.

You respond by increasing the fresh air ventilation. You just prevented a life threatening event from happening by responding, with knowledge. The correct fix is fresh air immediately to refresh your body with the oxygen it requires. 

Hypoxia takes many forms and you just found a very important way to avoid hypoxia in aircraft.