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Prepare for Hypoxia

Hypoxia is one of the most well-known physiological complications affecting pilots. While the FAA and DoD do an excellent job of educating pilots on the negative consequences of hypoxia and symptom recognition, there is not much readily obtainable information on what pilots can do to train and/or prepare their bodies to operate in a hypoxic situation. The purpose of this article is to provide a few evidence-based tips pilots can implement to improve the body’s blood circulation and maximal oxygen uptake (two mechanisms related to reducing the implications of hypoxia and extending useful time of consciousness).


Hypoxia is an environmentally dependent condition in which the body does not have adequate oxygen supply to perform necessary functions (Davis). It occurs when the tissues in the body do not receive enough oxygen. Hypoxia can be caused by several factors including an insufficient supply of oxygen, inadequate transportation of oxygen at the cellular level, or the inability of the body tissues to use oxygen properly.


Four types of hypoxia are relevant to pilots: hypoxic, hypemic, stagnant, and histotoxic.


  1. Hypoxic: This form of hypoxia is related to the partial pressure of oxygen in the atmosphere. As the pressure of the ambient air decreases, the molecules of oxygen separate and exert less pressure. At a threshold ambient PSI, the lungs become unable to transfer oxygen to the cells.

  2. Hypemic: Hypemic hypoxia is caused by the blood’s reduced ability to carry oxygen to the cell regardless of the percentage or pressure of oxygen in the air. This means that a pilot with adequate oxygen flow could still be hypoxic as their blood is not transporting the oxygen properly/sufficiently. The primary cause of hypemic hypoxia is carbon monoxide exposure/inhalation (heater malfunctions, engine manifold leakage, cockpit contamination, etc.). Carbon monoxide attaches itself to the hemoglobin about 200 times more easily than oxygen, preventing the blood from carrying oxygen.

  3. Stagnant: This is an oxygen deficiency in the body due to poor circulation of the blood (occurring at the circulatory level). This can result from inadequate blood pressure, arterial constriction, or cold temperatures (blood flow decreased to the extremities). During flight, stagnant hypoxia can be the result of pulling excessive sustained positive Gs, or while operating an aircraft in cold weather conditions without cabin heat.

  4. Histotoxic: The inability of cells to effectively use oxygen. Although oxygen may be present, the impairment of the cell simply does not allow for any oxygen uptake. This cellular impairment is usually attributed to alcohol, narcotics and poisons.

The physiological symptoms of hypoxia vary from person to person, but will ultimately lead to death if left untreated. Common symptoms include nausea, headaches, numbness or tingling in the arms and legs, blurred vision, denial, euphoria, and reduced dexterity. Below are a few tips our team recommends to ensure the body is as prepared as possible for a hypoxic situation in the cockpit:


  1. Breathe Diaphragmatically: To execute this breathing technique, inhale slowly and deeply through the nose. The diaphragm should inflate while the chest remains neutral. Exhale slowly through the nose, allowing the diaphragm and abdomen to to fall inward. Maintain this breathing cycle as frequently as possible until it becomes an autonomous habit.

  2. Denitrify the Body: To avoid ingesting excess nitrogen, ensure your water supply contains less than 10 mg of nitrate per liter, avoid cured meats (that are preserved with nitrate or sodium nitrate), and avoid deep sea diving within 24 hours of a flight.

  3. Minimize Distractions: The insidious nature and possibility of rapid onset hypoxia requires pilots to continually be self-aware. Ensuring pilots have the mental clarity to monitor their bodies for any symptoms of hypoxia is an essential skill for in-flight safety. Eliminate anything that leads to a distraction or deviation from the pilot action priorities (aviating, navigating, and communicating).

  4. Get Proper Rest: Our team recommends frequently reflecting on the quality of sleep you are getting and whether it is setting you up for peak performance. A few reflective questions include: Are you sleeping in total darkness? Are you breathing through your nose? Are you exercising or eating dinner within two hours of bed time?

  5. Improve Physical Fitness: Increasing oxygen uptake comes from using varied training modalities to condition the aerobic system. Increased oxygen to the brain, the release of endorphins, increased lean muscle mass and improved immune system function are a few of the benefits associated with consistent physical training.

  6. Utilize Oxygen Training Tables: Using a diaphragmatic breathing pattern, inhale for four seconds and exhale for eight seconds (4/8) while being as relaxed as possible. Continue this 4/8 cycle consistently for two minutes. At the end of the two minutes, perform a maximal breath hold. When you can no longer hold your breath, inhale through the nose and begin the 4/8 cycle again. The end of each maximal breath hold signifies the end of a set. Perform two-three sets on a daily basis.

  7. Attend Altitude Chamber Training: Participating in an altitude chamber training course is the best (and only) way to safely identify personal symptoms of hypoxia. In the Air Force, all rated personnel are required to attend a physiological altitude chamber training course. This course helps aircrew recognize personal symptoms of hypoxia and allows them to practice the procedure for a hypoxic situation in a controlled environment. My personal symptoms include euphoria and tingling in the hands and fingers. Should I ever experience these symptoms, I will ‘gang load’ the on-board oxygen generating system (or pull the supplemental oxygen) and immediately descend to below 10,000 feet MSL. Our team recommends attending an altitude chamber training session in order to experience a rapid decompression in a safe environment, and to identify personal symptoms of hypoxia.

We hope these seven tips provide you with a basic understanding of how to naturally increase circulation and maximal oxygen uptake, as well as how to prepare for a physiological incident at altitude. Applying these tips will help prepare the body for an unexpected hypoxic incident in the aircraft. As always, please consult a certified aviation medical examiner or flight surgeon with specific questions. For more information or to learn more about how our team is preparing pilots for peak performance, please contact our team at www.grindtofly.com/contact. Thank you for sharing and keep grinding!


Sources:

  1. https://www.faa.gov/pilots/training/airman_education/topics_of_interest/hypoxia/

  2. https://www.medicinenet.com/hypoxia_and_hypoxemia/article.htm

Attend an FAA Physiological Training Course:

https://www.faa.gov/pilots/training/airman_education/aerospace_physiology/cami_enrollment/



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