AHF 2203 AVIATION HUMAN FACTORS Presentation 2: The Atmosphere and Hypoxia

Recapitulate Lets recap what we have done last session: – Definition of Physiology and Flight Physiology. – Importance of Flight Physiology. – Basic Concept of The Nervous System. – Basic Concept of The Respiratory System. – Basic Concept of The Circulatory System.

Presentation Outline Part 1: Introduction to Earth’s Atmosphere Part 2: Hypoxia

Learning Outcomes At the end of this session, student should be able to: – Know that pressure plays the important role during altitude changes – Classify the types of hypoxia, it causes, symptoms, and prevention steps through the explanation. 4Presented by Mohd Amirul for AMC

EARTH’S ATMOSPHERE

Air is one of the primary things that makes life on Earth possible. Air is a synonym for atmosphere. The Earth’s atmosphere or air is made up of a variety of gases and other particles. Earth’s Atmosphere

Cont. What is the Atmosphere?? – layer of gases surrounding the planet Earth that is retained by Earth's gravity. Gases in atmosphere: – 78% - Nitrogen – 21% - Oxygen – 1% - Other gases (Argon, Carbon Dioxide, Neon, Helium)

Layers (Structure) of Atmosphere

Troposphere – Temperature will decrease constantly with altitude. – 75% of weight of atmosphere. – Contains almost all weather – Altitude (height) vary with: Latitude: lower at poles and higher at equatorial Seasons: higher in summer than winter – Almost all clouds in this layer. – Almost commercial aircrafts fly in this layer. Cont.

Stratosphere – Very small increase in temperature (almost constant) except at the top where temperature is zero at 50 kms. – Little water turbulence Cont.

Functions of the Atmosphere Source of oxygen and carbon dioxide Protection for the human on the Earth from the harmful cosmic ray, solar radiation and ultraviolet (UV) ray. Source of rain Maintains the temperature and climate that sustain life on earth

Variation in Atmosphere The earth’s atmosphere varies in – Temperature – Pressure – Density – Humidity

Atmospheric Pressure Atmospheric pressure is the combined weight of all the atmospheric gases, creating a force upon the surface of the earth – the cause of this force is gravity The atmospheric pressure can be measured in force / unit area (Pounds per square inch [Psi] or Millimeters of mercury [mm/Hg]) The standard atmospheric pressure at sea level is 760 mm/Hg. It is the combination of: GasesPressure [mm/Hg] Oxygen100 Carbon dioxide40 Nitrogen573 Water Vapor47 Total760

Pressure and Temperature Decrease with Altitude Altitude (Feet)Pressure (mm/ Hg) Temperature (degree Celsius) , , , ,

Pressure & Temperature Air Pressure – At sea level, the air pressure is about – At sea level, the air pressure is about 760 mm/Hg. – As the altitude increases, the air pressure decreases (and there is less oxygen to breathe). Temperature – As we ascend from the surface, the temperature falls steadily with altitude. – Temperature decreases at about 2°C per 1,000 feet.

Physiological Zones of the Atmosphere Atmosphere can be divided into 2 physiological zones, which are efficient and deficient. These zones can affect us medically and physiologically. EFFICIENT ZONE : Sea level to 10,000 feet DEFICIENT ZONE : 10,000 to 50,000 feet 10,000 50,000 18,000 ft 63,000 ft

Cont. Physiological-efficient zone Between sea level to approximately 12,000 feet Represents where the human body can adapt the environment. The oxygen levels are usually sufficient for human body requirements. Physiological-deficient zone Between 12,000 feet to about 50,000 feet. Human cannot adapt unless they are in a pressurized cabin. Here, there is increased risk of problems, especially hypoxia, trapped-gas, and evolved-gas situations.

Definition of Hypoxia Syndromes of lack of oxygen in blood Effect mainly the brain and other nervous system

How it can be happened?? (Physiologycal Process) Hemoglobin is primary transport to carry oxygen through blood. The ability of hemoglobin to carry oxygen is called as: Blood Oxygen Saturation (normally 95%-98% at sea level). It is measurable as we ascend.

Cont When altitude is increase, the pressure of oxygen decrease. Caused the lower pressure in lungs Transfer process of carrying oxygen affected As a result, not enough oxygen to the brain and affect other part of human body. Death will follow if lack of oxygen continues.

Time of Oxygen 1 Minute 2 Minutes 3 Minutes 4 Minutes 5 Minutes 6 Minutes Put Back on Oxygen

Types of Hypoxia hypoxic hypoxia hypemic hypoxia stagnant hypoxia histotoxic hypoxia

Reduced pO 2 in the lungs (high altitude) Body tissue Red blood cells Hypoxic Hypoxia (Altitude Hypoxia) A deficiency in Alveolar oxygen exchange

Cont. Most common type of Hypoxia occur in aviation. Hypoxic hypoxia occurs when not enough oxygen is in the air or when decreasing atmospheric pressures prevent the diffusion of O2 from the lungs to the bloodstream. The partial pressure of oxygen as it is presented to the blood within the lungs is too low to effectively carry and transfer enough oxygen to the cells of the tissues.

Cont.

Can be resulted from: – Altitude exposure – Strangulation (compression of air passage cause the respiration arrest) – Other: Failure of oxygen system in aircraft Improper use of equipment Failure of depressurization system Cont.

Reduced blood flow Blood moving slowly Adequate oxygen Red blood cells not replenishing tissue needs fast enough Stagnant Hypoxia

Occurs at circulatory level A condition that interferes within the normal circulation of blood arriving at the cells. An arm or leg going to sleep because the blood flow has accidentally been shut off is one form of stagnant hypoxia. Cont.

Can occur as the result of: – G forces from maneuvers (mostly aerobatic aircraft) – Disease of the blood vessels – Cardiac (Heart) Arrest – Shock – Exposure to Cold – Sudden change in posture Cont.

The g-force, on something is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces. Accelerations not produced by gravity are termed proper accelerations, and cause stresses and strains on objects. Because of these strains, large g-forces may be destructive.

Hypemic Hypoxia Low- Haemoglobin

Occurs at blood level. An oxygen deficiency due to reduction in the oxygen carrying capacity of the blood (Low Hemoglobin) Cont.

Caused by: – Anemia (A deficiency of red blood cells) – Bleeding – Taking some prescription drug. – *Blood donation – Other: Smoking ; cabin contamination with engine exhaust fume Carbon Monoxide interferes with oxygen binding to the blood Cont.

*Blood Donation:  Symptoms of hypoxia at lower altitudes  Most airlines: – No flight for 72 hours after donation of whole blood – No flight for 12 hours after donation of plasma Cont.

Red blood cells retain oxygen Inability of the cell to accept or use oxygen Poisoned tissue Adequate oxygen Histotoxic Hypoxia Alcohol

Occurs at cell level Interferes with the normal utilization of oxygen into the cells. – plenty of oxygen is being transported to the cells that need it, but they are unable to make use of it. Tissue cells are poisoned and unable to use oxygen Caused by Alcohol and Drug Cont.

Why important to recognize? If hypoxia is prolonged, serious problems develop with ultimate death. In extreme cases (prior to death), some brain cells are actually killed, and they cannot be regenerated. The single most dangerous characteristic of hypoxia is that if the crewmember is hypoxic and engrossed (complete attention) in flight duties, the pilot might not even notice the impairment.

Stage of Hypoxia INDIFFERENT STAGE – earliest symptoms-effect on the eye. (Decrease in night vision) COMPENSATORY STAGE – – Physiological compensations provide some defense against hypoxia so that the effects are reduced unless the exposure is prolonged or unless exercise is undertaken. Respiration may increase in depth or slightly in rate, and the pulse rate, the systolic blood pressure, the rate of circulation, and the cardiac output increases. – Symptoms: poor judgement, drowsiness(sleepy state), impaired coordination, impaired efficiency. DISTURBANCE STAGE – In this stage the physiological compensations do not provide adequate oxygen for the tissues. – Chance of recovery greatly diminished. – Symptoms: impaired in flight control, handwriting, speech, coordination CRITICAL STAGE – – Unconsciousness (e.g: blackout, faint) – In the critical stage consciousness is lost. Death follows shortly.

Sign and Symptoms of Hypoxia Sign- can detected by observer/ crew members Symptoms-perceived by crew members

Sign of Hypoxia Increase in depth and rate of breathing Cyanosis (A blurry effect of the skin, most noticeable on the lips and the fingernail) Delayed in reaction time Poor Judgment

Symptoms of hypoxia Air Hunger ( a feeling not enough breathable air) Feeling of fearful or anxiety (nervousness) Mental confusion Fatigue Nausea (just before vomit) Headache Dizziness Hot and cold flashes Tingling (Prickle) Visual Impairment (colour vision, night vision, blurred)

How to prevent?? Reduce tolerance to altitude (descends) – Don’t fly to high altitude By enriching the inspired air with oxygen from an appropriate oxygen system (Oxygen Tank & Mask) By maintaining a comfortable, safe cabin pressure altitude (Cabin Pressurization)

Avoid alcohol and smoking Healthy Diet Good physical condition Lower altitudes Avoid temperature extremes Slower Climb rates

Corrective action Once the symptoms/sign are identified, the corrective action must be taken (based on FAR): – Wear oxygen mask – Turn on Oxygen – Make sure all connection secure – Slow down your breath rate – Descend to altitude where supplementary oxygen no longer required.

Supplemental Oxygen

Effective Performance Time (EPT) EPT is the period of time that a pilot has from the time oxygen become less available until the time when he or she loses the ability to recognize and take action If someone goes beyond EPT, then he or she isn’t even aware of the problem and will not take corrective action The keyword is EFFECTIVE or USEFUL (He or she might be conscious but not making expected useful or effective decision). EPT decrease as altitude increases.

Conclusion The danger of hypoxia is that the pilot is probably unsuspecting that he/she is hypoxic. The key to flying safe at high altitude is to recognize: – The conditions under which you could be hypoxic. – The physical and mental symptoms that indicate you are hypoxic. – When a crewmate is susceptible to hypoxia in those conditions. 47Presented by Mohd Amirul for AMC

Key Points Atmospheric Layer Variation of pressure and temperature with altitude Physiological zone of atmosphere Definition of Hypoxia Physiological Process of Hypoxia Types of Hypoxia Stage of Hypoxia Sign and symptoms of Hypoxia Prevention and Correction of Hypoxia EPT 48Presented by Mohd Amirul for AMC

End of Presentation #2 5 Minutes for Q/A session 49Presented by Mohd Amirul for AMC