Atmospheric Effects on Human Performance

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Questions and Answers

What is the temperature at sea level in the International Standard Atmosphere (ISA)?

25 °C

15 °C (correct)

10 °C

0 °C

At what altitude is atmospheric pressure approximately ½ of mean sea level (MSL) pressure?

36,000 ft

8,000 ft

14,000 ft

18,000 ft (correct)

What happens to temperature as altitude increases according to the lapse rate?

Temperature increases

Temperature decreases (correct)

Temperature fluctuates unpredictably

Temperature remains the same

What is the approximate temperature at an altitude of 36,090 ft (11 km)?

-56.5 °C Signup and view all the answers

Which gas constitutes the largest percentage of the Earth's atmosphere?

Nitrogen (N2) Signup and view all the answers

What is the transition altitude (TA) in aviation?

The altitude aircraft use local barometer readings Signup and view all the answers

What does FL290 represent in aviation terms?

29,000 ft above sea level Signup and view all the answers

According to Boyle's Law, what happens to gas pressure when volume increases?

Pressure decreases Signup and view all the answers

Which of the following is NOT a risk factor for hypertension?

Being physically active Signup and view all the answers

What is considered primary (essential) hypertension?

Hypertension with no identifiable cause Signup and view all the answers

Which of the following methods is recommended to reduce high blood pressure?

Meditation or yoga Signup and view all the answers

Which condition is NOT a result of hypertension?

Enhanced cognitive function Signup and view all the answers

Which of the following dietary changes can help in managing blood pressure?

Eating more potassium-rich foods Signup and view all the answers

What is the correct definition of cardiac output?

The amount of blood pumped by each ventricle in one minute Signup and view all the answers

Which of the following is a secondary cause of hypertension?

Obstructive sleep apnea Signup and view all the answers

What can be a possible effect of excessive alcohol consumption on blood pressure?

Increased blood pressure Signup and view all the answers

What is the formula to calculate cardiac output (CO)?

CO = HR × SV Signup and view all the answers

What is the average stroke volume (SV) for a 70 kg individual?

70 mL Signup and view all the answers

Which of the following is NOT a common cause of coronary artery disease?

Regular exercise Signup and view all the answers

What is a common symptom of coronary artery disease?

Chest pain (angina) Signup and view all the answers

How much blood does an average adult male have?

5-6 litres Signup and view all the answers

What is the mean temperature of human blood?

38 degrees Celsius Signup and view all the answers

Which risk factor is associated with both coronary artery disease and high blood pressure?

Smoking Signup and view all the answers

What blood characteristic contributes to its higher viscosity compared to water?

Presence of blood cells Signup and view all the answers

What is one of the primary functions of hemoglobin in red blood cells?

Acting as a buffer Signup and view all the answers

Which of the following is NOT a function of platelets?

Carrying oxygen in the blood Signup and view all the answers

Anemia can be reported in a blood test as low:

Hemoglobin or hematocrit Signup and view all the answers

What can lead to insufficient oxygen carried in the blood?

Deficiency of iron Signup and view all the answers

How do platelets contribute to stopping bleeding?

By forming temporary platelet plugs Signup and view all the answers

What is the arterial oxygen saturation range in the Indifferent Stage/Zone?

98% to 87% Signup and view all the answers

At which altitude does the Compensatory Stage/Zone begin?

10 000 ft Signup and view all the answers

Which of the following symptoms occurs in the Disturbance Stage/Zone?

Drowsiness Signup and view all the answers

What is a critical symptom of the Critical Stage/Zone?

Loss of consciousness Signup and view all the answers

How does arterial oxygen saturation change in the Compensatory Stage/Zone?

Decreases from 87% to 80% Signup and view all the answers

Which altitude marks the end of the Disturbance Stage/Zone?

20 000 ft Signup and view all the answers

What physiological adaptation occurs in the Compensatory Stage/Zone to maintain homeostasis?

Increased respiratory rate Signup and view all the answers

What is one of the primary effects of hypoxia starting at around 12 000 ft?

Short-term memory loss Signup and view all the answers

Study Notes

Human Performance and Limitation

Human bodily functions can be affected by factors like altitude, pressure, temperature, acceleration and perception changes while in flight.

Atmosphere

The International Standard Atmosphere (ISA) is a model that shows how Earth's atmosphere changes with altitude.
The ISA at sea level has a temperature of +15°C, pressure of 1013.25 mbs (760 mm Hg), and density of 1225 g/m³.

Lapse Rate

Temperature decreases with altitude, with a lapse rate of 1.98°C/1000 ft (6.5°/km) up to 36,090 ft (11 km).
Above 36,090 ft, temperature remains constant at -56.5°C up to 65,617 ft (20 km).

Atmospheric Pressure

Pressure decreases with altitude.
At approximately 36,000 ft, pressure is ¼ of sea level pressure.
At approximately 18,000 ft, pressure is ½ of sea level pressure.
At approximately 8,000 ft, pressure is ¾ of sea level pressure.

Composition of the Atmosphere

Earth's atmosphere is composed of:
- Oxygen (O2) 21%
- Nitrogen (N2) 78%
- Argon (Ar) 0.93%
- Carbon dioxide (CO2) 0.03%
- Rare gases 0.04%
This composition remains relatively constant up to about 70,000 ft (21 km).

Altitude in Aviation

Altitude refers to elevation above mean sea level (MSL).
Height refers to the vertical distance of an aircraft above the airfield elevation.
Transition Altitude (TA) is the altitude above sea level where aircraft switch from using local barometric altitudes to flight levels.
Flight Level (FL) represents altitude in thousands of feet above a standard pressure datum of 1013.2 mb. For example, FL290 means the aircraft altimeter indicates 29,000 ft.
Cabin altitude refers to the pressure maintained within the aircraft cabin.

Physical Gas Laws

The text mentions key gas laws including Boyle's Law, Dalton's Law, Henry's Law, and the General Gas Law.

Hypertension (High Blood Pressure)

It's a condition where blood pressure is consistently high.
Primary (essential) hypertension has no identifiable cause.
Secondary hypertension is caused by other medical conditions:
- Obstructive sleep apnea
- Kidney problems
- Adrenal gland tumors
- Thyroid problems
- Certain birth defects in blood vessels
- Medications (birth control pills, cold remedies, decongestants, pain relievers)
- Illegal drugs (cocaine, amphetamines)

Hypertension Risk Factors

Age
Race
Family history
Being overweight or obese
Not being physically active
Using tobacco
Excessive salt intake
Low potassium intake
Drinking too much alcohol
Stress
Certain chronic conditions
Pregnancy (sometimes)

Reducing High Blood Pressure

Lifestyle Modifications:
- Increase activity and exercise.
- Lose weight if overweight.
- Reduce sugar and refined carbohydrates intake.
- Increase potassium intake and decrease sodium intake.
- Limit processed food consumption.
- Stop smoking.
- Manage stress.
- Try meditation or yoga.
Other Strategies:
- Eat dark chocolate.
- Use medicinal herbs.
- Ensure restful sleep.
- Consume garlic or take garlic extract supplements.
- Eat healthy high-protein foods.
- Take BP-lowering supplements.
- Moderate alcohol consumption.
- Reduce caffeine intake.
- Consider prescription medication.

Cardiac Output

Cardiac output (CO) is the amount of blood pumped by each ventricle per minute.
Stroke volume (SV) is the amount of blood pumped by each ventricle per beat.
Heart rate (HR) is the number of heart contractions per minute (beats per minute, bpm).
Mean CO for a 70 kg person is 5.25 L/min, with a range of 5.0–5.5 L/min for an average person.
CO is calculated as: CO = HR * SV

Major Factors Influencing Cardiac Output

This section points to a resource (video) for more information on factors influencing cardiac output.

Coronary Artery Disease

Occurs when blood vessels supplying the heart become diseased or damaged.
Symptoms include:
- Chest pain (angina)
- Shortness of breath
- Heart attack

Coronary Artery Disease Causes

Smoking
High blood pressure
High cholesterol
Diabetes or insulin resistance
Sedentary lifestyle

Coronary Artery Disease Risk Factors

Age
Diabetes
Sex
Overweight or obesity
Family history
Physical inactivity
Smoking
High stress
High blood pressure
Unhealthy diet
High blood cholesterol levels

Other Coronary Artery Disease Risk Factors

Sleep apnea
High-sensitivity C-reactive protein (hs-CRP)
High triglycerides
Homocysteine
Preeclampsia
Alcohol use
Autoimmune diseases

Facts About Blood

Blood makes up approximately 8% of an adult's body weight.
Females have about 4-5 liters of blood, while males have about 5-6 liters.
Blood temperature is about 38 degrees Celsius.
Blood pH is slightly basic, ranging from 7.35 to 7.45.
Blood is 4.5-5.5 times more viscous than water.
Arterial blood is brighter red due to higher oxygen levels.
There's no artificial substitute for human blood.

Platelets (Trombocitai)

Platelets have several functions:
- Secrete vasoconstrictors to constrict blood vessels during bleeding.
- Form temporary platelet plugs to stop bleeding.
- Secrete procoagulants to promote blood clotting.
- Dissolve blood clots when no longer needed.
- Digest and destroy bacteria.
- Attract neutrophils and monocytes to inflammation sites.
- Secrete growth factors to maintain blood vessel linings.

Platelet Function During Bleeding

The text explains the steps involved in blood clotting:
- Vascular spasms: Constriction of blood vessels.
- Platelet plug formation: Formation of a temporary plug over the injured area.
- Blood clotting (coagulation): Formation of a stable clot.

Hemoglobin (Hemoglobinas)

Hemoglobin is a metalloprotein found in red blood cells.
Normal hemoglobin levels:
- Male adults: 13.8 – 17.2 g/dL
- Female adults (non-pregnant): 12.1 – 15.1 g/dL

Hemoglobin Functions

Oxygen carrier
Carbon dioxide carrier
Gives blood its red color
Maintains red blood cell shape
Acts as a buffer
Interacts with other ligands
Degradation produces physiologically active catabolites

Insufficient Oxygen Carried

Causes of insufficient oxygen carried include:
- Anemia: Low number of red blood cells or hemoglobin.
- Insufficient oxygen pressure in the air
- Lack of iron

Anemia (Mažakraujystė)

Anemia is characterized by a low number of red blood cells.
Diagnosed through low hemoglobin or hematocrit readings in a blood test.

Altitude and Hypoxia

The text describes the four stages of hypoxic hypoxia at different altitudes:

1. The Indifferent Stage/Zone (GL - 10,000 ft)

Arterial oxygen saturation: 98% to 87%
Dark adaption is negatively impacted (can be affected as low as 5,000 ft).
Visual sensitivity decreases by approximately 10%.
Performance of new tasks may be impaired.
Heart and breathing rates increase slightly.

2. The Compensatory Stage/Zone (10,000 ft - 15,000 ft)

Arterial oxygen saturation: 87% to 80%
Physiological responses compensate for hypoxia to maintain homeostasis.
These responses include:
- Increased respiratory volume
- Increased cardiac output and blood pressure
Hypoxia-induced CNS effects include:
- Drowsiness
- Decreased judgment and memory
- Difficulty in performing complex tasks
- Short-term memory loss (detectable from about 12,000 ft)

3. The Disturbance Stage/Zone (15,000 ft - 20,000 ft)

Arterial oxygen saturation: 80% to 65%
Physiological responses are no longer sufficient for adequate oxygenation.
Symptoms:
- Euphoria
- Dizziness
- Sleepiness
- Headache
- Fatigue
- Intellectual impairment and slow thought processes
- Memory impairment
- Severely impaired motor performance
- Loss of judgment
- "Grey-out" and tunnelled vision

4. The Critical Stage/Zone (20,000 ft - 23,000 ft)

Arterial oxygen saturation: 65% to 60%
Mental performance deteriorates rapidly.
Confusion and dizziness occur within minutes.
Loss of consciousness and incapacitation occur with little warning.

Summary of Body Oxygen Requirement at Altitude

Factors influencing the severity and susceptibility to hypoxic hypoxia:
- Altitude

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Description

Explore how altitude, pressure, and temperature affect human bodily functions during flight. This quiz covers topics like the International Standard Atmosphere and the lapse rate, providing essential knowledge for understanding aircraft operations and human limitations at various altitudes.