Humans in Extreme Environmental Pressures PDF
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Uploaded by NiftySeal
University of Glasgow
Dr Greg Logan
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Summary
This document explores how humans respond to extreme environmental pressures, focusing on high and low pressure situations, altitude, and space. It evaluates the effects of total pressure, duration of exposure, and other factors on the human body. The document also briefly touches on the topic of acclimatization to altitude and the concept of the death zone related to high altitudes.
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HUMANS IN EXTREME DR GREIG LOGAN ENVIRONMENTAL [email protected] PRESSURES By the end of this session, you should be able to… Define what is meant by extreme environmental pressure Give examples of the types of environments you will find these extremes Expl...
HUMANS IN EXTREME DR GREIG LOGAN ENVIRONMENTAL [email protected] PRESSURES By the end of this session, you should be able to… Define what is meant by extreme environmental pressure Give examples of the types of environments you will find these extremes Explain how the human body reacts and adapts to pressure Describe future challenges humans may encounter with extreme pressures DEFINING PRESSURE Pressure is the amount of force applied at right angles to the surface of an object per unit area. The symbol for it is "p" or P. WHAT DO WE MEAN BY EXTREME PRESSURE? High pressure WHY? 214 metres EXTREME NATURAL PRESSURE WHAT DO WE MEAN BY EXTREME PRESSURE? Low pressure BUT WHAT ACTUALLY LIMITS HUMANS AT THESE EXTREMES? What are the main limiting variables for the human body at high and low pressures? EFFECTS OF PRESSURE ON THE HUMAN BODY The effects of pressure on the human body vary according to the following factors: Total pressure Duration of exposure to pressure State of activity (resting or exercising) Temperature Drugs in the body Gas mixtures inspired Rate of ascent/descent EFFECT OF EXTREME HIGH PRESSURE BOYLE’S LAW WHAT IS PARTIAL PRESSURE? The pressure exerted by an individual gas in a mixture is known as its partial pressure. HENRY’S LAW NITROGEN NARCOSIS Martini’s law Reduced mental acuity Perception of time affected Perceptual narrowing Light-headedness Vomiting THE BENDS Decompression sickness (DCS) Retention of dissolved nitrogen on decompression Causes bubbles Symptoms: Joint pain Rashes Paralysis Death What happens to the body under extreme oceanic pressure? Ear and sinus pressure Nitrogen narcosis Ruptured capillaries Blackout Inability to inspire gasses Collapsed lungs The bends Death ALTITUDE AND LOW PRESSURE LOW PRESSURE ENVIRONMENTS: ALTITUDE Density of air is not constant Altitude increase = non-linear air density decrease Air ‘gets thinner’ ACUTE EFFECTS OF EXTREME ALTITUDE When humans are exposed to altitude >5500m Partial Pressure of Oxygen (PaO2) decreases with altitude 1/3 of sea level POa2 at Everest summit (8848m) Arterial PO2 reduced Plasma volume decreases by ~20% Sensed by carotid body chemoreceptors: Increased respiratory rate Increased heart contractility and rate Increased urination Non-essential body functions suppressed ACCLIMATISATION TO ALTITUDE Occur > 4 days at altitude Adaptation can be approximated by multiplying the altitude in kilometres by 11.4 days Erythropoietin (EPO) produces more haemoglobin Increased ability to transport oxygen Decreased plasma volume Increased capillarisation in skeletal muscle tissue Increased muscle mitochondria Right ventricular hypertrophy ABOVE 8000M – THE DEATH ZONE 14 summits above 8000m Extreme hypoxia O2 used up faster than it can be replenished No human can acclimatize Rapid deterioration of bodily functions Loss of consciousness ACUTE DISORDERS AT ALTITUDE High-altitude cerebral oedema High-altitude pulmonary (HACE) oedema (HAPE) Retention of cerebral fluid Pulmonary hypertension “Brain swelling” Acute mountain sickness (AMS) Increased hydrostatic pressure Loss of consciousness Headache Increased permeability of Fever GI disturbance vascular epithelium Ataxia Nausea “Stress failure” Altered mental state Vomiting Leakage of cells and protein into Hypocapnia (low CO2) Insomnia alveoli Fatigue Dizziness EFFECTS OF NO PRESSURE: SPACE No gravity to move blood and other body fluids to legs – “puffy head, chicken legs” Reduced cardiac work – decreased CO Muscle wastage Reduction in bone density Dizziness FURTHER READING Extreme environments: https://www.physoc.org/careers/research/extreme-environments/ Under water: https://www.cambridge.org/core/journals/epidemiology-and-infection/article/human-physiology-under-high-pressure-i- effects-of-nitrogen-carbon-dioxide-and-cold/4E03863DF8C348A2AEB13803D1E3349A https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5801574/ Altitude: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2151873/ Space: https://www.physoc.org/careers/research/space-physiology/
