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Section 05:
Exercise Performance and
Environmental Stress
Chapter 25 – Exercise and Thermal Stress
Chapter 24 – Exercise at High and Medium Altitude
Chapter 26 – Sport Diving
Chapter 27 – Microgravity: The Final Frontier
HPHE 6710 Exercise Physiology II
Dr. Cheatham
Chapter 25
Exercise and Thermal Stress
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Chapter Objectives
• Understand the physiological mechanisms in response to heat and cold exposure
• Understand the physiological responses during exercise in the heat and the cold
• Understand heat and cold acclimatization
• Understand the different types of heat illness
• Understand factors that modify the responses to heat and cold
Introduction
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Part 1
Mechanisms of Thermoregulation
Thermal Balance
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Hypothalamic Regulation of Temperature
• Hypothalamus
– Central coordinating center for temperature regulation
• Activation of body’s heat‐regulating mechanisms
– Thermal receptors in the skin
– Changes in blood temperature perfusing the hypothalamus
Hypothalamic Regulation of Temperature
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Hypothalamic Regulation of Temperature
Hypothalamic Regulation of Temperature
0C, 32F
23C, 74F
36C, 97F
TCORE = 37.1C
TSET = 37.5C
TCORE = 37.1C
TSET = 37.1C
TCORE = 37.1C
TSET = 36.5C
I’m cold!
 Skin
Temp
I’m hot!
 Skin
Temp
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Hypothalamic Regulation of Temperature
Hypothalamic Regulation of Temperature
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Hypothalamic Regulation of Temperature
Thermoregulation in Cold Stress: Heat Conservation
and Heat Production
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Thermoregulation in Cold Stress: Heat Conservation
and Heat Production
Thermoregulation in Cold Stress: Heat Conservation
and Heat Production
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Thermoregulation in Cold Stress: Heat Conservation
and Heat Production
• Vascular adjustments
– Cutaneous cold receptors constrict peripheral blood vessels.
• 250 mL/min at thermoneutral; approaches zero with severe cold stress
• Begins when skin temperature < 35C and is maximal when skin temperature < 31C
– Skin temperature declines
• Muscular activity
– Shivering
• Maximal rates have been shown to be around 46% VO2max
• Hormonal output
– Epinephrine and norepinephrine (short term)
– Thyroxine (long term)
Thermoregulation in Cold Stress: Heat Conservation
and Heat Production
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Thermoregulation in Cold Stress: Heat Conservation
and Heat Production
• Individual Factors Modifying Responses to Cold
– Anthropometric Characteristics
• Surface area to mass ratio
• Body Composition
Thermoregulation in Heat Stress: Heat Loss
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Thermoregulation in Heat Stress: Heat Loss
• Radiation
– Electromagnetic heat waves
• Conduction
– Direct contact between molecules
• Convection
– Movement of adjacent air or water molecules
• Evaporation
– Vaporizing water
• Evaporative heat loss at high ambient temperatures
• Heat loss in high humidity
Thermoregulation in Heat Stress: Heat Loss
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Thermoregulation in Heat Stress: Heat Loss
Thermoregulation in Heat Stress: Heat Loss
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Thermoregulation in Heat Stress: Heat Loss
• Integration of Heat Dissipating Mechanisms
– Circulation
• Body can control dry heat loss by varying skin blood flow and thus skin temperature
• After sweating has begun, skin blood flow serves primarily to deliver to the skin the heat that is being removed by sweat evaporation.
• Skin blood flow is affected by temperature in two ways:
– Local effect on smooth muscle
– Reflexes operating through the SNS
Thermoregulation in Heat Stress: Heat Loss
36C (97F), 60% RH, 105 Watts
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Thermoregulation in Heat Stress: Heat Loss
Thermoregulation in Heat Stress: Heat Loss
• Integration of Heat Dissipating Mechanisms
– Evaporation
• Sweating begins within several seconds of the start of vigorous exercise.
• The onset time of thermoregulatory sweating is influenced by skin temperature, acclimatization status, hydration status, and non‐
thermal stimuli.
• Sweating closely parallels increase in body temperature
– First, recruitment of sweat glands increases
– Second, sweat secretion per gland increases
• Chest and back sweat first, followed by limbs
• Cooled blood returns to core to absorb additional heat.
– Hormonal adjustments
• Vasopressin and aldosterone help maintain blood volume.
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Thermoregulation in Heat Stress: Heat Loss
36C (97F), 60% RH, 105 Watts
Effects of Clothing on Thermoregulation
• Clothing Insulation (CLO Units)
– Index of thermal resistance
– A clo unit of 1 maintains a sedentary person at 1 MET indefinitely in an environment at 21C (68.8F) and 50% RH
– Factors:
Wind speed
Body movements
Chimney effect – baggy clothes
Bellows effect – movement increases ventilation of air layers
• Water vapor transfer
• Permeation efficiency factor – clothes absorb sweat
•
•
•
•
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Effects of Clothing on Thermoregulation
• Cold‐weather clothing
–Layers trap air
–Moisture properties
• Warm‐weather clothing
–Light in color
–Moisture properties
Effects of Clothing on Thermoregulation
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Effects of Clothing on Thermoregulation
Part 2
Thermoregulation and Environmental Stress During Exercise
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Exercise in the Heat
• Core Temperature During Exercise
Exercise in the Heat
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Exercise in the Heat
36C (97F), 60% RH, 105 Watts
Exercise in the Heat
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Exercise in the Heat
Exercise in the Heat
• Circulatory Adjustments
– Two competing cardiovascular demands:
• Adequate muscle blood flow for metabolism
• Adequate peripheral blood flow for thermoregulation
• Also, maintenance of blood pressure
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Exercise in the Heat
Exercise in the Heat
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Exercise in the Heat
Cardiovascular Responses
Exercise in the Heat
Cardiovascular Responses
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Exercise in the Heat
Cardiovascular Responses
Exercise in the Heat
Cardiovascular Drift
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Exercise in the Heat
• HR
– Higher in heat
• SV
– Lower in heat
• Q
– At low intensity will increase
– At higher intensities usually maintained
• a‐vO2 difference
– Usually higher in heat
• Blood Pressure
– Lower in heat
• TPR
– Usually lower in heat
Exercise in the Heat
• Exercise Performance Limitations
– Performance Effects
• VO2max is lower in hot compared to temperate environments
– 0.25 L/min lower in 49C compared to 21C
• Why?
– Decrease in muscle blood flow
– Decrease in central blood flow and thus maximal CO
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Exercise in the Heat
Exercise in the Heat
• Water Loss in the Heat: Dehydration
– Magnitude of fluid loss
• The more prolonged or intense the exercise, the greater the loss.
• Sweat rates can exceed 3 L/hour
– Significant consequences
• Dehydration may threaten health.
• Physiologic and performance decrements occur.
• For every liter of sweat loss, HR can increase by 8 b/min with a corresponding 1.0 L/min decrease in Q
– Diuretics
• Cause greater fluid loss from plasma than sweating
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Exercise in the Heat
• Water Loss in the Heat: Dehydration
– Dehydration by more than 2% of body weight will negatively impact endurance exercise
• Increased hyperthermia
– Core temperature elevations ~ 0.2C for every 1% decrease in BW
– Lowers the core temperature that can be tolerated before heat exhaustion from heat strain
– Sweating is reduced
• Increased cardiovascular strain
• Altered metabolic function
• Altered CNS function
Maintaining Fluid Balance
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Maintaining Fluid Balance
Factors That Modify Heat Tolerance
• Acclimatization
– Physiologic changes that improve heat tolerance
– Optimal acclimatization requires adequate rehydration.
– Three classical signs:
• Lower HR
• Lower core temperature
• Higher sweat rate
– After acclimatization, the threshold for sweating occurs at a lower core temperature
– Lower skin temperatures decrease cutaneous BF requirements for heat balance
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Factors That Modify Heat Tolerance
Factors That Modify Heat Tolerance
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Factors That Modify Heat Tolerance
Factors That Modify Heat Tolerance
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Factors That Modify Heat Tolerance
• Training status
–
–
–
–
Increased sensitivity and capacity of sweating response Plasma volume increases
Greater skin and GI blood flow
Larger volumes of more dilute sweat
• Age
– Age‐related differences in heat tolerance
– Some age‐related factors affect thermoregulatory dynamics.
– Children
• Lower sweating rate and higher core temperature
• Sweat is more concentrated.
Factors That Modify Heat Tolerance
• Gender
– When studies control for fitness level and relative exercise intensity, no gender differences are observed.
– Sweating – Women
– Sweat less prolifically than men despite having more heat‐activated sweat glands
– Sweat smaller volumes
– Begin sweating at higher skin and core temperatures
• Compared to men, women tend to cool faster.
• Menstrual cycle alters skin blood flow and sweating response.
• Body fat insulates body, retards heat dissipation, and adds to metabolic cost of weight‐bearing activities.
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Complications from Excessive Heat Stress
• Heat Cramps (Involuntary Muscle Spasms)
– Core temperature typically in normal range
– Due to an imbalance in fluid levels and electrolyte concentrations
– Those at risk tend to have high sweat rate and high sweat sodium concentrations
– Prevention
• Adequate fluid and electrolyte intake before and during exercise
Complications from Excessive Heat Stress
• Heat Exhaustion
• Ineffective circulatory adjustments, depletion of extracellular volume (especially PV)
• Peripheral pooling occurs, central blood volume decreases, cardiac output usually decreases
– Symptoms:
•
•
•
•
•
Weak, rapid pulse
Low blood pressure
Dizziness, headache, overall weakness
Possible decrease in sweat rate
Core temperature is elevated but not to dangerous levels (i.e. > 40C or 104F)
– Treatment
• Move to cooler location, rapid body cooling, fluids (possibly intravenously)
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Complications from Excessive Heat Stress
• Heat Stroke
– The failure of the heat‐regulating mechanisms from an excessively high core temperature
– Classic Form:
• Environmental heat overloads the body’s heat dissipating mechanisms.
• Symptoms:
– Core temp > 105F, altered mental status, absence of sweating, multisystem organ dysfunction.
– Exertional Heat Stroke:
• Extreme hyperthermia from:
– Metabolic heat load in exercise
– Challenge in heat dissipation from a hot‐humid environment
Complications from Excessive Heat Stress
• Heat Stroke (cont’d)
– Exertional Heat Stroke (cont’d):
• Symptoms:
–
–
–
–
–
Core temp > 41.5C
Sweating diminishes, skin becomes dry and hot
Inordinate strain on the CV system
Rapid breathing
Altered mental status
• Treatment:
– Rapid cooling: ice packs, alcohol rubs, whole‐body immersion in cold water or ice, intravenous fluids, EMS medical attention, drug treatment (endotoxins)
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Complications from Excessive Heat Stress
Exercise in the Cold
• Cardiovascular Responses
– At Rest:
•
•
•
•
•
Higher Q
Higher SV
No change in HR
Higher BP and TPR
a‐vO2 diff
– Lower if muscle temp decreases
– Similar between cold and neutral if muscle temp remains the same
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Exercise in the Cold
• Cardiovascular Responses
– During Exercise:
• Increased Q
• Increased SV
• No change or slight decrease in HR
• Increased BP and TPR
Note to self: Get better figure for this slide
Exercise in the Cold
• Oxygen Uptake and Systemic Oxygen Transport
– “Man in the cold is not necessarily a cold man”
– If cold stress is sufficient to decrease core temperature or muscle temperature, then:
• VO2max may be reduced
• Impairment of myocardial contractility
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Exercise in the Cold
Exercise in the Cold
• VO2max in the Cold
– Matsui et al. (1978)
• Acute exposures to 5C, 18C, and 35C
• No differences in VO2max
– Astrand and Saltin (1961)
• 20C and ‐5C
• No difference in VO2max
– Bergh (1980)
• 5 to 6% decrease for every 1C drop in core
• Probably related to decrease in max HR and thus maximum Q
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Exercise in the Cold
• Individual Factors Modifying Responses to Cold
– Anthropometric Characteristics
• Surface area to mass ratio
• Body Composition
Acclimatization to Cold
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Acclimatization to Cold
Acclimatization to Cold
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Chapter 24
Exercise at Medium and High Altitude
Chapter Objectives
• Fill in
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The Stress of Altitude
• Reduced PO2 creates a metabolic challenge.
• Oxygen transport cascade
– Progressive change in environment’s oxygen pressure and in various body areas
• Acclimatization
– Adaptations occurring due to a change in the natural environment
• Acclimation
– Adaptations produced in a controlled laboratory setting
The Stress of Altitude
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The Stress of Altitude
The Stress of Altitude
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The Stress of Altitude
Sea Level
159
94
4300 m
149
84
53
104
40
40
25
96
40
23
The Stress of Altitude
• Oxygen Loading at Altitude
– No meaningful change in Hb saturation until an elevation of 3048 m
• Examples
– At 1981 m (6500 feet)
• PAO2 at sea level = 100 mmHg (97.2% saturated)
• PAO2 at 6500 feet = 78 mmHg (~ 94% saturated)
– Mexico City Olympics (1968) (2300 m, 7546 feet)
• PaO2 = 120 mmHg (80% saturated)
• Performance decrement
– Sudden exposure to 4300 m
• VO2max decreases by 32%
– Mt. Everest
• VO2max decrease of 70%
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The Stress of Altitude
The Stress of Altitude
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The Stress of Altitude
Acclimatization
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Acclimatization
• Immediate Response to Altitude
• Increase in respiratory drive to produce hyperventilation
• Increase in blood flow during rest and submaximal exercise
– Hyperventilation
• Low PaO2 sensed by peripheral chemoreceptors
• When PIO2 drops below 110 (normal = 150) or PaO2 is less than 60 (normal = 96) ventilation increases
• Beyond these levels, ventilation increases in proportion to level of hypoxia
• Increase in ventilation increases PAO2 and decreases PACO2
• What happens during rapid exposure to low O2
– First few minutes = dramatic increase in VE
– After initial minutes = slight blunting of VE but still more than normal
– Why? Ventilation induced hypocapnia
Acclimatization
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Acclimatization
• Immediate Response to Altitude (cont’d)
– Increased cardiovascular response
• Resting SBP increases
• Submaximal exercise heart rate and cardiac output can rise to 50% above sea level values (no change in SV)
• At a given absolute workload:
–
–
–
–
Q is increased at altitude
HR is increased at altitude
SV is the same
Compensation for lower a‐vO2 difference
• However, a given absolute workload is a greater relative workload because VO2max is reduced at altitude
• If same relative workload is performed, no difference between normoxia and hypoxia
Acclimatization
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Acclimatization
• Catecholamine Response
– Plasma and urine catecholamines are higher at altitude
• Mostly due to increase in NE not E
– During first few minutes, no difference in NE
• Production is increased, but removal is also increased
– Within 14‐18 hours, an increase in NE is observed
• Production is increased, but removal is decreased
• Splanchnic removal is proportional to arterial concentration
Acclimatization
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Acclimatization
Acclimatization
• Longer‐Term Adjustments to Altitude
• Regulation of acid‐base balance altered by hyperventilation
• Synthesis of hemoglobin and red blood cells
• Elevated sympathetic neurohormonal activity
– Acid‐Base Readjustment
• Hyperventilation causes a decrease in PCO2
– Increase in pH
– Kidneys begin to excrete bicarbonate
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Acclimatization
• Longer‐Term Adjustments to Altitude (cont’d)
– Hematologic Changes
• Initial plasma volume decrease
– Shift from intravascular space to interstitial and intracellular space
» Increases red blood cell and hemoglobin concentration
– Diuresis
» Maintains fluid balance between the compartments even though total body water is reduced
• Red blood cell mass increases
Acclimatization
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Acclimatization
• Longer‐Term Adjustments to Altitude (cont’d)
– Cellular Changes
• Capillary adjustments
• Increased myoglobin
• Increased mitochondrial density
• Increased 2,3‐DPG levels
Altitude Training and Sea‐Level Performance
• Performance upon return is not improved if using VO2max as the criteria
• Altitude acclimatization improves ability to perform at altitude.
• Decrement in absolute training level at altitude
– Athletes cannot train as intensely while at altitude.
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Altitude Training and Sea‐Level Performance
Combine Altitude Stay with Low‐Altitude Training
• Live high–train low appears to be the best scenario for improving performance.
• Capitalize on stress of altitude and acclimatization
• Train lower so intensity can be maintained
– At‐Home Acclimatization
• Methods of simulating hypobaric conditions
– Cause altitude‐induced physiologic adaptations
• Gamow hypobaric chamber
• Wallace altitude tent
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Simulated Altitude
Simulated Altitude
http://www.youtube.com/watch?v=RRCBbAKW1DU&feature=player_embedded
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Simulated Altitude
http://www.youtube.com/watch?v=izuDBEu4BhY&feature=player_embedded
Simulated Altitude
http://www.youtube.com/watch?v=p6WHPd7yHdk
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Chapter 26
Sport Diving (Hyperbaria)
Chapter Objectives
• Fill in
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Introduction
Pressure‐Volume Relationships and Diving Depth
• Diving Depth and Pressure
– Hyperbaria
– Water is noncompressible.
– As a diver descends, the pressure increases.
• Two forces produce this external pressure
– Weight of the column of water above the diver
– Weight of the atmosphere at the water’s surface
• Every 33 feet of sea water represents another atmosphere of pressure.
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Pressure‐Volume Relationships and Diving Depth
Pressure‐Volume Relationships and Diving Depth
• Diving Depth and Gas Volume
– Boyle’s law
• At a given temperature, the volume of a gas varies inversely with its pressure.
P1V1 = P2V2
• Greater pressure compresses the gas into a smaller volume.
– So, volume of air underwater is less than that same amount of air measured at sea level
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Pressure‐Volume Relationships and Diving Depth
• Diving Depth and Gas Volume (cont’d)
– Example:
• What is the volume of 1 liter of gas (measured at sea level) at a depth of 100 feet (4 ATM)?
• (1)(1) = (4)(X)
X = 1/4 Liter Pressure‐Volume Relationships and Diving Depth
• Diving Depth and Gas Volume (cont’d)
– If a rigid container was submersed underwater, the pressure in the container would not change
– But, the human body is not a rigid container
– Therefore, the contents of the human body will compress as the pressure increases as water depth increases
– Water cannot compress (but the pressure of water can increase), so the air spaces within the body will compress
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Pressure‐Volume Relationships and Diving Depth
• Diving Depth and Gas Volume (cont’d)
– Which air spaces are susceptible to damage?
• Natural Air Spaces
–
–
–
–
Lungs
Middle Ear
Sinuses
Gastrointestinal Tract
• Artificial Spaces
– Cavities within teeth
– Face Mask
– Air spaces within diving suit
Pressure‐Volume Relationships and Diving Depth
• Diving Depth and Gas Volume (cont’d)
– What happens to the lungs?
• A breath hold diver with a TLC of 6L and a RV of 1.5L takes a full inspiration and dives downward
• At 100 feet, pressure equals 4 ATM and lung volume equals:
• (6L)(1ATM) = (X)(4ATM)
• X = 1.5 L
• Residual volume has been reached and lung volume can decrease no further
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Pressure‐Volume Relationships and Diving Depth
Pressure‐Volume Relationships and Diving Depth
• Diving Depth and Gas Volume (cont’d)
– What happens if the diver goes deeper?
• Pulmonary capillary and venous congestion displaces air in thorax decreasing RV and equalizing pressure
• Problem with this:
– The increase in vascular pressures may lead to ruptures of the microvasculature – Pulmonary edema and hemorrhage
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Pressure‐Volume Relationships and Diving Depth
Pressure‐Volume Relationships and Diving Depth
• Diving Depth and Gas Volume (cont’d)
– What happens to diver during ascent?
•
•
•
•
•
•
•
At 100 feet, diver is running out of air
He fills his lungs with air from the tank
As he ascends, pressure decreases
Volume of air expands because pressure is decreasing
Volume of air is too large to occupy lung space
Lung bursts
Only happens if breath holding during ascent
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Pressure‐Volume Relationships and Diving Depth
Snorkeling and Breath‐Hold Diving
• Limits to Snorkel Size
– Inspiratory capacity and diving depth
• Pressure of water reduces lung expansion
– Snorkel size and pulmonary dead space
• The snorkel adds to the dead space.
• Larger snorkel sizes are not effective due to too much dead space, which limits alveolar ventilation.
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Snorkeling and Breath‐Hold Diving
• Breath‐Hold Diving
– Duration depends on
• Time to CO2 build‐up reaches breath‐hold breakpoint (PCO2 ~ 50 mmHg)
• Relationship between diver’s TLC and RLV
– Hyperventilation • Decreases PCO2, increases breath‐hold time
• Increases susceptibility to blackout
– Thoracic squeeze
• Limits depth of breath‐hold diving to about 100 FSW
Snorkeling and Breath‐Hold Diving
• A Diving Reflex in Humans?
– Physiologic responses to water immersion
•
•
•
•
Bradycardia
Decreased cardiac output
Increased peripheral vasoconstriction
Lactate accumulation
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Snorkeling and Breath‐Hold Diving
Scuba Diving
• Open vs. Closed Circuit Scuba
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Special Problems With Breathing Gases at High Pressure
• Henry’s law
– Gas dissolved in a liquid at a given temperature depends upon pressure differences between the gas and liquid and gas solubility in the liquid.
– Air must be delivered at sufficient pressure to overcome force of water against diver’s thorax.
Special Problems With Breathing Gases at High Pressure
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Special Problems With Breathing Gases at High Pressure
• The “Bends”
– At high pressures, the partial pressure of all gases increases
– The partial pressure of Nitrogen especially increases
– Nitrogen is fat soluble and thus enters the fatty tissues
– Upon ascent, the pressure decreases and thus the gases must be released
– The lungs cannot get rid of the nitrogen quickly enough
– Thus, the nitrogen begins to bubble out of the tissues and the nitrogen content of the body increases
Special Problems With Breathing Gases at High Pressure
• The “Bends” (cont’d)
– Treatment
• Recompression allows the nitrogen to enter into solution again
• The pressure is then gradually decreased
• This allows time for the nitrogen to escape through the respiratory system
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Special Problems With Breathing Gases at High Pressure
Special Problems With Breathing Gases at High Pressure
• Oxygen Poisoning
– Exposure to a high partial pressure of oxygen can have severe effects on the lungs and the CNS
– A high PO2 causes much oxygen to be dissolved in solution
– The O2 dissolved in solution is the first O2 to be used by the tissues
– Because the dissolved O2 is high, it is sufficient to supply the tissues with O2
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Special Problems With Breathing Gases at High Pressure
• Oxygen Poisoning (cont’d)
– Thus, O2 does not have to dissociate from hemoglobin
– Hemoglobin in venous blood contains high amount of O2
– What problem does this cause?
• Hemoglobin normally binds CO2 in the venous circulation
• CO2 builds up since it cannot bind to hemoglobin
Special Problems With Breathing Gases at High Pressure
• Oxygen Poisoning (cont’d)
– Symptoms of O2 poisoning
• The high PO2 can cause cerebral blood vessels to constrict
• Visual distortion
• Rapid and shallow breathing
• Convulsions
• Irritation of the respiratory tract leading to pneumonia
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Special Problems With Breathing Gases at High Pressure
• Nitrogen Narcosis
– Nitrogen is not metabolically active
– Can act like an anesthetic gas
– Diver develops symptoms similar to alcohol intoxication
• Every 15 meter descent is equal to the consumption of one martini on an empty stomach
• Impairment of judgment and diver may not recognize a problem exists
– Divers who dive below 30 meters will use a helium mixture
Chapter 27
Microgravity: The Last Fronteir
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Chapter Objectives
• Fill in
Introduction
• Microgravity and Weightlessness
– Microgravity: Gravitational forces acting on the long axis of the body are minimized.
– Gravity depends on the:
• Person’s mass, earth mass, and distance from the center of the earth (increases 5% during spaceflight)
• So, gravity is only slightly decreased in space
– Weightlessness:
• Caused in space due to the fact that the spacecraft is in free fall.
– The craft’s centrifugal force counterbalances the force of gravity. Therefore, the perception is weightlessness
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Introduction
Introduction
• Space Flight
– Microgravity – unloads body tissues and redistributes body fluids
– Light and dark cycles are altered
– Very little ultraviolet radiation
– Carbon dioxide levels are elevated
– Psychological stress
– Vigorous physical activity
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Introduction
• Simulated Microgravity
– Bed Rest
• Loss of muscle mass and strength within 2 weeks
• Decrease in bone mineral density (~12 weeks)
• Decrease in cardiac mass (~6 weeks)
• Exercise impairment (~ few days)
• Decrease in maximal exercise capacity (~ few weeks)
– Immersion
– Suspension and Immobilization
Introduction
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Physiologic Adaptations to Microgravity
• Cardiovascular System
– Decrease in plasma volume
– Lower resting heart volume
– Cardiac atrophy
• May actually be negative caloric balance and body weight
– Cardiac contractility probably not affected
– Increases in cardiac compliance
• But, these decrease after two weeks of bed rest
– Increased venous compliance (decrease VR)
– Decreased PNS, increased HR, increased SNS
Physiologic Adaptations to Microgravity
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Physiologic Adaptations to Microgravity
Physiologic Adaptations to Microgravity
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Physiologic Adaptations to Microgravity
Physiologic Adaptations to Microgravity
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Physiologic Adaptations to Microgravity
Physiologic Adaptations to Microgravity
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Physiologic Adaptations to Microgravity
Physiologic Adaptations to Microgravity
• Musculoskeletal adaptations
– Increased calcium loss
• Skeletal muscle adaptations
– Concentric and eccentric strength
– Muscle ultrastructural changes
•
•
•
•
Altered muscular coordination
Delayed‐onset muscle soreness
General weakness and fatigue
Max explosive leg power decreases.
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Physiologic Adaptations to Microgravity
Physiologic Adaptations to Microgravity
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Physiologic Adaptations to Microgravity
Physiologic Adaptations to Microgravity
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Physiologic Adaptations to Microgravity
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