Environmental Physiology

Question 1

Diving response

Answer 1

. Occurs when head is placed underwater
. Enhanced in cold water
. Reflex includes simultaneous expiratory apnea, parasympathetic bradycardia, and sympathetic peripheral vasoconstriction
. Oxygenated blood is preferentially shunted to the brain and heart and away rom skeletal m. And viscera
. Prolongs underwater duration
. Response helps people survive 30+ minutes of submergence in icy water

Question 2

Diving bell

Answer 2

. Surrounds diver on all sides except the bottom

. Compressed air is pumped from above the water surface through a hose that keeps water out of bell

Question 3

Caisson

Answer 3

. Modern-day diving bell

Question 4

Helmet diving

Answer 4

. Individual divers wear diving suits w/ spherical helmets

. Used in commercial and military diving

Question 5

Scuba diving

Answer 5

. In line open-circuit equipment in which compressed air is inhaled from tank through 2-stage regulator system
. Exhaled into the water
. Gas provided at ambient pressure, regulators ensure the diver can inhale and exhale naturally and virtually effortless, regardless of depth

Question 6

Drowning

Answer 6

. Suffocation by submersion
. Most important blood gas changes are severe hypoxemia, combined w/ hypercapnia and respiratory acidosis
. Metabolic acidosis may persist after drowning event
. Initial cause of hypoxemia is blood flow through unventilated lung

Question 7

What occurs when fresh water is aspirated?

Answer 7

. Interferes w/ function of pulmonary surfactant and can lead to atelectasis
. BV inc. in fresh water drowning due to rapid transfer of hypotonic fluid into circulation

Question 8

What occurs when sea water is aspirated?

Answer 8

. Moves additional fluid into the lung from the blood through osmotic forces
. Causes a dec. in BV

Question 9

Hyperbaria

Answer 9

. On the way down in water the air compartments in your body compress
. Upon ascent these air compartments will expand
. Divers must exhale during ascent to prevent overinflation and possible rupture of alveoli

Question 10

Decompression sickness

Answer 10

During deep sea diving, the high partial pressure of N forces N2 gas into body tissues
.particularly occurs in adipose
. If decompression is too rapid, N2 bubbles can develop in body fluids
. Some bubbles occur w/o consequence, but formation of large bubbles can cause pain esp. in joints
. Known as the bends
. Severe cases can cause neurological damage in bubbles form in CNS and obstruct blood flow
. Breathing N2 gas at high partial pressure can depress the CNS leading to nitrogen narcosis

Question 11

What kind of air can be breathed in to prevent decompression sickness when diving?

Answer 11

. Helium oxygen mix

. He is 1/7 of the molecular weight and diffuse more rapidly through tissues than N2 dec. risk of the bends

Question 12

Oxygen toxicity

Answer 12

. Inhalation of 100% O2 at 1atm can damage lungs and lead to pulmonary edema
. Breathing 100% O2 at higher pressures can affect CNS leading to convulsions w/in 30 min.
. High O2 levels helpful w/ CO positioning and treatment of gangrene bc the bacteria Clostridium perfringens dies in O2 rich environments

Question 13

Hyperventilation

Answer 13

. Most important initial feature of acute acclimatization to high altitude
. Caused by stimulation of peripheral chemoreceptors (mostly in carotid body) due to developing hypoxemia
. Consequence is that partial pressure of CO2 will dec. causing pH of arterial blood and brain ECF to inc.
. Respiratory alkalosis dec. central chemoreceptors estimation and inhibit any further inc. in ventilation limiting the magnitude of initial inc. in ventilation

Question 14

Ventilation after 2 or 3 days at altitude

Answer 14

. Ventilation will inc. again
. Due to renal excretion of HCO3 and inc. in sensitivity carotid body chemoreceptors to prolonged hypoxia
. Compensatory mechanisms slowly bring arterial blood and brain ECF pH back to normal levels
. Central chemoreceptors are no longer limiting a further inc. in ventilation, ventilation can now inc.

Question 15

O2-Hb dissociation curve at moderate altitudes

Answer 15

. Right shift
. Dec. affinity of Hb for O2 facilitating better unloading of the O2 in the tissues
. Inc. in concentration of 2,3-DPG that develops from respiratory alkalosis from hyperventilation

Question 16

What is the stimulus for polycythemia?

Answer 16

Hypoxemia

Question 17

Circulatory changes that occur with exposure to high altitude

Answer 17

. CO, HR, and pulmonary artery pressure inc.
. Pulmonary vasoconstriction occurs in response to alveolar hypoxia
. Inc. pulmonary arterial pressure and work done by right side of heart
. Pulmonary hypertension is exaggerated by polycythemia that raises the viscosity of the blood
. Sometimes assoc. w/ pulmonary edema even though pulmonary venous pressure is normal
. Edema fluid has high protein contain which indicates that permeability of capillaries has inc.

Question 18

Alveolar PO2 and arterial PO2 in response to high altitude

Answer 18

. Both dec.
. Alveolar due to dec. barometric pressure
. Arterial due to hypoxemia

Question 19

Ventilation rate response to high altitude

Answer 19

. Inc. due to hypoxemia

Question 20

Arterial pH response to high altitude

Answer 20

. Inc. due to registration alkolosis

Question 21

Hb concentration response to high altitude

Answer 21

. Inc due to polycythemia

Question 22

2,3-DPG conc. In response to high altitude

Answer 22

. Inc.

. Shifts O2-Hb curve to the right

Question 23

Pulmonary vascular resistance response to high altitude

Answer 23

. Inc. due to hypoxic vasoconstriction

Question 24

Pulmonary arterial pressure response to high altitude

Answer 24

. Inc. secondary due to inc. pulmonary resistance

Question 25

Acute mountain sickness

Answer 25

. Hypoxemia, respiratory alkolosis, and possibly mild cerebral edema
. Intolerance to altitude is relieved by descent to lower altitude or by administration of acetazolamide and/or oxygen
. Small percentage of people who ascend rapidly to altitude can die due to high altitude cerebral edema (HACE) and high altitude pulmonary edema (HAPE)

Question 26

Acceleration in aviation and space

Answer 26

. during liftoff astronauts experience G forces that shift BV away from the direction of acceleration
. Astronauts sit w/ backs perpendicular to direction of acceleration so that G force acts across the chest from front to back to minimize the effects of acceleration of body function
. G forces shift BV away from head resulting in transient reductions in cerebral blood flow and O2 delivery that can lead to blackout
. Some people wear counterpressure shoots to oppose the pooling of blood in extremities and helps maintain sufficient cardiac filling, CO, and cerebral blood flow

Question 27

Weightlessness

Answer 27

. Microgravity: near-zero G force
. Acute effec causes BV to redistribute towards head
. Expands central BV
. Causes inc. cardiac preload, inc. interstitial filtration in facial region that produces bloated facial appearance, and a small inc. in cerebral arterial pressure
.these regional changes don’t affect TPR so astronaut’s MAP and CO are not very different in space than on earth
. Practice experiencing thing via prolonged head-down tilt

Question 28

Effects of spaceflight

Answer 28

. Over 50% astronaut’s experience motion sickness in initial days of microgravity from conflicting sensory input to the brain regarding body position
. Inc. blood flow and BV can cause headache and nausea
. Symptoms resolve in 4 days

Question 29

Effects of prolonged time in microgravity

Answer 29

. Cardiovascular deconditioning
. Reductions in body water content, plasma and red cell volume, N stores, muscle mass, and total-body Ca and P
. Degree of bone loss and m. Atrophy is related to duration in microgravity environment
. Bone demineralization releases Ca, P, and other slats into blood
. Inc. likelihood of kidney stone formation
. Astronauts exercise using bungee cords and ergometric stationary bikes to help prevent dec. in muscle mass and bone