Flashcards in Bergdahl- Chapter 26 and 27 Deck (46):
How does Boyle's law relate to diving ?
therefore, in diving, when the pressure increases, the lung volume is severely reduced. Also, when the diver returns to the surface, the air volume re-expands to its original volume, which will make lung tissues rupture if the extra air cannot escape through the nose or mouth
is water compressible ? what are the implications of this ?
water is noncompressible. this means that its pressure against a diver's body increases directly with the depth of the dive
what is hyperbaria ?
increased external pressure
what are the two forces that produce hyperbaria ?
1) weight of the column of water directly above the diver
2) weight of the atmosphere at the water's surface
what in our body makes us less prone to increased external pressure in diving ?
the fact that water is a large portion of our body
what happens after about 30 seconds of snorkelling ?
the carbon dioxide level in arterial blood increases causing the diver to sense the need to breathe and surface quickly
what are the limits to snorkel size ? (2)
snorkelling adds to the volume of the anatomical dead space. it shouldn't be too big therefore or it'll enroach on alveolar ventilation
increased hydrostatic pressure as one descends beneath the water
the duration and depth of a breath-hold dive depends on two things :
1) until arterial carbon dioxide pressure reaches the breakpoint (about 50 mmHg)
2) the relationship between a diver's TLC and RV
how does exercise reduce breath holding time ?
more carbon dioxide is being produced with exercise intensity
what happens if you hyperventilate before a breath-hold dive ?
what are the physiological reasons behind blacking out
hyperventilation preceding breath-hold, which means that PCO2 decreases to 15 mmHg. this extends the breath hold duration until the PCO2 increases to a level that stimulates ventilation
what determines the critical diving depth before lung squeeze
the TLC/ RV ratio
should be 4 at the surface
basically if TLC> RV all is cool
if not, pulmonary pressure becomes less than the external water pressure, and blood goes into the alveoli
what is the diving reflex ? what are the 4 physiological responses that it consists of ?
permits diving mammals to stay underwater for a while
1) bradycardia -the colder the water, the faster the reaction
2) decreased CO (CO= HR x SV so if HR smaller, CO is smaller- SV doesnt change)
3) increased peripheral vasoconstriction causes reduced blood flow to the limbs ensuring that oxygen sensitive organs like the brain and heart receive oxygen.
4) lactate accumulation in underperfused muscle (because the blood is going to the brain and heart)
what is Henry's Law ?
the quantity of gas dissolved in a liquid at a given temperature varies directly with the pressure differential between the liquid and gas solubility in the liquid
basically more molecules are soluble at a higher pressure
as the diver ascends to the surface, how will the air volume breathed underwater expand ? what are the implications of this ?
in direct proportion to the reduction in external pressure.
therefore, if a diver takes a full breath and then fails to exhale while ascending, the rapidly expanding gas eventually ruptures the lungs. emboli (air bubbles) enter the pulmonary venous system, flow to the heart, block the blood supply
what is pneumothorax caused by ?
air forced through the alveoli when lung tissue ruptures migrates laterally to burst through the pleura that covers the lungs. this means an air pocket forms in the chest cavity outside the lungs, and the continued expansion of trapped air during ascent collapses the ruptured lung
what is mask squeeze ? how to avoid it ?
air in a facemask before a dive equals ambient air pressure, but then when you go deeper, the pressue differential develops between the inside and outside of the mask which creates a relative vacuum within the mask
you can avoid this by periodically exhaling through the nose in the mask to balance the pressures
aerotitis- what is it ?
problem equalizing pressure within the air space of the Eustachian tubes which generally resist airflow
can cause middle ear hemorrhage and eardrum rupture
what is aerosinusitis ?
congested sinuses prevent air pressure in these cavities from equalizing in diving
sinus air pressure that doesnt equalize during descent remains at atmospheric pressure while external pressure increases
this means that there can be a sinus squeeze due to the pressure differential, and sinus can bleed as blood occupies the space to equalize the pressure differential.
what is nitrogen narcosis ?
when you dive too deep, the nitrogen basically acts as alcohol. the partial pressure of any gas increases in the tank as you go down, so the nitrogen will double value to 1200 mmHg
it dissolves in the myelin membranes
what is the standard depth we go to maximally to avoid nitrogen narcosis ?
300 feet of sea water
what is decompression sickness ?
when dissolved nitrogen moves out of solution and forms bubbles in body tissues and fluids
usually when ascending to surface too rapidly
how to treat decompression sickness ?
lengthy recompression in hyperbaric chamber to force nitrogen gas back into solution
gradual decompression then to provide time for gas to leave body
what is oxygen poisoning ?
breathing high pressures of O2
what are the three ways oxygen poisoning acts ?
1) irritates respiratory passages and induces bronchopneumonia
2) constricts cerebral blood vessels and alters CNS function
3) depresses CO2 elimination (Hb is saturated with O2, which causes buildup of CO2 because usually Hb transports considerable amounts of CO2)
what are the three mixes used in mixed-gas diving ?
1) nitrox- for relatively shallow recreational dives. it reduces O2 poisoning but still, the nitrogen amount can be dangerous
2) heliox- deep diving, reduces resistance imposed by nitrogen, however, can result in high pressure nervous syndrome
3) trimix - helium, nitrogen, oxygen: dives to depths that may produce high pressure nervous syndrome (nausea, tremors, other CNS effects)
what are two negative effects of breathing helium?
1) voice change
2) heat loss from helium's high thermal conductivity
how does the energy cost of diving compare to normal exercise ?
can be 30% more at slow speeds
what is microgravity ?
weightless feeling because the gravitational pull on a rocket decreases as it moves farther from the Earth
what happens to bodily fluids in microgravity ?
blood and fluids shift upwards and move into thoracocephalic region
(puffy face, decrease in waist, eye redness, skinny legs, headache)
how do kidneys respond to the fluid shift ?
they up urine production
how does the decrease in total fluid volume in microgravity change the cardiovascular function ?
reduces heart's total work
overall heart size decreases from reduced LV
how does the heart change sizes in microgravity ?
first it becomes bigger due to UB fluid shift. then, there's negative feedback to regulate fluid balance by decreasing thirst and augmenting urine output
then the heart shrinks below normal size
how does CO, SV, HR change in space ?
HR remains the same, but SV decreases
how does SV change in space ?
at first, it increases because venous return increases but then with the decrease in plasma volume it decreases.
what is space anemia ?
decrease in O2 since there's a decrease in RBC
either due to RBC destruction or decreased RBC production
what is the most persistent short term problem in space ?
space motion sickness
in flight lower body negative pressure. what are its two functions ?
1) assesses orthostatic deconditioning during space flight and post landing
2) countermeasure against changes
applies negative pressure to the lower limbs to force fluid in vascular system to migrate downward
do people gain or lose weight in space ?
what supplements do astronauts take ?
protein, but doesn't seem to help
how does body composition change in space ?
no changes in body fat or extracellular water
decline in FFM and body mass
what are the 2 main physical stressors in space travel ?
1) decreased hydrostatic pressure gradients within the cardiovascular system
2) decreased weight loading on muscles
increase physiologic strain
how does VO2max change in space ?
how does MAP increase in the upper body ?
from 70 to 100 mmHg
how many weeks do we need to see a 10% change in deconditioning response of the cardiovascular system ? 10% change in body fluid redistribution ? 5% decline in bone mass ?
a 10% change in deconditioning response of the cardiovascular system ? 3 weeks
10% change in body fluid redistribution ? 2 weeks
5% decline in bone mass ? 3 months