Hypobaric and Hyperbaric Physiology Flashcards
How does increased or decreased pressure affect the volume of gas?
Boyle’s law - P1V1 = P2V2
Gas volume decreases in direct proportion to applied pressure
What cavities in the body need to accommodate Boyle’s Law during compression on descent (Increased pressure)?
Mask squeeze - negative pressure in the mask can cause capillary rupture and conjuctivea hemorrhage
Ear drum - pressure change can rupture the eardrum if the canal is blocked
Middle ear squeeze - failure to equalize pressure during descent can cause the eustachian tube to collapse (and also cause ear drum rupture)
What are the dangers associated with ascending from a dive without exhaling?
Air in the lungs will double in volume if not exhaled
Can cause pneumothorax, dissection of the mediastinum, gas emboli and death
What is oxygen toxicity?
Alveolar and endothelial membrane damage
Exceeding 760 torr of O2 for any extended time will cause damage
What is Nitrogen toxicity?
Increased PiN2 increases the amount of nitrogen dissolved in the lipid membranes of the CNS
Acts as an anesthetic, and affects divers much the same way as EtOH - poor decision-making
Called Nitrogen Narcosis
What is decompression sickness?
“Bends” or “Caisson’s disease”
Rapid rise to the surface causes the creation of nitrogen bubbles in blood vessels, heart, joints, brain..etc.
Causes pain, dyspnea and death
Treatment is immediate recompression with gradual pressure to allow the gas to dissolve slowly
What occurs to the partial pressure of oxygen at high altitudes or hypobaric conditions?
In decreases significantly
What is the acute ventilatory adjustment made by the body during ascension?
Ventilation increases, simultaneously causing an increase in PA02 and decrease in PACO2
This is a result of acute hypoxia as sensed by peripheral chemoreceptors
The increased ventilation can also cause acute respiratory alkalosis
What physiological changes occur to acclimate to altitude?
Hyperventilation
Increased hematocrit and blood volume - increases O2 capacity
Increased capillary growth in tissue - reduces diffusion distance and reduces vascular resistance
Plasma volume decreases - due to hyperventilation and reduced water intake
What is acute mountain sickness?
Symptoms include nausea, insomnia, weakness, and dyspnea
Occurs 5hrs - 5 days after reaching altitudes over 8000 feet
Associated with fluid retention, usually treated with diuretic
What is High Altitude Cerebral Edema (HACE)?
Ataxia and inability to walk heel-to-toe is significant warning sign of impending problems
Swelling causes brain ischemia and herniation
What is High Altitude Pulmonary Edema (HAPE)?
Most serious, highest mortality
Aggravated by physical exercise, most commonly seen in athletic young males
Mandates immediate return to lower altitude
