barotrauma and hyperbaric gas toxicities

• barotrauma


  any injury caused due to abnormal air pressure
• SCUBA 


  self contained underwater breathing apparatus
• henry's law


  gas solubility in tissues increases with gas partial pressure
• heliox or tri-mix 


  N2 has either been diluted or replaced by helium or argon
• oxygen toxicity 


  pure O2 toxic at 6m, air-mix toxic at 66m
• nitrogen narcosis


  causes loss of motor function and deterioration in decision making ability
• arterial gas embolism 


  bubbles enter the bloodstream and block blood flow
• shallow water blackout 


  lose consciousness if pO2 drops below 0.1atm
• Gamow bag 


  portable hyperbaric chamber, treats altitude sickness
• High-altitude pulmonary edema


  fluid on the lungs
• high altitude cerebral edema


  fluid on the brain
• exhalation 


  passive process
• Laplace's law predicts


  the smaller the alveoli will collapse first
• surfactant 


  prevents alveoli from collapsing, water. strongly attracted to surfactant, more so than water itself
• surfactant during inhalation 


  surfactant surface concentration decreases, surface tension increases
• surfactant during exhalation


  surfactant molecules move closer together, surface concentration increases, surface tension decreases
• lysis - hypotonic


  cell inflates and bursts
• lysis - hypertonic


  cell shrivels up (krenation)
• near drowning - aspirated sea water 


  hypertonic, osmosis forces plasma into lungs and they fill with fluid (secondary drowning)
• near drowning - aspirated fresh water 


  hypotonic, osmosis forces water from lungs and into bloodstream