hyperoxyc test in man mudr. dobroslav hájek, csc. mudr. michal jurajda
TRANSCRIPT
Hyperoxyc test in man
MUDr. Dobroslav Hájek, CSc.
MUDr. Michal Jurajda
The atmosphere
• N2 78,1%
• OO2 2 20,9%20,9%
• CO2 0,03%
• noble gases 1%
Concentration of gases
• Partial pressure- pressure of the given gas in the mixuture of gases.
ipP
• atmospheric pressure ????
Ventilation under extrem pressure conditions
• High altitudes – low pressure
• Diving – high pressure
• Remember: optimal pO2 cca 21 kPa
Hyperbaric oxygenation
• - increases physically dissolved oxygen in blood and tissues
Hyperbaric therapy is used in:
• CO intoxication.
• Air embolism.
• Decompression.
• Anaerobic infections.
• Non healing wounds
Hemoglobinu saturation
Oxygen measurements
• saturometer – saturation of Hb (%)• oxymeter - paO2 (Pa)
lung function Fi O2
paO2
Right to left shunt
• Hypothetical fraction of blood flow (right ventricle output) passing the lungs without beeing oxygenated.
Right to left shunt
• Anatomical
• Functional
Functional
Dead space
The dead space (alveoli with low ventilation/perfusion ratio) incrase the right-to left shunt.
• paO2 = S.pvO2+(1-S).piO2
• paO2 = S.pvO2-S.piO2+ piO2
• S.pvO2-S.piO2 = paO2-piO2
• S.(pvO2-piO2) = paO2-piO2
• S = (paO2-piO2)/(pvO2-piO2)
• S = (piO2-paO2)/(piO2-pvO2)
Remember
• When the increased right-to left shunt is caused by vascular bed involvement (typically: lung embolism) the response of partial oxygen pressure in arterial blood (paO2) to oxygen administration is very poor. (The paO2 increase is very low when oxygen is administered)
Clinical cases
• Poisoning by hyptotic or sedative drugs (e.g. barbiturates, benzodiazepins, morphin)
• Foreign body (corpus alienum) in bronchus with its obstruction
• Ventilation/perfusion unbalance.
The objective
• Estimate rght to left shunt
Material
• Transcutaneous oxymetr
• Medicinal oxygen in gas bottle with pressure reduction valve and flow regulation valve.
• Mask with gas blender and delivery hose
Leland C. Clark
The method
• Increasing FiO2 increases paO2
• paO2 can be measured in arterial blood or in arterialised capillary blood by transcutaneous oxymeter (heated electrode).
• The incerease of paO2 is dependent on FiO2
and right to left shunt.