This is an extract of our Gas Carriage document, which we sell as part of our Respiratory System Notes collection written by the top tier of Bristol University students.
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Lecture 7 Gas carriage
Explain the difference between PaO2, SaO2 and CaO2 o PaO2
? Partial pressure of oxygen dissolved in blood (mmHg ) o SaO2
? Percentage saturation of haemoglobin with oxygen
? Sigmoidal relationship to PaO2 o CaO2
? Total volume of oxygen contained per unit volume of blood (ml)
? Depends on volume bound to Hb and volume dissolved in blood Using the oxyhaemoglobin dissociation curve, explain the relationship between PaO2
& CaO2 o SaO2 = (amount of oxygen bound to Hb/oxygen binding capacity) X 100
Describe the effect of a voluntary breath hold upon arterial saturation o Causes a fall in arterial saturation with O2 o If held for long enough can fall below 90 o Experiment in lecture Describe the use of pulse oximeter o Indirectly monitors the oxygen saturation of a patient's blood o Acceptable normal ranges for patients (without COPD etc.) problem are 95 to 99%
o How it works
? Pair of small LEDs facing a photodiode through a translucent part of the patient's body, usually a fingertip or an earlobe.
? One LED is red and the other is infrared
? Absorption at these wavelengths differs significantly between oxyhemoglobin and its deoxygenated form Describe and explain the carriage of O2 by haemoglobin o Primary function of hemoglobin (Hb) is to transport oxygen o O2 not very soluble in water, so oxygen transport protein must be used to allow oxygen to be 'soluble' o Iron is the site of oxygen binding; each can bind one O2 molecule thus each hemoglobin molecule is capable of binding a total to four (4) O2 molecules o Primary factor that determines how much oxygen is actually bound to hemoglobin is the partial pressure of oxygen (pO2) in the hemoglobin solution
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