⭕️Oxygen satisfaction ( PaO2 ) is the pressure of oxygen molecules dissolved in fiery fellow, and is measured by ABG analytics with units of kPa or mmHg
⭕️Oxygen fulness ( SaO2 ) is a measure of the percentage of haemoglobin sites that be the subject of oxygen bound, commonly measured with a pulse oximeter
⭕️Oxygen content ( CaO2 ) is the absolute measure of blood oxygen quantity for example it accounts for dissolved and haemoglobin border oxygen. (i.e. CaO2 directly reflects the TOTAL tell of oxygen molecules in arterial blade, both bound and unbound to hemoglobin. It is given in the same proportion that the volume of oxygen carried in each 100 ml blood (mL O 2 /100 mL). Normal CaO2 ranges from 16 to 22 ml O2/dl.
⭕️Oxygen repletion ( SaO2 ) is expressed as the percentage of haemoglobin-band sites that are occupied by oxygen, by that means forming oxyhaemoglobin.
⭕️Arterial line is normally at 97–98% O 2 repletion (i.e. 98% of the to be turned to account haemoglobin is combined with O 2 ), whereas venous blood is normally at 74% O2 saturation.
⭕️O2 constitutes 21% of the atmosphere by volume and atmospheric PO2 is 159 mmHg at surge level . At an alveolar pressure of 104 mmHg, alveolar oxygen diffuses into pulmonary venous blood and raises its O2 ease from 15 mL/100 mL to 20 mL/100 mL. Of this footing 19.75 mL is combined through haemoglobin and 0.25 mL is ‘free’ or dissolved in straightforward solution in the plasma. At this character impressed of alveolar O2 , haemoglobin in the arterial noble extraction normally becomes 98% saturated and and 2% of the haemoglobin productions reduced, i.e. free of oxygen.
⭕️PaO2 is determined ~ dint of. alveolar PO2 and the state of the alveolar-delicate interface, not by the amount of hemoglobin to be availed of to soak them up. PaO2 is not a dependent of hemoglobin content or of its characteristics. This explains for what cause, for example, patients with severe anemia or carbon monoxide poisoning or methemoglobinemia can (and often do) have a regular PaO2.
⭕️The most general physiologic disturbance of lung architecture, and from here of a reduced PaO2, is ventilation-perfusion (V-Q) imbalance. Less stale causes are reduced alveolar ventilation, extension block, and anatomic right to left shunting of kindred.
⭕️Think of PaO2 because the driving pressure for oxygen molecules entering the red descendants cell and chemically binding to hemoglobin; the higher the PaO2, the higher the SaO2.
⭕️ In exhibit a ~ to the other two variables, CaO2 depends steady the hemoglobin content and is speedily related to it; Since the dissolved oxygen contributes minimally to CaO2 in a state of inferiority to physiologic conditions, CaO2 is determined for the most part entirely by hemoglobin content and SaO2, and is of the same family linearly to either variable.
CaO2 = Hb (gm/dl) x 1.34 ml O2/gm Hb x SaO2 + PaO2 x (.003 ml O2/mm Hg/dl).
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(Chapter 5 of Dr. Martin’s part All You Really Need to Know to Interpret Arterial Blood Gases, 2nd number printed at once, published February 1999 by Lippincott Williams & Wilkins, Understanding ABGs & Lung Function Tests,Pocket Tutor, Muhunthan Thillai ,Keith Hattotuwa )
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