Home > Uncategorized > Respiratory Physiology Lecture 3: Blood Gas Transport

Respiratory Physiology Lecture 3: Blood Gas Transport


Today, we will spend 42 minutes on the oxygen dissociation curve.  The lungs are the second most important organ after the heart, which is why we study them. 



After pulmonary gas exchange, blood gas transport is the next in the chain leading to the mitochondria. 

Dry air is 21% oxygen.  [O2] = 21 ml/dl.  FO2 = 0.21.

P barametric = 760 mm Hg

pO2 = .21 * 760 mm Hg = 160 Hg

P barametric = 760 mm Hg

The Effect of Water Vapor

P H2O = 47 mm Hg

P dry = 713 mm Hg

PO2 = .21 x 713 mm Hg = 150 mm Hg

O2 in Physical Solution

After Equilibrium Between Water and Air

Air : pO2 = 150 mm Hg
Water: pO2 = 150 mm Hg
Air : [O2] = 21 ml/dl
Water: [O2]=45 ml/dl

At 37 C, Solubility = 0.45/150 = 0.003 ml/dl

Transport of O2 in Solution During Exercise

Solubility = 0.003 mL/dL

PO2 in arterial blood = 100 mm Hg

[O2] = 0.3 ml/dl =3 ml/L

Cardiac Output = 30 L/min

Minimum O2 Available = 90 ml/minute

O2 need = 3000 ml/min

The antartic icefish has no hemoglobin.  At cold temperatures, the solubility of O2 is increased. 

Hemoglobin has a heme or iron proforin compound.  2 beta chains, 2 alpha chains, and Fe2+. 

Hemoglobin A is adult hemoglobin.  There are other forms.  Hemoglobin F is fetal hemoglobin and as a higher affinity for O2.  For sickle cell anemia, the hemoglobin crystallizes into strange shapes. 

Oxygen Dissociation Curve

The oxygen capacity is the total amount of O2 the blood can carry.  Developed by passing gas over blood in a glass tonometer.  The curve is S shaped.  It has to do with the change of conformation of hemoglobin with increase in pO2. 

Anchor Points 

pO2 100, O2 saturation is 97% (arterial blood)

pO2 27, O2 saturation 50%

pO2 40 , O2 Saturation 75% (venous blood)

Total Oxygen in the Blood is the Sum of Bound Hb and Dissolved O2

Total [O2] = 1.39 x [Hb] x %Saturation/100 + 0.003PO2

Arterial Blood = 0.39 x 15 x 0.97 + 0.003 x 100 = 20.5 ml/dl

The curve shifting is a change in oxygen affinity of the hemoglobin.  There are four factors that shift the curve to the right or reduce the affinity: temperature, pCO2, pH and DPG or 2,3 di phoso glycerate. 

In exercising muscle, temperature increases, unload more O2 for a given O2, we are creating more pCO2, the proton concentration increases, and DPF is a product of red cell metabolism.  In stored blood, DPG can be depleted, making O2 difficult to unload. 

The CO dissociation curve is flat.  It’s the same as O2, but CO is saturated very quickly, like in the first 2 mm Hg.  CO can tie up a large amount of O2. 

Carbon Dioxide is carried in 3 forms:

Dissolved, Bicarbonate, Carbamino Compounds

Solubilty of O2 is 0.003 ml/dl.  The solubility of CO2 is 0.067 ml/dl. 

Arterial: 5% dissolved,  90 as HCO3-,  5 as carbamino

Venous: 10% dissolved,  60 as HCO3-,  30 as carbamino

CO2 + H2O = H2CO3 (by carbonic anhydrase) = H+ + HCO3-

NH2 + CO2 = Hb NH COOH

Reduced hemoglobin HHb is much better at forming carbaminos rather than the oxygenated form HbO2. 


Visible Light – 400 to 700 nm

Aromatic: planar, cyclic, Huckels Rule – 4n+2 electrons

Fibrous – sclera, cornea

Sensory – retina

Vascular – choroid, iris, pupil, ciliary body

Kingdoms – monera, protista, fungi, plant, animal

HSbF6 pKa = 25

Electrophiles are positive, nucleophiles are negative

EDTA is a tetraprotic acid.

Activators donate electrons to the ring, deactivators take electrons from the ring

Acetone pKa = 24.2

Technical Analysis: the market discounts everything, the past predicts the future,

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