31. Carriage of Oxygen and Carbon Dioxide Flashcards
How is oxygen transported in the blood?
.3/100 ml is physically dissolved
Remainder combines with haemoglobin
How is the percentage saturation found?
Oxygen content/oxygen capacity
Measure by a pulse oximeter
What is Oxygen Capacity?
Volume of O2 carried when Hb is 100% saturated
What moves the oxyhaemoglobin dissociation curve to the right?
High PCO2
H+
Temperature
2,3-DPG
What is the Bohr effect?
Increased PCO2 and H+ causes Hb to release more O2
What causes levels of 2,3-DPG to rise?
Exercise, altitude, anaemia, respiratory disease
Why does foetal haemoglobin bind oxygen better than adult haemoglobin?
Has gamma chains instead of beta
2,3-DPG doesn’t bind as well to gamma chains
What are 4 situations that involve abnormal transport of oxygen?
Anaemia
Oxidation
Carbon monoxide poisoning
Sickle cell anaemia
How might iron in the blood be oxidised from Fe++ to Fe+++?
Chemicals and drugs
Eg. Nitrates, nitrites, sulfonamides
What does oxidation cause?
Forms methaemoglobin which doesn’t bind oxygen
Methaemoglobinaemia
Treat with methylene blue
What does Hb bound to CO form?
Carboxyhaemoglobin
Carboxyhaemoglobinaemia
What is central cyanosis caused by?
Arterial blood desaturation
What is peripheral cyanosis caused by?
Restricted blood flow
How is carbon dioxide transported?
Physically dissolved
Carbamino compounds (Hb and plasma proteins or NH2)
Bicarbonate ions
How is bicarbonate produced from carbon dioxide?
H20 + CO2 > H2CO3 > H+ + HCO3-
Why don’t H+ and HCO3- build up?
Hb removes them from the RBC
What is the chloride shift?
Protein mediated transport exchanges HCO3- for Cl-
Lack of products shifts the equilibrium to the right
What is the Haldane effect?
Deoxygenation of blood increases its ability to carry CO2
What effect does hyperventilation have on blood pH?
Makes blood pH more acidic
Lack CO2 so equilibrium shifts to left and less HCO3-
What effect does hypoventilation have on blood pH?
Respiratory acidosis due to more H+
