Haemoglobin and Gas Transport Flashcards
How many ml of O2 dissolve per litre of plasma
3ml
How much does Haemoglobin in RBC increase O2 carrying capacity
200ml/L
How is the bulk of CO2 transported
In various forms of solution in plasma
Define Arterial Partial Pressure
Refers to the O2 in solution and is determined by O2 solubility and the partial pressure of O2 in the gaseous phase driving it into solution
Values assigned to the partial pressure of a gas in solution are equal to the partial pressure in gaseous phase that is driving that gas into solution (T/F)
T
What is the solubility of O2 in water
0.03ml/L/mmHg (for every litre of plasma 1 moleucle of O2 dissolves in 0.03 ml of plasma)
What is the partial pressure of O2 in 3ml/L plasma
3/0.03 = 100 mmHG
O2 delivery to tissues =
Arterial O2 content X Cardiac Output
What would be the O2 delivery to tissues if the arterial blood content was 3ml/L and the cardiac output was 5L/min
15ml/min
What is the O2 demand for resting tissues
250ml/min
If you add Hb (150g/L, 1.34 ml O2 per g) how much does the O2 delivery to tissues increase by
200ml/L X 5L/min = 1000ml/min
What percentage of arterial O2 is extracted by peripheral tissues
25%
What maintains the partial pressure gradient that allows the movement of O2 out of the alveoli
Haemoglobin
How long does it take for saturation to be complete once in contact with the alveoli
0.25s (total contact time 0.75s)
More than 98% of oxygen is bound to Hb where is the rest
Dissolved in plasma
How many oxygen molecules can bind to Hb
4
How much oxygen binds to each gram of Hb
1.34ml
92% of Hb is in RBCs where is the remaining 8%
HbA2 (delta chain replaces beta chain)
What can be used to detect and monitor diabetes
Glycosylated Hb (HbA1a, HbA1b, HbA1c)
What is the major determinant of the degree to which Hb is saturated with oxygen
Partial pressure of oxygen in arterial blood
The affinity of O2 changes in response to
changes in certain chemical factors such as PH, PCO2, Temp and DPG
Exercise moves the curve to the
Right- PH decreases
Co2 increases
Temperature increases
Makes O2 more accessible as tissue oxygen demand increases
Cold weather moves the curve to the left
Left- PH increases
CO2 decreases
Temperature decreases
Hb holds on more tightly to the oxygen- unloading more difficult but aid cillection of oxygen in pulmonary circulation
What is DPG
Metabolite produced by RBCs under stress (Cardiac, respiratory disease, high altitude)- decreases affinity for oxygen
Compared to normal Hb wish side would a curve for HbF and myoglobin shift
Left (wants to hold on to oxygen more tightly)
CO binds to Hb to form
Carboxyhaemoglobin
What is CO affinity for Hb
250 time greater than O2
Symptoms of CO poisoning
Hypoxia Anaemia Nausea Headaches Cherry red skin Mucous membranes
What is Hypoxia
Inadequate supply of oxygen to tissues
Hypoxaemic Hypoxia
Reduction in oxygen diffusion at lungs either due to decreased PO2 (atmosphere) or tissue pathology
Anaemic Hypoxia
Reduction in oxygen carrying capacity due to anaemia
Stagnant Hypoxia
Heart disease results in inefficient pumping of blood to lungs/around the body
Histotoxic Hypoxia
Poisoning prevents cells utilising oxygen delivered to them e.g. CO and Cyanide
Metabolic Hypoxia
Oxygen delivery to the tissues does not meet increased oxygen demands
Describe CO2 transport (6)
- Diffuse from tissue into blood
- 7% remains in plasma and erythrocytes
- 23% combines in the erythrocytes with deoxyhaemoglobin to form carbamino compounds
- 70% combines in the eryhtorcytes with water to form carbonic acid, which dissociates to yield carbonate ions and H+
- Chloride shift: most bicarbonate moves out of erythrocytes into plasma in exchange for Cl- ions
- Excess H+ ions bind to deoxyhaemoglobin
- The reverse occurs in the pulmonary capillaries and CO2 moves down its concentration gradient from blood to alveoli
Pathway of CO2 (4)
Peripheral Tissue
Systemic Capillary
Venous circulation
Pulmonary capillary
Hypoventilation causes
CO2 retention and decrease in PH (Hugh H+) (Acidosis)
Hyperventilation causes
Blowing off more CO2 increase in PH (low H+) Alkalosis