Respiratory Physiology Lecture 4: Gas Transport in the Blood – Part 1 Flashcards
What order of oxygen partial pressure from highest to lowest is the Gas, tissues, Arterial, air, pulmonary capillary.
Air(atmosphere), gas,(slightly less) pulmonary capillary, (slightly less) arterial, tissues.
What is the symbols used for oxygen partial pressures?
P(small O2) kPa
What is Henry’s law?
The amount of a given gas dissolve in a given type and volume of liquid at a constant temp is proportional to the partial pressure of the gas in equilibrium.
What is the partial pressure of a gas in solution?
The partial pressure of the gas in the mixture with which it is in equilibrium.
How does dissolved oxygen in the blood fit into Henry’s law?
The O2 amount dissolves in blood is proportional to the partial pressure.
How much dissolved O2 per litre of blood is at a P02 of 13.3 kPa?
3ml
How much dissolved O2 is taken to tissues at resting conditions on average?
15ml/min
How much dissolved O2 is taken to tissues at strenuous exercise in a average person?
90ml/min
How much O2 consumption at rest on a average person?
250ml/min way too much for just dissolved oxygen!!
During strenuous exercise how much oxygen is consumed compared to resting?
up to 25 times!
What other mechanism is involved in O2 transport in the blood other than dissolved oxygen?
Haemoglobin
Normal O2 concentration in the blood is what? and what is the normal haemoglobin (Hb) concentration?
200ml per L of O2 and 150g of Hb per L
What are the percentages of O2 carried bound to haemoglobin and in dissolved form?
Haemoglobin is 98.5% while dissolved oxygen is 1.5%.
What does Hb do?
It can form a reversible combination with oxygen.
What is Hb made from?
4 haem groups
When is haemoglobin considered fully saturated?
When all Hb present is carrying its maximum oxygen load.
What is the primary factor which determins the percent saturation of Hb with O2?
P(small O2)
What is the average resting P02 of blood at systemic capillaries?
5.3 kpa
What is the normal PO2 at pulmonary capillaries?
13.3
What happens to the Hb saturation when Hb concentration increases?
Nothing!
What is the oxygen delivery index?
An equation that tells how much oxygen is being delivered to tissue.
Oxygen delivery index (DO2L)=Oxygen content of arterial blood (CaO2) times by cardiac index (Cl)
In the oxygen delivery index, what is the units for each bit?
DO2l - ml/min/metre(squared)
CaO2 - ml/L
Cl - L/min/metre(squared)
What is the cardiac index?
The cardiac output in relation to the body surface area.
How is the O2 content of the arterial blood (CaO2) determined?
CaO2=1.34 times by concentration of Hb times by SaO2.
The 1.34 comes from how much O2 1 gram of Hb can carry when fully saturated.
What 3 things can impare oxygen delivery to the tissues?
Respiratory disease, heart failure, or anaemia.
What happens to the atmospheric pressure when altitude increases?
It decreases.
How do you find out the partial pressure of oxygen in the alveolar air?
PAO2 (partial pressure of O2 in alveolar air) = PiO (Partial pressure of O2 in inspired air) take away the (PaC2/0.8)
What is the 0.8 in the partial pressure of oxygen in the alveolar air equation?
The respiratory exchange rate - ratio of CO2 produced/02 consumed in a person with a mixed diet
How does Respiratory disease impair oxygen delivery to the tissues?
These can decrease aterial PO2 and hence decrease Gb saturation with O2 and O2 content of the blood.
How does Anaemia impair oxygen delivery to the tissues?
This decreases Hb concentration and hence decreases O2 content of the blood.
How does heart failure impair oxygen delivery to the tissues?
This decreases cardiac output.
What does the binding of one O2 to Hb do?
Co-operativity - increases the affinity for Hb for O2 on other haem molecules
What pattern is the increasing blood P02 have on the percentage of haemoglobin saturation? what is this significance?
A sigmoid - This has a flat upper portion which means that moderate fall in alveolar PO2 will not affect oxygen loading much.
- The steep lower part means that the peripheral tissue gets a lot of oxygen from a small drop in capillary PO2.
What is the Bohr effect?
This is the shift of the curve to the right in the sigmoid for Hb saturation and P02.
What does the Bohr effect cause?
An increase in PCO2, H+ CONC, temp, 2,3-biphosphoglycerate.
What is foetal haemoglobin?
Haemoglobin used in the stage of a foetus (and a few months after birth). It has 2 alpha and 2 gamma subunits while adult haemoglobin has two alpha and two beta subunits.
How does feotal haemoglobin function differently from adult?
It interacts less with 2,3-biphosphoglycerate in red blood cells and so has a higher affinity. This means the O2-Hb dissociation curve is shifted to the left and so allows O2 to transfer from mother to feotus even if the PO2 is low.
What is myoglobin?
This is present in skeletal and cardiac muscle to act as a storage of O2 for anaerobic conditions. It also fully saturates very quickly.
What is the structure of myoglobin?
It is a single haem group per myoglobin and so no cooperativity binding of O2.
What does myoglobin in the blood indicate?
Muscle damage.
