Respiratory Physiology Flashcards
how does gas move
gas movement through the conducting airways occurs by convection. Gas exchange across the blood gas barrier in the alveolous occurs by diffusion
Rate of oxygen transfer hamelgobin calculation
Dt = Kt x S x (1/t)
Rate of Oxygen transfers to hemoglobin
Rate at which oxygen travels through liquid krogh oxygen permeation coefficient
Mean Barrier Thickness
Oyxgen is transported in tow forms in blood
Oyxgen is transported in tow forms in blood
O2 bound to hemoglobin enlabes O2 offloading to tissues
Plasma Soluble O2 (less soluble than CO2)
what is oxygen content
Oxygen Content is determined by amount of Hb and O2 in blood
Saturation percentage
oxygen saturation is the portion of oxygen
Oxyhemoglobin / O2 carrying capacity of Hb
saturation stays the same when Hb content
what is P50
P50 value PO2 required for half maximal Hb saturation
V in the graph for Hb saturation
Steep phase of curve favours offloading of arterial oxygen to tissues. greater HBO2 dissociation for small changes in tissue PO2
A in the graph for Hb saturation
Arterial Plateau phase ensures maximal HbO2 saturation even if alveolar PO2 is below the normal oxygen tension
Left Shift for graph for HB saturation
Left Shift - increases HBO2 affinity and reduces O2 offloading to tissues
Right shift for graph for Hb Saturation
Right shift - decrease HB02 affinity and raised O2 offloading to tissues and may be induced stressors such as acidosis fever and hypoxia
Haemoglobin
Heterotetramer composed of 2a and 2b subunits
oxygen reversibly binds to Fe3+ ions in the centre of the heme ring
CO2 Ph AND 23 bpg alter this affinity by interacting with charged amino groups between a and b subunits
contains 4 iron binding HEME doamins
Bohr effect
Bohr effect is when pH alters the ability of oxygen to bind to hemoglobin
what does amino binds to
amino terminus of hemoglobin a subunit binds to the carboxy terminal histidine in b subunit this stabilises Hb structure
How is the interaction sensitive
this interaction is pH and O2 sensitive requires H+ and 2O2 released
Acidosis decrease pH favours the a b subunit interaction and reduces the binding of O2 to heme
Increase blood pCO2 releases O2 from Hb in two ways
production of carbonic acid
carbamate reaction at N terminal amino groups on Hb a subunit
Porduction of carbonic acid and carbamte reaction causes
Porduction of carbonic acid and carbamte reaction causes acid stabilisation of a b Hb subunit interaction Low Hb affinity for O2
three ways to CO2 transported in blood
CO2 is transported in three forms in blood by
Plasma Soluble CO2
Bicarbonate Ion
Carbamino Hemoglobin
Carbon dioxide dissociation curve
Hypoxia is higher than venous and lowest is alveolar
Deoxygenation of blood improves carriage of CO2
step one CO2 Release from Tissue
CO2 dissolves into plasma & red cellalong partial pressure gradient
step two CO2 Release from Tissue
Low tissue O2 favours CO2 carriageby blood (HALDANE EFFECT
step three CO2 Release from Tissue
Carbamate reaction reducesHbO2 affinity (BOHR EFFECT)
step four CO2 Release from Tissue
Carbonic Anhydrase reactiongenerates carbonic acid whichprotonates. HCO3- leaves cell andmaintains inward CO2 gradient
step five CO2 Release from Tissue
Increased red cell [H+] reducesHbO2 affinity by promoting ab Hbsubunit interaction (BOHR EFFECT)
CO2 release from red cell step one
O2 dissolves into plasma & red cellalong partial pressure gradient
CO2 release from red cell step two
High affinity of Hb for O2 reversesHb carbamation and protonation raisingavailabiity of high affinity Hb (BOHR EFFECT)
CO2 release from red cell step three
CO2 diffuses into alveolus alongpressure gradient. High PO2 decreasesCO2 affinity for Hb (HALDANE EFFECT)
CO2 release from red cell step four
Movement of CO2 out of red cell increases HCO3- uptake (Cl- moves out)
CO2 release from red cell step five
Proton release from Hb and [HCO3-] drive carbonic anhydrase reaction in reverse, maintaining outward CO2 gradient and lowering plasma bicarbonate
high altitude adaptation
conserve pAO2:
increasing breathing frequency - paCO2 decreases
high carbohydrate , RQ = 1
Climb when barometric pressure (Krogh)
poor ventilation and large blood flow
poor ventilation and large blood flow
need to reduce perfusion hypoxia constricts pulmonary arterioles
Good ventilation and poor blood flow
Good ventilation and poor blood flow
need to reduce ventilation - low CO2 constricts bronchioles
What is hypoxia
Hypoxia - constricts pulmonary arteries to increase pulmonary transit time of blood
Re directs blood flow to well ventilated areas of lung
what does CO2 do
Low CO2 - consitrcts bronchioles to area of vascular obstruction and re directs air flow in lungs away from obstruction
