gas transport Flashcards
what is partial pressure?
sum of all the partial pressures of a gas must be equal to total pressure
what is the formula for partial pressure of gas?
fraction of gas in gas mixture x barometric pressure
what are the 2 ways oxygen is transported?
dissolved and bound to haemoglobin
how much O2 in blood is in dissolved form?
a small %
how is dissolved O2 measured clinically?
in arterial blood sample PaO2
why is haemoglobin required?
transport of O2 in dissolved form is not adequate
what is haemoglobin?
a major transport molecules for O2 found in RBC’s
what is the structure of Hb?
4 heme groups joined to globin protein, 2 alpha, 2 beta chains, each heme contains iron in ferrous form- site of O2 binding
why does binding and dissociation of O2 occur in milliseconds to facilitate transport?
RBC’s are only in capillaries for 1 second
is O2 binding in Hb reversible?
yes
what is the consequence of a drop in PO2 from 100-60mmHg
minimal effect on Hb saturation
what is the consequence of a small change in PO2 under 60
a large amount of O2 is released from Hb, facilitating release into tissues
how many O2 atoms can each Hb bind?
up to 4
what does O2 saturation mean?
the amount of O2 bound to Hb relative to the maximal amount that can bind
how is O2 saturation measured?
pulse oximeters- measures ratio of absorption of red and infrared light by oxyHb and deoxyHb
how much CO2 is produced in normal conditions?
200ml/min
what is the respiratory exchange ratio?
ratio of expired CO2 to O” uptake
what is the respiratory exchange ratio in normal conditions?
0.8
how is CO2 carried in blood?
dissolved -7%, bound to Hb-23%, as bicarbonate - 70%
what do the systemic capillaries do to CO2
produced by tissues and expelled into blood
what do systemic capillaries do to CO2?
expelled into alveoli
what ions contribute to acidity?
CO2, bicarbonate and hydrogen
which can be used to stabilise pH?
changes in bicarb conc. - buffering reaction
what makes the bicarb buffering reaction strong?
the high concentration of bicarb
what are the 2 ways acidity can be regulated?
- using ventilation to adjust PCO2
2. using the kidneys to regulate bicarbonate concentration
