gas transport Flashcards
What does the prefixes P, F, S, C, Hb mean
P - partial pressure F - fraction S - Hb saturation C - content Hb - volume bound to Hb
What do the following subscripts mean: I, E, A, a, v, P, D
I - inspired E - expired A - alveolar a - arterial v- mixed venous P - peripheral D - dissolved
What is Dalton’s law
Pressure of a gas mixture is equal to the sum of the partial pressures of gases in that mixture
What is Fick’s law
Molecules diffuse from areas of high concentration to low concentration at a rate proportional to the concentration gradient, surface area and the diffusibility. Inversely proportionally to thickness
What is Henry’s law
At a constant temperature, the amount of a given gas that dissolves in a given type and volume liquid is directly proportional to the solubility 𝛼 of the gas and the partial pressure (P) of the gas in the equilibirum with that liquid
What is Boyle’s law
At a constant temperature, the volume (V) of a gas is inversely proportional to the pressure (P) of that gas
What is Charles’ law
At a constant pressure, the volume (V) of a gas is proportional to the temperature (T) of that gas
What is the partial pressure at sea level
21.3 kPa/ 160mmHg
How much can a nasal cannula or face mask increase inspired oxygen
increase by 60%
How does pressure change with altitude
As altitude increase, the ambient barometric pressure reduces. Although the gas fractions in inspired air are unchanged, they are taking fractions of a lower overall pressure.
What does respiratory conditioning involve and where does it occur
Structures with a high blood flow causally to the trachea. Blood is:
Warmed to a physiological temperature
Humidified to a PH20 of 6.3kPa (100% saturation)
Slowed
Mixed with air already in the lungs
Why is oxygen content reduced and carbon dioxide increased in the alveoli during ventilation
Fresh air entering the lungs mixes with the functional residue capacity (ERV + RV)
What is the total O2 delivery at rest
0.32 mL·dL-1
or
16 mL∙min-1
Describe haemoglobin
Hb is a tetrameric molecule consisting of 4 monomers with two parts
Haem and Globin
Describe haem
Ferrous iron ion (Fe2+) at the centre of a tetrapyrrole porphyrin ring. The ligand is able to reversibly bind to 1 O2. Once bound, haem and the connected chain change shape to affect other monomers, making them more receptive to binding oxygen (allosteric)
Describe globulin
protein chain. There are 4 common protein chains encoded by genes: Alpha chain (α) – produces Hbα Beta chain (β) – produces Hbβ Delta chain (δ) – produces Hbδ Gamma chain (γ) – produces Hbγ
What are the 3 common variants of Hb
HbA, HbA2, HbF
How is haemoglobin transported in the blood
Packed in erythrocytes that account for 45% of the blood
150 g/L
Explain cooperativity of haemoglobin
When Hb is fully deoxygenated, it shifts into a tense state where binding of the first oxygen is very difficult. As more oxygen binds it shifts to a relaxed state to increase infinity for oxygen. The affinity between the final binding site and oxygen is 300x greater than for the first.
Binding site for 2,3-DPG to bind which pushes Haemoglobin to have a tense state
Describe foetal haemoglobin
OD curve shift to the left
2 alpha and 2 gamma
Greater affinity for oxygen as HbF must be able to bind to oxygen that is already bound to maternal Hb within the placenta
In utero, proportion of HbF is dominant but switches to HbA postpartum
Describe methaemoglobin
Skin will become blue
0.5-1% of haemoglobin
Has a Fe3+ that does not bind oxygen
Describe myoglobin
Much greater affinity than adult HbA to store oxygen from circulating blood. Found in muscle. Curve very greatly shifted to the left.
What can be used to track how the oxygen dissociation curve changes
p50 (Partial pressure at 50% saturation)
What may cause a shift of the OD curve to the left
Decrease in temperature
Alkalosis
Hypocapnia
Decrease in 2,3-DPG
