1. Lung Volumes and Lung Function Testing 
 Blood Gas Transport - Oxygen 
Blood Gas Transport - Carbon Dioxide 

2. Lung Volumes and Lung Function Testing
Explain the special properties of surfactant and the role of surfactant in infant respiratory distress syndrome.
 Differentiate restrictive from obstructive deficits
 Explain simple flow-volume curves and the use of peak expiratory flow rate
 Define the various respiratory volumes which can be measured (VC, RV, FRC, IRV, ERV, TV and TLC)
 Interpret a lung function report

3. Surfactants High surface tension  hard to stretch
Type 2 alveolar cells produce surfactant = detergent = reduces surface tension = helps elasticity when breathing in
This happens when lungs are deflated  as lungs inflate, surfactant thins, surface tension increases maintaining pressure + shape of alveoli
IRDS: babies born early lack surfactant so have stiff lungs

4. Lung function testing
Measures mechanical condition of the lungs, the resistance of the airways and (fancy tests) diffusion
Maximal inspiration determined by compliance and force of inspiratory muscles
Maximal rate of expiration determined by airway resistance

5. Restrictive and Obstructive deficits
FVC = the maximum volume that can be expired from full lungs
FEV1.0= volume expired in the first second.

6. OBSTRUCTIVE Airways are narrowed
Can still fill to capacity = FVC normal(ish)
Resistance will increase on expiration
Air will come out more slowly = FEV1
COPD

7. RESTRICTIVE Lungs do not fill fully FVC
What has gone in is not stopped from coming out so FEV1 has a NORMAL RATE
However, because FVC is low, FEV1 looks
Diseases of the lung parenchyma/neuromuscular disorders

8. Obstructive
Restrictive
Combined
FVC
Normal(ish) ↓
FEV1
Normal in relative terms but looks ↓
FEV1/FVC
Normal

9. Vitalograph traces

10. Flow volume loop - obstructive

11. Flow volume loop - restrictive

12. Oxygen transport
Describe how oxygen is transported in blood and explain the affinity of haemoglobin for oxygen.
 Draw and label a typical oxyhaemoglobin dissociation curve for blood, showing the relationship between partial pressure, saturation and content of oxygen.
 Quantify the relationship between oxygen partial pressure and haemoglobin saturation.
 Describe the effects of changes in pH, PCO2, temperature and 2,3-DPG on the oxyhaemoglobin dissociation curve.
 Describe the main differences between adult haemoglobin and: fetal haemoglobin, methaemoglobin and myoglobin in terms of oxygen carriage.
 Define hypoxia and state the conditions under which it is likely to occur.
 Define cyanosis and state the conditions under which it is likely to occur.

13. Oxygen in the blood 1.5% plasma – poor solubility 98.5% in Hb in RBC
Hb: 4 polypeptide chains, each containing and Fe containing haem group, each haem can rapidly and reversibly bind 4 molecules of oxygen
First oxygen binds  conformational change  affinity for subsequent oxygens pregressively easier
First oxygen unloaded  affinity decreases  progressively easier to dissociate

14. Oxyhaemoglobin dissociation curve
Sigmoidal
Saturation dependent on partial pressure of oxygen

15. Curve explained Hb saturation (%) – depends on PO2, not Hb
Oxygen content – depends on PO2 and Hb content

16. Hb content Women: 11-13 g.dl-1 Men: 13 – 15 If reduced  anaemic
10 is low
At 8, transfusion
High Hb = polysythaemia 16.5/18.5

17. Pressure and saturation
Normal resting conditions: AA blood is at PaO2 of 13.3kPa, 98% saturation
VV blood: PaO2 of 6kPa, 75% saturation
Large decrease in P, small decrease in sats…
Hb almost completely saturated at 9.3kPa allows for changes in conditions

18. Bohr Shift Increase PO2  right shift  unload at higher PO2
Decrease in pH (acidic)  R shift
Increased CO2  R shift (as makes more acidic)
DPG (compound produced by RBC) Increased  R shift
Temp increase  R shift

19. Hypoxia
Hypoxaemic: reduced PaO2 – ventilation (CO poisoning)/low O2 (altitude)
Anaemic: low Hb
Ischaemic: blocked circulation
Histotoxic: body cant use even though its there (cyanide)
Cyanosis: blue discolouration in situations of low PaO2

20. Learn for this exam then forget…

21. Carbon dioxide transport
List the forms in which carbon dioxide is carried in the blood and the quantities transported in each form, and explain why there is more carbon dioxide than oxygen in arterial blood.
Describe the exchange of carbon dioxide and hydrogen carbonate between plasma and erythrocytes in capillaries in the lungs, and in metabolically active tissue.
Draw and label a typical carbon dioxide dissociation curve for blood, showing the relationship between the partial pressure and content of carbon dioxide, in both oxygenated and deoxygenated blood; and the effects of changing oxygen consumption and cardiac output.
State what is meant by the ‘chloride shift’, and explain the relationship between the Bohr and Haldane effects.

22. CO2 Controls blood pH CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+
CO2 is dissolved in plasma but reaction is reversible depending on conditions
PCO2 increases, pH decreases
In AA, PCO2 is a critical determinant of pH

23. Whole body control Bicarbonate in plasma depends on:
The reaction of CO2 in plasma
The reaction of CO2 in the red cell
Kidneys: excrete bicarb
Lungs: ventilation changes PCO2
Buffers change in pH
CO2 also binds to proteins (carbamines) which do not change acid-base- balance

25. Numbers to learn then forget
Arterial blood:
Plasma dissolves 1.2 mmol CO2 per litre of blood
Plasma contains 24 mmol.l-1 HCO3-.
Plasma has 0.8 mmol.l-1 carbamino-proteins.
Cells dissolve 1.2 mmol.l-1 CO2.
Cells have 8 mmol.l-1 HCO3-.
Cells have 2.8 mmol.l-1 carbamino-Hb.
Total is 38mmol CO2 per litre

26. 6-10% of CO2 in the blood =dissolved state in plasma/ intercellular fluid of blood cells
9-30% of CO2 = bound to haemoglobin (to form carbaminohaemoglobin)
60-85% of CO2 is bicarbonate ions (HCO3-)

27. Carbon dioxide in venous blood:
Increased by increased oxygen consumption.
Decreased by increased cardiac output.

28. CO2 binding Binds to globin, not haem
Loading and unloading depend on PCO2 and Hb saturation with O2
As O2 is unloaded at cell (Bohr effect – H+ ions give Hb lower affinity for O2)  affininy for CO2 increases
Visa vera at lungs as O2 loads

29. Names to remember Chloride shift: Bicarbonate exchanged for chloride
(helps buffer blood against pH changes)
Bohr effect: H+ ions cause Hb.O2 to give up O2 (helps unloading of O2 where required due to lowered pH near tissues) – change affinity to O2
Haldane effect:
CO2 binds more strongly to deoxygenated Hb
(helps removal of CO2 from tissues)