12. Respiratory Physiology - Gwen

Question 1

1. What is Fick’s law?

2. Give the diffusion rate equation

Answer 1

1. Describes influences on the rate of transfer of a gas

2. Diffusion rate = (alveolar SA / air-blood barrier thickness) X pressure gradient X diffusion constant

Question 2

1. Define Poiseulles law
2. What do bronchioles provide?
3. What can arterioles do?
4. What is resistance to flow inversely proportional to?

Answer 2

1. Air flow and blood flow are governed by the same principles of flow, pressure and resistance
2. Provide most resistance to airflow ventilation
3. Readily increase or decrease local blood flow rate
4. Radius to the power of 4

Question 3

Haemoglobin

1. How many polypeptide chains?
2. Haem contains which ion?
3. Adult Hb = Hb A = chains?
4. Foetal Hb = Hb F = chains?
5. What are the 2 states of Hb?
6. Oxygen binds to iron in which state?

Answer 3

1. 4
2. Iron (Fe2+)
3. 2 alpha and 2 beta
4. 2 alpha and 2 gamma
5. Oxyhemoglobin and deoxyhaemoglobin
6. Ferrous state = Fe2+

Question 4

Oxygen-Hb dissociation curve

1. Curve type? Shape change type? Binding type?
2. As each oxygen binds to a Haem group, what happens to the structure? How does this relate to affinity?

Answer 4

1. Sigmoid curve / allosteric shape change / co-operative binding
2. Quaternary structure changes / affinity of remaining sites for oxygen increases

Question 5

Right hand shift

1. What 2 things does a right hand shift lead to?
2. What 4 things can cause a right hand shift?

Answer 5

1. Reduce Hb-oxygen affinity
   Help oxygen unloading into tissues
2. Acidic pH
   Increased PaCO2
   Raised body temperature
   2,3 biphosphoglycerate

Question 6

Left hand shift

1. What 2 things does a left hand shift lead to?
2. What 4 things can cause a left hand shift?

Answer 6

1. Increase Hb-oxygen affinity
   Prevent oxygen unloading to tissues
2. Alkaline pH
   Reduced PaCO2
   Lowered body temperature
   Fetal Hb

Question 7

CO2 + red blood cell on systemic circulation

1. CO2 is produced by the tissues. What cell does it enter?
2. What does it combine with first? What enzyme is involved? What is the end result?
3. What two things does this split into?
4. When HCO3- diffuses out into the plasma, what diffuses in? What is this called?
5. The oxyHb in the cell dissociates to release what 2 things? What is the purpose of this?

Answer 7

1. Red blood cell in systemic circulation
2. Water / carbonic anhydrase / H2CO3
3. HCO3- and H+
4. Cl-
   Chloride shift
5. Oxygen and free Hb
   Hb can bind to H+ = HHb = buffer

Question 8

CO2 dissociation curve

Shape?

Answer 8

Linear

Question 9

1. Acidosis is blood pH below what?

2. Alkalosis is blood pH above what?

Answer 9

1. 7.35

2. 7.45

Question 10

Define pH

Answer 10

Power of hydrogen

=-log10 [H+]

Question 11

Give 3 mechanisms of metabolic production of acid

Answer 11

1. Carbonic acid
2. Non-volatile acid produced from nutrient breakdown
3. Organic acids from intermediate metabolism

Question 12

What are the 3 broad lines of defence against pH disorders?

Which one works in minutes and which one takes hours-days?

Answer 12

1. Chemical buffers
2. Adjusting ventilation to change PaCO2 (mins)
3. Adjusting renal acid or alkalis secretion (hours-days)

Question 13

State the 3 main extracellular buffer systems

Answer 13

1. Protein buffer system
2. Phosphate buffer system
3. Carbonic acid-bicarbonate buffer system

Question 14

The carbonic acid-bicarbonate buffer system

1. What is the equation?
2. This system cannot protect against pH changes due to what?

Answer 14

1. Carbon dioxide + water - (carbonic anyhydrase) - H2CO3 - H+ and HCO3-
2. Respiratory problems with too much/too little CO2

Question 15

Bicarbonate buffer system is tightly regulated

1. What is carbon dioxide regulated by? What does this work via? How long does this take?
2. What is bicarbonate ion and hydrogen ion regulated by? How long does this take?

Answer 15

1. Lungs
   Chemoreceptors
   Seconds
2. Kidneys
   Hours-days

Question 16

Henderson-Hasselbach equation

1. What is the equation?
2. What 2 types of disturbances can effect this?

Answer 16

1. pH is inversely proportional to bicarbonate divided by PCO2
2. Respiratory and non-respiratory (metabolic)

Question 17

Bicarbonate buffer system

1. Define respiratory cause
2. Define non-respiratory (metabolic) cause

Answer 17

1. Carbon dioxide is the main cause of the pH disturbance

2. Bicarbonate is the main cause of the pH disturbance

Question 18

Respiratory acidosis

1. Cause?
2. Due to?
3. Name 2 treatments

Answer 18

1. Elevation of PCO2 in blood
2. Lack of removal of CO2 from blood
3. IV administration of bicarbonate
4. Ventilation therapy to increase exhalation of CO2

Question 19

Respiratory alkalosis

1. Cause?
2. Due to?
3. What 2 things does renal compensation involve?
4. Treatment?

Answer 19

1. Arterial blood PCO2 is too low
2. Increased removal of CO2 from blood
3. Decrease in excretion of H+
   Increase in excretion of bicarbonate
4. Re-breathing expired air

Question 20

Oxygen carriage in blood

1. How much is physically dissolved? What can you say about oxygens solubility?
2. How much is bound to Hb in RBC? The total bound is influenced by what?

Answer 20

1. 1.5%
   Oxygen has low solubility compared to CO2
2. 98.5%
   Influenced by % saturation