12. Respiratory Physiology - Gwen Flashcards
- What is Fick’s law?
2. Give the diffusion rate equation
- 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
- Define Poiseulles law
- What do bronchioles provide?
- What can arterioles do?
- What is resistance to flow inversely proportional to?
- Air flow and blood flow are governed by the same principles of flow, pressure and resistance
- Provide most resistance to airflow ventilation
- Readily increase or decrease local blood flow rate
- Radius to the power of 4
Haemoglobin
- How many polypeptide chains?
- Haem contains which ion?
- Adult Hb = Hb A = chains?
- Foetal Hb = Hb F = chains?
- What are the 2 states of Hb?
- Oxygen binds to iron in which state?
- 4
- Iron (Fe2+)
- 2 alpha and 2 beta
- 2 alpha and 2 gamma
- Oxyhemoglobin and deoxyhaemoglobin
- Ferrous state = Fe2+
Oxygen-Hb dissociation curve
- Curve type? Shape change type? Binding type?
- As each oxygen binds to a Haem group, what happens to the structure? How does this relate to affinity?
- Sigmoid curve / allosteric shape change / co-operative binding
- Quaternary structure changes / affinity of remaining sites for oxygen increases
Right hand shift
- What 2 things does a right hand shift lead to?
- What 4 things can cause a right hand shift?
- Reduce Hb-oxygen affinity
Help oxygen unloading into tissues - Acidic pH
Increased PaCO2
Raised body temperature
2,3 biphosphoglycerate
Left hand shift
- What 2 things does a left hand shift lead to?
- What 4 things can cause a left hand shift?
- Increase Hb-oxygen affinity
Prevent oxygen unloading to tissues - Alkaline pH
Reduced PaCO2
Lowered body temperature
Fetal Hb
CO2 + red blood cell on systemic circulation
- CO2 is produced by the tissues. What cell does it enter?
- What does it combine with first? What enzyme is involved? What is the end result?
- What two things does this split into?
- When HCO3- diffuses out into the plasma, what diffuses in? What is this called?
- The oxyHb in the cell dissociates to release what 2 things? What is the purpose of this?
- Red blood cell in systemic circulation
- Water / carbonic anhydrase / H2CO3
- HCO3- and H+
- Cl-
Chloride shift - Oxygen and free Hb
Hb can bind to H+ = HHb = buffer
CO2 dissociation curve
Shape?
Linear
- Acidosis is blood pH below what?
2. Alkalosis is blood pH above what?
- 7.35
2. 7.45
Define pH
Power of hydrogen
=-log10 [H+]
Give 3 mechanisms of metabolic production of acid
- Carbonic acid
- Non-volatile acid produced from nutrient breakdown
- Organic acids from intermediate metabolism
What are the 3 broad lines of defence against pH disorders?
Which one works in minutes and which one takes hours-days?
- Chemical buffers
- Adjusting ventilation to change PaCO2 (mins)
- Adjusting renal acid or alkalis secretion (hours-days)
State the 3 main extracellular buffer systems
- Protein buffer system
- Phosphate buffer system
- Carbonic acid-bicarbonate buffer system
The carbonic acid-bicarbonate buffer system
- What is the equation?
- This system cannot protect against pH changes due to what?
- Carbon dioxide + water - (carbonic anyhydrase) - H2CO3 - H+ and HCO3-
- Respiratory problems with too much/too little CO2
Bicarbonate buffer system is tightly regulated
- What is carbon dioxide regulated by? What does this work via? How long does this take?
- What is bicarbonate ion and hydrogen ion regulated by? How long does this take?
- Lungs
Chemoreceptors
Seconds - Kidneys
Hours-days
Henderson-Hasselbach equation
- What is the equation?
- What 2 types of disturbances can effect this?
- pH is inversely proportional to bicarbonate divided by PCO2
- Respiratory and non-respiratory (metabolic)
Bicarbonate buffer system
- Define respiratory cause
- Define non-respiratory (metabolic) cause
- Carbon dioxide is the main cause of the pH disturbance
2. Bicarbonate is the main cause of the pH disturbance
Respiratory acidosis
- Cause?
- Due to?
- Name 2 treatments
- Elevation of PCO2 in blood
- Lack of removal of CO2 from blood
- IV administration of bicarbonate
- Ventilation therapy to increase exhalation of CO2
Respiratory alkalosis
- Cause?
- Due to?
- What 2 things does renal compensation involve?
- Treatment?
- Arterial blood PCO2 is too low
- Increased removal of CO2 from blood
- Decrease in excretion of H+
Increase in excretion of bicarbonate - Re-breathing expired air
Oxygen carriage in blood
- How much is physically dissolved? What can you say about oxygens solubility?
- How much is bound to Hb in RBC? The total bound is influenced by what?
- 1.5%
Oxygen has low solubility compared to CO2 - 98.5%
Influenced by % saturation