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CTB > CTB3 - Ventilation and Gas Transport > Flashcards

CTB3 - Ventilation and Gas Transport Flashcards

1
Q

Define the difference between volume and capacity.

A

Volumes are measurements that are taken with regards to ventilation.
Capacities are calculations obtained from two or more measurements - cannot be measured directly therefore require calculations.

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2
Q

What are the four volumes in ventilation? Give brief description of each.

A

Tidal volume - regular breathing volume for both inspiration and expiration.
Inspiratory reserve volume - maximum volume of air that can be inspired. Maximum can be reached.
Expiratory reserve volume - maximal volume of air that can be expired. Maximum cannot be reached I.e. lung does not fully empty.
Residual volume - leftover volume of lungs that cannot be expired no matter how forceful expiration is.

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3
Q

Why does residual volume exist?

A

If lungs completely emptied, they would collapse and become stuck to one another. This is difficult to overcome (lots of energy needed) which is not feasible.

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4
Q

How can different ventilation volumes be measured?

A

Using spirometry.

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5
Q

What are the capacities that can be calculated? What volumes are required to calculate each? Give brief description of each.

A

Total lung capacity - TV + IRV + ERV + RV - entire capacity of lungs including volumes that can be reached and those that can’t.

Functional residual capacity - ERV + RV - maximum volume of air that can be expired (actually and theoretically) beyond the tidal expiration.

Inspiratory capacity - TV + IRV - maximum volume of air that can be inspired including both normal breathing and forceful inspiration.

Vital capacity - TV + IRV + ERV - total volume that can be physically inspired and expired

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6
Q

What is dead space? What are the names of the three types of dead space?

A

Dead space refers to airway regions not participating in gaseous exchange.

Types - anatomical dead space, alveolar dead space, physiological dead space.

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7
Q

Describe each type of dead space and approx value in healthy individuals.

A

Anatomical dead space - conducting zone of the airways. Dead space as no gaseous exchange occurs at this stage. Approx 150mL in adults.

Alveolar dead space - respiratory tissues (alveoli) unable to take part in gaseous exchange due to damage. Should be 0 in healthy individuals.

Physiological dead space - sum of anatomical and alveolar dead space

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8
Q

What is alveolar ventilation? How can it be calculated?

A

Amount of air reaching the alveoli/gas exchange surface per minute. Difference in tidal volume and anatomical dead space multiplied by breathing frequency.

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9
Q

What is pulmonary ventilation and how can it be calculated?

A

Amount of air moving into and out of the lungs. Calculated by multiplying tidal volume by breathing frequency.

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10
Q

What happens to airway pressure and airflow velocity as you go through the airway generations?

A

Pressure and velocity decreases.

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11
Q

What are the lung parenchyma?

A

Refer to the alveolar where the gaseous exchange actually occurs.

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12
Q

Do long tubes have more or less dead space?

A

Longer tubes have more dead space (provided that they are not too narrow).

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13
Q

Give conditions that would affect alveolar dead space and how they affect this dead space.

A

Emphysema. Lung parenchyma fibrosis. COPD.
Increases alveolar dead space (from 0 to not 0) meaning that some alveoli are no longer able to take part in gaseous exchange.

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14
Q

What are the two types of breathing (with relation to pressure)? Briefly describe each with example.

A

Positive pressure breathing - pressure outside lung is increased. Mechanical ventilation.

Negative pressure breathing - pressure inside lung is decreased. Normal breathing.

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15
Q

At rest, what capacity describes the volume of the lungs? How is this calculated?

A

Functional residual capacity.

Residual volume + expiratory reserve volume = functional residual capacity.

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16
Q

What is the value for intrapleural pressure, and what happens to it when inspiration occurs?

A

Approx -5cmH2O. During inspiration, decreases to approx -8cmH2O.

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17
Q

Discuss the changes in respiratory muscles to allow inspiration to occur. What happens following these changes?

A

Diaphragm contracts - flattens.
External intercostal muscle contract - rib cage pulled up and Out.
Thoracic cavity volume is increased so pressure decreases. Pressure in lung is less than atmospheric pressure, causing air to rush into the lungs.

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18
Q

What happens to respiratory musculature during expiration?

A

Diaphragm relaxes and domes upwards. External intercostal muscles relax, pulling rib cage in and down. Thoracic cavity volume is decreased, meaning pressure is increased relative to atmospheric pressure. Air rushes out of the lungs.

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19
Q

What law is used to describe airway resistance? What are some key take away points from this law?

A

Poiseuille’s law. Small decrease in radius causes a large increase in resistance.

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20
Q

Describe the changes in resistance as the airway generations increase.

A

Initial increase in resistance. Following this, resistance decreases gradually reaching zero.

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21
Q

Why does resistance decrease overall as you go down the airway generations?

A

Despite individuals airway radius decreasing, the total cross sectional area increases (as there are multiple of the smaller airways).

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22
Q

What law can be used to determine diffusion rate? What are they key applications of this law?

A

Flicks law of diffusion. States that diffusion rate is dependent on concentric gradient, thickness of surface, diffusibility of the gas and surface area.

High diffusion rate is dependent on large surface area, small surface thickness, high concentration gradient, high gas diffusibility

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23
Q

What law is used to calculate dissolved gas concentration? What parameters are required?

A

Henry’s law. Concentration of a dissolved gas in solution is dependent on the solubility of the gas and the partial pressure.

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24
Q

Does temperature affect gas volume? What law can be used to describe this?

A

Charles law. Volume of gas is dependent on temperature as gases expand as they heat.

25
Q

With reference to Charles law, discuss the volume of inspired air relative to expired air?

A

Inspired air is at a lower temperature to expired air. As a result, this means that inspired air has a smaller volume. This is because Charles law indicates that volume and temperature of a gas is linked.

26
Q

How do you calculate partial pressure of a gas?

A

Multiply the gas fraction by the total pressure.

27
Q

What gases are found in atmospheric air, and in what amounts?

A 
Nitrogen - 78.2%
Oxygen - 20.9%
Argon - 0.9%
Carbon dioxide - 0.04%
Inert gases - 0.01% (neon, xenon, helium, hydrogen)
28
Q

What is barometric pressure equal to?

A

Approx 760mmHg or 101.3kPa. This is at sea level.

29
Q

What happens to barometric pressure as altitude increases? What is the effect on the partial pressure of oxygen?

A

Barometric pressure decreases as altitude increases. This means that there will be lower partial pressures of oxygen at higher altitudes.

30
Q

When would therapeutic oxygen be administered to a patient and what is the purpose of this?

A

Patients with respiratory diseases to ensure that sufficient oxygen supply is being provided to the body. Oxygen can be given as much as 100% pure oxygen in order to increase oxygen in body to approx 60%.

31
Q

What is the effect of carbon monoxide in the body?

A

Carbon monoxide binds to haemoglobin in the place of oxygen. This means CO is transported around the body instead of oxygen. Binding of CO to haemoglobin is irreversible meaning that eventually all haemoglobin is occupied and no more oxygen can be carried around the body.

32
Q

Does gas proportions change at different levels above sea? Relate this to the availability of oxygen at different levels.

A

No. Total pressure changes but ratios of each gas remain constant. The proportion of oxygen remains the same but because partial pressure of oxygen changes, this affects haemoglobin oxygen saturation.

33
Q

What modifications are done to the air when it is inspired into the airways?

A

Warming. Humidification. Slowing. Mixing with air within the lungs.

34
Q

Is the oxygen content of the air that is being inspired the same as the oxygen content of the air at the alveolar exchange surface?

A

No. Lungs never empty fully (residual volume). Residual air within the lungs will have some carbon dioxide and some oxygen. Inspired air will mix with this air, thus reducing the oxygen content.

35
Q

What law can be used to calculate the concentration of dissolved gas in the blood?

A

Henry’s law. Uses the partial pressure and solubility of the gas to determine dissolved concentration.

36
Q

What proportion of oxygen is carried in the blood and via haemoglobin?

A

Approx 2% dissolved in blood plasma. Remaining 98% uses haemoglobin.

37
Q 
Discuss the effect of the following factors on dissolved oxygen concentration:
Pulmonary oedema
Blood transfusion
Increasing breathing rate
Increased tidal volume
A

Pulmonary oedema - increases diffusion distance, decreased oxygen dissolved in blood due to decreased rate of diffusion.
Blood transfusion - no impact on dissolved oxygen but may affect oxygen in haemoglobin.
Increased breathing rate - no impact on dissolved oxygen as oxygen does not have the time to dissolve into the blood plasma.
Increased tidal volume - more oxygen reached alveolar gas exchange surface, concentration gradient maintained, allows more oxygen to dissolve into the blood plasma.

38
Q

What two parts make up a haemoglobin molecule? Briefly describe each.

A

Haem - chemical ring structure with iron ion which behaves as ligand for reversible binding of oxygen.
Globin - large protein chain.

39
Q

Is haemoglobin toxic? If yes/no, give example.

A

Can be. May cause renal failure if not packaged within the erythrocytes. Caused by haemolytic blood disorders .

40
Q

What is the haemotocrit and how can it be calculated?

A

Amount of erythrocytes within the blood. Should be approx 40-50% in healthy humans. Can be calculated by centrifugation of blood.

41
Q

What is the binding capacity of haemoglobin? Value and description.

A

Approx 1.34mL O2/g. Describes how much oxygen can bind per gram of haemoglobin.

42
Q

Discuss the positive cooperativity of haemoglobin. Relate this to tense and relaxed state of haemoglobin.

A

Binding of one oxygen molecule allows the binding of subsequent oxygen molecules to be easier. Displays allosteric characteristics.

Tense haemoglobin state is where no oxygen molecules are bound. Relaxed haemoglobin state is when oxygen molecule are bound.

43
Q

What cofactor is used for red cell energy production? Where does this bind to? What is its effect?

A

Cofactor - 2,3-DPG
Binds to binding site between two beta globin chains.
Causes haemgoblin structure to be tense. Promotes oxygen dissociating. Involved in energy production (oxygen must dissociate to allow energy to be produced).

44
Q

Is systemic or pulmonary circulation associated with a higher haemoglobin saturation? Discuss the changes in oxygen partial pressure and haemoglobin saturation for each system.

A

Pulmonary circulation has greater haemoglobin saturation.

Pulmonary - varying oxygen partial pressures have little effect on haemoglobin saturation.
Systemic - small change in oxygen partial pressures cause large differences in haemoglobin saturation,

45
Q

Give four conditions that can alter the ODC a either left or right. Give brief overview of what conditions are needed to either shift the curve left or right and what this means.

A

Temperature.
PH.
Carbon dioxide partial pressure.
Availability of 2,3-DPG.

Shifting to left and right determines unloading and loading ability of oxygen onto haemoglobin. Alters based on oxygen environments.

46
Q

What causes the ODC to shift left vs what causes the ODC atom shift right?

A

Left shift - decreased temperature, alkalosis, hypocapnia, decreased 2,3-DPG.

Right shift - increased temperature, acidosis, hypercapnia, increased 2,3-DPG.

47
Q

What conditions cause either an upward or downward shift of the ODC, and what does this functionally relate to?

A

Upward - polycythaemia. Associated with increased oxygen carrying capacity of haemoglobin. Increased erythrocyte presence in blood.
Downward - anaemia. Associated with decreased oxygen carrying capacity of haemoglobin. Decreased erythrocytes or inefficient haemoglobin.

48
Q

Discuss why anaemic patients may still have a sufficient haemoglobin saturation, but are considered anaemic.

A

All haemoglobin can become saturated - meaning that full saturation is present - however there is not enough haemoglobin to meet the oxygen demands of the body.

49
Q

Discuss the exact pathway through which oxygen diffuses from the alveolus to the bloodstream.

A

From alveolar space to pulmonary epithelial cells to interstitial space to vascular endothelial cells to blood plasma to erythrocytes to haemoglobin.

50
Q

How long does it take for alveolar gas to equilibriate with capillary blood?

A

Approx 0.25sevonds.

51
Q

Why is the post alveolar oxygen saturation only 97% not 100%?

A

Bronchial venous drainage. Some oxygen is lost meaning that saturation decreases.

52
Q

Discuss the exact oxygen diffusion pathway from the bloodstream to the tissues,

A

From the erythrocytes to the blood plasma to the vascular endothelial cell to the interstitial space, to the epithelial cells of the target tissue and then into the cells,

53
Q

What two changes are associated with oxygen flux?

A

Decreased content of aterial oxygen and oxygen utilisation rate.

54
Q

What are the three ways in which carbon dioxide is transported in the body?

A

Dissolved in blood plasma. Associated with haemoglobin to form carbaminohaemoglboin. Found as bicarbonate ions in the plasma.

55
Q

Why does an increase in carbon dioxide cause acidosis?

A

Carbon dioxide reacts with water to form carbonic acid which undergoes partial dissociation into protons and bicarbonate ions. Protons cause pH to reduce I.e. acidosis.

56
Q

Where is the production of carbonic acid faster, in blood plasma or erythcytoes? Why?

A

Faster in erythrocytes. Due to presence of carbonic anhydrase enzymes which catalyse reaction up to 5000X.

57
Q

What happens to bicarbonate ions within the erythrocytes? Discuss any changes in ions or other molecules that must occur to keep the balance.

A

Bicarbonate ions are pumped out of the erythrocytes whilst chloride ions are pumped in - via AE1 transport protein.
Water must be pumped in to maintain water content (as it is being pumped out in the form of bicarbonate ions).

58
Q

How does carbaminohaemoglobin form?

A

Carbon dioxide binds to amine group/N terminal of haemoglobin protein chains.

59
Q

Discuss briefly how carbon dioxide is unloaded at the lungs.

A

Carbon dioxide diffuses down its concentration gradient into the alveolus. Some bicarbonate ions re enter erythrocytes. They join with Protons forming carbonic acid. Carbonic anhydrase catalysed the conversion back into carbon dioxide and water. Carbon dioxide diffuses once more.

CTB (9 decks)

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