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HLB > Gas Exchange and Gas Transport > Flashcards

Gas Exchange and Gas Transport Flashcards

1
Q

What is respiration?

A

Respiration is the gas exchange between the alveoli and pulmonary cavities.

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2
Q

How does gas exchange occur during respiration?

A

Gas exchange during respiration occurs through the diffusion of oxygen (O2) and carbon dioxide (CO2) from an area of high concentration to an area of low concentration, driven by a concentration gradient.

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3
Q

How does the pressure in pulmonary circulation compare to systemic circulation?

A

The pressure in pulmonary circulation is lower than in systemic circulation.

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4
Q

Why is oxygen not very soluble in plasma?

A

Oxygen is not very soluble in plasma because it has limited solubility in water.

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5
Q

How is oxygen transported in the blood?

A

Oxygen is transported in the blood by binding to hemoglobin (Hb) to form oxyhemoglobin.

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6
Q

What happens to the oxygen dissociation curve at higher levels of saturation?

A

The oxygen dissociation curve flattens at higher levels of saturation, indicating that further increases in partial pressure of oxygen result in smaller increases in oxygen saturation.

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7
Q

How does hypoventilation or hyperventilation affect arterial oxygen content?

A

Hypoventilation or hyperventilation will result in little change in arterial oxygen content. These factors primarily affect carbon dioxide levels rather than arterial oxygen content.

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8
Q

What does P50 represent in the oxygen dissociation curve?

A

P50 represents the partial pressure of oxygen at which 50% of hemoglobin (Hb) is saturated. It indicates the affinity of Hb for oxygen.

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9
Q

What happens if the partial pressure of oxygen drops below 8kPA?

A

If the partial pressure of oxygen drops below 8kPA, there is a significant reduction in oxygen saturation, leading to respiratory failure.

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10
Q

What factors influence the affinity of hemoglobin for oxygen?

A

The affinity of hemoglobin for oxygen depends on pH, carbon dioxide (CO2) partial pressure, and temperature.

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11
Q

How does an increase in the concentration of 2,3-DPG affect the oxygen dissociation curve?

A

An increase in the concentration of 2,3-DPG results in a shift to the right in the oxygen dissociation curve. This shift indicates a decrease in hemoglobin’s affinity for oxygen, promoting oxygen release.

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12
Q

What does it mean if the oxygen dissociation curve moves to the right?

A

If the oxygen dissociation curve moves to the right, it means that the affinity of hemoglobin for oxygen is decreased. This shift indicates a larger tendency for hemoglobin to release oxygen rather than retain it.

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13
Q

What is the oxygen cascade?

A

The oxygen cascade refers to the falling pressure of oxygen from the air down to the mitochondria.

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14
Q

Where does air get humidified in the respiratory system, and why is it significant?

A

Air gets humidified in the upper conducting airways, which do not participate in gas exchange. Humidification is important to prevent drying and damage to delicate respiratory tissues.

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15
Q

How does water vapor affect the partial pressure of oxygen?

A

Water vapor decreases the partial pressure of oxygen in the respiratory system.

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16
Q

What happens to the oxygen content as it passes through each membrane or compartment?

A

The oxygen content decreases across each membrane or compartment along the oxygen cascade.

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17
Q

Describe the path of oxygen from air to the mitochondria.

A

Oxygen follows this path: air → conducting airways → alveoli → interstitial space containing fluid → across the interstitium → red blood cell → binds to hemoglobin (Hb) → tissue fluid → across the cell membrane → mitochondria.

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18
Q

What happens when oxygen binds to hemoglobin?

A

When oxygen binds to hemoglobin, it forms oxyhemoglobin, and the hemoglobin molecule is considered saturated.

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19
Q

What does deoxygenated hemoglobin contain?

A

Deoxygenated hemoglobin contains no oxygen and is considered desaturated.

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20
Q

What does an oxygen saturation probe measure?

A

An oxygen saturation probe measures the percentage of hemoglobin that is fully saturated with oxygen.

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21
Q

What is the purpose of the alveolar gas equation?

A

The alveolar gas equation is used to calculate the partial pressure of oxygen in the alveolus.

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22
Q

What factors determine oxygen delivery (DO2)?

A

Oxygen delivery (DO2) depends on cardiac output (CO) and arterial oxygen content (CaO2).
- DO2 = CO x CaO2

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23
Q

How is cardiac output (CO) calculated?

A

Cardiac output (CO) is calculated by multiplying heart rate by stroke volume.
- CO = heart rate x stroke volume

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24
Q

What does oxygen consumption (VO2) represent?

A

Oxygen consumption (VO2) refers to the amount of oxygen consumed per minute.

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25
Q

How is maximal oxygen consumption (VO2 max) calculated?

A

Maximal oxygen consumption (VO2 max) is calculated as the product of cardiac output (CO) and the difference between arterial oxygen content (CaO2) and venous oxygen content (CvO2).
- VO2 max = CO x (CaO2 – CvO2)

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26
Q

What is the typical resting oxygen consumption (VO2) in a healthy individual?

A

The resting oxygen consumption (VO2) in a healthy individual is approximately 250 ml/minute.

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27
Q

In a healthy person at rest, how does oxygen delivery (DO2) compare to oxygen consumption (VO2)?

A

At rest in a healthy individual, oxygen delivery (DO2) is greater than oxygen consumption (VO2).

28
Q

How does the solubility of CO2 in plasma compare to that of O2?

A

CO2 is more soluble in plasma than O2.

29
Q

What are the forms in which CO2 is carried in the blood?

A

CO2 is carried as carbaminohemoglobin, dissolved in plasma, and as bicarbonate ions.
- 30% of CO2 is carried as carbaminohemoglobin.
- 10% of CO2 is carried dissolved in plasma.
- 60% of CO2 is transported as bicarbonate ions.

30
Q

Describe the bicarbonate ion transport of CO2.

A

CO2 reacts with water (H2O) in the presence of carbonic anhydrase enzyme to form carbonic acid (H2CO3), which dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-).
- CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
- Enzyme involved: carbonic anhydrase

31
Q

What is the role of chloride ions (Cl-) in CO2 transport?

A

To maintain electrical neutrality, chloride ions (Cl-) diffuse into red blood cells (RBCs) in a process called the chloride shift.

32
Q

Why is there a high concentration of H+ in RBCs during CO2 transport?

A

CO2 dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-) inside RBCs, resulting in a high concentration of H+.

33
Q

What is the Haldane effect?

A

The Haldane effect refers to the phenomenon where deoxygenated hemoglobin (Hb) in tissues has an increased capacity to bind to carbon dioxide (CO2). In the alveoli, oxygenation of Hb results in the release of CO2.

34
Q

How does respiratory acidosis affect bicarbonate and deoxygenated Hb?

A

In respiratory acidosis, bicarbonate and deoxygenated hemoglobin (Hb) play an important role in binding and releasing carbon dioxide (CO2) depending on the pH.

35
Q

What happens in Type 2 Respiratory Failure and how does it relate to respiratory acidosis?

A

In Type 2 Respiratory Failure, there is an increase in carbon dioxide (CO2) levels, which leads to an increase in hydrogen ions (H+), resulting in decreased pH and respiratory acidosis.

36
Q

How can ventilation be estimated?

A

Ventilation can be estimated from the rate of carbon dioxide (CO2) production.

37
Q

What is the respiratory quotient (R)?

A

The respiratory quotient (R) or respiratory gas exchange ratio is the ratio of carbon dioxide (CO2) production to oxygen (O2) consumption.

38
Q

What is the respiratory quotient (R) for carbohydrates?

A

Carbohydrates have a respiratory quotient (R) value of 1.

39
Q

What does PAO2 represent?

A

PAO2 stands for alveolar partial pressure of oxygen, which represents the partial pressure of oxygen in the alveoli.

40
Q

What is an acinus in respiratory function?

A

An acinus refers to a unit of respiratory function located distal to the terminal bronchioles, composed of respiratory bronchioles, alveolar ducts, and alveoli.

41
Q

How are many acini grouped together?

A

Many acini together form a pulmonary lobule.

42
Q

What separates pulmonary lobules?

A

Pulmonary lobules are separated by septae, which are thin partitions or walls

43
Q

Why does individual acinus or unit of respiratory function not collapse?

A

Structural interdependence between the components of an acinus prevents the collapse of an individual unit.

44
Q

What factors determine the number of alveoli?

A

The number of alveoli depends on the height of an individual, while the size of alveoli depends on the volume of air in the lungs.

45
Q

What is the lining of the alveoli composed of?

A

The alveoli are lined by a thin layer of unciliated squamous epithelial cells.

46
Q

What are Type 1 Pneumocytes and their role in the alveoli?

A

Type 1 Pneumocytes are cells that rest on the Basement Membrane and closely interface with the capillary membrane, forming the alveolar-capillary unit.

47
Q

What does the interstitial space in the alveoli contain?

A

The interstitial space between the alveoli contains pulmonary capillaries, elastin, and collagen fibers.

48
Q

What are Type 2 pneumocytes and their role in the alveoli?

A

Type 2 pneumocytes are found at the junction between alveoli and produce surfactant, which reduces surface tension within the alveoli.

49
Q

What are Club cells, and where are they found?

A

Club cells, also known as bronchiolar exocrine cells, are found in the alveolar fluid. They produce glycosaminoglycans.

50
Q

What is the interstitium?

A

The interstitium is a microscopic space between the alveoli and the pulmonary capillary wall.

51
Q

Describe the thickness of the walls of the alveolus and pulmonary capillary.

A

Both the alveolus and the pulmonary capillary have thin walls.

52
Q

What factors affect the process of diffusion?

A

Several factors can affect diffusion, including the thickness of the membrane, the surface area of the membrane, the solubility of gas in the membrane, and the molecular weight of the gas.

53
Q

How is the movement of oxygen (O2) across the alveolar-capillary membrane estimated?

A

The movement of O2 across the alveolar-capillary membrane can be estimated using a small amount of carbon monoxide (CO).

54
Q

How is the amount of CO transferred across the alveolar-capillary membrane estimated?

A

The amount of CO transferred across the alveolar-capillary membrane per minute is estimated using a single-breath method. This measurement is known as the TLCO (transfer factor for carbon monoxide) or DLCO (diffusing capacity for carbon monoxide).

55
Q

What does TLCO/DLCO represent?

A

TLCO/DLCO represents the transfer factor or diffusing capacity for carbon monoxide. It quantifies the ability of the lungs to transfer CO from inspired gas to the bloodstream.

56
Q

In which conditions can TLCO be reduced?

A

TLCO may be reduced in conditions that affect the surface area available for gas exchange, such as emphysema, or in conditions that cause thickening of the membrane, such as pulmonary fibrosis.

57
Q

What is carboxyhemoglobin (COHb)?

A

Carboxyhemoglobin (COHb) is formed when Carbon Monoxide (CO) binds to hemoglobin (Hb) in the blood.

58
Q

How does hemoglobin’s affinity compare between oxygen (O2) and carbon monoxide (CO)?

A

Hemoglobin has a higher affinity for carbon monoxide (CO) than for oxygen (O2).

59
Q

What are the clinical symptoms of carbon monoxide (CO) poisoning?

A

Clinical symptoms of CO poisoning can appear as early as one hour after exposure and may include headaches, nausea, vomiting, dizziness, lethargy, weakness, confusion, coma, and even death within hours.

60
Q

How can the oxygen saturation (SaO2) readings be affected in the presence of carboxyhemoglobin (COHb)?

A

In the presence of carboxyhemoglobin (COHb), the oxygen saturation (SaO2) readings can be falsely “normal” since finger probes and pulse oximeters may mistakenly read CO-bound hemoglobin as oxygen-bound hemoglobin (Oxy-Hb).

61
Q

What is methemoglobin (MetHb)?

A

Methemoglobin (MetHb) occurs when the iron component in hemoglobin is oxidized, resulting in the ferric state (Fe3+) of iron.

62
Q

What is the consequence of methemoglobin (MetHb) formation?

A

Methemoglobin (MetHb) is unable to bind oxygen (O2) and therefore cannot participate in oxygen transport.

63
Q

What are the main causes of a pathological increase in methemoglobin (MetHb) concentration?

A

The main causes of a pathological increase in methemoglobin (MetHb) concentration include congenital/idiopathic methemoglobinemia, which is a genetic defect leading to a deficiency of a certain enzyme or protein, and acquired MetHb resulting from exposure to chemicals such as certain anesthetics, nitrobenzene, or specific antibiotics.

64
Q

What are the clinical manifestations in infants with congenital/idiopathic methemoglobinemia?

A

Infants with congenital/idiopathic methemoglobinemia may exhibit cyanosis, which is a bluish discoloration of the skin and mucous membranes caused by decreased oxygen levels in the blood.

65
Q

How is acquired methemoglobinemia managed?

A

The management of acquired methemoglobinemia typically involves oxygen therapy and the administration of methylene blue, a medication that can help convert methemoglobin back to hemoglobin.

HLB (40 decks)

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