Gas Exchange Flashcards

Question

What happens to the V/Q to alveoli being underperfused due to an embolism and how can you compensate?

Answer 1

→V/Q ratio increases in alveoli that is not being perfused → Increased perfusion to other alveoli and their V/Q ratio decreases →you can compensate by ventilating more

Answer 2

→ Heart failure → Blocked vessels → Loss/damage to capillaries

Answer 3

→ Perfusion without ventilation | → as deoxygenated blood returns to the left side of the heart from the right, without taking part in gas exchange.

Answer 4

→ Pneumonia → Acute lung injury → respiratory distress syndrome → atelectasis

Answer 5

→ The relationship between Co2 and O2 in inspired + expired air

Answer 6

→ VCO2 produced/VO2 consumed

Answer 7

→ PaO2 = F1O2 x (Pb-PH2O) - (Pa Co2/RER)

Answer 8

→ Difference between arterial and alveolar partial pressure

Answer 9

→ PaCo2 > 6kPa

Answer 10

→ A-a gradient should be less than 2 kPa

Answer 11

78% nitrogen, 21% oxygen, 1% other gases

Answer 12

0kPa in dry air to approximately 6kPa in fully warmed, humidified air within the lung

Answer 13

𝑃_𝑔𝑎𝑠=〖(𝑃〗_𝑏𝑎𝑟𝑜𝑚𝑒𝑡𝑟𝑖𝑐−𝑃_(𝐻_2 𝑂))×𝑛_𝑔𝑎𝑠 → Partial pressure of individual constituent gas → Atmospheric pressure → Water vapour pressure (0 kPa in dry air, 6 kPa in fully humidified air) → Mole fraction: the % of total moles represented by the individual gas (e.g. in air at sea level, O2 = 21%)

Answer 14

𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛=𝑃𝑎𝑟𝑡𝑖𝑎𝑙 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 ×𝑆𝑜𝑙𝑢𝑏𝑖𝑙𝑖𝑡𝑦

Answer 15

reflects the amount of gas that would dissolve (at equilibrium) if the liquid was placed in contact with a gas phase of equivalent partial pressure.

Answer 16

→ When blood passes through the pulmonary capillaries of healthy individuals, the partial pressures of respiratory gases almost completely equilibrate with those of alveolar air.

Answer 17

→ there must be sufficient blood (specifically haemoglobin binding sites) to absorb the quantity of oxygen arriving at the alveoli. →Therefore the level of ventilation (supply of oxygen) and perfusion (supply of blood) need to be closely matched.

Answer 18

the overall perfusion of the lungs as a whole may not decrease if blood is simply diverted through other pulmonary arteries/capillaries → In theory, increased ventilation of these areas of the lungs may compensate for the reduction in gas exchange in others.

Answer 19

→ regardless of degree of oxygenation occurring in blood perfusing well-ventilated alveoli, it will eventually mix with deoxygenated blood returning from areas affected by shunt, → reducing the overall PaO2

Answer 20

→The vast majority (>98%) of oxygen carried in blood is transported bound to haemoglobin. →As saturation of haemoglobin is typically >95% at physiological oxygen pressures, administering supplemental oxygen cannot increase oxygen saturation in well-ventilated regions of the lung sufficiently to compensate for the deoxygenated blood with which it will eventually mix.

Answer 21

→occurs when ventilation to an alveoli is reduced; →the decreased ventilation results in rising CO2 and falling O2 levels, →cause contraction of the vascular smooth muscle within nearby capillaries.

Answer 22

diverts blood to other capillaries that innervate better-ventilated alveoli.

Answer 23

the chronic hypoventilation that occurs within large sections of the lungs, →leads to prolonged and widespread pulmonary vasoconstriction. → increases resistance within the pulmonary vasculature, →in pulmonary hypertension. →lead to right heart hypertrophy and (eventually) right heart failure.

Answer 24

there will always be a volume of relatively deoxygenated blood returning to the systemic circulation, for which additional ventilation of more functional parts of the lung cannot compensate →(as there isn’t sufficient ‘spare’ unbound haemoglobin within the blood perfusing the better ventilated parts of the lung – O2 saturation is >95% at baseline)