Gas Exchange, Pathophysiology-Sinclair

Question 1

Barometric Pressure at Sea Level

Answer 1

760 mmHg

Question 2

Fractional Concentration of Oxygen

Answer 2

0.21 (21%)

Question 3

Fractional Concentration of Nitrogen

Answer 3

0.78 (78%)

Question 4

The total pressure in a system is equal to the sum of the partial pressures of each individual gas in the system.

Answer 4

Dalton’s Law

Question 5

Equation for Partial Pressure

Answer 5

(Barometric Pressure at a certain level) X (Fractional Concentration of gas)

Question 6

Does the fractional concentration of oxygen ever change with different altitudes?

Answer 6

No. Fractional Concentration is the same at all altitudes.

Question 7

Does the water vapor pressure ever change with different altitudes?

Answer 7

No. Water vapor pressure never changes.

Question 8

Water vapor pressure equals…

Answer 8

47 mmHg

Question 9

Equation for Minute Ventilation

Answer 9

(Tidal Volume) X (Respiratory Rate)

Question 10

Air which remains in the conducting zone after inspiration and, therefore, does not participate in gas exchange; not pathologic

Answer 10

Anatomic Dead Space

Question 11

Portion of alveoli which do not participate in gas exchange as a result of a lack of perfusion; usually pathologic

Answer 11

Alveolar Dead Space

Question 12

Equation for Physiologic Dead Space

Answer 12

(Alveolar Dead Space) + (Anatomic Dead Space)

Question 13

Normal value for Physiologic Dead Space in normal people

Answer 13

150 mL

Question 14

Equation for Alveolar (Effective) Ventilation

Answer 14

(Tidal Volume - Physiologic Dead Space) X Respiratory Rate

Question 15

The amount of dead space in a given individual is highly dependent upon…

Answer 15

Lean Body Weight

Question 16

Alveolar Gas Equation (Finding the alveolar partial pressure of oxygen)

Answer 16

PIO2 - [(PaCO2)/R], where R=0.8

Question 17

Value and Calculation of PIO2 (inspired pressure of Oxygen)

Answer 17

(760-47) X 0.21 = 150 mmHg

Question 18

Normal Value for PaCO2 at Sea Level

Answer 18

40 mmHg

Question 19

Normal Value for PAO2 at Sea Level

Answer 19

100 mmHg

Question 20

Best method for attaining PaO2

Answer 20

Arterial Blood gas Test (from Radial Artery)

Question 21

Equation for A-a gradient/difference

Answer 21

(PAO2-PaO2)

Question 22

Widened A-a gradient signifies (general)…

Answer 22

Lung disease

Question 23

Formula for Normal A-a gradient

Answer 23

(Age+4)/4; if value is greater, then lung disease may be evident

Question 24

Hypoxemia with Normal A-a gradient

Answer 24

No intrinsic lung disease; usually due to hypoventilation secondary to altitude changes.

Question 25

Equation for PACO2

Answer 25

[VCO2/Alveolar Ventilation] (k); k is a constant that can be ignored most of the time, however.

Question 26

Causes of Hypoxemia with Normal A-a gradient

Answer 26

1) Hypoventilation

2) Decreased PIO2

Question 27

Causes of Hypoxemia with a Widened A-a gradient

Answer 27

1) Diffusion Limitation
2) Right-to-left Shunts (VSD/ASD)
3) V/Q mismatch

Question 28

Hypoxemia due to Diffusion Limitation occurs if:

Answer 28

1) Diffusion capacity is severely decreased

2) Capillary transit time for RBC’s is decreased

Question 29

Can a shunt be improved with 100% O2 supplementation?

Answer 29

NO. Shunts cannot be improved with oxygen supplementation. V/Q mismatch, however, CAN.

Question 30

Both ventilation and perfusion are highest at which portion of the lung?

Answer 30

Base of the lung

Question 31

Diseases associated with Low V/Q values

Answer 31

1) COPD, Asthma [Obstructive Lung Diseases]
2) Pulmonary Edema
3) Shunt [MOST EXTREME DISEASE STATE]

Question 32

Diseases associated with High V/Q Values

Answer 32

1) Pulmonary Embolism

2) Increase in Dead space [MOST EXTREME DISEASE STATE]

Question 33

5 Pulmonary Causes of Hypoxemia

Answer 33

1) Decreased PIO2
2) Hypoventilation
3) Shunt
4) V/Q Mismatch
5) Diffusion Limitation