2. If alveolar pO 2 is 300 mmHg and alveolar pCO 2 is 40 mmHg, what is the piO 2

Question

2.   If alveolar pO2 is 300 mmHg and alveolar pCO2 is 40 mmHg, what is the piO2 (humidified inspired pO2)?

250 mmHg

300 mmHg

350 mmHg

400 mmHg

760 mmHg

ANS:

3.   Match the following with the letter indicating the most appropriate ANS: pO2 = 116 mmHg, pCO2 = 27 mmHg.

Atmospheric air

Alveolar air

Blood in the left heart

Blood in the right heart

Expired air

ANS:

4.   Twin patients, X and Y, both have respirations of 12/min, tidal volumes of 500 mL, and dead space of 100 mL. Patient X decreases the respiratory rate by half, and doubles the tidal volume. Patient Y doubles the respiratory rate and cuts the tidal volume in half. After two minutes, what conditions would best describe their alveolar gases, as compared to normal.

                                    Patient X Alveolar ventilation                                                 Patient Y Alveolar ventilation

            Alveolar pO2               Alveolar pCO2            Alveolar pO2               Alveolar pCO2

A. ­                                  ¯                                  ­                                  ¯

B. ¯                                  ­                                  ¯                                  ¯

C. ­                                  ¯                                  ¯                                  ­

D. ­                                  ­                                  ­                                  ­

E.   ¯                                  ­                                  ¯                                  ­

ANS:

5.   In an individual, the pO2 and pCO2 in different alveoli varies as follows:

pO2

pCO2

Alveolus A

100

40

Alveolus B

40

45

Alveolus C

150

0

Which of the following statements is true?

Alveolus B is indicative of a dead space ventilation

Alveolus C is indicative of pulmonary shunt

Breathing 100% O2 would increase PO2 in alveolus C

Hyperventilation would increase PO2 in alveolus B

ANS:

6.   A person with normal lungs at sea level (760 mmHg) is breathing 50% oxygen. What is the approximate alveolar pO2?

100

159

310

330

380

ANS:

7.   If a lung having a normal ventilation-perfusion ratio (=1) SUDDENLY develops ventilation-perfusion ratio <1, which of the following will occur?

A decrease in arterial pO2

An increase in alveolar pO­2

A decrease in cardiac output

A decrease in arterial pCO2

ANS:

8.   A 16-year-old girl is found unconscious in the street. She has no visible injuries and is taking shallow breaths of 6-8/min. An arterial blood gas shows a pO2 of 55 mmHg and her pCO2 is 75 mmHg. The cause of the hypoxemia is:

Low V/Q ratio

Intrapulmonary shunt

Increased dead space ventilation

Alveolar hypoventilation

Elevated V/Q ratio

ANS:

Questions 9-11: Consider a patient with an anatomical dead space of 100 mL, a normal respiratory rate of 12 breaths per minute and a normal tidal volume of 600 mL under resting conditions. Match each of the conditions in questions 9-11 with the correct set of respiratory rate, tidal volume, and metabolic changes. Answers may be used more than once.

Respiratory Rate                      Tidal Volume              Metabolic Rate           

A. 6                                              1,100                           normal                        

B. 24                                            500                              normal                        

C. 16                                            400                              4 times normal            

9. Systemic arterial pO2 >120 mmHg.

ANS:

10. Systemic arterial pO2 of approximately 100 mmHg.

ANS:

11. Systemic arterial pCO2 > normal.

ANS:

12. Perfusion of capillaries without ventilation of an alveolus:

Results in an decrease in alveolar pO2

Results in an increase in systemic arterial pO2

Results in an increase in alveolar pCO2

Results in a increase in systemic arterial pCO2

ANS:

13. For a patient at sea level (barometric pressure = 760 mmHg) and breathing 40%, oxygen calculate alveolar pO2 is:

149

159

235

285

304

ANS:

14. While lying supine in bed eating, a child aspirates a peanut into the left lung. What would be the V/Q ratio in the left Lung?

0

0.8

?

ANS:

15. Vertebrate Gas transfer system (5points) – schematic diagram required.***

16. Oxyhemoglobin dissociation curve (5points) – schematic diagram required.***

17. Dalton’s law ( 2 points)

pO2

pCO2

Alveolus A

100

40

Alveolus B

40

45

Alveolus C

150

0

Explanation / Answer

1.350mmhg is the piO2 when alveolar PO2 is 300mmhg and alveolar PCO2 is 40mmhg.

8.The cause of hypoxemia is alveolar hypoventilation.

9.1.6breaths/min,VT=1100ml

normal metabolic rate=systemic arterial Po2 of approximately

100mm hg

2.24 breaths/min,VT=500ml

normal metabolic rate=systemic artwriar PO2 of approximately 120mmhg

3.16breaths/min,VT=500ml,normal metabolic rate=systemic arterial PCO2 normal

14.The V/Q ratio is 0 in the left lung when a child aspirates a peanut into the left lung while lying supine in bed eating.

17.Daltons law states that partial pressure exerted by the gas.is directly proportional to the percentage of gas in total mixture.

Dalton's law states that partial pressure of specific gas in gas mixture is the pressure that it would exert if it occupied total volume in absence of other components.

10.100mmhg is an example for normal PO2.It can range from 80mmhg to 100mmhg

9.PO2>120mmhg shows the PO2 is elevated which means that there is increased oxygen level in the inhaled air.

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