Respiratory Physiology quizzes (Johns Hopkins Sch Med)
1. You exhale normally and then start to breathe into a spirometer containing 6-L of
helium. After several minutes, the helium concentration in the spirometer falls to
4%. Your FRC is approximately:
1.8 L
2.4 L
3.0 L
4.5 L
2. Martha and George are breathing normally. Martha decides to double her tidal
volume and decrease her respiratory rate to one-half of baseline. George decides to
halve his tidal volume and double his respiratory rate. Who has increased his or her
alveolar ventilation?
Both Martha and George
Just Martha
Just George
Neither one
3. What happens to the pleural pressure during forced expiration?
It becomes positive with respect to atmospheric pressure
It increases but must remain negative -- otherwise the lung would collapse
It exceeds alveolar pressure
4. Between breaths your pleural pressure is about -5 cm H2O. As inspiration proceeds,
the pleural pressure reaches about:
-8 cm H2O
-1 cm H2O
0 cm H2O
+1 cm H2O
+8 cm H2O
5. The respiratory muscles would have to work harder in all of the following
conditions EXCEPT:
A decrease in lung compliance
A decrease in airway resistance
A decrease in the production of surfactant
An increase in tidal volume
6. Your mixed expired gas contains 3.0% CO2, and the concentration of CO2 in your
alveoli is 4.5%. If your tidal volume is 450 ml, and you are breathing 8 times a minute,
what is the volume of your physiologic dead space?
135 ml
150 ml
225 ml
300 ml
675 ml
7. The large- and medium- sized airways provide roughly what percentage of total
airway resistance?
10 %
40 %
60 %
85 %
8. Who would be most likely to breathe shallowly and rapidly?
Someone in the middle of an asthma attack
Someone with bronchitis
Someone with pulmonary fibrosis
Someone with emphysema
9. A rich second cousin invites you to Aruba for a week. The two of you are scuba
diving to a depth of 66 ft. below sea level (2 atmospheres of water pressure). What is
the partial pressure of oxygen in the air that you are breathing?
160 mmHg
320 mmHg
480 mm Hg
960 mmHg
10. If you exhale to RV, close your glottis and relax your chest muscles, what will
happen to your alveolar pressure?
The alveolar pressure will become greater than atmospheric pressure because
the lungs will want to elastically recoil, but there will be no outlet for the air
with the glottis closed, driving alveolar pressure up.
The alveolar pressure will remain at atmospheric, because with the glottis
closed there is no air flow in or out of the lungs to change the pressure.
The alveolar pressure will fall below atmospheric because at RV, the recoil of
the chest wall out is stronger than the recoil of the lung in, so that the
respiratory system will experience a net outward recoil which will create a
negative alveolar presure.
11. Which of the following is true about functional residual capacity?
At FRC, the inward recoil of the lungs exactly matches the outward recoil of
the chest wall.
At FRC if one closed one's glottis and relaxed the chest wall, the alveolar
pressure would become positive.
It can be measured via spirometry.
12. An individual with emphysema:
Would have an elevated FEV1/FVC ratio.
Would have less compliant lungs than is considered normal.
Would show decreased flow on forced expiration largely due to loss of
elastic recoil of the lung.
Would have a smaller (more negative) pleural pressure than normal at TLC.
Would have increased bronchial smooth muscle tone.
13. Spirometry can be used to measure:
Residual volume.
Functional residual capacity.
Vital capacity.
Total lung capacity.
14. Who would be most likely to show increased lung compliance?
An infant with insufficient surfactant production.
A person with pulmonary fibrosis.
A healthy 90 year old.
A person with bronchitis.
15. One reason that surfactant renders the alveoli so stable is that:
Surfactant causes surface tension in the alveoli to be constant over all lung
volumes.
Surfactant lowers the compliance of the lung.
Surfactant eliminates the forces of surface tension in the alveoli.
Surfactant makes surface tension in the alveoli vary with lung volume.
Surfactant causes the pressure-volume curve to show hysteresis.
KEY
1. The correct answer is 3 L from the law of the conservation of matter:
F1 x V1 = F2 x (V1+ V2)
(.06)(6) = (.04)(6+V2)
(.36/.04) = (6+V2)
(9-6)=V2
V2=3
2. The correct answer is Martha:She is taking fewer deeper breaths, wasting less
inspired air in the anatomic dead space. George's numerous shallow breaths are
wasting more inspired air in his anatomic dead space, decreasing the air reaching his
alveoli.
3. it becomes positive, with respect to atmospheric pressure. The abdominal
muscles contract and force up the diaphragm, causing pleural pressure to become
positive.
4. The correct answer is: -8 cm H2O As the lungs expand the recoil pressure of the
lung increases; the pleural pressure must fall to oppose this increasing tendency of the
lungs to collapse.
5. a decrease in airway resistance. Since a lower airway resistance requires a
smaller pressure difference
6. 150 ml VD/VT= (PaCO2-PECO2)/(PaCO2)
VD/450=(4.5-3.0)/(4.5)
VD=(450)(1.5)/(4.5)
VD=150 (your breathing rate is not important here)
7. 85% Resistance to air flow depends largely on the number of parallel pathways
present; therefore resistance in the smaller but extremely numerous bronchi and
bronchioles is quite small.
8. Someone with pulmonary fibrosis Because their lungs are so poorly compliant, it
is difficult for them to inflate their lungs much, and they tend to breathe shallowly and
rapidly.
9. 320 mm Hg Each component in a gas mixture exerts a pressure proportional to its
concentration in the mixture. In air at 2 atmospheres (2 x760 mmHg) the partial
pressure of oxygen would be 0.21 x 2 x 760 = 320 mmHg.
10. The alveolar pressure will fall below atmospheric because at RV, the recoil of
the chest wall out is stronger than the recoil of the lung in, so that the respiratory
system will experience a net outward recoil which will create a negative alveolar
pressure.
11. At FRC the inward recoil of the lungs exactly matches the outward recoil of the
chest wall.
12. would experience early closure of the airways during expiration
Due to the loss of elastic fibers in the lung, the airways tend to collapse during
expiration, trapping air in the lung
13. vital capacity
14. a healthy 90 year old Compliance of the lung does in fact increase with age
15. Surfactant makes surface tension in the alveoli vary with lung volume.