Transcript Anesthesia ICU Board Review -Dr Jalou

Anesthesia ICU Board Review
ITE
SANAA JALOU, M.D.
02/01/2013
1. True statements concerning pulmonary vascular
resistance (PVR) include which of the following?
A. PVR increases with increasing lung volume from
functional residual capacity
B. PVR increases with decreasing lung volume from
functional residual capacity
C. PVR decreases with increasing cardiac output
D. PVR increases with decreasing PaO2
E. all of the above
1. Answer is E
Many factors including vasoactive peptides and hormones, cardiac output, and
mechanical forces, interact in a complex manner to determine PVR. Lung volume
has a significant effect on PVR. In the normal lung, PVR increases with an
increase or decrease in lung volume from functional residual capacity. The effect
of lung volume on PVR is related to the direct effects of tissue expansion and
collapse on the caliber of the extra-alveolar vessels and alveolar capillaries. At low
lung volumes, PVR is elevated because the extra-alveolar vessels are compressed.
At high lung volumes, PVR is elevated because the alveolar capillaries are
compressed. Cardiac output also has a significant effect on PVR. PVR is directly
proportional to the mean pulmonary perfusion pressure and is inversely
proportional to cardiac output. As cardiac output increases, PVR decreases. The
mechanisms responsible for this inverse relationship between cardiac output and
PVR are the processes of recruitment and distention of pulmonary vessels.
Recruitment of previously closed capillaries in nondependent regions of the lungs
is the predominant mechanism for the fall in PVR as cardiac output and
pulmonary artery pressure increase from low levels. However, distention of
pulmonary vessels is the predominant mechanism for the fall in PVR at relatively
high cardiac outputs and pulmonary vascular pressures (Miller: Anesthesia, ed 4,
pp 582 & 584; West: Respiratory Physiology, ed 5, pp 35-38).
2. Factor(s) that determine the diffusing capacity of
the lungs for carbon monoxide (DLCO) include the
A. Area of the alveolar membrane
B. Blood volume of the pulmonary vasculature
C. Thickness of the alveolar membrane
D. Red blood cell hemoglobin concentration
E. all of the above
2. Answer is E
The diffusing capacity of the lungs is determined by several processes: 1)
diffusion of a gas through the alveolar walls . The mathematical
expression of the diffusing capacity of the lungs is as follows: DL = DM +
(0. Vc), where DL is the diffusing capacity of the lungs, DM is the
diffusing capacity of the alveolar membrane, 0 is the rate (in mL/min) a
gas can combine with 1 mL of blood/min , and Vc is the volume of blood
in the pulmonary capillaries.Thus, DL is determined by the area and
thickness of the alveolar membrane, the blood:gas solubility and
molecular weight of the gas, the transmembrane partial pressure
difference of the gas, pulmonary blood volume, and hemoglobin
concentration.
3. On arterial blood gas sampling, an oxygen
saturation of 95% is noted with a Pa02 of 60 mm
Hg. Possible explanations for this include
A. Sepsis
B. Intracardiac shunt
C. Cyanide toxicity
D. Abnormal hemoglobin
3. Answer is D
Normal adult hemoglobin has a P50 equal to 27 mm Hg meaning it
will be 50% saturated in a P02 of 27 mm Hg. The same hemoglobin would
be 90% saturated if the P02 were 60 mm Hg. If hemoglobin binds oxygen
more tightly, i.e. if the P50 is less than 27 mm Hg, a leftward shift of the
oxyhemoglobin dissociation curve has occurred. There are a number of
causes for a leftward shift such as hypothermia, metabolic or respiratory
alkalosis, decreased red cell 2,3-DPG, carboxyhemoglobin,
methemoglobin, fetal hemoglobin, or other abnormal hemoglobin.
Likewise, if the P50 for hemoglobin is greater than 27 mm Hg, a rightward
shift is said to have taken place. Most of these are the opposite of the
factors causing a left shift and include hyperthermia, respiratory or
metabolic acidosis, increased red cell 2,3-DPG, pregnancy, inhalational
anesthetics, and abnormal hemoglobin. Sepsis, shunting, and cyanide
toxicity, unless they cause an acidosis, do not affect the P50 of
hemoglobin and if they were to cause an acidosis, a rightward not
leftward shift in the oxyhemoglobin dissociation curve would result. The
three items do not share one common feature. They can produce an
elevated mixed venous oxygen saturation (Miller: Anesthesia, ed 4, pp
596-597).
4. PVR is increased by which of the
following?
A. Hypocarbia
B. Vasopressin
C. Hyperthermia
D. Metabolic acidosis
E. B and D
4. Answer is E
Factors that increase pulmonary vascular resistanc
include acidosis, hypoxia, hypercarbia, sympathetic
stimulation, atelectasis, and high hematocrit.
Hypocarbia causes alkalosis which decreases pulmonary
vascular resistance (Barash: Clinical Anesthesia, ed 2, p
1015).
5. All of the following respiratory variables can be
measured by simple spirometry EXCEPT?
A. Vital capacity
B. Expiratory reserve volume
C. Inspiratory capacity
D. Residual volume
5. Answer is D
Static lung volumes can be divided into those that can
be measured by simple spirometry and into those that
cannot. The functional residual capacity and residual
volume cannot be measured by simple spirometry.
However, these two variables can be measured using gas
dilution techniques or body plethysmography (West:
Respiratory Physiology, ed 5, p 12).
6. Which of the following will increase the
closing capacity?
A. Smoking
B. Obesity
C. Supine position
D. Aging
E. all of the above
6. Answer is E
The closing capacity is the product of residual volume
and the volume remaining in the lung when airway
closure occurs (i.e., closing volume). Measurement of
the closing capacity is a sensitive test of early small
airway diseases, such as emphysema, asthma, bronchitis,
and pulmonary interstitial edema. Smoking tobacco,
obesity, aging, and the supine position increase the
closing capacity (Miller: Anesthesia, ed 4, pp 590-593).
64 Basic Sciences
7. Compensatory mechanism(s) for metabolic acidosis
include which of the following?
A. Secretion of H+ and absorption of HC03 by the renal
tubules
B. Increased VA caused by direct stimulation of the
carotid bodies by H+
C. Buffering of nonvolatile acids by bone
D. Buffering of nonvolatile acids by hemoglobin
E. all the above
7. Answer is E
The compensatory mechanisms for metabolic acidosis can be
divided into two groups: acute compensatory responses and
chronic compensatory responses. The acute compensatory
responses include increased VA, which is caused primarily by
stimulation of the carotid bodies by H+, and the buffering of H+
by HCO3, hemoglobin, phosphates, and proteins. The chronic
compensatory responses include secretion of H+ and the
reabsorption of HCO3 by the proximal and distal renal tubules,
and the buffering of H+ by bone (Stoelting: Basics of
Anesthesia, ed 3, pp 217 & 224).
8. The factors that influence the rate of diffusion of
molecules through a lipid membrane are described in ?
A. Laplace’s Law
B. Graham’s Law
C. Boyle’s Law
D. Fick’s Law
E. B and D
8. Answer is E
Graham’s law states that rate of diffusion of a gas through a
lipid membrane is directly proportional to the solubility of the gas
and is inversely proportional to the square root of the molecular
weight of the gas. Fick’s law states that the rate of diffusion of a
gas through a lipid membrane is directly proportional to the
pressure gradient of the gas across the membrane and the area of
the membrane, and is inversely proportional to the thickness of
the membrane (West: Respiratory Physiology, ed 5, pp 169 & 170;
Barash: Clinical Anesthesia, ed 2, pp 1 62-164).
9. Effects of carboxyhemoglobin include all the
following Except?
A. A leftward shift of the oxyhemoglobin dissociation
curve
B. Overestimation of SP02 by pulse oximeters
C. Negative inotropic effect on the heart
D. Increased incidence of deep vein thrombosis
9. Answer is D
Patients who smoke cigarettes have a higher incidence of postoperative
pulmonary complications than those who do not smoke cigarettes. It is
thought that part of the morbidity associated with cigarette smoking is
associated with the adverse effects of carbon monoxide on the O2carrying capacity of hemoglobin. Carbon monoxide combines with
hemoglobin to produce carboxyhemoglobin causing a leftward shift of the
oxyhemoglobin dissociation curve, which increases the affinity of
hemoglobin for 02 In addition, carbon monoxide has a negative inotropic
effect on myocardial contractility. Although the effects of carbon
monoxide on the cardiovascular system are short-lived and readily
reversible with cessation of smoking, short-term abstinence from
cigarettes prior to elective surgery has not been shown to decrease the
incidence of postoperative pulmonary complications.
Carboxyhemoglobin will cause dual-wavelength pulse oximeters to
display falsely elevated arterial 02 saturations There is no evidence that
carboxyhemoglobin associated with cigarette smoking will increase the
incidence of deep vein thrombosis in the postoperative period (Miller:
Anesthesia, ed 4, p 1263; Stoelting: Anesthesia and Co-existing Disease,
ed 3, p 140). Respiratory Physiology 65
10. Structures that contribute to physiologic
shunt include ALL EXCEPT?
A. Thebesian veins
B. Bronchial veins
C. Pleural veins
D. Nonperfused alveoli
10. Answer is D
Physiologic shunt is that portion of the cardiac output that
perfuses areas of the lungs that are not ventilated. In the normal
patient, physiologic shunt accounts for approximately 5% to 10%
of the cardiac output. There are several anatomic sources for
physiologic shunt. These include bronchial vessels, which
supply blood and 02 to the main conducting airways of the
lungs, the Thebesian veins, which drain blood from the
coronary vessels that supply the myocardium, and pleural veins,
which drain blood that has supplied 02 to the pleura. Alveoli
that are poorly perfused but are adequately ventilated
contribute to physiologic dead space ventilation (West:
Respiratory Physiology, ed 5, pp 55-5 7).
11. All of the following is associated with a
decreased DLCO, EXCEPT ?
A. Emphysema
B. Severe anemia
C. Pulmonary hypertension
D. Asthma
11. Answer is D
The DLCO is determined in part by the volume of blood
(hemoglobin concentration) within the pulmonary capillaries.
Thus, diseases associated with a reduction in pulmonary blood
volume, such as anemia, emphysema, dehydration, and
pulmonary hypertension, will result in a decrease in DLCO.
Although the mechanism is not known, acute asthma is
associated with an increase in DLCO (West: Respiratory
Physiology, ed 5, pp 28 & 29; Miller: Anesthesia, ed 2, p 1375).
12. All of the following can cause the formation
of Methemoglobinemia EXCEPT ?
A. O-toluidine
B. Nitroglycerin
C. Sodium nitroprusside
D. Phencyclidines
12. Answer is D
Methemoglobin is oxidized adult hemoglobin (i.e., the iron is oxidized
from the ferrous to the ferric form). Because methemoglobin is not able
to bind 02, it causes cyanosis despite an adequate pa02 Causes of
methemoglobinemia include congenital absence of methemoglobin
reductase, the enzyme that reduces methemoglobin to normal
hemoglobin, and nitrate-containing compounds. O-toluidine, a
metabolite of the local anesthetic prilocaine, oxidizes adult hemoglobin
to methemoglobin. Sodium nitroprusside and nitroglycerin are
metabolized within erythrocytes by a nonenzymatic reaction which
requires the oxidation of oxyhemoglobin to methemoglobin (Miller:
Anesthesia, ed 4, p 515; Barash: Clinical Anesthesia, ed 2, p 529; Stoelting:
Anesthesia and Co-existing Disease, ed 3, p 403).
13. The respiratory quotient?
A. Describes the relationship between the rate of CO2
production and the rate of O2 utilization
B. Is not dependent on diet
C. Is increased when the diet consists predominately of
carbohydrates
D. Is increased when the diet consists predominately of
fats
E. A and C
13. Answer is E
The respiratory quotient is the ratio of the rate of CO2
production to the rate of 02 consumption. Metabolic
substrate is an important determinant of the rate of CO2
production and thus affects the respiratory quotient
(Miller: Anesthesia, ed 4, pp 2521 & 2522).
14. The cilia of the respiratory tract ?
A. Are not affected by the temperature and humidity of
inspired gases
B. Are inhibited by the presence of a cuffed
endotracheal tube
C. Are part of goblet cells
D. Are a protective mechanism for removing particles
from conducting airways
E. B and D
14. Answer is E
The cilia of the respiratory tract extend from the
columnar cells lining the conducting airways. They
propel a double layer of mucus up to the epiglottis, an
important mechanism for removing small particles from
the conducting airways. The rhythmic motion of cilia is
altered by changes in gas temperature and humidity
(Miller: Anesthesia, ed 4, pp 133 & 134).
15. Anatomic dead space is ?
A. Dependent on lung size
B. Approximately 1 mL/kg body weight
C. Affected by anesthesia equipment
D. Of less importance in the newborn than in the
adult
E. A and C
15. Answer is E
Anatomic dead space consists of the conducting
airways that contain no alveoli and therefore take no
part in gas exchange. Anatomic dead space is
approximately 1 mL/lb of body weight (Miller:
Anesthesia, ed 4, p 594; West: Respiratory Physiology, ed
5, pp 2 & 19).
16. The vital capacity is composed of all the
following EXCEPT?
A. Expiratory reserve volume
B. Inspiratory reserve volume
C. Tidal volume
D. Functional residual capacity
16. Answer is D
The vital capacity is the volume of gas that can be
exhaled during a maximal expiration. It is composed of
the inspiratory and expiratory reserve volumes, and the
VT (Miller: Anesthesia, ed 4, p 590).
17. Which one of the following is true regarding zone 1
of the lung?
A. It is the largest of the four zones
B. It has the largest amount of blood flow out of all
of the zones
C. Little or no zone 1 exists under normal conditions
D. Ppa>Pa>Ppv (where Ppa=pulmonary artery
pressure; Pa=alveolar pressure;Ppv=pulmonary venous
pressure)
E. Ppa <Pa<Ppv
17. Answer is C
There is little to no blood flow in zone 1, therefore
gas exchange cannot take place. This zone is
functionally deadspace. In zone 1 Pa>Ppa>Ppv, so if
Ppa is decreased (e.g. shock) or Pa is increased (e.g.
positive-pressure ventilation), zone 1 increases, thus
increasing deadspace.
18. Pleural pressure increases ?
A. 0.15 cm H2O every centimeter down the lung
B. 0.25 cm H2O every centimeter down the lung
C. 0.5 cm H2O every centimeter down the lung
D. 0.25 cm H2O every centimeter up the lung
E. Does not change
18. Answer is B
Ppl (Pleural pressure) is highest in the dependent
basilar lung regions. Hence, the alveoli in this region
are more compressed and smaller vs. the apical
alveoli which are larger.
19. Which of the following has the highest
blood:gas partition coefficient?
A. Desflurane
B. Halothane
C. Sevoflurane
D. Isoflurane
E. N2O
19. Answer is B
An agent with a high BGPC (Halothane, 2.5) at
equilibrium will have 2.5 times the concentration of
anesthetic in the blood versus the alveolar space.
Halothane is therefore a soluble agent versus
Sevoflurane (BGPC 0.69) which has a low BGPC.
Sevoflurane is therefore an insoluble agent (in
blood) and at equilibrium is mainly in the alveolar
space. This explains why a Sevoflurane induction
will occur much faster than a Halothane induction.
It also explains why emergence from Sevoflurane
anesthesia is much faster than emergence from
Halothane. From the highest to the lowest,
blood:gas partition coefficients are as follows:
Methoxyflurane 12, Halothane 2.5, Enflurane 1.8,
Isoflurane 1.4, Sevoflurane 0.69, N2O 0.47,
Desflurane 0.42
20 Hypoxic pulmonary vasoconstriction (HPV) is
decreased by ?
A. Indomethacin
B. Acetylsalicylic acid
C. Ibuprofen
D. Prostaglandins
E. Leukotrienes
20. Answer is D
Answers A, B, and C all block the Cyclooxygenase
pathway breakdown of Arachidonic acid which shifts
more Arachidonic acid to the Lipoxygenase pathway
which produces Leukotrienes that increase HPV.
21. All of the following statements are true
concerning arterial blood gases EXCEPT ?
A. Small bubbles in the ABG sample have greater
effects on readings than do large bubbles
B. pH decreases with time
C. The blood gas electrode used in most labs is
maintained at 30 degrees Celsius
D. Excessive Heparin in the collecting syringe can
falsely lower the pH
E. pH decreases faster at 37C versus 20C
21. Answer is C
Bubbles in the syringe of a blood sample allow Oxygen
and CO2 exchange between the sample and the bubbles.
The end result is usually a lowering of the values in the
blood sample. Blood samples are often put on ice (unless
the lab immediately tests the sample) to delay
metabolism. If the blood sample is allowed to sit at room
temperature, metabolism ensues (CO2 production) and
the pH will artfactually decrease. Heparin is acidic and
excessive amounts in the collecting syringe can cause the
subsequent ABG to have a falsely low PH. Most labs have
their blood: gas electrodes maintained at 37C.
22. Which one of the following statements correctly
describes the mechanics of pressure support
ventilation?
A. A subatmospheric pressure initiates the inspiratory
cycle, pressure rapidly builds in the system to a preset
level until a low flow limit is reached
B. A subatmospheric pressure initiates the inspiratory
cycle, pressure rapidly builds in the system to a preset
time
C. Same as B but with a reversed I:E ratio
D. Patient kept in a continued positive-pressure phase
and pressure is intermittently released to produce a tidal
volume
E. Small tidal volumes, continued positive pressure, and
rapid cycling
22. Answer is A
A newer mode for ventilation is pressure support ventilation
(PSV) made possible by use of microprocessor control in current
ventilator technology. When a subatmospheric pressure initiates
the inspiratory cycle, pressure rapidly builds in the system to a
preset level and does not stop until a low flow limit is reached.
thus instead of an inspiratory spike as in controlled mechanical
ventilation (CMV), there is more of a plateau phase. It is a true
ventilatory mode and the patient is weaned by gradually
decreasing the preset pressure level. Pressure control ventilation
(PCV) is a similar principle to PSV except it is time cycled rather
than flow limited. Another slight variation is called pressure
control inverse ratio ventilation (PCIRV). Because of the reversed
I:E ratio, the inspiratory phase will be prolonged supposedly
allowing better distribution of oxygen. Another novel mode is
airway pressure release ventilation (APRV). This is a rather
unique mode in which the patient is kept in a continued positive
pressure phase and the pressure is intermittently released to
produce a tidal volume. High frequency positive pressure
ventilation (HFPPV) is a form of CMV with low tidal volumes,
and rapid cycling.
23. Which one of the following respiratory
mechanics is the same in adults and infants?
A. Respiratory rate
B. Vital capacity
C. Tidal volume
D. Total lung capacity
E. Respiratory insensible water loss
23. Answer is C
There are many differences between the adult and
infant respiratory systems. The only parameter that is
the same is the tidal volume at 6-8 ml/kg.
24. Normal vital capacity ?
A. Is 2500 ml
B. Is the maximal amount of gas that can be exhaled
C. Is the sum of the tidal volume (TV) and the
inspiratory reserve volume (IRV)
D. Varies inversely to height
E. Is lower in supine patients
24. Answer is E
Vital capacity (VC) is the sum of TV, IRV, and
expiratory reserve volume (ERV). It varies directly
with height, and inversely to age. It is the maximal
amount of gas that can be exhaled following a
maximal inhalation, and is lower in supine patients
versus sitting patients. Normal VC is approximately
4500 ml.
25. Functional residual capacity (FRC)
?
A. Can be measured directly from spirometry
B. Can be measured by nitrogen wash out
C. Varies with age
D. Does not change with induction of anesthesia
E. Decreases 30% by changing from the supine to
upright position
25. Answer is B
FRC can also be measured by helium dilution and
body plethysmography. FRC varies with position,
(decreasing 30%) by changing from the upright to
supine position. FRC is thought to be independent of
age, however, there is some data suggesting a slight
increase with age.
26. A 63-year-old man with chronic lung disease is in the operating room
scheduled for an open cholecystectomy. Since his oxygen saturation on
inspired oxygen of 50% is less than 95%, the anesthetist decides to use a
10 cm PEEP valve. Shortly thereafter, the patient is noted to have
subcutaneous crepitus around the shoulders and chest. The MOST likely
cause of this reaction is ?
A. Seepage of air under the diaphragm as a result of the
surgery
B. The subcutaneous emphysema is probably due to the
use of nitrous oxide
C. The subcutaneous emphysema most likely represents
a fistula between the upper airway and subcutaneous
tissue
D. Subcutaneous emphysema in this patient group results
from cardiovascular compromise and the use of PEEP
E. The subcutaneous emphysema represents disruption of
alveoli and tracking of the air into the subcutaneous plane
26. Answer is E
The use of PEEP in this case is probably to improve
oxygenation. The principal mechanism is to recruit
partially collapsed alveoli. The use of PEEP in patients
with chronic lung disease, in particular, those with
emphysema, should be done with caution since
overdistention and rupture of alveoli may occur. Usually
disruption of alveoli occurs at a PEEP of 15 cm of H20,
however rupture can occur at 10 cm of H20. Disruption
allows air to track from the bronchi to the mediastinum.
From here, air can rupture into the pleural, pericardial,
or subcutaneous planes. Failure of an air leak to seal can
result in a bronchopleural fistula.
27. A 47-year-old man status post an exploratory
laparotomy for a gun shot wound to the chest and
abdomen which required massive transfusion is
taken to the ICU and placed on a ventilator. His
intraoperative course was long and complicated,
consisting of a large bowel resection. At the end of
the procedure, his Hct was 22 and his acid base
deficit was -18. After two days in the intensive care
unit, the patient develops adult respiratory distress
syndrome (ARDS), and inverse ratio mechanical
ventilation is recommended. The benefits of inverse
ratio mechanical ventilation is:
Continue Q 27
A. The inspiratory time is decreased so there is ample time
for exhalation and improved oxygenation
B. The use of inverse ratio ventilation at higher inspiratory
times decreases the risk of barotrauma
C. The maximum benefits occur with an inverse ratio of I:E
greater than 1:3
D. Inverse ratio can be beneficial to patients with
obstructive pulmonary disease
E. The improvement in oxygenation in patients with severe
ARDS occurs because airway pressure is increased allowing
for recruitment of additional alveoli during a longer and
slower inspiratory stage
27. Answer is E
The use of inverse ratio ventilation can be useful in
patients with ARDS. Its use is controversial, as the
inspiratory time goes beyond the usual maximum 50% of
the respiretory cycle. As the inspiratory time is prolonged,
there may be an improvement in oxygenation. This
improvement may be due to:
 an increase in peak airway pressure
 recruitment of additional alveoli with the longer
inspiratory time and slower flow
 development of PEEP.
The maximum benefits are attained at a 2:1 ratio (I:E).
Also, the slow inspiratory flow may decrease the
development of barotrauma.
28. In a 17-year-old woman with idiopathic
kyphoscoliosis, which of the following preoperative
values is the BEST predictor for the need of
postoperative mechanical ventilation after spine
surgery?
A. Resting Pa02 of 60 mmHg breathing room air
B. Forced expiratory volume (FEV) at 60% of
predicted
C. Forced vital capacity (FVC) decreased 70%
D. Maximum voluntary ventilation decreased
20%
E. Resting PaCO2 of 50 mmHg breathing room
air
28. Answer is C
Two main factors significantly affect respiratory
function in scoliosis patients:
1.The degree of the curve
2. the association of a neuromuscular disease.
Significant changes in respiratory function seldom
occur when the curve is less than 65 degrees.
Patients with vital capacities above 35% predicted,
usually tolerate surgery well. If the vital capacity is
below 30% of normal, the patient usually needs
overnight mechanical ventilation postoperatively.
29. In a patient scheduled for a Pneumonectomy, which
preoperative pulmonary function value suggests a high
risk for perioperative pulmonary morbidity?
A.
B.
C.
D.
E.
VO2 max of 10ml/kg/min
FEV1 of 2.5L
DLCO of 60%
FVC of 2L
FEV1/FVC of 40%
29. Answer is A
Pulmonary function criteria which suggest increased risk
for perioperative complications have been determined for
various types of thoracic and upper abdominal surgery. For a
proposed pneumonectomy, a FVC <70% predicted or < 1.7 L,
a FEV1 < 2 L, a FEV 1/FVC ratio of< 35%, and a DLCO of <
50% predicted suggests increased perioperative morbidity.
Recently the use of maximal oxygen consumption has been
shown to have predictive value, because it not only assesses
pulmonary function, but cardiac, peripheral vascular
function, as well as motivation and endurance. A level less
than 15 ml/kg/min suggests greater morbidity and mortality.
30. Airway obstruction ?
A.
B.
C.
D.
FEF 25%-75% is reduced
FEV1/FVC is decreased
FVC is normal
A reduced FEF 25%-75% is more specific for
airway obstruction than a decreased FEV1
E. all the above
30. Answer is E
FEF 25%-75% (e.g., forced mid-expiratory flow
between 25% and 75% of expired volume) is a better
test than FEV1 for obstruction because it is not effort
dependent like FEV1
31. all of the folowing increase the
operative risk of pneumonectomy Except?
A.
B.
C.
D.
FEV1 less than 2L
FEV1/FVC less than 5O%
Hypercapnia on room air
Predicted postoperative (via split function tests)
FEV1 less than one L in the remaining lung
31.Answer is D
Factors that increase operative risk for
pneumonectomy include: Hypercapnia on RA,
FEV1/FVC less than 50%, FEV1 less than 2 L,
RV/TLC greater than 50%, blood flow to diseased
lung Greater than 70%, FEV1 less than 0.85 L in
remaining lung (obtained by split function tests).
Greater than 30-40 mmHg increase of mean PAP
during temporary occlusion of main PA.
32. All of the following can improve arterial
oxygenation in one lung ventilation Except?
A. Temporary ventilation of the non-dependent
(hypoxic) lung
B. Selective PEEP
C. Clamping the PA to the non-dependent lung
D. Administering low dose IV nitroglycerin
32. Answer is D
Regional hypoxic pulmonary vasoconstriction (HPV)
is inhibited by most systemic vasodilator drugs (e.g.,
Nitroglycerin, Nitroprusside, Dobutamine), so these
drugs could worsen hypoxemia in one lung
ventilation.
33. All of the following are the same in
infants and adults except?
A.
B.
C.
D.
Dead space
Tidal volume
Oxygen consumption
Functional residual capacity
33. Answer is C
Things that Don’t change in the infant and adult are
FRC, TV, and Dead-space as the constant respiratory
parameters.
34. Pulmonary changes which occur with pregnancy
include?
A. A decrease in functional residual capacity
B. Mucosal swelling of pharynx, larynx, and trachea
C. A decrease in MAC
D. Increased oxygen consumption
E. All of the above
34. Answer is E
Changes in respiratory function in pregnancy are
important to the anesthesiologist. Decreases in FRC
combined with increases in minute volume increase the
speed of induction with inhalation agents. A decrease in
MAC may produce loss of protective airway reflexes at
“safe’ concentrations of inhalation agents, for nonpregnant women. Mucosal edema may make it difficult to
pass normal sized endotracheal tubes and increase the
chance of nasal bleeding from instrumentation of the
nose. Increased oxygen consumption, along with a
decrease in FRC, will shorten the interval during which an
apneic parturient will become hypoxemic.
35. A 4o years old male who weigh 70 Kg and is 178 cm
tall, complain of weakness and rapid fatigability of
muscles during repetitive use followed by partial
improvement with rest
his PFT `s most likely will show
A.
B.
C.
D.
E.
FEV1 of 2.9L
FEV1 of 3.5L
FVC of 3.5L
FVC of 5L
A and C
35. Answer is E
The patient described has Myasthenia Gravis and
will therefore have a Restrictive lung pattern. Normal
FEV1 for a male with similar height and weight is 4.1
liters, normal FVC would be 5 liters. Although both an
FEV1 of 2.9 L and FVC of 3.5 L are considered
decreased or abnormal, the FEV1 /FVC ratio is still
83% or normal which is consistent with restrictive
lung pattern.
36. A 58-year-old patient has severe shortness of breath and
“wheezing.” On examination, the patient has inspiratory and
expiratory strider. Further evaluation reveals marked extrinsic
compression of the proximal trachea by a tumor. The type of air
flow at the point of obstruction within the trachea is ?
 A. Laminar flow
 B. Orifice flow
 C. Undulant flow
 D. Stenotic flow
 E. None of the above
36.Answer is B
Orifice flow occurs when gas flows through a
region of severe constriction such as described in
this question. Orifice flow is a special case of
turbulent gas flow where the diameter of the tube
is considerably smaller than its length (e.g., in
the larynx). Laminar flow occurs when gas flows
down parallel-sided tubes at a rate less than
critical velocity. When the gas flow exceeds the
critical velocity, it becomes turbulent (Miller:
Anesthesia, ed 4, p 191; Ehrenwerth: Anesthesia
Equipment: Principles and Applications, pp 224
& 225).
37. Concerning the patient in last question,
administration of 70% helium in O2 instead of 100% O2
will decrease the resistance to air flow through the
stenotic region within the trachea because ?
 A. Helium decreases the viscosity of the gas mixture
 B. Helium decreases the friction coefficient of the gas
mixture
 C. Helium decreases the density of the gas mixture
 D. Helium decreases the Reynold’s number of the gas
mixture
 E. None of the above
37. Answer is C
During orifice flow, the resistance to gas flow is
directly proportional to the density of the gas
mixture. Substituting helium for nitrogen will
decrease the density of the gas mixture, thereby
decreasing the resistance to gas flow (as much as
threefold) through the region of constriction (Miller:
Anesthesia, ed 4, p 586; Ehrenwerth: Anesthesia
Equipment: Principles and Applications, pp 224 &
225).
38. The relationship between intra-alveolar pressure,
surface tension, and the radius of an alveolus is
described by ?
 A. Graham’s law
 B. Beer’s law
 C. Newton’s law
 D. Laplace’s law
 E. Bernoulli’s law
38. Answer is D
The relationship between intra-alveolar pressure,
surface tension, and the radius of alveoli is described by
Laplace’s law for a sphere, which states that the surface
tension of the sphere is directly proportional to the radius
of the sphere and pressure within the sphere. With regard
to pulmonary alveoli, the mathematical expression of
Laplace’s law is as follows: T = ½ PR, where T is the
surface tension, P is the intra-alveolar pressure, and R is
the radius of the alveolus. In pulmonary alveoli, surface
tension is produced by a liquid film lining the alveoli. This
occurs because the attractive forces between the
molecules of the liquid film are much greater than the
attractive forces between the liquid film and gas. Thus,
the surface area of the liquid tends to become as small as
possible, which could collapse the alveoli (Miller:
Anesthesia, ed 4, pp 585 & 586).
39. The normal FEV1/FVC ratio is ?
A. 0.95
B. 0.8
C. 0.6
D. 0.5
E. 0.4
39. Answer is B
The forced expiratory volume in one second (FEV1)
is the total volume of air that can be exhaled in the
first second. Normal healthy adults can exhale
approximately 75% to 80% of their forced vital
capacity (FVC) in the first second. Therefore, the
normal FEV1/FVC ratio is 0.80. In the presence of
obstructive airway disease, the FEV1/FVC ratio is <
0.80. This ratio can be used to determine the severity
of obstructive airway disease and to monitor the
efficacy of bronchodilator therapy (Miller:
Anesthesia, ed. 4, p 884).
40. The degree of trans-pulmonary shunt can be
estimated to equal 1% of the cardiac output for each?
A. 10 mm Hg increase in the alveolar-to-arterial
difference in O2 tension P(A — a)O2
B. 20 mm Hg increase in the P(A — a)O2
C. 30 mm Hg increase in the P(A — a)O2
D. 40 mm Hg increase in the P(A — a)O2
E. 50 mm Hg increase in the P(A — a)O2
40. Answer is B
The fraction of the cardiac output shunted through
the lungs without exposure to ventilated alveoli (i.e.,
trans-pulmonary shunt) can be estimated using the
general rule that for every increase in the alveolarto-arterial difference in O2 tension P(A — a)O2 of
20 mm Hg, there is a shunt fraction of approximately
1% of the cardiac output (i.e., Qp/Qs = P(A —
a)O2/20, where Qp/Qs is the shunt fraction)
(Stoelting: Basics of Anesthesia, ed. 3, p 227).
41. During the first minute of apnea, the PaCO2
will rise ?
A. 2 mm Hg/min
B. 4 mm Hg/min
C. 6 mm Hg/min
D. 8 mm Hg/min
E. 10 mm Hg/min
41. Answer is C
During apnea, the PaCO2 will increase
approximately 6 mm Hg during the first minute and
then 3 to 4 mm Hg each minute thereafter (Miller:
Anesthesia, ed. 4, p 1717).
42. What is the maximum compensatory increase in
serum bicarbonate concentration (HCO3) for every 10
mm Hg increase in PaCO2 with chronic respiratory
acidosis?
A. 1 mEq/L
B. 3 mEq/L
C. 7 mEq/L
D. l0 mEq/L
E. l5 mEq/L
42. Answer is B
The kidneys respond to chronic respiratory acidosis by
conserving bicarbonate (HCO3-) and secreting hydrogen
(H+). In respiratory acidosis, there is an immediate
hydration of CO2 in plasma to produce HCO3-. This acute
process produces approximately 1 mEq/L of HCO3- for
every 10 mm Hg increase in PaCO2. Hydration of CO2 in
the proximal and distal renal tubules stimulates the
secretion of H+ into the urine. This compensatory
response requires 12 to 48 hours. The compensatory
response to chronic respiratory acidosis is rarely complete
such that the pH does not fully return to 7.4. The
maximum compensatory increase in serum bicarbonate
concentration ([HCO3-]) in response to chronic respiratory
acidosis is 3 mEqIL for each 10 mm Hg increase in PaCO2
(Stoelting: Basics of Anesthesia, ed 3, p 222).
43.O2 requirement for a 70-kg adult under
general anesthesia is?
A. 150 mL/min
B. 250 mL/min
C. 350 mL/min
D. 450 mL/min
E. 550 mL/min
43. Answer is B
The 02 requirement for an adult under general
anesthesia is 3 to 4 mL/kg/min. The 02 requirement for a
newborn under general anesthesia is 7 to 9 mL/kg/min.
Alveolar ventilation (VA) in neonates is double that of
adults to help meet their increased 02 requirements. This
increase in VA is achieved primarily by an increase in
respiratory rate as tidal volume (VT) is similar to that of
adults. Although CO2 production is also increased in
neonates, the elevated VA maintains the PaCO2 near 38 to
40 mm Hg (Barash: Clinical Anesthesia, ed 2, p 1313).
Respiratory Physiology 53
44. The functional residual capacity is composed
of the ?
A. Expiratory reserve volume and residual volume
B. Inspiratory reserve volume and residual volume
C. Inspiratory capacity and vital capacity
D. Expiratory capacity and tidal volume
E. Expiratory reserve volume and tidal volume
44. Answer is A
A comprehensive understanding of respiratory physiology
is important for understanding the effects of both regional
and general anesthesia on respiratory mechanics and
pulmonary gas exchange. The volume of gas remaining in
the lungs after a normal expiration is called the functional
residual capacity. The volume of gas remaining in the lungs
after a maximal expiration is called the residual volume.
The difference between these two volumes is called the
expiratory reserve volume. Therefore, the functional
residual capacity is composed of the expiratory reserve
volume and residual volume (Stoelting: Pharmacology and
Physiology, ed 2, pp 723 & 724).
45. Which of the following statements correctly defines the
relationship between minute ventilation VE), dead space
ventilation (VD), and PaCO2?
A. If VE is constant and VD increases, then
PaCO2 will increase
B. If VE is constant and VD increases, then
PaCO2 will decrease
C. If VD is constant and VE increases, then
PaCO2 will increase
D. If VD is constant and VE decreases, then
PaCO2 will decrease
E. None of the above
45. Answer is A
The volume of gas in the conducting airways of the lungs
(and not available for gas exchange) is called the
anatomic dead space. The volume of gas in ventilated
alveoli that are unperfused (and also not available for gas
exchange) is called the functional dead space. The
anatomic dead space together with the functional dead
space is called the physiologic dead space. Physiologic
dead-space ventilation can be calculated by the Bohr
dead-space equation which is mathematically expressed
as follows: Vd/Vt=PaCO2-PeCO2/PaCO2 where Vd/Vt is
the ratio of physiologic dead-space ventilation (VD) to VT,
and the subscripts a and e represent arterial and mixed
expired, respectively. Of the choices given, only the first
is correct. A large increase in physiologic dead-space
ventilation will result in an increase in PaCO2 (West:
Respiratory Physiology, ed 5, pp 2 & 19). 54 Basic Sciences
46. A 22-year-old patient who sustained a closed head injury is
brought to the operating room from the ICU for placement of a
dural bolt. Hemoglobin has been stable at 15 gm/dL. Blood gas
analysis immediately prior to induction reveals a Pa02 of 120 mm
Hg and an arterial saturation of 100%. After induction the PaO2
rises to 150 mm Hg and the saturation remains the same. How
has the oxygen content of this patient’s blood changed?
A. It has increased by 10%
B. It has increased by 5%
C. It has increased by less than 1%
D. Cannot be determined without PaCO2
E. Cannot be determined without pH
46. Answer is C
The oxygen content of blood can be calculated with the
following formula: O2 content = (1.39 x hemoglobin x
arterial saturation) + 0.003 x PaO2 first oxygen content
(1.39 x 15 x 1.0) + .003 x 120 = 21.21 ml/dL
second oxygen content = (1.39 x 15 x 1.0) + .003 x 150=
21.30 ml/dL The difference in the oxygen content is 0.09
ml/dL. This represents a change of 0.42% (Stoelting:
Basics of Anesthesia, ed. 3, p 229).
47. Inhalation of CO2 increases VE by ?
A. 0.5 L/min/mmHg increase in PaCO2
B. 1 to 3 L/min/mmHg increase in PaCO2
C. 3 to 5 L/min/mmHg increase in PaCO2
D. 5 to 10 L/min/mmHg increase in PaCO2
E. 10 to 20 L/min/mmHg increase in PaCO2
47. Answer is B
The degree of ventilatory depression caused by volatile
anesthetics can be assessed by measureing resting PaCO2,
the ventilatory response to hypercarbia and the
ventilatory response to hypoxemia. Of these techniques,
the resting PaCO2 is the most frequently used index.
However, measuring the effects of increased PaCO2 on
ventilation is the most sensitive method of quantifying the
effects of drugs on ventilation. In awake, unanesthetized
humans, inhalation of CO2 increases minute ventilation
(VE) by approximately 1 to 3 L/min/mmHg increase in
PaCO2. Using this technique, halothane, isoflurane,
enflurane, and N20 cause a dose-dependent depression of
the ventilation (Stoelting: Basics of Anesthesia, ed. 3, p
49).
48. What is the O2 content of whole blood if the
hemoglobin concentration is 10 mg/dL, the Pa02 is 60
mm Hg, and the Sa02 is 90%?
A. 10mL/dL
B. 13mL/dL
C. 15mL/dL
D. 18mL/dL
E. 21 mL/dL
48. Answer is B
The amount of O2 in blood (O2 content) is the sum of the
amount of 02 dissolved in plasma and the amount of 02
combined with hemoglobin. The amount of 02 dissolved in
plasma is directly proportional to the product of the
blood:gas solubility coefficient of O2 (0.003) and PaO2.
The amount of O2 bound to hemoglobin is directly related
to the fraction of hemoglobin that is saturated. One gram
of hemoglobin can bind 1.39 mL ofO2. The mathematical
expression of O2 content is as follows: O2 content = 1.39.
[Hgb] SpO2+ 0.003 (Pa02), where [Hgb] is the hemoglobin
concentration (mg/dL), Sp02 is the fraction of hemoglobin
saturated with O2, and 0.003 (PaO2) is the amount of 02
dissolved in plasma. The O2 content of blood in this
patient is approximately 13 mL/dL (Miller: Anesthesia, ed.
4, pp 596).
49. Each of the following will cause erroneous readings
by dual-wavelength pulse oximeters EXCEPT ?
A. Carboxyhemoglobin
B. Methylene blue
C. Fetal hemoglobin
D. Methemoglobin
E. Nail polish
49. Answer is C
The presence of hemoglobin species other than
oxyhemoglobin can cause erroneous readings by dualwavelength pulse oximeters. Hemoglobin species, such as
carboxyhemoglobin and methemoglobin, dyes such as
methylene blue and indocyanine green, and nail polish
will cause erroneous readings. Since the absorption
spectrum of fetal hemoglobin is similar to that of adult
oxyhemoglobin, fetal hemoglobin does not significantly
affect the accuracy of these types of pulse oximeters.
High levels of bilirubin have no significant effect on the
accuracy of dualwavelength pulse oximeters, but may
cause falsely low readings by nonpulsatile oximeters
(Miller: Anesthesia, ed. 4, pp 1263-1265).
50. The mechanism for the compensatory shift of the
oxyhemoglobin dissociation curve toward normal in
response to chronic ( >24 hours) respiratory alkalosis is ?
A. Increased renal excretion of HCO3B. An influx of potassium into red blood cells
C. Altered erythrocyte 2,3-diphosphoglycerate
(2,3-DPG) metabolism
D. Decreased sensitivity of the central nervous
system to changes in PaCO2
E. None of the above
50. Answer is C
The compensatory shift of the oxyhemoglobin
dissociation curve toward normal in response to
chronic acid-base abnormalities is a result of altered
erythrocyte 2,3-diphosphoglycerate (2,3DPG)
metabolism (Miller: Anesthesia, ed. 2, p 1135).
Respiratory Physiology 55
51. The P50 for normal adult hemoglobin is
approximately ?
A. l5
B. 25
C. 35
D. 45
E. 50
51. Answer is B
P50 is the PaO2 required to produce 50% saturation
of hemoglobin. The P50 for adult hemoglobin is 26
mm Hg (Stoelting: Anesthesia and Co-existing Disease,
ed. 3, p 394).
52. During a normal VT (500 mL) breath, the transpulmonary
pressure increases from 0 to 5 cm H2O. The product of
transpulmonary pressure and VT is 2,500 cm H2O.mL. This
expression of the pressure-volume relationship during breathing
determines what parameter of respiratory mechanics?
A. Lung compliance
B. Airway resistance
C. Pulmonary elastance
D. Work of breathing
E. Closing capacity
52. Answer is D
The work of breathing is defined as the product
of trans-pulmonary pressure and VT. The work of
breathing is related to two factors: the work
required to overcome the elastic forces of the
lungs and the work required to overcome airflow
or frictional resistances of the airways. Volatile
anesthetics cause a marked increase in the elastic
component of the work of breathing (Miller:
Anesthesia, ed. 4, pp 588 & 589).
53.An acute increase in PaCO2 of 10 mm Hg
will result in an immediate compensatory
increase in plasma [HCO3] of?
A. 1 mEq/L
B. 2mEq/L
C. 4mFq/L
D. 5mEqIL
E. 7 mEq/L
53. Answer is A
A prolonged increase in PaCO2 of 10 mm Hg will result in a
maximum compensatory increase in HCO3 of 3 mEq/L. An acute
increase in PaCO2 of 10 mm Hg results in an immediate
compensatory increase in [HCO3] of 1 mEq/L. This immediate
compensatory increase in [HCO3] is caused by the hydration of
CO2 in plasma to produce HCO3. An acute decrease in PaCO2 of
10 mm Hg will cause an immediate compensatory decrease in
[HC03] of 2 rnEq/L, and a chronic decrease in PaCO2 of 10 mm
Hg will cause a maximum compensatory decrease in [HCO3] of
5 mEqIL (Stoelting: Basics of Anesthesia, ed 3, pp 221 & 222).
54. The normal vital capacity for a 70-kg
man is ?
A. 1L
B. 2L
C. 5L
D. 7L
E. 9L
54. Answer is C
The volume of gas exhaled during a maximum
expiration is the vital capacity. In a normal healthy
adult, the vital capacity is 60—70 mL/kg. In a 70-kg
patient, the vital capacity is approximately 5 L
(Stoelting: Pharmacology & Physiology in Anesthetic
Practice, ed 2, p 724).
55. The most important mechanism for the
transport of CO2 from peripheral tissues to
the lungs is ?
A. CO2 dissolved in plasma
B. Carbonic acid
C. Carbaminohemoglobin
D. HCO3E. C03 - -
55. Answer is D
CO2 is transported from the peripheral tissues to the lungs,
primarily in the form of HCO3. The conversion of CO2 to HCO3 occurs
within erythrocytes and is catalyzed by the enzyme carbonic
anhydrase. HCO3then diffuses out of the cell in exchange for a
chloride ion to maintain electrical neutrality. This exchange of HCO3
for Cl is called the chloride shift. CO2 is also transported, dissolved in
blood, and bound to proteins as carbamino compounds. Carbamino
compounds are formed by the combination of CO2 with terminal
amine groups on blood proteins, primarily hemoglobin. This reaction
occurs very rapidly without enzymatic catalysts. Approximately 60% of
CO2 is transported from peripheral tissues to the lungs in the form of
HCO3, 30% in the form of carbaminohemoglobin, and 10% dissolved in
plasma (Miller: Anesthesia, ed 4, p 599; West: Respiratory Physiology,
ed 5, pp 76-79).
56. An increase in PaCO2 of 10 mm Hg will
result in a decrease in pH of?
A. 0.01 pH units
B. 0.02 pH units
C. 0.04 pH units
D. 0.08 pH units
E. None of the above
56. Answer is D
Respiratory acidosis is present when the PaCO2 exceeds 44
mm Hg. Respiratory acidosis is caused by decreased elimination
of CO2 by the lungs (i.e., hypoventilation) or increased
metabolic production of CO2. An acute increase in PaCO2 of 10
mm Hg will result in a decrease in pH of approximately 0.08 pH
units. The acidosis of arterial blood will stimulate ventilation
via the carotid bodies and the acidosis of cerebrospinal fluid
will stimulate ventilation via the medullary chemoreceptors
located in the fourth cerebral ventricle. Volatile anesthetics
greatly attenuate the carotid body-mediated and aortic bodymediated ventilatory responses to arterial acidosis, but have
little effect on the medullary chemoreceptor-mediated
ventilatory response to cerebrospinal fluid acidosis ( Stoelting:
Basics of Anesthesia, ed 3, p 49).
57. A 20-year-old, 80-kg patient with a history of insulindependent Diabetes Mellitus arrives in the emergency
room in Diabetic Ketoacidosis. The arterial blood gases
(on room air) are as follows: pH 6.95, PaCO2 30 mm Hg,
Pa02 98 mm Hg, [HCO3-] 6 mEq/L. What is the total body
deficit of HCO3 in this patient?
A. 500 mEq
B. 400 mEq
C. 300 mEq
D. 200 mEq
E. 100 mEq
57. Answer is C
Metabolic acidosis occurs when the pH is less than 7.36 and
HCO3 is below 24 mEqIL. A decrease in HCO3 is caused by
decreased elimination of H+ by the renal tubules (e.g., renal
tubule acidosis) or increased metabolic production of H+
relative to HC03 (e.g., lactic acidosis, ketoacidosis, or uremia).
Total body deficit in HCO3 can be estimated using the following
formula: Total Body Deficit (mEq) = Total Body Weight (kg)x
Deviation of HC03 From 24 mEq/Lx Extracellular Fluid Volume
as a Fraction of Body Mass (L) The total body deficit in HCO3 in
this patient is: 80 . (24 — 6) . 0.2 = 288 mEq (Stoelting: Basics
of Anesthesia, ed 3, p 225).
58. 44-year-old patient is hyperventilated to a
PaCO2 of 24 mm Hg for 48 hours. What [HCO3]
would you expect (normal [HCO3-] is 24 mEq/L)?
A. 10mEq/L
B. 12mEq/L
C. 14mEq/L
D. 16mEq/L
E. 18mEq/L
58. Answer is D
Respiratory alkalosis is present when the PaCO2 is less than 36
mm Hg. There are three compensatory mechanisms responsible
for attenuating the increase in pH that accompanies respiratory
alkalosis. First, there is an immediate shift in the equilibrium
of the HCO3 buffer system, which results in the production of
CO2. Second, alkalosis stimulates the activity of
phosphofructokinase, which increases glycolysis and the
production of pyruvate and lactic acid. Third, there is a
decrease in reabsorption of HCO3 by the proximal and distal
renal tubules. These three compensatory mechanisms result in
a maximum decrease in [HCO3] of approximately 5 mEq/L for
every 10 mm Hg decrease in PaCO2 below 40 mm Hg (Stoelting:
Basics of Anesthesia, ed 3, pp 222 & 223).
59. The normal arterial-to-alveolar ratio
(a/A) is greater than ?
A. 0.1
B. 0.65
C. 0.75
D. 0.5
E. 0.25
59. Answer is C
Arterial hypoxemia is defined as a decrease in Pa02 below 60
mm Hg. Arterial hypoxemia can be caused by low PAO2,
hypoventilation, or shunt. Shunt can be caused by a right-toleft transpulmonary or intracardiac shunt, or mismatching of
ventilation to perfusion. Diffusion limitation to the passage of
02 from the alveoli to blood has not been documented as a
cause of arterial hypoxemia in humans. The degree of shunt can
be estimated by calculating the P(A — a)O2 or arterial-toalveolar (a/A) ratio. It is easier to use the a/A ratio to calculate
shunt fraction because the normal range for the P(A — a)O2
changes with the P02 of inspired gas. The normal a/A ratio
should be greater than 0.75 (Stoelting: Basics of Anesthesia, ed
3, p 229).
60. What is the rate of O2 transported to peripheral
tissues in a healthy 70-kg patient with a hemoglobin
concentration of 10 mg/dL, a Pa02 of 60 mm Hg, an Sa02
of 90%, and a cardiac output of 5 L/min?
A. 300 mL/min
B. 400 mL/min
C. 500 mL/min
D. 600 mL/min
E. 700 mL/min
60. Answer is D
The amount of 02 transported from the lungs to
peripheral tissues is determined by the 02 content
and the cardiac output. The mathematical expression
of 02 transport is as follows: 02 transport = CO. 02
content, where CO is the cardiac output (mL/min). In
this patient, 02 transport is approximately 600
mL/min (Miller: Anesthesia, ed 4, pp 594-597).
61. The P50 of sickle cell hemoglobin
is ?
A. 19
B. 26
C. 31
D. 35
E. 40
61. Answer is C
A P50 less than 26 mm Hg defines a leftward shift of the
oxyhemoglobin dissociation curve. This means that at any given PaO2,
hemoglobin has a higher affinity for 02. A P50 greater than 26 mm Hg
describes a rightward shift of the oxyhemoglobin dissociation curve.
This means that at any given PaO2, hemoglobin has a lower affinity
for 02. Conditions that cause a rightward shift of the oxyhemoglobin
dissociation curve are metabolic and respiratory acidosis,
hyperthermia, increased erythrocyte 2,3-DPG content, pregnancy, and
abnormal hemoglobins, such as sickle cell hemoglobin or thalassemia.
Alkalosis, hypothermia, fetal hemoglobin, abnormal hemoglobin
species, such as carboxyhemoglobin, methemoglobin, and
sulfhemoglobin, and decreased erythrocyte 2,3-DPG content will
cause a leftward shift of the oxyhemoglobin dissociation curve
(Stoelting: Anesthesia and Co-existing Disease, ed 3, p 401; Stoelting:
Pharmacology and Physiology in Anesthetic Practice, ed 2, pp 737 &
738).
62. The leftward shift of the oxyhemoglobin
dissociation curve caused by hypocarbia is known
as the ?
A. Fick principle
B. Bohr effect
C. Haldane effect
D. Law of Laplace
E. None of the above
62. Answer is B
The effects of PaCO2 and pH on the position of the
oxyhemoglobin dissociation curve is known as the
Bohr effect. Hypercarbia and acidosis shift the curve
to the right, and hypocarbia and alkalosis shift the
curve to the left. The Bohr effect is attributed
primarily to the action of CO2 and pH on erythrocyte
2,3-DPG metabolism (Miller: Anesthesia, ed 4, pp 597
& 600).
63. Which of the following is the correct mathematical
expression of Fick’s law of diffusion of a gas through a
lipid membrane (V rate of diffusion, D = diffusion
coefficient of the gas, A = area of the membrane, P1 — P2
= transmembrane partial pressure gradient of the gas, T
thickness of the membrane)?
A. V=D. A.T/P1-P2
B. V= A.T/D(P1- P2)
C. V=D.A(P1-P2)/T
D. V=D.T(Pt-P2)/A
E. V=D.T.A/P1-P2
63. Answer is C
The rate that a gas diffuses through a lipid
membrane is directly proportional to the area of
the membrane, the transmembrane partial
pressure gradient of the gas, and the diffusion
coefficient of the gas, and is inversely proportional
to the thickness of the membrane. The diffusion
coefficient of the gas is directly proportional to the
square root of gas solubility and is inversely
proportional to the square root of the molecular
weight of the gas. This is known as Fick’s law of
diffusion (West: Respiratory Physiology, ed 5, pp 21
& 22).
64. Each of the following is decreased in elderly
patients compared with their younger
counterparts EXCEPT ?
A. Pa02
B. FEV1
C. Ventilatory response to hypercarbia
D. Vital capacity
E. Closing volume
64. Answer is E
Aging is associated with reduced ventilatory volumes and
capacities, and decreased efficiency of pulmonary gas exchange.
These changes are caused by progressive stiffening of cartilage and
replacement of elastic tissue in the intercostal and intervertebral
areas, which decreases compliance of the thoracic cage. In addition,
progressive kyphosis or scoliosis produces upward and anterior
rotation of the ribs and sternum, which further restricts chest wall
expansion during inspiration. With aging, the functional residual
capacity, residual volume, and closing volume are increased, while
the vital capacity, total lung capacity, maximum breathing capacity,
FEV1, and ventilatory response to hypercarbia and hypoxemia are
reduced. In addition, age-related changes in lung parenchyma,
alveolar surface area, and diminished pulmonary capillary bed density
cause ventilation/perfusion mismatch, which decreases resting Pa02
(Stoelting: Anesthesia and Co-existing Disease, ed 3, p 632).
65. The shift of the C02-hemoglobin dissociation
curve which occurs in response to changes in O2
known as ?
A. Fick principle
B. Bohr effect
C. Haldane effect
D. Law of Laplace
E. Le Chatelier principle
65. Answer is C
The shift of the C02-hemoglobin dissociation curve
which occurs in response to changes in PaO2 is known
as the Haldane effect. Because of this effect,
deoxygenated hemoglobin (in peripheral tissues) has
a greater affinity for CO2 than does oxygenated
hemoglobin (Miller: Anesthesia, ed 4, p 600).
66. Which of the following acid-base disturbances
is the least well compensated?
A. Metabolic alkalosis
B. Respiratory alkalosis
C. Increased anion gap metabolic acidosis
D. Normal anion gap metabolic acidosis
E. Respiratory acidosis
66. Answer is A
The degree to which a person can hypoventilate to
compensate for Metabolic Alkalosis is limited and
hence, this is the least well compensated acid-based
disturbance. Respiratory compensation for Metabolic
Alkalosis is rarely more than 75% complete.
Hypoventilation to a PaCO2> 55 mm Hg is the
maximum respiratory compensation for metabolic
alkalosis. A PaCO2 > 58mm Hg most likely reflects
concombined respiratory acidosis (Stoelting: Basics of
Anesthesia, ed 3, p 226).
67. What is the PAO2 of air in a patient in Denver,
Colorado (assume a barometric pressure of 630
mm Hg, respiratory quotient of 0.8, and PaCO2 of
34 mm Hg)?
A. 40mmHg
B. 50mmHg
C. 60mmHg
D. 70mmHg
E. 80mmHg
67. Answer is E
PAO2 can be estimated using the alveolar gas
equation which is as follows: Pa CO2XPAO2=(PB—
47)FIO2— R where PB is the barometric pressure (mm
Hg), FiO2 is the fraction of inspired 02, PaCO2 is the
arterial CO2 tension (mm Hg), and R is the respiratory
quotient (West: Respiratory Physiology, ed 5, p 69).
68. A venous blood sample from which of the
following sites would correlate most reliably
with PaO2 and PaCO2?
A. Jugular vein
B. Subclavian vein
C. Antecubital vein
D. Femoral vein
E. Vein on posterior surface of a warmed hand
68. Answer is E
When arterial sampling is not possible, “arterialized”
venous blood can be used to determine arterial blood
gas tensions. Because blood in the veins on the back of
the hands have very little 02 extracted, the 02 content in
this blood best approximates the 02 content in a sample
of blood obtained from an artery (Stoelting: Basics of
Anesthesia, ed 4, p 226).
69. Which of the following pulmonary function tests is
least dependent on patient effort?
A. FEV1
B. FVC
C. FEF800-I200
D. FEF25-75
E. MVV
69. Answer is D
Pulmonary function tests can be divided into those that
assess ventilatory capacity and into those that assess
pulmonary gas exchange. The simplest test to assess
ventilatory capacity is the FEV 1/FVC ratio. Other tests to
assess ventilatory capacity include the maximum midexpiratory flow (FEF25-75, maximum voluntary ventilation
(MVV), and flow-volume curves. The most significant
disadvantage of these tests is that they are dependent on
patient effort. However, since the FEF25-75 is obtained from
the mid-expiratory portion of the flow-volume loop, it is least
dependent on patient effort (Barash: Clinical Anesthesia, ed
2, p 936).
70. A 33-year-old woman with 20% carboxyhemoglobin
is brought to the emergency room for treatment of
smoke inhalation. Which of the following is LEAST
consistent with a diagnosis of carbon monoxide
poisoning?
A. Cyanosis
B. Pa02 105 mm Hg, oxygen saturation 80% on initial
room air ABGs
C. 98% oxygen saturation on dual wave pulse oximeter
D. Dizziness
E. Oxyhemoglobin dissociation curve shifted far to the
left
70. Answer is A
Carbon monoxide binds to hemoglobin with an affinity 200 to 250
times that of oxygen. This stabilizes the oxygen hemoglobin complex and
hinders release of oxygen to the tissues, i.e. a leftward shift of the
oxyhemoglobin dissociation curve. The diagnosis is suggested when there
is a low oxygen hemoglobin saturation in the face of a normal PaO2. The
two-wave pulse oximeter cannot distinguish oxyhemoglobin from
carboxyhemoglobin so that a normal oxyhemoglobin saturation would be
observed in the presence of high concentrations of carboxyhemoglobin.
Carbon monoxide poisoning is not associated with cyanosis (Rogers:
Principles and Practice of Anesthesiology, p 578; Stoelting: Anesthesia
and Co-existing Disease, ed 3, p 536; Miller: Anesthesia, ed 4, pp 243 12432).
71. The P(A — a)O2 of a patient breathing 100% O2 is 240 mm Hg.
The estimated fraction of the cardiac output shunted past the
lungs without exposure to ventilated alveoli (i.e.,
transpulmonary shunt) is ?
A. 5%
B. 12%
C. 17%
D. 20%
E. 34%
71. Answer is B
p(A-a)O2 Qs/Qt= 20 where Qs is the cardiac output
that is shunted past the lungs without exposure to
ventilated alveoli, Qt is the total cardiac output, and
p(A-a)O2 is the alveolar-to-arterial difference in 02
tension. Qs=12% (Stoelting: Basics of Anesthesia, ed 3,
p 227).
72. Each of the following will alter the position or slope
of the CO2-ventilatory response curve EXCEPT ?
A. Hypoxemia
B. Fentanyl
C. N2O
D. Volatile anesthetics
E. Ketamine
72. Answer is E
Measuring the ventilatory response to increased PaCO2 is a sensitive
method for quantifying the effects of drugs on ventilation. In general, all
volatile anesthetics (including N2O), narcotics, benzodiazepines, and
barbiturates depress the ventilatory response to increased PaCO2 in a
dose-dependent manner. The magnitude of ventilatory depression by
volatile anesthetics is greater in patients with chronic obstructive
pulmonary disease (COPD) than in healthy patients. Thus, it is
recommended that arterial blood gases are monitored during recovery
from general anesthesia in patients with COPD. Ketamine causes minimal
respiratory depression. Typically, respiratory rate is decreased only 2 to 3
breaths/min and the ventilatory response to changes in PaCO2 is
maintained during ketamine anesthesia (Miller: Anesthesia, ed 4, pp 139
& 140• West: Respiratory Physiology, ed 4, p 126; Stoelting: Pharmacology
and Physiology in Anesthetic Practice, ed 2, p 139).
73. Which of the following statements concerning the
distribution of alveolar ventilation (VA) in the upright
lungs is true?
A. The distribution of VA is not affected by body posture
B. Alveoli at the apex of the lungs (nondependent alveoli)
are better ventilated than those at the base
C. All areas of the lungs are ventilated equally
D. Alveoli at the base of the lungs (dependent alveoli) are
better ventilated than those at the apex
E. Alveoli at the central regions of the lungs are better
ventilated than those at the base or apex
73. Answer is B
The orientation of the lungs relative to gravity has a
profound effect on efficiency of pulmonary gas exchange.
Because alveoli in dependent regions of the lungs expand
more per unit change in transpulmonary pressure (i.e., are
more compliant) than alveoli in nondependent regions of the
lungs, VA increases from the top to the bottom of the lungs.
Because pulmonary blood flow increases more from the top
to the bottom of the lungs than does VA, the
ventilation/perfusion ratio is high in nondependent regions
of the lungs and is low in dependent regions of the lungs.
Therefore, in the upright lungs, the pAO2 and pH are greater
at the apex, while the PACO2 is greater at the base (West:
Respiratory Physiology, ed 5, pp 19 & 20, 38-41, 61-66).
74. In the resting adult, what percent of total
body O2 consumption is due to the work of
breathing?
A. 2%
B. 5%
C. 10%
D. 20%
E. 50%
74. Answer is A
The work required to overcome the elastic recoil of the
lungs and thorax, along with airflow or frictional resistances
of the airways, contributes to the work of breathing. When
the respiratory rate or airway resistance is high, or pulmonary
or chest wall compliance is reduced, a large amount of energy
is spent overcoming the work of breathing. In the healthy,
resting adult, only 1% to 2% of total 02 consumption is used
for the work of breathing (Stoelting: Pharmacology and
Physiology in Anesthetic Practice, ed 2, p 721).
75. The anatomic dead space in a 70-kg male is ?
A. 5OmL
B. I5OmL
C. 25OmL
D. 500mL
E. 700 to 1,000 mL
75. Answer is B
The conducting airways (trachea, right and left mainstem
bronchi, and lobar and segmental bronchi) do not contain
alveoli and therefore do not take part in pulmonary gas
exchange. These structures constitute the anatomic dead
space. In the adult, the anatomic dead space is approximately
1 mL/lb or 2 mL/kg. The anatomic dead space increases
during inspiration because of the traction exerted on the
conducting airways by the surrounding lung parenchyma. In
addition, the anatomic dead space depends on the size and
posture of the subject (Stoelting: Pharmacology and
Physiology in Anesthetic Practice, ed 2, p 725).
76. Reynold`s number is an important factor in
the determination of ?
A. 02 transport
B. Surface tension
C. Turbulent vs. laminar flow
D. Physiologic dead-space ventilation
E. Functional residual capacity
76. Answer is C
Reynold’s number is a calculated value that represents the
overall ratio of inertial forces to viscous forces during flow.
Reynold’s number is directly proportional to the density of
the substance, the flow velocity of the substance, and the
radius of the container through which the substance is
flowing, and is inversely proportional to the viscosity of the
substance. In general, flow through a long, straight, smoothwalled container becomes turbulent when the Reynold’s
number is greater than 2,300 (Miller: Anesthesia, ed 4, p 1101;
West: Respiratory Physiology, ed 5, pp 103-105).
77. A decrease in PaCO2 of 10 mm Hg will result
in ?
A. A decrease in serum potassium concentration [K+]
of 0.5 mEq/L
B. A decrease in [K+] of 1.0 mEq/L
C. No change in [K+] under normal circumstances
D. An increase in [K+] of 0.5 mEq/L
E. An increase in [K+] of 1.0 mEq/L
77. Answer is A
Cardiac dysrhythmias are a common complication
associated with acid-base abnormalities. The etiology of
these dysrhythmias is related partly to the effects of pH on
myocardial potassium homeostasis. As a general rule, there is
an inverse relationship between [K] and pH. For every 0.08
unit change in pH, there is a reciprocal change in [K] of
approximately 0.5 mEqIL (Stoelting: Pharmacology and
Physiology in Anesthetic Practice, ed 2, p 274).
78. An increase in [HCO3-] of 10/L will result in
an increase in pH of ?
A. 0.10 pH units
B. 0.15 pH units
C. 0.20 pH units
D. 0.25 pH units
E. None of the above
78. Answer is B
There are several guidelines that can be used in the initial
interpretation of arterial blood gases that will permit rapid
recognition of the type of acid-base disturbance. These
guidelines are as follows: 1) a 1 mm Hg change in PaCO2
above or below 40 mm Hg results in a 0.008 unit change in
the pH in the opposite direction; 2) the PaCO2 will decrease
by about 1 mm Hg for every 1 mEq/L reduction in [HCO3]
below 24 mEq/L; 3) a change in [HCO3] of 10 mEq/L from 24
mEq/L will result in a change in pH of approximately 0.15 pH
units in the same direction (Stoelting: Pharmacology and
Physiology in Anesthetic Practice, ed 2, pp 219-226)
79. A 28-year-old female (70 kg) with ulcerative colitis is undergoing general
anesthesia for colon resection and ileostomy. Current medications include
sulfasalazine and corticosteroids. Induction of anesthesia and tracheal
intubation are uneventful. Anesthesia is maintained with isoflurane, N2O and
50% 02, and fentanyl, and the patient is paralyzed with atracurium. The
patient’s lungs are mechanically ventilated with the following parameters:
VE 5,000 mL, respiratory rate 10 breaths/min. How would VA change if the
respiratory rate were increased from 10 to 20 breaths/min?
A. Increase by 500 mL
B. Increase by 1,000 mL
C. No change
D. Decrease by 750 mL
E. Decrease by 1,500 mL
79. Answer is E
A patient with a VD of 150 mL and a VA of 350 mL
(assuming a normal VT of 500 mL) will have a (VD) of
1,500 mL and a (VA) of 3,500 mL (at VE of 5,000 mL) at a
respiratory rate of 10 breaths/min. If the respiratory rate
is doubled but VE remains unchanged, then the VD
would double to 3,000 mL, an increase in VD of 1,500 mL
and decrease in VA of 1,500 mL (Stoelting:
Pharmacology and Physiology in Anesthetic Practice, ed
2, p 725).
80. Each of the following will shift the oxyhemoglobin
dissociation curve to the right EXCEPT?
A. Volatile anesthetics
B. Decreased pa02
C. Decreased pH
D. Increased temperature
E. Increased red blood cell (RBC) 2,3-DPG content
80. Answer is B
In addition to the items listed in this question, other
factors that shift the oxyhemoglobin dissociation curve to the
right include pregnancy and all abnormal hemoglobin such
as hemoglobin S (sickle cell hemoglobin). For reasons
unknown, volatile anesthetics increase the P50 of adult
hemoglobin by 2 to 3.5 mm Hg. A rightward shift of the
oxyhemoglobin dissociation curve will decrease the transfer
of 02 from alveoli to hemoglobin and improve release of 02
from hemoglobin to peripheral tissues (Stoelting:
Pharmacology and Physiology in Anesthetic Practice, ed 2, p
738).
81. The half-life of carboxyhemoglobin in a patient
breathing 100% O2is ?
A. 5 minutes
B. 1 hour
C. 2 hours
D. 4 hours
E. 12 hours
81. Answer is B
The most frequent immediate cause of death from fires is carbon
monoxide toxicity. Carbon monoxide is a colorless, odorless gas that
exerts its adverse effects by decreasing 02 delivery to peripheral tissues.
This is accomplished by two mechanisms. First, because the affinity of
carbon monoxide for the 02 binding sites on hemoglobin is 240 times that
of 02, 02 is readily displaced from hemoglobin. Thus, 02 content is
reduced. Second, carbon monoxide causes a leftward shift of the
oxyhemoglobin dissociation curve, which increases the affinity of
hemoglobin for 02 at peripheral tissues. Treatment of carbon monoxide
toxicity is administration of 100% 02. Breathing 100% 02 decreases the
half-time of carboxyhemoglobin from 250 minutes to approximately 50
minutes (Stoelting: Anesthesia and Co-existing Disease, ed 3, p 536).
82. The most important buffering system in the
body is ?
A. Hemoglobin
B. Plasma proteins
C. Bone
D. HCO3E. Phosphate
82. Answer is D
The HCO3 buffer system is the most important system and
represents >50% of the total buffering capacity of the body.
Other important buffer systems include hemoglobin, which
is responsible for approximately 35% of the buffering capacity
of blood, phosphates, plasma proteins, and bone (Miller:
Anesthesia, ed 4, pp 1386 & 1387; Stoelting: Basics of
Anesthesia, ed 3, p 217).
83. Which of the following statements concerning the
distribution of O2and CO2 in the upright lungs is true?
A. PAO2 is greater at the apex than at the base
B. PACO2 is greater at the apex than at the base
C. Both PAO2 and PACO2 are greater at the apex than
at the base
D. Both PAO2 and PACO2 are greater at the base than
at the apex
E. The PACO2 is equal throughout the lung
83. Answer is A
The ventilation/perfusion ratio is greater at the apex of
the lungs than at the base of the lungs. Thus, dependent
regions of the lungs are hypoxic and hypercarbic
compared to the nondependent regions (West:
Respiratory Physiology, ed 5, pp 6166).
84. All of the following choices correctly describes the
effect a bilateral carotid endarterectomy resulting in
denervation of the carotid bodies would have on the
control of breathing EXCEPT?
A. Loss of the ventilatory response to CO2
B. Loss of the ventilatory response to hypoxia
C. Loss of the ventilatory response to hydrogen ions
D. Loss of the ventilatory response to fever
84. Answer is D
Breathing is controlled by the respiratory center which is a widely
dispersed group of neurons located in the medulla and pons. Breathing is
regulated in response to a variety of physiologic factors which include
PaCO2, PaO2, hydrogen ion concentration and temperature. Peripheral
chemoreceptors which respond to pH, PaCO2, and PaO2 are located in
the aorta (aortic bodies) and at the bifurcation of the common carotid
artery (carotid bodies). Denervation or removal of the latter results in a
30% decrease in the ventilatory response to CO2 and elimination of the
ventilatory response to hypoxemia (Stoelting: Pharmacology and
Physiology in Anesthetic Practice, ed 2, pp 727-728).
85. A 22-year-old black male comes to the emergency room
diaphoretic and short of breath. The patient is given 100% O2
by Nonrebreathing face mask. Arterial blood gases are as
follows: Pa02 309 mm Hg, PaCO2 24 mm Hg, pH 7.57, and SaO2
89%. Causes of these findings could include the presence of ?
A. Methemoglobin
B. Carboxyhemoglobin
C. Sulfhemoglobin
D. Sickle cell hemoglobin
E. A and C
85. Answer is E
Abnormal hemoglobin species, such as Methemoglobin,
Sulfhemoglobin, bind O2 less avidly than does normal
hemoglobin which greatly reduces the O2 carrying capacity
of blood. The presence of these abnormal hemoglobin
species is suggested by a low SpO2 in the presence of a
normal PaO2. The diagnosis of these abnormal hemoglobin
species is confirmed by direct measurement in plasma
(Stoelting: Anesthesia and Co-existing Disease, ed 3, pp 401403).
86. Adverse effect(s) of respiratory or metabolic
acidosis include?
A. Increased incidence of cardiac dysrhythmias
B. Hypovolemia
C. Increased serum potassium concentration
D. Increased pulmonary vascular resistance
E. all of the above
86. Answer is E
Adverse physiologic effects of respiratory or metabolic
acidosis include central nervous system depression,
cardiovascular system depression (which is a result of the direct
depressant effects of the acidosis on the vasomotor center,
arteriolar smooth muscle, and myocardial contractility),
increased incidence of cardiac dysrhythmias, hypovolemia
(which is a result of decreased precapillary and increased
postcapillary sphincter tone), pulmonary hypertension, and
hyperkalemia. Depression of the cardiovascular system is
partially offset by increased secretion of catecholamines and
elevated Ca2+ until severe acidosis occurs (Stoelting: Basics of
Anesthesia, ed 3, p 219).
87. All of the following can increase physiologic deadspace ventilation EXCEPT ?
A. PEEP
B. Venous air embolus
C. Hypotension
D. Pregnancy
87. Answer is D
Physiologic dead-space ventilation is the ventilation of
areas of the lungs that are poorly perfused. Except for
pregnancy, all of the choices will increase physiologic
dead-space ventilation (Miller: Anesthesia, ed 4, pp 585,
611, & 612; Shnider: Anesthesia for Obstetrics, ed 3, p 3).
88. Which of the following can cause a rightward
shift of the oxyhemoglobin dissociation curve?
A. Methemoglobinemia
B. Carboxyhemoglobinemia
C. Rapid transfusion of large amounts of citrate-
preserved packed erythrocytes
D. Pregnancy
88. Answer is D
factors that shift the oxyhemoglobin dissociation
curve to the right include pregnancy and all abnormal
hemoglobins such as hemoglobin S (sickle cell
hemoglobin).
89. All of the following suggest the need for
mechanical ventilation EXCEPT ?
A. Vital capacity less than 25 mL/kg
B. Vd/Vt greater than 0.6
C. PaCO2 greater than 50 mmHg
D. Pa02/Fi02 less than 250 mmHg
E. Peak negative pressure of -20 cmH2O
89. Answer is A
A vital capacity less than 15 mL/kg would suggest
the need for mechanical ventilation. The normal
vital capacity is 70 ml/kg. Normal peak negative
pressure is between -50 and -100 cm H2O.
Normal Pa02/Fi02 is 400 mmHg or greater and
Vd/Vt is normally 0.3.
90. Closing capacity (CC) is increased by all of
the following EXCEPT ?
A. Age
B. Obesity
C. Smoking
D. Supine position
E. Gender
90. Answer is E
Closing capacity (CC) is a sensitive test of early small
airway disease. Patients are instructed to exhale to
residual volume. The patient then inhales, from residual
volume, toward total lung capacity (TLC). At the
beginning of the inhalation a tracer gas (helium) is
injected into the inspired gas. A closing volume (CV) is
subsequently measured and the CC is calculated
(CC=closing volume + residual volume). CC=FRC in the
supine position at 44 years of age. CC=FRC in the upright
position at 66 years of age. Smoking, aging, obesity, and
the supine position all increase CC.