86.
Closing capacity is the sum of residual volume and closing volume.
An increase in closing capacity leads to a situation where lung volume is
so much reduced below functional residual capacity that small alveoli and
airways in the dependent regions of the lungs are closed.
Which of the following conditions is least likely to lead to elevation of
closing capacity:
A.
Infancy
B.
Bronchiolitis
C.
Cystic fibrosis
D.
Asthma
E.
Pulmonary edema
Click
here for answer
87.
In conditions associated with increased closing capacity, the most
appropriate therapeutic
intervention includes:
A.
Increase residual volume
B. Control pulmonary secretions and use of bronchodilators
C.
Use of CPAP
D.
Use of PEEP when on mechanical ventilation
Click here for answer
88.
The Ventilation/Perfusion (V/Q) ratio remains stable as one moves from
the base of the lung up to the third rib, but then as one moves towards the
apex, the V/Q ratio changes exponentially because:
A.
Blood flow falls more rapidly than ventilation with distance up the lung
B. Ventilation increases more rapidly down the lungs than perfusion
C.
Both ventilation and perfusion increase exponentially down the lungs
D.
Ventilation decreases linearly but perfusion exponentially down the lungs
Click here for answer
89.
Regarding the compliance and resistance of the ventilatory circuits and
their interaction with the patient, which of the following statements is most
accurate:
A.
If the compliance of the ventilator circuit and the patient are equal,
adequate delivery of tidal volume to the patient is assured
B.
Large circuit compliance leads to delay in the delivery of an assisted
breath
C.
Use of rigid short tubing aggravates loss of tidal volume
D.
Distribution of volume delivered by a positive pressure ventilator
between the ventilator circuit and the patient is determined entirely by the
patient’s respiratory compliance and resistance
Click here for answer
90.
Modifications of ventilator circuiting for pediatric mechanical
ventilators, in order to substantially
reduce the ventilator system compliance,
include all of the following except:
A.
Small diameter circuit tubing
B. Rigid tubing with inspiratory circuit as short as possible
C.
Decreasing humidifier size
D.
Positioning of exhalation valve away from the airway opening
E.
Maintaining humidifier fluid level
Click here for answer
91.
The most common clinical application of hyperbaric O2 therapy
is:
A. Carbon monoxide poisoning
B. Decompression sickness
C.
Gas embolism
D.
Radiation necrosis
E.
Crush injury
Click here for answer
92.
Use of hyperbaric O2 therapy for carbon monoxide poisoning is
probably the most common application of this technology.
All of the following statements regarding this application are true
except:
A.
The beneficial effect of hyperbaric O2 therapy is directly
related to the associated increase in PaO2
B.
The half-life of carbon monoxide as measured by carboxy-hemoglobin is
decreased to 53 minutes at 3 atmospheric pressure
C.
Hyperbaric O2 therapy helps reverse binding of carbon monoxide
to cytochrome a3
D.
Hyperbaric O2 therapy is indicated in patients who suffer
unconsciousness or display signs of CNS depression
Click here for answer
93.
The least likely complication of hyperbaric oxygen therapy is:
A.
Tympanic membrane perforation
B.
Pneumomediastinum
C.
Fire and ignition accidents
D.
Significant central nervous system toxicity at 2.5 atm pressure
Click here for answer
94.
Helium is a low density gas that, when used in combination with O2,
has proven particularly useful. All
of the following statements are true except:
A.
The use of helium/O2 mixture is not feasible in patients
requiring higher than 0.4 FiO2
B.
Helium/O2 mixture may improve gas exchange and decrease peak
inspiratory pressure in asthmatics requiring ventilatory support
C.
In children with large airway obstruction helium/O2 mixture
improves alveolar O2 component
D.
Helium/O2 mixture decreases work of breathing
E.
Helium/O2 mixture can not be used in patients whose airway has
been instrumented
Click here for answer
95.
A 6 kg infant with pneumonia is being ventilated with conventional
mechanical ventilation at a rate of 35 bpm on an FiO2 of 0.6.
The peak inspiratory pressure is 32 cm H2O and positive
end-expiratory pressure is 6cm H2O.
The inspiratory time is set at 0.5 seconds and the flow of gas through
the ventilator circuit is set at 8 liters/min.
The approximate tidal volume is:
A.
11 ml/kg
B. 5 ml/kg
C.
7 ml/kg
D.
9 ml/kg
E.
None of the above
Click here for answer
96.
Most of gas exchange during mechanical ventilation with a normal I:E
ratio occurs during:
A.
Inspiration
B. The inspiratory plateau
C.
Exhalation
D.
Gas exchange is uniform throughout the respiratory cycle
Click here for answer
97.
Time-limited, constant-flow ventilators are one category of ventilators
that are sometimes used in the
Pediatric ICU.
True statements pertaining to this category of ventilators include all of
the following
except:
A.
Use is restricted to the asynchronous mode
B. Tidal volume can only be estimated
C.
Inspiratory flow limits of these ventilators do not provide adequate flow
for patients weighing in excess of 15 kg
D.
The peak inspiratory pressure relief valve is housed in the inspiratory
circuit in these ventilators
Click here for answer
98.
In the assist-control mode of mechanical ventilation:
A.
A pre-set tidal volume is delivered in response to every
patient-initiated effort
B. The patient must perform inspiratory work to open the inspiratory valve
and initiate each tidal volume
C.
Ventilator trigger sensitivity and peak inspiratory flow are controlled
by the operator
D.
Ventilator peak inspiratory flow and trigger sensitivity affect work of
breathing
E.
All of the above
Click here for answer
99.
Intermittent mandatory ventilation allows spontaneous breathing between
positive pressure breaths with a pre-set tidal volume and frequency.
Which one of the following statements least accurately describes intermittent mandatory ventilation:
A.
To minimize work of breathing, the inspiratory gas flow in continuous
flow circuit should not exceed the patient’s own peak inspiratory flow rate
B.
A flow-by system avoids problems associated with continuous flow and
demand flow systems in terms of work of breathing
C.
Intermittent mandatory ventilation is likely to be associated with more
stable hemodynamics compared to continuous mandatory ventilation
D.
Intermittent mandatory ventilation is more likely to be associated with
improved V/Q matching compared to continuous mandatory ventilation
E.
The need for frequent administration of sedatives and/or muscle relaxants
seems to be decreased by using intermittent mandatory ventilation compared to
continuous mandatory ventilation
Click here for answer
100.
In describing pressure support ventilation, which one of the following
options is least accurate:
A.
The ventilator retains control of the cycle length as well as the depth
and flow characteristics
B.
It has been shown to abolish diaphragmatic muscle fatigue in patients who
fail conventional weaning attempts
C.
Pressure support ventilation helps compensate for work of breathing due
to the inspiratory demand valve and endotracheal tube impedance
D.
Patient effort, length of pressure support and the respiratory system
impedance determine the tidal volume
Click here for answer
101.
Inverse-ratio ventilation is performed using:
A.
Pressure-limited breaths with decelerating inspiratory flow rates and
adjustment of inspiratory time to the desired level
B. Volume-limited breaths with low inspiratory flow rates to achieve the
desired inspiratory time
C.
Volume-limited breaths with normal inspiratory flow rate and prolonged
inspiratory pause to maintain a prolonged inspiratory phase
D.
All of the above
Click here for answer
102.
During pressure-control inverse-ratio ventilation, tidal volume is a
function of:
A.
Respiratory system compliance and resistance
B. The pre-set pressure limit
C. The ratio of inspiratory time to total duty cycle
D. Frequency
E. All of the above
Click here for answer
103.
Positive pressure ventilatory support in the setting of respiratory
failure is aimed at elevating the functional residual capacity or mean lung
volume through the application of continuous positive airway pressure (CPAP) or
positive end expiratory pressure (PEEP). Appropriate
statements pertaining to this application include all of the following except:
A.
Application of appropriate levels of PEEP/CPAP can decrease work of
breathing
B.
High levels of PEEP have the potential to increase work of breathing
C.
The decrease in oxygen delivery associated with high levels of PEEP is
often resistant to fluid resuscitation and inotropic support
D.
In the absence of pulmonary artery catheter, PEEP should be gradually
increased to maintain an A-a gradient < 250 torr with adequate perfusion
E.
As a general rule, a pulmonary artery catheter is recommended to monitor
cardiac output when PEEP of > 15 cm is used
Click here for answer
104.
When deciding to discharge a patient home who is ventilator dependent,
the least important factor to consider is:
A.
Presence of an established tracheostomy with healed stoma
B.
PaO2 > 60 torr with FiO2 < 0.3 and PaCO2
< 50 torr using home ventilatory settings
C.
No need for PEEP
D.
The underlying disease
E.
Stabile ventilatory settings for one month
Click here for answer
105.
Adverse hemodynamic effects of PEEP are related to:
A.
Decreased venous return
B. Ventricular interdependence
C.
Increased RV afterload
D.
Reflex neurohormonal factors leading to ventricular dysfunction
E. All of the above
Click here for answer
106.
Barotrauma is a recognized complication of mechanical ventilatory support
and has a number of clinical manifestations.
Which of the following is always considered clinically significant:
A. Pulmonary interstitial emphysema
B. Pneumomediastinum
C. Subcutaneous emphysema
D.
Pneumoperitoneum
E.
None of the above
Click here for answer
107.
Tension pneumothorax is a life-threatening complication of trauma or
positive pressure ventilation that requires immediate intervention.
True statements regarding tension pneumothorax include all of the following except:
A.
Tension pneumothorax occurs when a communication exists between the
pleural space and either the alveoli or the atmosphere, so that air enters the
pleural space during inspiration but is unable to exit during exhalation
B. Tension pneumothorax occurs when intrapleural pressure continues to
remain subatmospheric
C. Obstruction of venous return occurs
D. Treatment is by closed chest thoracotomy tube
Click here for answer
108.
Features of veno-venous extra-corporeal life support include all of the
following except:
A.
It depends on patient’s native heart for O2 delivery to
tissue
B. Usually requires lower extracorporeal flow
C.
It reduces the risk of embolization with an intact heart
D.
It maintains well oxygenated pulmonary blood flow
E.
It requires the right ventricle to work unremittingly in the face of
pulmonary hypertension
Click here for answer
A.
Veno-arterial extra-corporeal life support
B.
Veno-venous extra-corporeal life support
C.
Both
D.
Neither
109.
____ Maintain(s)
pulmonary blood flow with oxygenated blood
____ Assist(s)
systemic circulation
____ Decrease(s)
pulmonary artery pressure
Click here for answer
110.
Which of the following equations best describes the O2
saturation that is obtained using the pulse oximetry?
A.
= HbO2 / HbO2 + Hb + HbCO + Hb met
B.
= HbO2 / Hb
C.
= HbO2 / HbO2 + Hb
D.
= HbO2 + Hb / HbO2
Click here for answer
111.
You have made a diagnosis of nitrite poisoning and decide to administer
methylene blue intravenously at a dose of 1 mg/kg over few minutes.
As the nurse is injecting the methylene blue, you notice that the
saturation on pulse oximetry decreases precipitously from 99% to 85%.
The most likely explanation and the appropriate course of action is:
A.
Shock with hypotension; stop the medication
B. Formation of carboxyhemoglobin
C.
Methylene blue is misinterpreted by the pulse oximeter as reduced
hemoglobin resulting in a low saturation; this should resolve in two minutes
without any intervention
D.
None of the above
Click here for answer
A.
Carboxy hemoglobin
B.
Hemoglobin
C.
Oxyhemoglobin
112.
____ High level
of this compound leads to a low fractional saturation but relatively high
functional saturation.
Click here for answer
113.
Which of the following is least likely to interfere with an accurate
reading of saturation on pulse oximetry?
A.
High levels of HbCO
B.
High levels of met Hb
C.
An external light source such as a surgical lamp, bilirubin lamps or
fluorescent lights
D.
Hyperbilirubinemia
E.
Shock with low perfusion states
Click here for answer
114.
Which of the following clinical conditions is not associated with a low
mixed venous oxygen saturation:
A.
Low Hb
B. Low arterial oxygen saturation
C.
Low cardiac output
D.
Increased O2 delivery
E.
Increased O2 consumption
Click here for answer
115.
Which of the following clinical conditions is not associated with a high
mixed venous oxygen saturation:
A.
Increased O2 delivery
B. Decreased O2 extraction by the tissue
C.
Severe mitral regurgitation
D.
A wedged pulmonary artery catheter
E.
Increased O2 consumption
Click here for answer
116.
The above figure represents the capnogram obtained from a patient on SIMV
mode of mechanical ventilation and a ventilator with a demand valve mechanism.
The best course of action would be:
A.
Substitute the neuromuscular blockade agent used with a non-depolarizing
agent
B.
Calm the patient and reassure him
C.
Add a bronchodilator and intravenous corticosteroid
D.
Add 20 cm H2O of pressure support
E.
None of the above, as this represents a normal variation of capnography
Click here for answer
117.
Which one of the clinical conditions listed below is not expected to be
associated with a sudden decline in end tidal CO2:
A.
Cardiac standstill
B. Air embolism
C.
Obstruction of the endotracheal tube
D.
Leakage in the circuit or discontinuation of the ventilator suddenly
E.
Hypoventilation
Click here for answer
118.
You are preparing to draw an arterial blood gas sample from a patient in
the Pediatric ICU. In discussing with your medical students, the technical errors associated with this process,
which one of the following statements would you not make:
A.
A gas bubble in the syringe will falsely elevate PaCO2
B. The major blood gas error associated with excess heparin in the sample is
a drop in PaCO2
C.
When a sample that is obtained from a patient breathing room air is
interfaced with a bubble, the PaO2 obtained will be close to 150 torr
D.
In a patient on high FiO2 with normal lungs, the presence of
an air bubble in the syringe may spuriously lower PaO2
Click here for answer
119.
Alterations in blood gas values occur if the sample is not immediately
analyzed leading to spurious results; generally this effect is most noticeable
in patients with:
A.
Hyponatremia and hypercalcemia
B. Leukopenia
C.
Neutropenia
D.
Leukocytosis and reticulocytopenia
E.
Reticulocytosis with high band forms
Click here for answer
120.
Which one of the following drugs leads to a high anion gap metabolic
acidosis:
A.
Acetazolamide
B.
Aldactone
C.
Arginine HCL
D.
Aspirin
E.
Cholestyramine and Sulfamylon
Click here for answer
121.
Which of the following is not a characteristic feature of posterior
choanal atresia:
A.
Clinical symptoms have been noted to persist after surgical correction in
some infants
B.
Most cases are unilateral
C.
Has a familiar occurrence
D.
Other associated anomalies are extremely uncommon
Click here for answer
122.
Nasal encephalocele is a recognized cause of nasal obstruction in
children. Which one of the
following statements does not accurately describe this condition:
A.
Usually communicates with the subarachnoid space
B. May be seen as a nasofrontal or a nasoethmoidal mass
C.
The mass is soft, compressible and may be pulsatile, but biopsy is
contraindicated
D.
Nasal obstruction does not occur when the mass is located at the base of
skull
Click here for answer
123.
Nasopharyngeal angiofibromas
A.
May extend to the nasal passages and cause obstruction
B. Tend to cause symptoms typically at puberty
C.
Rhinorrhea and epistaxis are common symptoms
D.
Treatment is radiation therapy or surgery
E.
All of the above
Click here for answer
A.
Infant
B. Adult
C.
Both
D.
Neither
124.
____ Vocal cords
are concave and at an angle to the trachea
____ The main
bronchi branch from the trachea at equal angles
____ The glottis
is located at C6
____ The tracheal
length from glottis to bifurcation is 11 cm
Click here for answer
125.
The true statement regarding the pediatric airway is:
A.
The lateral diameter of the newborn glottis is 10 mm
B. At birth, the trachea is approximately 10 cm in length
C.
At 4-6 months, the epiglottis loses contact with the soft palate and
becomes more erect
D.
The glottis assumes the adult location at the level of the 6th
cervical vertebra by 6 years of age
Click here for answer
126.
During spontaneous respirations, the major contribution to total
respiratory resistance is by:
A.
Nasal airway and mouth
B. Glottis
C.
Trachea
D.
Bronchi
Click here for answer
127.
A child with an airway that has a diameter of 8 mm develops a respiratory
infection with airway inflammation and circumferential edema which leads to a 1
mm uniform reduction in the size of the airway; this will decrease the
cross-sectional area of the airway by:
A.
34%
B. 44%
C.
56%
D.
64%
E.
74%
Click here for answer
128.
Laryngospasm is induced by reflexes in the nose, oropharynx, epiglottis
and vocal cords and may be seen in response to mucous, saliva, emesis or blood.
It necessitates immediate interventions which may include:
A.
Positive pressure ventilation by a mask
B. Removal of the offending agent
C.
Elevation of the mandible
D.
Use of a muscle relaxant
E.
All of the above
Click here for answer
129.
In children younger than 2-1/2 years with chronic stridor, the most
common etiology is:
A.
Infection of the larynx and surrounding structures
B. Congenital anomalies of the larynx
C.
Foreign body aspiration
D.
Trauma
Click here for answer
130.
Laryngomalacia is characterized by all of the following except:
A.
It is the most common congenital laryngeal anomaly
B. Aryepiglottic folds fall into the glottis on inspiration
C.
Voice is hoarse leading to abnormal cry
D.
Resolves by 18-24 months
E.
Tracheostomy may be required if the problem interferes with feeding and
growth
Click here for answer
131.
All of the following congenital abnormalities lead to abnormal cry and
hoarseness of voice except:
A.
Laryngocele
B. Laryngeal web
C.
Laryngomalacia
D.
Laryngeal cyst
E.
Laryngotracheoesophageal cleft
Click here for answer
A.
Laryngomalacia
B. Airway hemangioma
C.
Both
D.
Neither
132.
____ Symptoms
usually occur before six months of age
____ Treatment is
conservative, since most cases resolve by two years of age
Click here for answer
133.
Syndromes associated with difficult airway management due to micrognathia
is/are:
A. Hallermann-Streiff Syndrome (Occulomandibulodyscephaly)
B. Mobius Syndrome
C.
Noonan’s Syndrome
D.
DiGeorge Syndrome
E.
All of the above
Click here for answer
134.
Post-operative complications associated with cleft lip/palate repair
include:
A.
Edema leading to nasopharyngeal obstruction
B. Nasopharyngeal blockage from secretions
C.
Laryngospasm from excessive secretion and bloody drainage
D.
All of the above
Click here for answer
135.
Macroglossia with a short neck combine to produce a difficult airway in
which of the following clinical disorders:
A.
Hurler’s Syndrome
B. Scheie’s Syndrome
C.
Both
D.
Neither
Click here for answer
136.
A difficult airway due to a short and rigid neck is seen in:
A.
Hurler’s and Marqio’s mucopolysaccharidoses
B. Klippel-Feil Syndrome
C.
Myositis ossificans
D.
Ankylosing spondylitis
E. All of the above
Click here for answer
137. A 2-1/2 year old white male who has a 2-day history of an upper
respiratory tract infection and fever, is now having mild stridor and dysphagia.
His immunizations are up to date. You
suspect retropharyngeal abscess. Which
one of the following statements is incorrect regarding this patient:
A.
Age of the patient is somewhat atypical
B. Inspiratory radiograph films are more informative than expiratory films
C.
A chest radiograph should be obtained to evaluate mediastinal extension
D.
The retropharyngeal space extends from the base of the skull to the level
of the 2nd thoracic vertebra
E.
The usual organisms are staphylococci, group A streptococci and anaerobes
Click here for answer
138.
A 3-year-old is admitted to the Pediatric ICU with a diagnosis of
bacterial tracheitis. True
statements regarding this condition include all of the following except:
A.
Diagnosis is confirmed by thick purulent secretions suctioned from the
trachea or the presence of a pseudomembrane, or ulcerations intratracheally
B. Intermittent tracheal suctioning should be avoided
C.
Intubation may be required in cases of severe airway obstruction
D.
Repeated bronchoscopy aids secretion removal and assessment of disease
progression
E.
Extubation criteria include lack of fever, presence of air leak around
the tube, signs of healing at bronchoscopy and a decreased need for suctioning
Click here for answer
139.
A 2-1/2 year old with viral croup required intubation for increasing CO2
and acidemia three days ago. Extubation
is recommended when:
A.
An air leak around the tube can be heard with coughing
B. An air leak around the tube can be heard with a positive pressure
insufflation of < 40 cm H20
C.
The amount of endotracheal secretions has diminished
D.
All of the above
Click here for answer
140.
With regard to orofacial trauma caused by external forces, all of the
following statements are true except:
A. Nasotracheal intubation should be avoided with midfacial fractures
B. Provided the cervical spine is stable, hemorrhage at the base of the
tongue should be managed by having the patient in the prone or lateral position
with the head down to allow drainage of blood
C.
A skateboard-associated injury to the neck usually involves an area of
soft tissue and an underlying skeletal injury
D.
The amount of subcutaneous emphysema of the neck correlates with the
severity of airway injury
Click here for answer
141.
In children with acquired subglottic stenosis, the most common etiology
is:
A.
Endotracheal intubation
B.
External neck trauma
C.
Burns
D.
High tracheostomy sites
E.
Tumors
Click
here for answer
142.
Among the risk factors for the development of subglottic stenosis is the
duration of mechanical ventilation. The
acceptable time for the duration of intubation is:
A.
2 days
B. 4 days
C.
7 days
D.
10 days
E.
None of the above
Click here for answer
143.
With regard to thermal and chemical injuries to the head and neck region,
all of the following statements are true except:
A.
If there are flame burns of the face or singed facial hairs, the
temperature is high enough to result in a respiratory burn
B. Thermal injury usually affects the nasopharynx and larynx
C.
A child with a history of caustic ingestion requires examination of the
larynx
D.
Helium-O2 has not been shown to be effective in the management
of post-extubation stridor in burn victims
Click here for answer
144.
Papillomas are the most common airway tumors in children with symptoms
usually appearing before age 7. True
statements about papillomas include all of the following except:
A.
Most commonly located on vocal cords
B.
Initial symptoms involve a change in voice such as stridor
C.
Often these children have personality changes
D.
The natural history is life-long recurrence
E.
The goal of therapy is to remove most of the lesions to prevent
spreading, while preserving airway anatomy
Click here for answer
145.
The predominant pathophysiologic abnormality leading to hypoxemia in
bronchiolitis due to respiratory syncytial virus infection is:
A.
Ventilation/perfusion mismatch
B.
Right-to-left intrapulmonary shunting
C.
Hypoventilation with relative alveolar hypoxemia
D.
Diffusion barrier
E.
All of the above
Click here for answer
146.
A 5-month-old with severe respiratory syncytial virus bronchiolitis is
noted to be slightly edematous with puffiness of the periorbital area and low
urine output. Past medical history
is unremarkable for prematurity or other perinatal disorders.
It is also negative for any liver or kidney diseases.
Physical examination does not reveal evidence of hepatomegaly or
pronounced component of the second heart sound.
Laboratory data shows that serum electrolytes are within normal limits.
The most likely explanation for this finding is:
A.
Hypoalbuminemia
B. Hyponatremia with low urine Na+
C.
Congestive heart failure due to cor pulmonale
D.
High anti-diuretic hormone levels with hyperaldosteronism
E.
None of the above
Click here for answer
147.
Evaluation of urine for the patient in the previous question will most
likely show:
A.
Low urine Na+
B. High urine Na+
C.
Normal urine Na+
D.
Any of the above
Click here for answer
148.
In acute asthma, which one of the following demonstrates the most severe
decrease:
A.
Maximum mid-expiratory flow rate
B. Mean expiratory forced reserve
C.
Functional vital capacity
D.
Forced expiratory volume 1.0 (FEV1.0)
Click here for answer
149.
After treatment of an acute attack of asthma, which of the following is
least likely to improve:
A.
Maximum mid-expiratory flow rate
B. Mean expiratory forced reserve
C.
Functional vital capacity
D.
Forced expiratory volume 1.0 (FEV1.0)
Click here for answer
150.
Which one of the following parameters is least likely to decrease during
an acute attack of asthma:
A.
Inspiratory capacity
B. Vital capacity
C.
Expiratory reserve volume
D.
Maximum expiratory flow rate
E.
Residual volume
Click here for answer
151.
Pathophysiologic changes that occur in an acute episode of asthma include
all of the following except:
A.
Hypocapnia is caused by alveolar hyperventilation secondary to activation
of pulmonary reflexes
B. Hypocapnia correlates with the degree of airway obstruction
C.
The degree of hyperoxia correlates well with the degree of airway
obstruction as measured by FEV1.0
D.
Elevated PaCO2 occurs when (FEV1.0) falls below 20%
predicted
E.
Elevated PaCO2 is not seen if peak expiratory flow rate is
> 25% predicted
Click here for answer
152.
True statements regarding an acute asthmatic attack include:
A.
Left ventricular afterload is advantageously lowered by the significantly
negative intrathoracic pressure with inspiration
B. A decrease in pulsus paradoxus always indicates an improvement in the
patient’s clinical condition
C.
Hypocapnia seen in the early stages of an attack correlates with the
degree of airway obstruction
D.
Pulsus paradoxus is due to a combination of increased left ventricular
afterload and ventricular interdependence during inspiration
E.
None of the above
Click here for answer
153.
Hypoxemia during status asthmaticus results from:
A.
Ventilation/perfusion mismatch
B.
Increased O2 requirement
C.
Increased interstitial lung fluid
D.
All of the above
Click here for answer
154.
FEV1.0 is an important parameter in the evaluation of a
patient in status asthmaticus because of all of the following, except:
A.
FEV1.0 correlates with PaO2
B. FEV1.0 inversely correlates with PaCO2
C.
PaCO2 elevation occurs when FEV1.0 falls below 20%
predicted
D.
Pulsus paradoxus is present in all patients with an FEV1.0
less than 20% predicted
Click here for answer
155.
At an FEV1.0 < 20% predicted:
A.
PaCO2 rises
B. Hypoxemia occurs
C.
Pulsus paradoxus is present in all patients
D.
All of the above
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Answers
86-87.
E, B
Pulmonary edema is more likely to lead to a decrease in functional
residual capacity rather than an increase in closing capacity.
Elimination of secretions and use of effective bronchodilators are useful
strategies to improve closing capacity.
88.
A
Because blood flow falls more dramatically than ventilation from the base
of the lung towards the apex of the lung, the ventilation perfusion ratio
increases exponentially as one moves up the lung.
(West JB. Ventilation/Blood
Flow and Gas Exchange, 3rd Edition; Oxford, Blackwell Scientific,
1977; pp 30)
89-90. B, D
A significant portion of the tidal volume dissipates when the compliance
of the ventilatory circuit is high. Patient’s
compliance and resistance also affects the actual delivered tidal volume.
The exhalation valve is usually kept close to the airway opening in order
to minimize the circuit volume. (Rogers
MC. Textbook of Pediatric Intensive
Care, 2nd Edition, 1992; pp 147-150)
91-93. A, B, D
In clinical medicine, carbon monoxide poisoning is probably the most
common application of hyperbaric O2 therapy.
The half-life of carbon monoxide is actually decreased to 23 minutes at
3.0 atmospheric pressure, as opposed to 180 minutes with 100% oxygen at the
normal atmospheric pressure. Sixty to ninety minutes of hyperbaric oxygen at 2 to 2.5
atmospheric pressure seems to be safe, without significant CNS toxicity,
although other side effects mentioned in the question are possible. (Rogers MC,
et al. Textbook of Pediatric
Intensive Care, 2nd Edition, 1992; pp 156-157)
94.
E
With turbulent airflow, the resistance to airflow is proportionate to
density (as opposed to viscosity with laminar flow).
Because helium is a less dense gas than nitrogen, it has a beneficial
role in patients with upper airway obstruction such as croup.
More recently, the helium-O2 mixture has also been shown to
improve gas exchange in patients with acute asthma with or without ventilatory
support. Helium-O2
mixture minimizes work of breathing by altering the resistance to airflow.
In patients, breathing > 40% O2, the gas mixture becomes
too dense to be beneficial. Helium-O2
mixture is most beneficial at 80:20 or 70:30 ratios. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; p 157)
95.
A
The flow through the ventilator circuit is set at 8 liters/min.
Therefore, 8,000 ¸
60 ´ 0.5 = 66
¸ 6 = 11 ml/kg.
96.
C
Most of gas exchange takes place during exhalation. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 2nd Edition, 1992; pp
156-159)
97-99. D, A, A
The inspiratory pressure relief valve is housed in the expiratory limb of
the circuit in these ventilators. Actually,
in order to minimize work of breathing, the inspiratory gas flow in the
continuous flow circuit should meet the patient’s inspiratory flow rate
demand. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition, 1992; pp 156-159)
100.
A
In the pressure support mode of ventilation, the length of the cycle as
well as depth and flow characteristics, are determined by the patient. (Rogers
MC, et al. Textbook of Pediatric
Intensive Care, 2nd Edition, 1992;
pp 156-159)
101-102.
D, E
All three options are methods of providing an inverse ratio ventilation,
which has been used successfully to improve oxygenation and ventilation at a
reduced peak inspiratory pressure. During
inverse ratio ventilation, the tidal volume is a function of multiple factors,
some of which are enumerated in the question.
(Tharralt RS, et al. Chest,
1988; 94:755)
103.
C
The decrease in oxygen delivery associated with elevation of PEEP is
usually responsive to adequate fluid resuscitation and inotropic support, unless
one is using extremely high levels of PEEP. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 3rd Edition; pp 297-300)
104.
D
(Rogers MC, et al. Textbook
of Pediatric Intensive Care, 3rd Edition; pp 184)
105.
E
All of these factors are operative when it comes to the adverse
hemodynamic effects of PEEP. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 2nd Edition; pp 186)
106.
E
Unless they progress to a tension pneumothorax or a tension
pneumoperitoneum, none of these manifestations of barotrauma mentioned are
usually clinically significant (i.e., do not require immediate intervention).
(Rogers MC, et al. Textbook of
Pediatric Intensive Care, 2nd Edition; pp 186-188)
107.
B
During tension pneumothorax, the intrapleural pressure is consistently
higher than the atmospheric pressure. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 3rd Edition; pp 307-309)
108.
B
Veno-venous extra-corporeal life support (VV-ECLS) usually requires a
higher rate of flow because of the recirculation of the previously oxygenated
blood. This is true when the
pulmonary bed is totally non-functional. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 3rd Edition; pp 317-318)
109.
B, A, A
Veno-venous extra-corporeal life support (VV-ECLS) maintains pulmonary
blood flow with oxygenated blood, but it does not assist the systemic
circulation. On the other hand,
veno-arterial extra-corporeal life support (VA-ECLS) does assist the systemic
circulation and it also tends to decrease the pulmonary artery pressure. (Rogers
MC, et al. Textbook of Pediatric
Intensive Care, 3rd Edition; pp 317-318)
110.
C
The oxygen saturation that is obtained using pulse oximetry is called a
functional saturation, and the pulse oximetry obtains the ratio of oxyhemoglobin
divided by the total hemoglobin. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 3rd Edition; pp 333-336)
111.
C
Methylene blue absorbs light maximally at 668nm.
The pulse oximeter interprets this extra absorbance as reduced
hemoglobin, and therefore a lower oxygen saturation is obtained.
The oxygen saturation obtained by the pulse oximetry could drop
dramatically within 30 seconds of an intravenous administration of methylene
blue, and it remains reduced for approximately 2 minutes.
(Scheller M. Anesthesiology,
1986; 65:550)
112.
A
Carboxyhemoglobin and Met-hemoglobin produce these findings.
(Barker SJ. Anesthesiology,
1987; 66:677)
113.
D
With an increase in Met-hemoglobin concentration, the saturation on the
pulse oximeter decreases and plateaus at approximately 85%. Met hemoglobin absorbs light significantly at both 660 nm
and 940 nm wave lengths, thereby confusing the pulse oximeter photo detector
into believing that both oxyhemoglobin and reduced hemoglobin are increased.
This results in increases in both the denominator and numerator.
As this happens the microprocessor driven algorithm of the red absorbance
and infrared absorbance approaches unity and this gives rise to a saturation of
approximately 85% on the calibration curve. Hyperbilirubinemia does not
interfere with reading of the pulse oximetry.
(Barker SJ, et al. Anesthesiology,
1988; 68:279)
114-115.
D, E
In the presence of normal oxygen extraction and utilization by the
tissue, an increase in oxygen delivery will not result in decreased mixed-venous
oxygen saturation. Increased oxygen
consumption leads to a decrease in mixed venous oxygen saturation, and not vice
versa. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 210-211)
116.
D
This capnogram reveals irregularity in the pattern of the exhalation of
the CO2 which most likely reflects irregularity in the pattern of
breathing of this patient. Adding
20 cm H2O of pressure support will decrease the work of breathing by
overcoming the work that is necessary to open the demand valve mechanism that is
operating in this ventilator. It
will also help to overcome some of the resistance of the endotracheal tube.
(Carlon G, et al. Crit Care Med, 1988; 16:550)
117.
E
Hypoventilation is likely to lead to a gradual increase in the level of
end tidal CO2. All other
clinical conditions indicated in the question lead to a sudden decline in end
tidal CO2 levels. (Carlon
G, et al. Crit Care Med, 1988; 16:550)
118.
A
The presence of a gas bubble in a syringe will usually affect the PaO2.
The effect on the PaO2 will depend on the amount of oxygen
that is inspired by the patient. In
patients on room air, this will lead to a false elevation of PaO2
(atmospheric PO2 is usually higher than alveolar PO2).
On the other hand, in patients who are receiving a high fraction of
inspired oxygen and have normal lungs, the presence of an air bubble in a
syringe may spuriously lower the PaO2. Excess heparin does lead to a drop in PaCO2 but
usually there are no changes in the pH level because it is neutralized by the
acidity of heparin. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 3rd Edition; pp 353-359)
119.
E
Reticulocytes and band forms are highly metabolic immature cells that are
most likely to lead to a change in the blood gas results. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 3rd Edition; pp 355-359)
120.
D
Aspirin, especially with overdose, is likely to lead to high anion gap
metabolic acidosis. All other drugs
do not. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 3rd Edition; p 361)
121.
D
Other abnormalities of the central nervous system, esophagus, and
cardiovascular system have been reported in association with choanal atresia.
Therefore, evaluation for possible other anomalies should be done in
patients with posterior choanal atresia. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 2nd Edition; pp 231-233)
122.
D
Nasal obstruction is usually seen when the mass is located at the base of
the brain. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 231-233)
123.
E
All are features of angiofibroma. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 2nd Edition;
pp 231-233)
124.
A, A, B, B
Vocal cords in infants are concave, and the anterior attachment to the
trachea are lower and the glottis is located higher in the neck compared to an
adult. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition;
pp 231-233)
125.
C
At 4-6 months of age, the epiglottis loses contact with the soft palate
and assumes a more erect posture, and this allows oral (mouth) breathing.
The lateral diameter of the newborn glottis is only about 4-5 mm
and at birth the trachea is approximately 5-7 cm in length.
The glottis assumes the adult location at C6 by about 12 years of age.
(Rogers MC, et al. Textbook of
Pediatric Intensive Care, 2nd Edition; pp 231-233)
126.
A
127.
B
p
R2 = 16 p
when the diameter is 8 mm which gives rise to a radius of 4 mm.
With a uniform 1 mm reduction in the size of the airway, this will
decrease the diameter from 8 mm to 6 mm, and decrease the radius from 4 mm
to 3 mm. Now p
R2 = 9 p,
9 ¸ 16 = 54%, which means that the diameter of the airway has been
decreased by 44%. (Rogers MC,
et al. Textbook of Pediatric
Intensive Care, 2nd Edition; pp 231-233)
128.
E
All of these are measures that may be needed to intervene with
laryngospasm. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 233-234)
129.
B
Congenital anomalies are the most common cause of chronic stridor in
children less than 2 years of age. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 2nd Edition; pp 235-238)
130.
C
(Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 235-238)
131.
C
Laryngotracheomalacia is characterized by normal voice. (Rogers MC, et
al. Textbook of Pediatric Intensive Care, 2nd Edition;
p 236)
132.
C, C
Both laryngomalacia and airway or subglottic hemangioma usually present
with symptoms before 6 months of age. In
both cases, the treatment is conservative, since in most cases, the problem
resolves spontaneously by the end of the 2nd birthday. (Rogers MC, et
al. Textbook of Pediatric Intensive
Care, 2nd Edition; pp 235-238)
133.
E
All of these conditions pose difficult airway management. (Rogers MC, et
al. Textbook of Pediatric Intensive
Care, 2nd Edition; pp 235-238)
134.
D
All of these are complications that may be noted in the post-operative
period following repair of cleft lip and cleft palate. Occasionally bronchospasm is also seen. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 2nd Edition; pp 235-238)
135.
C
Both these conditions are characterized by macroglossia with a short
neck, which combine to produce a difficult airway.
Both of these conditions belong to the mucopolysaccharidoses. (Rogers MC,
et al. Textbook of Pediatric
Intensive Care, 2nd Edition; p 241)
136.
E
(Rogers MC, et al. Textbook of
Pediatric Intensive Care, 2nd Edition; p 241)
137.
A
The typical age for this condition is less than 3 years. It is important to obtain inspiratory radiographs to evaluate
the thickness of the retropharyngeal soft tissue.
Measurement of this soft tissue is important in the diagnosis of the
retropharyngeal abscess. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 2nd Edition; p 242)
138.
B
In fact, frequent tracheal suctioning is necessary in these patients to
prevent airway obstruction because the infection/inflammation induce an increase
in airway secretions. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 242-245)
139.
D
These are the indications for extubation in a patient with a viral croup.
(Rogers MC, et al. Textbook of
Pediatric Intensive Care, 2nd Edition; pp 244-246)
140.
D
The amount of subcutaneous emphysema of the neck area does not correlate
with the severity of airway injury. Nasotracheal
intubation should be avoided in patients with midfacial fractures, and also in
patients suspected of having a fracture of the base of the skull. (Rogers MC, et
al. Textbook of Pediatric Intensive
Care, 2nd Edition; pp 245-248)
141.
A
70-80% of subglottic stenosis occur following endotracheal intubation.
(Rogers MC, et al. Textbook of
Pediatric Intensive Care, 2nd Edition; pp 245-248)
142.
E
The accepted duration of time for intubation to prevent subglottic
stenosis is unknown. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 245-248)
143.
D
A helium-oxygen mixture in various combinations has been shown to be
effective in the management of post-extubation stridor and burn victims with
significant stridor. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; p 245)
144.
D
Most of these airway papillomas resolve by the teenage years.
(Rogers MC, et al. Textbook of Pediatric Intensive Care, 2nd Edition;
p 252)
145.
A
Therefore these patients respond to relatively low concentrations of
inspired oxygen. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 258-260)
146.
D
High antidiuretic hormone levels in association with elevation of renin
has been reported in patients with bronchiolitis.
(Gozal D, et al. Pediatric
Research, 1990; 27:204-209)
147.
C
High ADH in association with high aldosterone levels has been reported in
patients with respiratory syncytial virus bronchiolitis. Because of this combination of hormonal abnormalities, there
is a decrease in urine output associated with a normal urine sodium
concentration. (Gozal D, et al.
Pediatric Research, 1990; 27:204-209)
148-151.
A, A, E, B
Maximum mid-expiratory flow rate is one of the flow volume parameters
that demonstrates the most severe decrease during an attack of asthma.
This is also the parameter that is the last to improve following
treatment for acute asthma. Patients
with asthma, particularly those that are in status asthmaticus, have an
increased residual volume. (Rogers MC, et al.
Textbook of Pediatric Intensive Care, 2nd Edition; pp 264-270)
152-153.
D, D
Transmural pressure = intraluminal pressure – extraluminal pressure.
With higher negative inspiratory pressure, as seen with status
asthmaticus, there is an increase in afterload during inspiration with a
subsequent decrease in left ventricular output which is followed by a sharp
increase in left ventricular output during subsequent expiration.
This leads to the phenomenon of pulsus paradoxus (PP).
A decrease in PP may indicate an improvement in the patient’s condition
(i.e., a smaller fall in pleural) but it may also indicate the patient’s
fatigue and worsening clinical condition. Another
factor that contributes to PP is ventricular interdependence which can be
exaggerated by the pulmonary hypertension as it may be seen with severe status
asthmaticus. The hypoxia that is
seen during status asthmaticus is due to V/Q mismatch, excessive O2
requirement secondary to increased metabolic demand and a degree of interstitial
edema. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 268-270)
154.
A
The degree of hypoxemia does not correlate with the degree of airway
obstruction as assessed by the reduction in FEV1.
(McFaden ER, et al. New Engl
J of Med, 1968; 278:1029)
155.
D
As the FEV1 drops below 20% predicted, PCO2 rises,
hypoxemia occurs and pulsus paradoxus is present in almost all of these
patients. (McFaden ER, et al. New
Engl J of Med, 1968; 278:1029)
156.
B
0.3 liters = 1 PSI
c
liters 1100 PSI
therefore:
c
= 1100 x 0.3 =
330 liters
= 82.5 min
1
4 liters/min
157.
B
Both perfusion and ventilation (V/Q) increase as one moves from the apex
of the lungs towards the base of the lung.
However, perfusion increases more than ventilation.
Therefore, apical regions are underperfused with a V/Q of approximately
3, while basal regions of the lungs are underventilated in relation to perfusion
with a V/Q of approximately 0.6. (West
JB. Ventilation / Blood Flow and
Gas Exchange, 3rd Edition. Oxford,
Blackwell Scientific, 1977; pp 30-31)
158.
C
The major indication for tracheostomy in early burn management is upper
airway obstruction which may be due to edema, a foreign body or laryngeal trauma
such that an endotracheal tube cannot be passed.
(Carvajal HF, Parks DM. Burns
in Children, Pediatric Burn Management, Yearbook Medical Publishers, Inc., 1988;
pp 167-168)
159.
D
In the human, there are five (5) stages of lung development:
1)
Embryonal (Day 26 – Day 52): characterized
by development of trachea and major bronchi
2)
Pseudoglandular (Day 52 – Week 16):
characterized by development of remaining tracheobronchial tree
3)
Canalicular (Week 17 – Week 28): characterized
by development of vascular bed and framework of acinus
4)
Saccular (Week 29 – Week 36): characterized
by increased complexity of saccules
5)
Alveolar (Week 26 – Term): characterized
by development of alveoli
The lungs emerge as a bud from the pharynx at Day 26 following
conception. This bud elongates,
separates from the esophagus, and continues to divide to form the main bronchi.
Extensive subdivision in the pseudoglandular stage leads to formation of
the conducting airway, the most peripheral of which are the terminal bronchioles
which give rise to respiratory bronchioles and alveolar ducts during the
Canalicular stage. During this
later stage, the acinus is formed. An acinus is the gas exchange unit associated with a single
terminal bronchiole and will eventually contain three orders of respiratory
bronchioles: alveolar ducts,
alveolar sacs, and alveoli.
The Saccular stage was formerly thought to be the last stage of lung
development prior to birth. However,
because alveoli form before birth, the termination of this period is now
arbitrarily set at 35-36 weeks gestation. At
the beginning of this phase (28 weeks gestation) the terminal structures are
call saccules. They are cylindrical
structures with a smooth wall. They
become subdivided by ridges call secondary crests.
Further subdivision between crests result in small spaces termed
subsaccules. Exactly when these
subsaccules can be termed alveoli is a matter of debate.
The range of timing is between 29-36 weeks gestation.
Most of post-natal formation of alveoli occurs over the first 1-1/2 years
of life. Pores of Kohn are not established until several years after
birth. (Langston C, Kida K, Reed M,
et al. Human lung growth in late
gestation and in the neonate. Am
Rev Resp Dis, 1984; 129:607)
160.
B
PaO2
=
PiO2 -
PaCO2
RQ
=
(747 – 47) x 0.4
- 40
0.8
=
280 -
50 = 230
Alveolar arterial O2 gradient
= PAO2 - PaO2
= 230 -
100
= 130
(Kandra TG, Rosenthal M. The
pathophysiology of respiratory failure. International
Anesthesiology, 1993; Vol. 31(2), pp 119-121)
161.
B
(Jodka PG, Heard SO. Management
of the septic patient in the operating room.
International Anesthesiology, 2000; Vol. 35(4), pp 1-10)
162.
E
Bronchopleural fistulae (BPF) can result from blunt trauma, barotrauma or
inflammatory diseases of the lung. Patients
with BPF can present acutely due to pulmonary flooding or tension pneumothorax,
or subacutely with an insidious clinical course.
A persistent air leak without evidence of technical problem in the
pleural drainage apparatus also indicates a BPF. Several techniques can be employed using bronchoscopy to
localize the proximal endobronchial site of the fistulous tract.
Occasionally, air bubbles can be seen emanating from the segmental
bronchus. Washing the suspected
segment with saline and coughing may accentuate the bubbling.
Techniques for obliteration of the fistula bronchoscopically have also
been described. (McManigle JE, et
al. Bronchoscopy in the management
of bronchopleural fistula. Chest,
1990; Vol. 97, pp 1235-1238)
163.
C
After a delay of 2-8 minutes, intramuscular ketamine (4-8 mg/kg/BW)
produces anesthesia for 20-40 minute. Over
90-92% of ketamine is absorbed after an intramuscular injection.
(White PF, Way WL, Trevor AJ. Ketamine
– its pharmacology and therapeutic uses.
Anesthesiology, 1982; Vol. 56, p 119)
164.
D
The cellular proliferative phase, after alveolar injury, is characterized
by Type II cellular hyperplasia, which appears to be a reparative process.
These cuboidal cells may virtually cover the entire alveolar surface.
They will later transform into the thin, Type I alveolar epithelial
cells. (Royall JA, Matalon S.
Pulmonary edema and ARDS, In: Fuhrman
BP, Zimmerman JJ. Pediatric
Critical Care, Mosby Yearbook 1992, pp 445-456)
165.
A
Tachypnea is the earliest sign of respiratory muscle fatigue. As a compensation for the decrease in efficient tidal volume,
the respiratory rate increases in an attempt to maintain minute ventilation.
(Nunn JF. Applied
Respiratory Physiology, 3rd Edition.
Boston: Butterworth, 1987, p
109)
166.
C
CO2 binds with deoxyhemoglobin (deoxyHb) to form
carbaminohemoglobin, which is one of the forms in which CO2 is
transported in the blood. However
only 10% of CO2 in blood is transported in this form.
Myoglobin approaches full saturation at a PO2 of 15-30 mmHg
which is the level pertaining to voluntary muscle.
The bulk of its oxygen may be released only at very low O2
tension. 2,3 DPG decreases the
affinity of O2 for hemoglobin, and thus, facilitates release of O2
to tissues and so does carbon dioxide. This
latter phenomenon is also known as the Bohr effect.
O2 binds to one of the six coordination bonds of the iron
atom. Hydrogen binds to the
imidazole ring of Histidine on the globin chains of the hemoglobin molecule.
(Nunn JF. Applied
Respiratory Physiology, 4th Edition.
Boston: Butterworth/Heinemann,
1993; pp 273-275. Guyton AC. Textbook
of Medical Physiology, 8th Edition. WB Saunders Co., 1991; pp 440-442)
167.
E
Increasing PEEP will diminish left-to-right shunting by increasing the
pulmonary vascular resistance. All
other measures stated in the question would increase left-to-right shunt flow.
(Meliones JN, et al. Respiratory
Support in Infants & Children. Mosby,
1995; p 352)
168.
D
Linoleic acid is the primary precursor of arachidonic acid. (Abman S, Stenmark K. Am
J Physiology, 1992; Vol 262: L214)
169.
C
O2 delivery (DO2)
=
Cardiac output (CO)
x Arterial O2
Content (CaO2)
CaO2 =
Hb (gm%) x
1.34 x
O2 Sat +
PaO2 x
0.003
In this case, increasing the hemoglobin from 9 gm% to 14 gm% will
increase O2 delivery the most. (Fahey
JT, Lister G. “Oxygen demand,
delivery and consumption.” Fuhrman
BP, Zimmerman JJ. Pediatric
Critical Care, 2nd Edition; Mosby, 1998; pp 235-240)
170.
A
171.
C
Pulmonary capillary endothelial damage is one of the earliest changes in
ARDS. Capillary congestion with
intraluminal aggregation of platelets, fibrin, and neutrophils. Pulmonary capillary endothelial cells undergo swelling and
focal necrosis with destruction of mitochondria, endoplasmic reticulum and
ribosomes during the first few hours of ARDS.
(Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 297-298)
172.
A
The Mapleson D breathing circuit (shown in the diagram below) can be
described as a T-piece with an expiratory limb.
The fresh gas inlet is located near the patient, and the expiratory
pressure release valve (PRV) is near the reservoir bag.
The PRV opens as pressure increases during expiration and a portion of
the expired gas along with fresh gas is released into the atmosphere.
During the next inspiration, the patient receives a combination of fresh
gas and the exhaled gas. The
content of this inspired gas is determined by:
1)
Rate of fresh gas flow: A
fresh gas flow > 2 times the minute ventilation prevents rebreathing
2)
Patient’s tidal volume: the
amount of rebreathing increases as the tidal volume increases
3)
Duration of expiration: a
short expiratory pause provides inadequate time to flush the alveolar gas
(occurs with faster respiratory rate); this allows rebreathing
(Barash PG, Cullen BF, Stoelting RK.
Clinical anesthesia, 2nd Edition; pp 654)
173.
C
When peak airway pressure is allowed to increase to a level beyond that
which is necessary to maximally distend the lungs, barotrauma and lung injury
result. Since regional differences
in lung resistance and compliance often co-exist, maintaining a constant tidal
volume may overdistend areas of the lung that are aerated if the remainder of
the lung is collapsed. Similarly
maintaining a constant inspiratory flow pattern when regional differences in
lung units exist will selectively increase distention of lung units with lower
resistance. (Haake R, et al.
Barotrauma: pathophysiology,
risk factors and prevention. Chest, 1987; Vol. 1:608)
174.
D
Pulmonary conditions associated with decreased compliance such as
pulmonary fibrosis and ARDS or increased airway resistance such as bronchial
asthma and COPD have the potential for being homogenous. This homogeneity can
result in regional over-distention during positive pressure ventilation. Hyperinflation secondary to airway narrowing or collapse such
as seen with auto-PEEP increases end-expiratory lung volume but does not result
in lung expansion of the hyperinflated lung units until airway pressure exceeds
the level of auto-PEEP. Although
the work of breathing during spontaneous breathing is increased by auto-PEEP,
end-inspiratory lung volumes do not increase.
(Bone RC, Stober G. Mechanical
ventilation in respiratory failure. Med
Clin Noth Am, 1983; Vol. 67:599)
175.
D
Changes in intrathoracic pressure correlate highly with changes in lung
volume. Changes in intrathoracic
pressure are independent of lung compliance.
An increase in respiratory rate with lung conditions associated with
increased expiratory airway resistance will result in dynamic hyperinflation
because there is inadequate time for exhalation. Examples are COPD, asthma, and
other causes of intrathoracic airway obstruction.
Thus, over-distention is possible with a fixed tidal breath or tidal
volume. Since regional lung
compliance, even in healthy individuals, is different under all conditions,
uniform expansion of all lung units by positive pressure ventilation at any
setting probably never occurs. (Marini
JJ. Ventilatory management in
severe airflow obstruction found in
Pinsky MR, Dhainaut JFA, Ed. Pathophysiologic
Foundations of Critical Care, 1993; pp 453-471)
176.
B
(Marini JJ. Ventilatory
management in severe airflow obstruction found
in Pinsky MR, Dhainaut JFA, Ed. Pathophysiologic
Foundations of Critical Care, 1993; pp 453-471)
177.
A
Nitric oxide is synthesized from the amino acid arginine by the action of
the enzyme nitric oxide synthetase. (Nichols
DG, et al. Critical Heart
Disease in Infants and Children. Mosby,
1995; pp 36, 78, 111, 206)
178.
D
Systemic to pulmonary shunt is often created in neonates and infants with
an underlying cardiac defect in order to improve pulmonary blood flow and
oxygenation. Examples are the
(modified) Blalock-Taussig shunt that connects the subclavian artery to the
pulmonary artery using a synthetic material, and the aortic to pulmonary window
which usually connects the ascending aorta to the pulmonary artery.
Conditions that lead to a reduction in pulmonary artery pressure and
pulmonary vascular resistance would increase the flow across the shunt with an
increase in left to right shunt. Examples
include: Alkalosis, vasodilators such as hydralazine and nitroprusside, an
increase in the concentration of inspired oxygen, and selective pulmonary
vasodilators such as nitric oxide. Interventions
that lead to an increase in pulmonary vascular resistance such as increasing
PEEP would lead to a reduction in pulmonary blood flow and a reduction in the
left to right shunt. (Nichols DG,
et al. Critical Heart Disease in
Infants and Children. Mosby,
1995; pp 460)
179.
B
Tachypnea in this infant would be the earliest evidence of inspiratory
muscle fatigue. (Nichols DG, et al.
Critical Heart Disease in Infants and Children.
Mosby, 1995; pp 319-332)
180.
C
Nitric dioxide is the toxic by-product.
The rate of formation of this toxic product is dependent on the duration
of contact between oxygen and nitric oxide.
(Nichols DG, et al. Critical
Heart Disease in Infants and Children.
Mosby, 1995; pp 36, 78, 111, 206)
181.
E
(Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 157, 245-246)
182.
C
Histological features of infants with bronchopulmonary dysplasia (BPD)
include squamous metaplasia of the airway epithelium (large and small airways),
increased peribronchial smooth muscle with fibrosis, submucosal edema and
inflammation with hypertrophy of submucosal glands.
In the parenchyma, there are areas of fibrosis with atelectasis
alternating with areas of hyperinflation which, on gross examination of the
lungs has a cobblestone appearance. In
more long-standing cases, there is diminution in alveolarization and surface
area. The decrease in the number of
alveoli, probably reflect the onset of the insult with subsequent failure of the
ability to regenerate new alveoli.
This is associated with increased number of small pulmonary arteries,
which
may contribute to pulmonary hypertension.
The pulmonary arterial tree shows
proliferation of the intima, smooth
muscle hypertrophy, distal extension of smooth
muscles, and adventitial
thickening. (Abman SH, Groothius
JR. Pathophysiology
and treatment
of BPD. Pediatr Clin North Am,
1994; 41(2), pp 277-291)
183.
C
Upper airway obstruction usually does not lead to an alveolar-arterial
oxygen gradient. On rare occasions,
when upper airway obstruction is complicated by post-obstruction pulmonary
edema, this is possible. (Rogers
MC, et al. Textbook of Pediatric
Intensive Care, 2nd Edition; pp 231-296)
184.
E
The lungs have a tendency to collapse, while the chest wall has a
tendency to move outward. Thus the
elastic forces of the lung and the chest wall are in opposite directions. These two opposing forces are linked by the pleural surfaces
and the nest pressure is the intrapleural pressure. (Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 145)
185.
B
Bronchogenic cyst accounts for 5% of mediastinal masses.
It is found in five major locations:
right paratracheal region (20%); carinal region (51%); hilar region (9%);
paraesophageal (14%); and pericardial/retrosternal.
(Taussig LM. Pediatric Respiratory Medicine, 1999; p 1118)
186.
E
Hysteresis refers to the failure of a system to follow identical paths of
response during application and during withdrawal of a force.
In the lungs, this is due mainly to surface properties and alveolar
recruitment-derecruitment. In the
chest wall, this is due to muscle and ligaments, both of which exhibit
hysteresis. (Taussig LM.
Pediatric Respiratory Medicine, 1999; pp 100-101)
187.
A
Increasing the length of muscle fibers (to a limited extent) would
increase the force of contraction and thus the efficiency of the diaphragm. The diaphragm is most efficient at the lung volume that
corresponds to the functional residual capacity (FRC) and thus increasing the
end-expiratory lung volume above this does not improve the efficiency of the
diaphragm. Increasing the radius of
curvature increases the efficiency of the diaphragm. The diaphragm of an infant has less radius of curator than
that of an adult, and is less efficient. (Fuhrman
BP, Zimmerman JJ. Pediatric
Critical Care, 2nd Edition; pp 407)
188.
A
BAL in ARDS is characterized by predominance of PMNs, of 10 > 85%.
(Reynolds HY. Am Rev Resp Dis, 1987; Vol. 135, pp 250-263)
189.
B
Massive hemoptysis is relatively uncommon in cystic fibrosis patients.
It occurs in 10% of adolescents and adult patients with cystic fibrosis.
Massive hemoptysis usually
occurs from the bronchial circulation due to the higher systemic pressure
compared to the pulmonary circulation. Often
an untreated exacerbation of the disease is a triggering factor, but sometimes
there is no clear cause. If
hemoptysis persists, bronchial artery embolization is warranted; this requires
bronchial arteriography. (Sweeney
N, Fellows K. Bronchial artery
embolization for severe hemoptysis in cystic fibrosis.
Chest, 1990; pp 1322-1326)
190.
B
In infants, the continuous muscle tone of the thorax is important to
maintain functional residual capacity (FRC), because the chest wall is very
compliant and lacks the rigidity necessary to oppose the elastic recoil of the
lung, which tends to lower FRC. With
age, as chest wall compliance decreases and the chest wall becomes more rigid
and capable to oppose the elastic recoil of the lungs, FRC increases.
(Rogers MC, et al. Textbook of Pediatric Intensive Care, 2nd
Edition; p 112-128)
191.
B
A helium-oxygen mixture is less dense that a nitrogen-oxygen (air)
mixture. With turbulent flow (seen
with upper airway obstruction such as subglottic stenosis), resistance to air
flow is proportionate to density. A
helium-oxygen mixture is useful in reducing the resistance to flow and work of
breathing. ((Rogers MC, et al.
Textbook of Pediatric Intensive Care, 3rd Edition; pp
275-276)
192.
B
Refer to the answer for Question #182 on the previous page.
193.
D
PAO2 =
(BP – Vapor Pressure) X
FiO2 – PaCO2 / RQ
Since PaCO2 and RQ are assumed to remain constant, they will
remain the same under both situations: (760 – 47) X
0.27 = 192.51
In order to keep the PaO2 the same, and therefore compensate for the same
degree of Alveolar-arterial oxygen gradient as the atmospheric pressure
decreases, the alveolar oxygen tension must remain the same (i.e., 192.51).
Therefore,
(632
- 47)
X Unknown fraction of
inspired oxygen = 192.51
FiO2 =
192.51 / 632-47 =
192.51 / 585 = 0.3290
(Rogers MC, et al. Textbook
of Pediatric Intensive Care, 2nd Edition; pp 116-117)
194.
B
The function of this protein is to promote formation of a surfactant
layer. It is, therefore, essential
for effective reduction of the surface tension induced by surfactant.
(Fuhrman BP, Zimmerman JJ. Pediatric
Critical Care, 2nd Edition; pp 382-383)
195.
E
Type I alveolar cells are less in number than Type II alveolar cells
(which synthesize surfactant), but they cover a much larger area of the lung.
Their primary function is to reduce the barrier to gas exchange.
(Fuhrman BP, Zimmerman JJ. Pediatric
Critical Care, 2nd Edition; pp 445-446)
196.
C
Forced vital capacity (FVC) is easily measured during spirometry.
Data obtained from a specific patient can be compared with those from
subjects who have the same height, weight and age.
FVC is highly reproducible and has a narrow range of normal values.
It is affected in both obstructive and restrictive lung diseases. FVC may decline in the sup8ine position by up to 20% in
normal subjects and up to 38% in patients with underlying neuromuscular
diseases. (Civeta JM, et al. Critical Care, 2nd Edition; pp 565-566)
197.
A
Work =
Force x Distance. When it
comes to the respiratory system, “work” is defined as the pressure that is
generated by the respiratory muscle to move a particular volume of gas.
(Rogers MC, et al. Textbook of Pediatric Intensive Care, 2nd
Edition; pp 129-130)
198.
B
Alveolar O2 tension = (Barometric Pressure – Vapor Pressure)
x FiO2 – PaCO2 / RQ
(760 – 47) x 0.21 – 85 / 0.8
713 x 0.21 – 106.25 =
43.38
PAO2 - PaO2 = 10
Therefore:
PaO2 =
43 – 10 = 33 mmHg
(Rogers MC, et al. Textbook
of Pediatric Intensive Care, 3rd Edition; p 90)
199-200.
E, A
The half-life (t½) of a drug is function of clearance (CL) and volume of
distribution (Vd) according to the following formula:
T½ =
0.693 x
Vd / CL
Thus half-life is affected not only by elimination, but also by volume of
distribution. For instance, during
ECLS, most of the increase in the half-life is due to an increase in the volume
of distribution, rather than a change in drug clearance.
A drug’s half-life can also be used to determine the time it takes for
the drug to reach a steady-state concentration, a state in which the amount of
drug administered equals the amount cleared by the body.
After 3 half-lives
87% of steady-state concentration is achieved
After 4 half-lives
93% of steady-state concentration is achieved
After 5 half-lives
97% of steady-state concentration is achieved
(Fuhrman BP, Zimmerman JJ. Pediatric
Critical Care, 2nd Edition; p 1281. Behrman BE, et al.
Nelson Textbook of Pediatrics, 15th Edition; p 294)