# # Pediatric Critical Care Review Hasan Pappas

1. Which of the following is true regarding endotracheal intubation in infants and children: A. The presence of a Murphy eye side hole provides absolute protection against obstruction of the endotracheal tube B. Tube obstruction in infants is as high as 30% C. Incidence of obstruction with small tubes is similar to the incidence with large tubes D. The endotracheal tube insertion guide is the channel on the straight blade E. Age is a more reliable determinant of endotracheal tube size than height Click here for answer 2. The incidence of subglottic stenosis following intubation in children is approximately: A. 5% B. 10% C. 15% D. 20% Click here for answer 3. Predisposing risk factors for tracheal injury and subglottic stenosis following tracheal intubation include: A. General medical condition of the patient B. Seizures C. Head position D. Endotracheal tube material E. All of the above Click here for answer 4. Regarding post-extubation croup: A. Occurs in 50% of children B. Begins within 18 hours, peaks at 48 hours and resolves by 5 days C. Less prevalent in patients with frequent coughing D. More prevalent in children 1-4 years of age who have undergone neck surgery E. All of the above Click here for answer 5. Post extubation croup is most closely associated with which of the following: A. Failure to lubricate the endotracheal tube prior to insertion B. Failure to use analgesic sprays C. Excess humidification D. History of upper respiratory infection prior to intubation E. Surgery within the neck area Click here for answer 6. Regarding tracheostomy: A. The highest complication rate occurs in infants B. Mortality rate of up to 3% has been reported C. Complications are higher with emergency tracheostomy compared to tracheostomy following endotracheal intubation D. Airway secretions are increased 24-48 hours following tracheostomy E. All of the above Click here for answer 7. Acute post-operative complications of tracheostomy include: A. Subcutaneous emphysema B. Pneumothorax C. Pneumomediastinum D. Increased airway secretions E. All of the above Click here for answer 8. Immediate post-operative care of a child with a new tracheostomy include: A. Evaluation of a chest radiograph for tube position B. Evaluation for subcutaneous emphysema C. Monitoring for bleeding D. More frequent suctioning E. All of the above Click here for answer 9. Which of the following is/are true pertaining to tracheostomy tubes: A. Must measure 0.5 mm smaller in size than the previously used endotracheal tube B. Initial tracheostomy change may be done by the bedside nurse C. Cuffed tracheostomy tubes are not suitable for infants due to the small diameter of the airway D. All of the above Click here for answer 10. A 9-year-old boy with a tracheostomy in place for 8 years is emergently transferred to the Pediatric Intensive Care Unit because copious amounts of fresh blood had been noted coming out of the tracheostomy tube. Regarding the diagnosis and immediate intervention: A. A cuffed tracheostomy tube must be passed and the cuff inflated immediately B. Erosion of the thyroid vein is the most likely diagnosis C. The patient should be intubated orally and the tracheostomy tube removed D. Tracheal granuloma is the most likely diagnosis E. All of the above Click here for answer 11. A 3-year-old with a tracheostomy for 2-1/2 years is being decanulated. Immediately following decannulation, he develops stridor and respiratory distress. Possible etiologies include all except: A. Tracheal stenosis or granulation tissue B. An obstructing flap of the posterior tracheal wall C. Fusion of vocal cords D. Temporary laryngeal abductor failure Click here for answer 12. Regarding use of tracheostomy for a prolonged period of time, which of the following is true: A. The tracheostomy tube is placed above the narrowest portion of the airway in children B. The tracheostomy stoma frequently needs suture closure C. In infants, the tracheostomy tube is plugged prior to decannulation D. Bronchoscopy is often indicated prior to decannulation Click here for answer 13. Select whether the following statements are true or false regarding a child with globe injury: ____ A. Apply the same principles of treatment for closed head injury, i.e., complete sedation and relaxation prior to attempts at intubation; one option is to use thiopental 2-4 mg/kg and vecuronium (0.2-0.25 mg/kg) ____ B. Avoid succinyl choline because it increase intraocular pressure Click here for answer 14. Contraindications to nasotracheal intubation include: A. A platelet count of 18,000/mm3 B. A prothrombin time of 18 seconds C. Fracture of the cribriform plate of the ethmoid bone D. All of the above Click here for answer 15. Which of the following medication combinations is most appropriate for intubating a 5 year-old with a closed head injury who has a capillary refill of 5 seconds and fractured right femur due to a crushing injury he sustained 5 hours ago: A. Succinyl choline, thiopental and lidocaine B. Ketamine, succinyl choline, and lidocaine C. Vecuronium, lidocaine, and low-dose thiopental D. Pancuronium, thiopental and lidocaine Click here for answer 16. A 2-year-old male with a history of vomiting and diarrhea for two days is admitted to the Pediatric ICU from the emergency department. He appears very lethargic; P 195/min; BP 60/P and capillary refill is 6 seconds. In preparing for tracheal intubation, which of the following combinations of drugs is best? A. Ketamine, vecuronium B. Thiopental, vecuronium C. Thiopental, pancuronium and lidocaine D. Thiopental, succinyl choline Click here for answer 17. The relationship between helium and the effect on airway resistance is best described by which of the following: A. Helium-O2 mixtures have much lower viscosity than O2-Nitrogen mixtures B. Use of oxyhood is highly recommended in children with croup C. To minimize airway resistance, helium must be mixed with at least 60% oxygen D. When Helium-O2 mixture is administered through the ventilator direct volume measurements are necessary Click here for answer 18. Acute pulmonary edema has been described in children with the relief of airway obstruction with: A. Epiglottis B. Laryngotracheobronchitis C. Laryngospasm D. Obstructed endotracheal tube E. All of the above Click here for answer 19. Bronchopulmonary dysplasia occurs in association with the following conditions in the neonate: A. Pulmonary hypoplasia B. Hyaline membrane disease C. Diaphragmatic hernia D. Tracheoesophageal fistula E. All of the above Click here for answer 20. Risk factors for development of bronchopulmonary dysplasia is/are: A. Male sex B. White race C. Birth weight < 750 grams D. All of the above Click here for answer 21. Factors that promote formation of pulmonary edema include all of the following except: A. More negative pleural pressure B. Higher pulmonary blood flow C. Lower plasma protein D. More positive pleural pressure Click here for answer 22. Infections likely to predispose the pre-term infant to bronchopulmonary dysplasia include: A. Group B streptococcal infection B. Ureaplasma urealyticum C. Respiratory syncytial virus infection soon after birth D. Cytomegalovirus infection E. All of the above Click here for answer 23. Pulmonary interstitial emphysema promotes: A. Pulmonary edema B. Hyperinflation C. Higher airway resistance D. Pneumoperitoneum, pneumopericardium and subcutaneous emphysema E. All of the above Click here for answer 24. The primary event in the development of pulmonary interstitial emphysema is: A. Subcutaneous emphysema B. Increased airway resistance C. Impaired lymphatic drainage D. Epithelial necrosis Click here for answer 25. Physiologic changes unique to pre-term infants with bronchopulmonary dysplasia that places them at higher risk for respiratory failure is least likely to include which of the following: A. Low intercostal muscle activity during REM sleep B. Disuse atrophy following prolonged mechanical ventilation C. A blunted response to hypoxia D. Absence of the peripheral chemoreceptor response Click here for answer 26. In infants with bronchopulmonary dysplasia, progressive pulmonary hypertension can lead to all of the following except: A. Systemic to pulmonary anastomoses with intrapulmonary shunting B. Increased right ventricular preload C. Restriction of right coronary blood flow to diastole D. Subendocardial ischemia E. Restriction of blood flow through the right coronary artery to systole Click here for answer 27. The single most essential drug for infants with bronchopulmonary dysplasia (BPD) is: A. Oxygen B. Theophylline C. Lasix D. Furosemide E. Caffeine Click here for answer 28. Side effects of aerosolized b2 agonist include all except: A. Tachycardia B. Hypokalemia C. Impaired mucociliary clearance D. Tremor E. Arrhythmia Click here for answer 29. Regarding use of bronchodilators and anti-inflammatory medications in infants with bronchopulmonary dysplasia, which of the following statements is least accurate: A. Methylxanthines decrease chemoreceptor sensitivity to CO2 B. Cromolyn Na+, like methylxanthine, has anti-inflammatory effects C. Combination of ipatropium bromide and b2 agonist appears more effective than either one alone D. Improved mucociliary function is a recognized effect of b2 agonists Click here for answer 30. Side effects of methylxanthines include all of the following except: A. Hyperglycemia B. Hypokalemia C. Hypothermia D. Agitation and seizures Click here for answer 31. Which one of the following is the least likely effect of diuretics when used in patients with bronchopulmonary dysplasia: A. Improved pulmonary mechanics B. Improved survival C. Decreased pulmonary vascular resistance D. Improved lymphatic drainage from lungs Click here for answer 32. Regarding use of furosemide in bronchopulmonary dysplasia: A. Chloride depletion induced by furosemide has been associated with poor outcome B. The hypokalemic metabolic alkalosis induced by furosemide can decrease minute ventilation leading to elevation of PCO2 C. Furosemide is associated with renal calcification D. All of the above Click here for answer 33. Advantages of tracheostomy for infants with bronchopulmonary dysplasia include: A. A stable, chronic access to airway B. A decrease in work of breathing C. More freedom of mobility and physical therapy D. Pleasant oral stimulation such as nippling E. All of the above Click here for answer 34. Factors which contribute to decreased respiratory muscle capacity include: A. Respiratory acidosis B. Hyperinflation C. Disuse atrophy D. All of the above Click here for answer 35. In infants with bronchopulmonary dysplasia, factors that may adversely lead to elevation of CO2 include all of the following except: A. Agitation with patient ventilator asynchrony B. Fever C. Hyperalimentation with 68% carbohydrate D. Tracheostomy Click here for answer 36. Increased dead space contributes significantly to work of breathing. In a setting of increased dead space, a small increase in CO2 production may require significant increases in minute ventilation for adequate CO2 elimination. The ratio of dead space to tidal volume can be improved by: A. Allowing patient’s spontaneous respiratory rate to have a higher contribution to the total ventilatory support B. Use of pulmonary vasodilators C. Tracheostomy D. A and C only E. A, B and C are true Click here for answer 37. In infancy, congenital anomalies are the most common cause of death. The second most common cause of death in infancy is due to disorders in: A. The cardiovascular system B. The respiratory system C. The central nervous system D. The gastrointestinal system E. The cardiovascular system Click here for answer 38. Whenever lung disease leads to respiratory failure, the most common mechanism responsible for abnormal gas exchange is: A. Ventilation-perfusion mismatch B. Diffusion defect C. Alveolar hypoventilation D. Shunt Click here for answer 39. A newborn diagnosed with a left-sided diaphragmatic hernia at the 22nd week of gestation underwent complete repair on the 1st day of life. He is on mechanical ventilation and recovering from surgery. In the ensuing several months, it is expected that: A. Progressive branching of airways will occur B. Progressive regression of airways will occur C. Airway branching will occur albeit very slowly over the next few years D. Post-natal branching of airways will not occur and left lung hypoplasia is irreversible E. The airway branching will continue in the left lung but growth of the distal airway will lag behind the proximal airway in the 1st five years of life Click here for answer 40. Developmental changes in lungs that predispose the infant to respiratory failure include all of the following except: A. Bronchial cartilage is incomplete and continues to increase in number for several months. This cartilaginous deficiency predisposes the infant to dynamic compromise B. Growth of the distal airway lags behind growth of the proximal airway in the 1st five years of life C. The smaller alveolar size and number predisposes the infant to airway collapse D. Absence of pores of Kohn E. The presence of canals of Lambert Click here for answer A. Pores of Kohn B. Canals of Lambert C. Both D. Neither 41. ____ Appear in the 2nd year of life ____ Do not appear until the frontal sinuses start forming Click here for answer 42. A 4-year-old (20kg) child is breathing at a rate of 20 bpm. The concentration of CO2 in the alveolar gas is estimated to be 40 torr, whereas the concentration of CO2 in the exhaled gas is estimated to be 30 torr. Assuming that the spontaneous tidal volume is 5 ml/kg, the total volume of the anatomic dead space is: A. 100 ml B. 200 ml C. 300 ml D. 400 ml E. 500 ml Click here for answer 43. A 3-month-old with bronchiolitis is on mechanical ventilation for respiratory failure. The arterial PCO2 is 55 mm Hg whereas the end tidal CO2 on capnography that is attached to the end of the endotracheal tube is 35 mm Hg. The infant is being ventilated with a tidal volume of approximately 50 ml at a rate of 35 bpm. The physiologic dead space in this patient is: A. 235 milliliters B. 345 milliliters C. 636 milliliters D. 725 milliliters E. 125 milliliters Click here for answer 44. The physiologic dead space in this infant is: A. Normal B. Slightly increased C. Slightly decreased D. Cannot be determined from this data Click here for answer 45. Infants have a very compliant chest wall and a reduced elastic recoil. Both these factors lead to higher intrapleural pressure with subsequent collapse of airways and alveoli in dependent lung regions. However, functional residual capacity is maintained by: A. Expiratory braking B. Grunting constantly C. Increasing closing capacity D. Increasing closing volume Click here for answer 46. Regarding expiratory braking in infants, all of the following are true except: A. It is decreased during active sleep in premature infants B. It is increased during active sleep in premature infants C. Absence of expiratory braking in premature infants during active sleep exacerbates loss of O2 stores during apnea D. Abolished by anesthesia Click here for answer 47. Regarding respiratory physiology, which one of the following statements is least accurate: A. With laminar flow, resistance to flow is proportional to viscosity B. With turbulent flow, resistance to flow is proportional to density C. Specific compliance is the same for adults and children but specific conductance is higher in children D. Peripheral airway resistance in children < 5 years is four fold higher than in older children or adults Click here for answer 48. The above diagrams schematically represent two compartment lung units. If inflation were interrupted prematurely in the above examples: A. Units A & C will have higher volumes of gas B. Units D & B will contain higher volumes of gas C. Units A & C are considered fast units D. The pressure within C will be higher than in D Click here for answer 49. Regarding developmental changes of pulmonary blood flow and lung development, all of the following are true except: A. Pulmonary blood flow plays a significant role in the growth of lungs B. Diaphragmatic hernias adversely affect airway and alveolar development but not pulmonary vascular development C. In the newborn, muscular arteries end at the level of terminal bronchioles D. The onset of congestive heart failure from left to right shunt occurs earlier in the premature than full term infant Click here for answer 50. With regard to pulmonary circulation in infants and children, which one of the following statements is least accurate: A. The hypoxic pulmonary vasoconstriction response is more dramatic in infants than in the older child B. During hypoxic pulmonary vasoconstriction, driving pressure increases much more than flow in the whole lung C. Regional hypoxic pulmonary vasoconstriction increases pulmonary vascular resistance dramatically D. Newborns who live at high altitudes have persistent right ventricular hypertrophy Click here for answer 51. Examples of “shunt” include which of the following: A. Cyanotic congenital heart disease B. Bronchial circulation C. Thebesian circulation D. Blood flow through completely atelectatic lung segments E. All of the above Click here for answer 52. The alveolar air equation: PaO2 = PIO2 – PaCO2 / R does not make which one of the following assumptions: A. There is no inert gas exchange B. There is no differences in inspired and expired gas volume C. Normally more O2 is consumed than CO2 is produced D. Normally the amount of O2 consumed and CO2 produced are the same Click here for answer 53. Regarding the oxygen cascade and O2 transport, all of the following statements are true except: A. If the percentage of shunt (QS/QT) is close to zero, the response to increasing FiO2 is linear B. An increase in FiO2 will have a negligible effect on PaO2 with a QS/QT of 50% C. If cardiac output falls while O2 consumption remains constant, then mixed venous content must fall D. If O2 consumption rises for a constant cardiac output, mixed venous oxygen content will increase Click here for answer 54. The normal newborn exhibits a lower PaO2 than an adult. The mechanism that contributes least to this phenomenon is: A. A right to left shunt through the foramen ovale B. A right to left shunt through the patent ductus arteriosus C. Shunting due to atelectatic areas of the lungs D. Low V/Q segments Click here for answer 55. The alveolar capillary membrane is the physical barrier that separates alveolar gas from pulmonary capillary blood and thus acts as a gaseous diffusion barrier and as a fluid transfer barrier. Statements that are true in describing this barrier include all of the following except: A. Diffusion block is rarely if ever the sole cause of significant hypoxemia B. Diffusion is measured by diffusing capacity C. In practice, diffusing capacity is measured by using the diffusing capacity for carbon monoxide instead of O2 D. Transfer factor refers to diffusing capacity in relation to alveolar ventilation E. Transfer factor increases with age and height Click here for answer 56. The type of hemoglobin and the position of the O2–Hb dissociation curve play a significant role in O2 delivery to tissues. All of the following statements are true regarding this topic except: A. 2,3-DPG lowers O2 affinity to hemoglobin by binding to either b-chain or g-chain of the hemoglobin B. The interaction of 2,3-DPG and g-chain does not lower O2-Hb affinity to as great an extent as the interaction of DPG with the b-chain C. Hemoglobin-S has a lower P50 than hemoglobin-A D. The iron in hemoglobin-F is more resistant to oxidation than the iron in hemoglobin‑A Click here for answer 57. Newborns are particularly susceptible to methamoglobinemia following exposure to nitrates because: A. Of their smaller size B. Iron in hemoglobin F is less readily oxidized C. Of exposure to city water at such an early age D. Of the relative deficiency in the enzyme methemoglobin reductase Click here for answer 58. Regarding O2 delivery to and O2 consumption by tissues, which of the following least accurately describes these two processes: A. A normal O2 delivery with a resultant normal mixed venous O2 content does not guarantee adequate tissue oxygenation B. In the newborn, if environmental temperature drops from 33oC to 31oC, O2 consumption doubles C. The normal O2 extraction is 0.25 D. Resting O2 consumption in a 1-week-old is approximately half of that for an adult based on kilogram body weight basis E. Electron transfer requires a minimum of 1 mm Hg of O2 for the mitochondria to properly utilize O2 Click here for answer 59. Mixed venous PO2 is least dependent on which of the following factors: A. Oxygen delivery (DO2) B. Circulatory distribution C. Inferior vena cava pressure D. P50 E. Oxygen consumption (VO2) Click here for answer 60. With regard to neural and humoral control of respirations, which of the following options is not true: A. Carotid bodies respond to falling PaO2 in an exponential fashion B. Peripheral chemoreceptors respond to falling SaO2 in an exponential fashion C. Central chemoreceptors respond to increasing PaCO2 in a linear fashion D. Hypoxia increases the slope of the minute ventilation curve in response to increasing CO2 Click here for answer 61. There are a number of pulmonary receptors that modulate breathing; true statements pertaining to this include all of the following except: A. Chemical or mechanical stimulation of the oropharynx lead to apnea and bradycardia B. Stimulation of laryngeal receptors produces cough and wheezing in experimental animals C. Excess interstitial fluid results in bradycardia, hypotension and even apnea via stimulation of juxtacapillary receptors D. Laryngeal and bronchial receptors respond to CO2 in an exponential fashion Click here for answer 62. The resting PaCO2 in the neonate is 33-34 torr as opposed to 40 torr in the older child or adult. Which one of the following statements least accurately explains the reason for this phenomenon: A. The O2 demand for the young infant is double of that for the adult based on a kilogram per kilogram body weight basis B. The lower CO2 is the result of higher minute ventilation required to meet the increased O2 demand C. The CO2 response curve is shifted to the left D. The CO2 response curve is shifted to the right Click here for answer 63. Chemical and neural control of respirations in the preterm infant differ from that of the full-term infant. All of the following statements are true except: A. In preterm infants with periodic breathing, the CO2 response curve is shifted to the right B. The PaCO2 is closer to 40 torr as in adults C. The CO2 response is flatter than in the term infant D. Premature infants do not have carotid bodies Click here for answer 64. The reason for the progressive reduction in total respiratory system compliance with age is: A. Individual variations of the operator performing the test B. A progressive reduction in lung compliance with age C. A progressive increase in airway resistance with age D. A progressive reduction in chest wall compliance with age E. None of the above Click here for answer 65. The majority of tidal breathing in the infant takes place in the range of closing capacity. All of the following statements pertaining to this phenomenon are true except: A. This increases the risk of atelectasis B. This is because of the very low elastic recoil pressure of the newborn chest wall C. Closing capacity refers to the volume of the lung below the functional residual capacity at which the alveoli and airways in the dependent regions of the lung close D. All of the above Click here for answer 66. The highly compliant chest wall of the infant: A. Means that the infant must generate more pressure and perform more work to move the same tidal volume B. Is clinically manifested as retractions C. Is responsible for respiratory muscle fatigue and ultimate apnea, with any respiratory distress D. All of the above Click here for answer 67. When infants are confronted with the need to increase work of breathing because of underlying pulmonary disease, a certain percentage of them will fatigue and ultimately develop apnea. Which one of the following is a contributing factor: A. Functional residual capacity is much greater than closing capacity in infants B. The small tidal volume in infants C. The highly compliant chest wall D. The CO2 response curve of infants is shifted to the right Click here for answer 68. Infants and newborns are more susceptible to diaphragmatic muscle fatigue because: A. Closing volume is lower than in adults B. Of smaller residual volume C. Of abundant sarcoplasmic reticulum in the muscle fibers of the diaphragm D. Of the long contraction-relaxation time of diaphragmatic muscle fibers Click here for answer 69. In the face of prolonged respiratory distress, some infants develop fatigue and apnea. The reasons for this phenomenon include all of the following except: A. These infants are unable to recruit intercostal muscle activity B. Rapid chest wall distortion with respiratory distress prematurely terminates inspiration C. The young infant cannot compensate for this respiratory load during active sleep D. The short contraction-relaxation time of the respiratory muscles Click here for answer 70. Which of the following statements inaccurately describes apnea in infants and children: A. Premature infants less than 60 weeks conception are at risk of life-threatening apnea following general anesthesia B. Aminophylline helps apnea by significantly altering the pH and PaCO2 around the respiratory center C. The association between apnea and gastroesophageal reflux is well accepted D. Children with obstructive sleep apnea due to adenotonsillar hypertrophy, may have deranged central control of respiration post-operatively due to increased opioid activity in the cerebrospinal fluid Click here for answer 71. Cervical spine injury below C5 in an infant will not result in: A. Ineffective cough B. Chest wall retraction with each contraction of the diaphragm C. Mucus plugging D. Respiratory failure E. Decreased work of breathing Click here for answer 72. Unilateral phrenic nerve paralysis is clinically more significant in infants and young children compared to adults because of all of the following except: A. Hemi-diaphragmatic paralysis in this age group is equivalent to massive flail chest in an adult B. Of the excessively compliant chest wall of the young child C. Of the poor ability of intercostal muscles to stabilize the chest wall in the young infant D. Less compliant chest wall of the young child E. With inspiration the ipsilateral intercostal muscles and the paralyzed diaphragm are sucked in Click here for answer 73. Airway resistance would appear to be the most direct measurement of airway obstruction. It is not used as frequently as tests of forced expiration in children because: A. It requires use of plethysmography B. It is not as accurate as FEV1 C. Physiologically important changes in pulmonary airways can be obscured by less important changes in the upper airway which may be responsible for 50% of airway resistance D. None of the above Click here for answer 74. Match the statements to the curves in the figure above. ____ Alveolar PO2 ____ Arterial PCO2 Click here for answer 75. Which of the following does not increase the likelihood of having West “Zone 1” in the lungs: A. Mechanical positive pressure ventilation with hyperinflation B. A pulmonary artery occlusion pressure of 22 mm Hg C. Pulmonary embolism D. A capillary refill of 6 seconds in the lower extremity Click here for answer 76. Regarding West “Zone 4” of the lung, which of the following is true: A. Blood flow in this zone is regulated by the gradient between pulmonary artery pressure and pulmonary venous pressure B. Blood flow in this zone is regulated by the gradient between pulmonary artery pressure and alveolar pressure C. Transduction of fluid across the capillary barrier exceeds the rate of lymphatic drainage from the lungs D. Zone 4 blood flow exceeds Zone 3 blood flow Click here for answer 77. In the pulmonary circulation, active vasoconstriction occurs when: A. Cardiac output decreases and pulmonary artery pressure increases or remains constant B. Cardiac output increases and pulmonary artery pressure is constant C. Cardiac output decreases and pulmonary artery pressure decreases D. All of the above Click here for answer A. Generalized hypoxic pulmonary vasoconstriction B. Regional hypoxic pulmonary vasoconstriction C. Both D. Neither 78. ____ Result(s) in elevation of pulmonary artery pressure ____ Protective mechanism(s) for the host Click here for answer 79. Compliance is the relationship between changes in volume (rV) for a given change in the distending pressure (rP). Regarding this relationship, all of the following statements are true except: A. Compliance of the lungs is determined by rV and the difference between alveolar pressure and pleural pressure B. Compliance of the chest wall is determined by rV and the difference between alveolar pressure and ambient pressure C. Compliance of the total respiratory system is determined by rV and the difference between alveolar pressure and the ambient pressure D. Chest wall compliance is the rV divided by the difference between pleural pressure and the ambient pressure Click here for answer 80. Conditions associated with decreased total respiratory system compliance due to increased elastic recoil of the lungs include all of the following except: A. Adult Respiratory Distress Syndrome (ARDS) B. Pneumocystis carinae pneumonia C. Pulmonary edema due to severe mitral stenosis with circulatory failure D. Near-drowning E. Bronchiolitis Click here for answer 81. Please refer to the above diagram to answer the following questions: A. The decrease in pressure from A to B is due to redistribution of gas into more compliant alveoli B. This diagram indicates that dynamic compliance is greater than static compliance C. The diagram indicates that static compliance is greater than dynamic compliance D. A and C are true statements Click here for answer 82. Conditions associated with decreased total respiratory system compliance include all of the following except: A. Thermal injury of the lower respiratory tract B. Erect posture C. Atelectasis D. Abdominal distention E. High positive end-expiratory pressure Click here for answer 83. All of the following statements about airway resistance in children are true except: A. Airway resistance accounts for less than 50% of total non-elastic resistance B. With laminar flow, the pressure drop down the airway is proportional to the flow rate C. With turbulent flow, the pressure drop down the airway is proportional to the square of the flow rate D. Peripheral airways account for 50% of total airway resistance in children younger than 5 years E. Airway resistance increases with increased flow and decreased functional residual capacity Click here for answer 84. The time constant (t) describes the time required for the lung compartments to achieve a change in volume following the application or withdrawal of a constant distending pressure and is the product of compliance and resistance. Regarding this concept, which of the following statements is most accurate? A. Time constant is expressed in terms of flow in liters per second B. When a constant pressure is applied to the mouth, the component overcoming air flow resistance is maximal at first and declines exponentially C. When a constant pressure is applied to the mouth the pressure required to overcome compliance is maximal initially and decreases exponentially D. Mathematically, 63% of lung inflation or deflation occurs within 3 time constants Click here for answer 85. An 8-year-old male with post-traumatic ARDS is being ventilated with a pressure limited “mode “ of ventilation with an inspiratory time of 1 second, SIMV of 20 bpm, PIP of 30 cm H2O and PEEP of 8 cm H2O. The chest radiograph has shown significant improvement over the past 24 hours, and FiO2 has been decreased from 0.7 to 0.55. Failure to decrease the inspiratory time may result in all of the following except: A. Decreased venous return B. Decreased physiologic dead space C. Auto PEEP D. Pneumomediastinum Click here for answer Answers 1. E The Murphy eye side hole does not provide protection against obstruction of the endotracheal tube. The incidence of tube obstruction is approximately 5% in the pediatric population, and approximately 80% of tube obstructions occur in endotracheal tubes which are 3.5 mm in diameter or smaller. The channel on the straight blade is the visual pathway for the person performing the intubation. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 59-64) 2. A Subglottic stenosis occurs in 2-6% of pediatric patients following tracheal intubation. (Parkin JL, et al. Ann Otolaryngology, 1976; 85:673) 3. E All are true. (Rogers, MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 65-76) 4-5. D, E Post-extubation croup occurs in approximately 5% and usually resolves in 24 hours. It is more common in patients with frequent coughing episodes and in patients who move more frequently while intubated. It has been shown to be more prevalent in children 1-4 years or age, particularly in association with any type of surgery in the head/neck area. (Kemper, et al. Critical Care Medicine, 1991; 19:352) 6-8. E, E, E The mortality rate (MR) for tracheostomy is 1-3%. The MR and complications are highest in infants. Following tracheostomy there appears to be an increase in airway secretions for 24-48 hours during which time the patient will need frequent suctioning. The patient will also need to be evaluated for possible air leak, such as subcutaneous emphysema or pneumomediastinum and monitoring for post-operative bleeding. (Zeifouni A, et al. J Otolaryngology, 1993; 22:431-434; Crysdale, WS. Ann OtoRhinolaryngology, 1988; 97:493) 9. C The tracheostomy tubes, in fact, may measure 0.5 mm larger than the previously used endotracheal tube because the site of insertion is below the cricoid cartilage. The initial change of the tracheostomy tube must be done with the surgeon in attendance as a precaution against complications. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 72-73) 10. A This is a rare complication of prolonged tracheostomy, and it is most likely due to erosion of the innominate artery. Under these circumstances, a cuffed tracheostomy tube should be passed beyond the site of bleeding and immediately inflated. (Crysdale WS. Ann Otorhinolaryngology, 1988; 97:493-499) 11. B An anterior (and not a posterior) tracheal flap at the operation site for tracheostomy is one of the etiologies of obstruction following decannulation. Other etiologies include: fusion of vocal cords, granuloma and temporary adductor failure. (Carter P, et al. Ann Otorhinolaryngology, 1983; 92:398-401; Sasaki CT, et al. Ann J. Dis Child, 1978; 132:266-269) 12. D Tracheostomy tubes are not plugged prior to decannulation, as this may increase the airway resistance significantly, and a tracheostomy stoma is usually left to heal on its own. Plastic tracheostomy tubes have been associated with less evidence of stricture and subsequent tracheal stenosis. Tracheostomy tubes are placed below the cricoid cartilage. (Sasaki CT. Am J. Dis Child, 1978; 132:266-269) 13. T, T The same principles applied for tracheal intubation in a patient with closed head injury should be applied here. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 65-68) 14. D Contraindications to nasotracheal intubation include bleeding diatheses and suspicion of basilar skull fracture. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 65-68) 15. C In a patient with closed head injury, one should avoid ketamine because it increases intracranial pressure, possibly through a cholinergic mechanism. In a setting of hypotension and shock, thiopental, particularly in the usual dose of 2-4 mg should be avoided because it may potentiate hypotension which might be detrimental to the patient. Vecuronium seems to cause minimal hemodynamic disturbances, and therefore, in combination with lidocaine and low-dose (1-2 mg/kg) thiopental would be the most appropriate combination in this patient. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 63-70) 16. A In a patient with hypovolemia or shock, ketamine seems to be the most appropriate choice because it is a cardiorespiratory stimulant; along with vecuronium, which is associated with minimal hemodynamic disturbances would be most the most appropriate combination. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 63-70) 17. D With turbulent airflow, the resistance to airflow is proportionate to density. A helium-O2 mixture has a lower density than an O2-nitrogen mixture. This leads to a reduced resistance to airflow. Use of an oxyhood is not recommended since helium tends to separate as a layer at the top of the oxyhood. It usually is given through a tight fitting face mask. As the concentration of helium decreases to < 60%, it becomes less and less effective. The ventilator transducer is calibrated with an air-O2 mixture, and therefore, with a helium-O2 mixture, the tidal volume may not be accurate, unless it is measured directly. (Kemper KJ. Critical Care Medicine, 1991; 19:356; Ellean C. J Pediatrics, 1993; 122:132-135) 18. E The theory is that increased negative interstitial pressure is a contributing factor to the development of pulmonary edema in association with upper airway obstruction. To further review theories that explain the development of pulmonary edema in children with croup and epiglottitis, see the following references. (Travis KW, et al. Pediatr 1977; 59:695; Lichtenstein S. Fed Proc 1975; 34:436) 19-20. E, E Children who develop hyaline membrane disease or have pulmonary hypoplasia due to a wide variety of reasons including diaphragmatic hernia, children with tracheoesophageal fistula, and those who develop early neonatal infections due to but not limited to group B streptococcal infection, ureaplasma, respiratory syncytial virus, or cytomegalovirus, seem to be at a higher risk of developing bronchopulmonary dysplasia. Other risk factors include male sex, white race, and a birth weight of less than 750 grams. One of the factors that is considered the best predictor of development of bronchopulmonary dysplasia is the need for oxygen therapy at 36 weeks chronological age. (Kennedy KA. Seminars Perinatol, 1993; 17:247) 21. D Negative rather than positive pleural pressure has a tendency to promote formation of pulmonary edema. All other factors in the question tend to promote pulmonary edema. (Robin ED. N. Engl J Med, 1973; 288:239) 22. E. Refer to answer #19-20. 23-24. E, D Air within the connective tissue sheath leads to compression of the surrounding peripheral airway with subsequent increased airway resistance and hyperinflation. Impaired lymphatic drainage promotes pulmonary edema. Once extra-alveolar air develops, it may dissect into the subcutaneous space and mediastinum. Further extension into the pericardium and peritoneum may occur. The primary event appears to be epithelial necrosis. (Watts, JL. Pediatr 1977; 60:273; Hansen TN. Clin Perinatol 1984; 11:653) 25. D Infants with bronchopulmonary dysplasia (BPD) have been shown to have a blunted arousal response to hypoxia. Increased chest wall compliance places these infants at a mechanical disadvantage, particularly during periods of decreased or low intercostal muscle activity such as during rapid eye movement during sleep. The peripheral chemoreceptors are intact in these babies. Prolonged ventilatory support may lead to disuse atrophy of respiratory muscles. (Gray M. Pediatr 1988; 82:59; Knosely AS. J Pediatr 1988; 113:1074) 26. E Normally, the blood flow through the right coronary artery occurs during both diastole and systole as opposed to restriction of flow during diastole with the left coronary artery. In infants with bronchopulmonary dysplasia with the development of pulmonary hypertension and particularly with progressive pulmonary hypertension, the blood flow through the right coronary artery becomes limited to diastole as right ventricular pressure and volume increase. (Berman W. Pediatrics, 1982; 70:708) 27. A Infants with BPD have been shown to develop a significant reduction in pulmonary vascular resistance in response to low flow oxygen therapy. Acute, recurrent hypoxia precipitated by a variety of factors such as handling, feeding, or infection may precipitate pulmonary hypertension or pulmonary hypertensive crises with sudden death. (Long, LA. Pediatrics, 1980; 65:203; Grag M. Pediatrics, 1988; 81:635) 28-30. C, C, C Improved mucociliary clearance is a recognized effect of b2-agonists. Methylxanthines increase chemoreceptor sensitivity to carbon dioxide and induce hyperthermia rather than hypothermia. (Santa-Cruz R. Am Review of Resp Dis 1974; 109:458; Aranda JV. Clin Perinatol, 1979; 6:87) 31-32. D, D Diuretics cause decreased transvascular efflux of fluid in the lung. Recognized side effects of furosemide include chloride depletion, metabolic alkalosis, renal calcification, and ototoxicity. Some of these factors have been implicated in poor growth and poor outcome in infants with BPD. (Perlman JM. Pediatr, 1986; 77:212; Hurnagle KG. Pediatr, 1982; 70:360) 33-35. E, D, D Respiratory acidosis, hyperinflation, and disuse atrophy from prolonged mechanical ventilation and tracheal intubation has been associated with decreased respiratory muscle capacity. Advantages of tracheostomy include: a stable airway with more freedom of mobility and oral stimulation. Tracheostomy decreases anatomic dead space and therefore is unlikely to lead to elevation of carbon dioxide. It also decreases work of breathing partly through the same mechanism. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 183-186) 36. D Use of pulmonary vasodilators would lead to ventilation-perfusion mismatch which is likely to increase the dead space. Allowing the patient’s spontaneous respiratory rate to have a higher contribution to the total ventilatory support while on mechanical ventilation will decrease dead space, as does tracheostomy. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 183-186) 37. B Self explanatory. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 97-98) 38. A Diffusion defect as the only cause of gas exchange abnormalities is extremely rare. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 97-98) 39. D Diaphragmatic hernia, if not detected and corrected before 16 weeks of gestation, will lead to irreversible changes in the lung, in this case, the left lung, which is expected to remain hypoplastic. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 105-106) 40. E Canals of Lambert do not develop until approximately 6 years of age. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 105-106) 41. A, B The intra-alveolar Pores of Kohn do not develop until after 2 years of age. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 105-106) 42. E Dead space ventilation = alveolar ventilation ´ (alveolar CO2 – exhaled CO2) ¸ alveolar CO2. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 107-108) 43. C Dead space ventilation = (arterial CO2 – exhaled CO2) ¸ arterial CO2 ´ alveolar ventilation. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 107-108) 44. B The normal ratio of dead space ventilation to alveolar ventilation is 0.3 or less. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 107-108) 45-47. A, B, C Expiratory braking refers to the increase in airway resistance in the upper airway during exhalation, which leads to an increase in end expiratory lung volume. This would lead to an increase in functional residual capacity (FRC). It is decreased during active sleep because it is arousal dependent. Specific compliance and specific conductance are the same for adults and children. (Kosch PC, Stark AR. Dynamic Maintenance of End-Expiratory Volume in Full-Term Infants. J Appl Physiology, 1984; 57:1126-1133) 48. B Time constant = resistance ´ compliance. It is a dimensionless number. Whenever one of the components of the time constant (i.e., either the resistance or the compliance) increases, the movement of air from one lung unit to another would be prolonged, leading to an increase in time constant. Therefore, applying these principles in the diagram, since the resistance in the airway leading to unit A is increased, and the compliance of unit C is also increased, these two units will contain less volume of gas when inflation is interrupted prematurely. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 104-106) 49. B Diaphragmatic hernia adversely affects the pulmonary vasculature and lead to pulmonary hypoplasia if it is not corrected before 16 weeks of intrauterine life. (Please see Answer #40) 50. C Regional or localized hypoxic pulmonary vasoconstriction does not increase pulmonary vascular resistance significantly. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 106-112) 51. E All statements are examples of a shunt. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 110-112) 52. D The alveolar air exchange equation makes all of the above assumptions. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 110-111) 53. D Cardiac output equals oxygen consumption divided by arteriovenous oxygen content difference, and therefore, if oxygen consumption increases for a constant cardiac output, the mixed venous oxygen content must decrease. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 108-109) 54. D This is the major mechanism (i.e., low V/Q segments) in adults. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 111-112) 55. E Transfer factor decreases with age. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 112-113) 56. D Hemoglobin-F is more easily oxidizable compared to hemoglobin-A. (Martin H, et al. Formation of Ferrihemoglobin in isolated human hemoglobin types by sodium nitrite. Nature, 1963; 200:898-900) 57. D Neonates and young infants are more susceptible to the development of methemoglobinemia because 1) the iron in HbF is oxidized more readily; and 2) the young infant is relatively deficient in the enzyme, methemoglobin reductáse. When the levels of methemoglobin exceed 30-40%, cyanosis and symptoms of decreased O2 transport are noted. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 114-116) 58. D Resting oxygen consumption in a 1-week-old infant is 3 times that of an adult based on the body weight per kilogram. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 118) 59. C O2 consumption (VO2) = Cardiac Output CaO2 – CVO2 Where CaO2 = arterial O2 content CVO2 = mixed venous O2 content O2 delivery (DO2) = Q x CaO2 (where Q = Cardiac Output) CaO2 = Hb (grams%) x 1.34 x O2 saturation + PaO2 x 0.003 Therefore alterations in cardiac output or peripheral circulatory disturbances (that alter blood flow at the capillary level) will affect O2 consumption. P50 affects the unloading of O2 from Hb. The higher the P50, the more the unloading of O2 to tissue. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; p 118) 60. B Peripheral chemoreceptors respond to a falling oxygen saturation in a linear fashion by increasing the inspired minute ventilation. There is an exponential increase in minute ventilation as PaO2 falls, particularly at PaO2 < 60 torr. (Berger AJ, et al. New Engl J Med, 1977; 297:194-198) 61. D Laryngeal and bronchial receptors respond to increasing CO2 in a linear fashion. (Berger AJ, et al. New Engl J Med, 1977; 297:194-198) 62. D The carbon dioxide response curve which relates alveolar CO2 to alveolar ventilation is shifted to the left in the neonate. (Rigatto H. Apnea. Pediatr Clin North Am, 1982; 29:1105) 63. D Preterm infants have a characteristic breathing pattern referred to as periodic breathing (i.e., pauses in respirations lasting 5-10 seconds). Due to the higher O2 demand, newborn infants compensate by having a higher minute ventilation and a shift in CO2 response curve to the left. The carotid bodies are present in preterm infants. (Rigatto H. Apnea Pediatr Clin North Am, 1982; 29:1105) 64. D Total respiratory system compliance equals lung compliance plus chest wall compliance. With age, there is a progressive reduction in chest wall compliance which accounts for a reduction in the total respiratory system compliance. (Sharp JT, et al. Total respiratory compliance in infants and children. J Appl Physiology, 1970; 29:775-780) 65-67. D, D, C Closing capacity (CC) is the lung volume below the functional residual capacity (FRC) where alveoli in dependent lung regions have a tendency to collapse. In infants, CC is often equal to or greater than FRC, and therefore, tidal breathing often takes place in the range of CC. This phenomenon is due to the very low elastic recoil of the chest and it increases the risk of atelectasis. (Smith CA. The Physiology of the Newborn Infant. Springfield, IL, 1976; pp 206-207) 68-69. D, D This may result in ischemia of respiratory muscles at a high respiratory rate. Low levels of sarcoplasmic reticulum in fetal diaphragmatic muscle has been observed. (Maxwell LC, et al. Development of histo…. J Appl Physiol, 1083; 54:551) 70. B Babies who were born prematurely continue to be at high risk of apnea post-operatively (following general anesthesia) and therefore, should be monitored for 24-48 hours after anesthesia. Aminophylline will increase breathing without significantly altering the CO2 and pH around the respiratory center. Patients with adenotonsillar hypertrophy who undergo surgical resection may be admitted to the PICU because of airway obstruction from post-operative edema or sometimes due to decreased ventilatory drive after anesthesia. The increased opioid activity found in the spinal fluid in these patients may be a contributing factor to decreased ventilatory drive noted perioperatively. (Kurth CD, et al. Post-operative apnea in preterm infants, Anesthesiol, 1987; 66:483; Gislason T, et al. Chest 1989; 96:250; Lavaher S. Thorax, 1989; 44:121) 71. E Work of breathing is increased due to chest wall distortion secondary to instability of the chest wall. (Robotham JL. Crit Care Med, 1979; 7:563) 72. D The more compliant chest wall of the young child contributes to the clinical manifestation of diaphragmatic paralysis. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 3rd Edition; pp 123, 247) 73. C The upper airway contributes, to a much higher degree, to total respiratory resistance in children than in adults. This may mask the physiologically more important airway resistance. (Cook LD, et al. J Clin Investigate, 1957; 36:440) 74. B, A The relationship between alveolar ventilation and both PaO2 and PaCO2 are non-linear, as depicted on the graph. (Benumof J. Respiratory Physiology and Respiratory Function During Anesthesia, IN; Miller RD. Anesthesia, Churchill, Livingstone, NY 1981; pp 699) 75. B West Zone I occurs when ventilation is wasted. Alveolar pressure remains constant, whereas pulmonary artery pressure tends to increase from apex to base in the erect posture. Hyperinflation, pulmonary embolus, and shock all lead to a decrease in pulmonary blood flow with consequent wasting of ventilation. (Benumof J. Respiratory Physiology and Respiratory Function During Anesthesia, IN; Miller RD. Anesthesia, Churchill, Livingstone, NY 1981; pp 699) 76. C The so-called West Zone 4 of the lung develops when there is interstitial edema, and under those circumstances, there will be less transduction of fluid across the capillary membrane. (Benumof J. Respiratory Physiology and Respiratory Function During Anesthesia, IN; Miller RD. Anesthesia, Churchill, Livingstone, NY 1981; pp 699) 77. A Pressure = Flow ´ Resistance (i.e., mean pulmonary pressure = CO x pulmonary vascular resistance). (Rogers MC, et al. Textbook of Pediatric Intensive Care, 2nd Edition; pp 138) 78. A, B Regional hypoxic pulmonary vasoconstriction does not result in significant elevation of pulmonary artery pressure, and it seems to be a protective mechanism for the host. (Fishman AP. Civc Research, 1976; 38:221) 79-80. B, E Compliance of the chest wall is described in option D. Bronchiolitis primarily affects the airway. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 2nd Edition, 1992; pp 138-139) 81. B Dynamic compliance is smaller than static compliance because dynamic compliance is equal to the change in volume divided by peak inspiratory pressure minus PEEP, as opposed static compliance which equals volume divided by plateau pressure minus PEEP. Since peak inspiratory pressure is greater than the plateau pressure, the dynamic compliance would be smaller than the static compliance. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 2nd Edition, 1992; pp 138-139) 82. B All other conditions are associated with decreased compliance. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 2nd Edition, 1992; pp 138-139) 83. A In fact, airway resistance accounts for more than 80% of non-elastic resistance. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 2nd Edition, 1992; pp 140-142) 84. B Time constant is the product of compliance and resistance, and therefore, it is a dimensionless number. Mathematically, 63% of lung inflation or deflation occurs with one time constant. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 2nd Edition, 1992; pp 142-143) 85. B Hyperinflation leads to increased physiologic dead space. (Rogers MC, et al. Textbook of Pediatric Intensive Care, 2nd Edition, 1992; pp 142-143) Go To Respiratory - Part 2