Question Answer
a centruy after laplace described the relationship of transuraface pressure and surface tension of gas-fluid interface in a sphere what did neergaard discover about the retractile force of the lung? that it was dependaent on the surface tension in the alveoli
how is surface tension created? by the attraction of water molecules to one another at the liquid gas interface
ehat does the laplace law postulate about the alveoli in the lung? that alveoli would collapse as they got smaller
which physiological consequqnces would develop if the liquid gas interface were without surfactant? every breath would require more pressure to expand lung w inspiration and all the alveoli would collapse during exhalation
what physiological conditions result from the presence of normal amounts of pulmonary surfactant in the lung? uniform gas distribution during inspiration and functional residual capacity is maintained
what structure is responsible for producing pulmonary surfactant? type II pmeumocytes
what components comprise pulmonary surfactant? dipalmitoyl phosphatidylcholine, phosphatidylinositol, and phospholipids
what following proteins are known to comprise human pulomary surfactant? SP-B, Sp-C, Sp-D
What is the role of SP-d in human pulmonary surfactant? suppresses proinflammatory responses, enhances killing of microbes, enhances phagocytosis
what relationship id correct rearding to the composition of amniotic fluid as it relates to determining fetal lung maturity? PG and lecithin increase while sphingomyelin decreases during gestation
what is the most commone form of surfactant abnormality? inactivation by proteins
full term infants with RDS, surfactant nonresponders and infancts who can’t be extubated in the first weeks of life because of a respiratory condition should be evaluated for? alpha antitrypsin deficiency, SPB deficiency
what cardiovascular conditions can cause surfactant inactivation? pulmonary hemorrhage and hemorrhagic edema
what pathophysiologic conditions are components of meconium aspiration? surfactant inactivation and chemical pneumonitis
How is pna in a neo believed to adversely affect surfactant? by bacteria directly attacking type II pneumo and by microorganisms releasing substances altering surfactant components
which proteins are found to be deficient in the sputum of pts with asthma? SP-A
what are the physiologic benegits of surfactant? prevents capillary leakage of fluid into alveoli, optimizes surface area for gas exchange and protects epithelium of lung
what causes upper airway obstruction and may require an artifical airway? laryngotracheobronchitis, epiglottitis, subglottic stenosis
on the bases of illustration of neo et indetify murpheys eye b hole at the distal end of the tube
therapist about to perform ett on a 2 yo infant what size tube? 4.5mm ID
why are some ped ETT available without cuffs? because in some infants ETT creats a seal against cricoid cartulage
where in the upper airway if an infant should the laryngoscope blade be placed to expose the glottis during ett? epiglottis directly lifted with tip of laryngoscope blade
which statement describes the LMA? potential for aspiration greater than with tranlaryngeal intubation as well as LMA good alternative as an emergency airway when ppv needed
whats the purpose of placing small towel under occiput of 4 yo? to align oral cavity, pharynx, and larynx
when should sellicks maneuver be performed? when pt is at risk for regurgitating or aspirating during intubation
how should therapist determine depth of insertion of ETT in infant during intubation at pt where single heavy black line just moves beyond the glottis
what anatomical difference between larynx of an infant to an adult makes intubation of the infant more difficult? larynx of infant is more cephalad and anterior
what conditions are considered disadvantages of nasotracheal intubation in neonates? postextubation atelectasis among very low birth weight infants, pressure necrosis of nares
what forms of et will neonate w pierre robin syndrome likely undergo? anterior commissure intubation
5 yo child brought to er in severe respiratory distress w diagnosis of epiglottis, what measures must be performed to secure childs airway? child needs to be transported to OR intubated
a child is orally intubated because of laryngotracheal stenosis has an air leak at 25 cm h2o what action does therapist take now? therapist must insert an oral ETT large enough to stop leak
Which following areas of an infant’s upper airway are most prone to develop edema as a result of ett? subglottic area
what equipment is essential for performing extubation? stylet, yaunkerm opa
how do arched and angled trach tubes compare to each other? angled tube is longer
what are most common causes pf death in a trach dependant child? accidental decannulation and mucous plugging
what typr of x-ray view is obtained when xray plate is between pt’s back and bed w x-ray tube in front of pt’s chest? anteriorposterior view
lateral decub view is front x-ray projection wherby side down can be evaluated for presence of ____ and side up may better define _____ a pleural effusion, pneumothorax
what xray would be best suited for eval of fractured ribs in peds pt? oblique view
how will well expanded air filled lungs appear on an x-ray? black
therapist is viewing x-ray of peds pt recently awoke form anesthesia after upper abd surgery. Right hemidiaphragm is elevated w atelectasis seen as long thich horizontal line w/in right lower lobe. what term describes this atelectasis? plate
peds pt w pna has infiltrate in lower half of right lung. Right heart border is obliterated. which lobes of right lung is infiltrate located? right middle lobe
what structures on an x-ray projects to the left causing a prominent bulge of superior mediastinum and mild indentation on trachea? aortic arch
AP x-ray neo examined and structure projecting away from mediastinum toward the right upper lung. structure looks like a sail w sharp inferior margin and lateral margins w wavy contours. what structure are you seeing? thymus
minor fissure on r side of lung seperates which of folloing lobes? middle from upper lobe
x-ray 18m/ boy trachea is truncated and right lung is collapsed. what situations or conditions may have caused this situation? mucous plug in the right mainstem bronchus
therapist is viewing frontal chest x-ray of neonate has just been ett. therapist notices tip of ett located between thoracic inlet and carina what to do? nothing ett good placement
what xray view provides best perspective for ascertaining position of ett in pt esophogus? lateral view
therapist viewing frontal and lateral nech x-rays of 12mth notices steeple sign subglottic narrowing below vocal chords and an overdistended hypopharynx. what condition is this? laryngotracheobronchitis
lateral view of neck x-ray 18 mth enlarged epiglottis, aryepiglottic folds are thickened and hypopharynx is overdistended what condition is this? epiglottitis
42 week infnat sga. x-ray reveals coards patch opacities secondary to atelectasis from bronchial obstruction alternating w areas of hyperinflation. what clinical disorder? meconium aspiration syndrome
which term refers to abnormally low levels of o2 in the tissues hypoxia
where does fetal oxyhemoglobin dissociation curve reside in comparison w normal adult diss curve? fetal oxyhemoglobin lies to the left of the adult curve
therapist eval neo o2 PaO2 40, SpO2 80, what to do? add FiO2 to raise SpO2 to 90%
which problems occur as result of abs atelectasis? increased intrapulmonary shunting and decreased alveolar volumes
what tyoes of neo and pped O2 delivery are applied clinically? low flow, high flow, fixed and variable performance
what O2 delivery devices be most suitable for an infant being treated for chanal atresia? O2 hood
how should nasal cannula be secured in an active infant? secure cannula to face and tighten cannula behind head.
when weaning infant receiving O2 from nasal cannula attched to low flowmeter set at 100% what range is recomended? 0.1-0.2 L/min
whats the concern when admin O2 to sedated infant wearing a nasal cannula? too high an FiO2 can be given
what ranges of O2 flow need to be set when admin O2 to an infant via simple mask? 6-10L/min
therapist noices reservoir bad on partial rebreathing mask being worn by peds pt collapses during inspiration what to do? increase O2 flow
what gas delivery devices are most suitable for admin of heliox? nonrebreathing mask
whats the purpose of attaching 22mm humidification collar to an air entrainment mask despite adding no humidification to delived gas? safeguard against bedlinings obstructing air entrainment port
how will excess condensate present in aerosol tubing affect delivered FIo2 increase FiO2
for which of following conditions is a high flow nasal cannula indicated? apnea of prematurity
which features characterize a self inflating neo resus bag? max Vt 200-300ml, one way valved preventing rebreathing of exhaled gas, reservoir to achieve high O2 concentrations, pressure relief valve preventing excess pressure
noe w min vent of 2L/min about to be bvm w non self inflating resu bad what flow should be set? 4-6 L/min
what are advantages of non-self inflating resus system? amt of PEEP can be set, 100% fio2, inspiratory pressure can be regulated
what percentage does breath holding increase particle deposition in the lungs? 10%
what mechanism is the primary mechanism for deposition of particles w a diameter of 5 micro g or greater? inertial impaction
what factors increase the rate of inertial impaction of particles greater than 2 micro grams in diameter? bifurcations and obstructed airways
what term best describes activity of aerosol particles less than 3 micrograms in diameter throughout distal airways? diffusion and browning movement
what characteristic of an aerosol influences its ability to penetrate mucous barrier? solubility of aerosol particles, charge, size of particles
pneumatic nebulizers operate according to whcih physical tenets? bernoulli principle
what % of nominal dose would remain in nebulizer of nebulizer had a residual volume of 1ml and fill volume of 2ml 50%
while nebulizing alb to pt via svn therapist hears sputtering sound originiating from neb how should respond? terminate treatment
why pass over humidifiers preferred over pneumatic nebulizers? pass over trasnmit fewer pathogens
which following considerations is most important when using large volume nebulizer to provide oxygen and humidification to an infant in an incubater? preventing a high noise level from developing
how can pt avoid problem of terminating inhalation when a plume from oressurized mdi impacts the oropharynx? use a valved holding chamber
ped pt w inspiratory flow 20l.min enters emergency department wheezing and sob what devices would be most effective? svn
which functions are served by spacer and holding chambers in conjunction with pMDIs reduction in oropharyngeal deposition of drug, elimination of cold freon effect, and improvement in lower respiratory tract deposition
why should pMDI containing steroids be used with a valved holding chambe? reduce risk of thrush/ yeast infection
for which of following types of pts would DPI be contraindicated? 4 yo, 85 yo w copd, altered loc teen
physician in er attending to a 12 yo exacerbation of asthma, physician asks therapist to recommend a med w synergistic effect w b2 agonist during asthma exacerbations ipratropium bromide
18 mth pt brought to er exhibiting s/s acute athma episode and administered as a B2 agonist to pt doesn’t respond favorably what conditions could be responsible? aspiration of foreign object
therapise receoves an order to admin bronchodilator in line to infant, must not significanlty increase pts delivered todal volume what deliver device to use? vibrating mesh neb, ultrasonic, and pMDI
what methods are acceptable for delivering drug via pMDI to an intubated neonate receiving mechanical vent? through resuc bag
chest physiotherapy procedure includes which of the following techniques? postural drainage, percussion, coughing
when performing et suction on neonate why should therapise routinely avoid advancing the catheter tip beyond the distal tip? prevent development of bronchial stenosis and granulation
what maneuver is characterized by having ot forcibly exhale from middle middle to low lung volume though an open glotts? active cycle of breathing
during autogenic drainage at which of following levels does pt begin breathing? expiratory reserve volume
by which of following mechanisms are high frequency chest compressions supported to mobilize tracheal secretions? by generating high expiratory air velocities
what do postural drainage postitive expiratory pressure therapy autogenic drainage forced expiration techniques and high frequency chest compressions have in common? they attempt to prevent dynamic airway collapse
what most commonly cited complication of chest physiotherapy? hypoxemia
how chould pt receiving CPT while in an icu be monitored? spo2, rr, pulse
what the most important variable used to assess efficacy of CPT? amount of mucus ontained during and after treatment
whaich of the following pts is incentive spiromtery contraindicated? uncooperative, physically dissabled, and very young
what components should be considered when preopertaively teching a child how to do is? paretns involvment, reason, demonstration
during postop what should be volume goal dor is? 75% if preop
what are some problems w admin ippb to peds? coordinating deep breath, securing pt cooperation, asynchronouse breathing
when giving ippb tx to ped pt what determins level of pressure set by therapist? achieving volume goal, observing minimal volume increase, seeing pt becomines intolerant of pressure increase
which assessments used to evaluate pt response to Ippb? heart rate and respiratory rate
whaich aspects of IPPB treatmentneed to be documented in the pts chart after the treatment? peak flow, sensitivity setting
which of following assesment used to eval ots response to IPPB? heart rate and respiratory rate
which aspect ippb treatment need to be documents in pts chart after treatment? peak flow, sensitivity setting
vascular smooth muscle is largel dependent on which of the following intracellular ions? ca
smooth muscle contractions begin w release of which of the following ions from the sarcopasmic reticulum? ca
which substance prevents relase of ca from sarcoplasmic reticulum? cGMP-dependant kinase
what is the primary physiologic activity of inhaled notric oxide? pulmonary vasodilation
which of the following meds contribute to an increased right to left intrapulmonary shunting? nitroprusside and prostacyclin
whats the product of reaction between o2 and nitric oxide? no2
early scavenger systems were designated to protect health care workers from which of the following gases? no2
whats the putpose of admin heliox to pts? reduce wob
what type of flow pattern prevails in healthy person from glottis to 10th airway generation? turbulent flow
how does heliox comair to air o2 as carrier gas? more aerosol deposited w heliox
terapist is using o2 flowmeter to deliver 80:20 heliox to pt reading flowmeter is 10 lpm what is actually being received? 18 lpm
what potential benefit of using heliox while mechanically vent pt w status asthmaticus minimize air trapping
what aspects of mech vent are affected by use of heliox? inspiratory gas flow and volume
what are some problems w heliox as soutce has during mech vent? high thermal conductivity of helium rapidly cools wire flow anemometer stimulating high flow condition
which anomalies are features of hypoplastic left sided heart syndrome aortic shunting and absent or small left ventricle
what are consequences of ratio of puml blood flow to systemic blood flow? significantly above 1.0? decreased renal blood flow and metabolic acidosis
whats relationship between cold pink extremities and the QpQs ratio qp qs prob too high
whats therapeutic goal of admin of fractional concentration of fio2 of 0.18 to an infant? increase pulmonary vascular resistrance
whcih inhaled anesthetic gases have demonstrated possibility to treat status asthmaticus? halothane, isoflurane, sevoflurane
ehaich inhaled anesthetics should therapise recomment to admin via face mask to conscious spont breathing ped pt asthma halothane
xenotransplantation is the use of___organs in humans animal
in 1980’s what was the major indication for heart transplantation? cardiomyopathy
whats predominant priblem leading to heart transplant in children younger than 1 year congential cardiac lesions
whats predominant cause of early postop mortality associated w heart transplant graft failure
what problems are associated w long term heart transplant pts? cad, coronary vasculopathy
which cardiac problems is responsible for cast majority of neo cardiac transplant hypoplastic left ventricular
what are some reasons for decline in heart lung transplant among infants? difficulty of donor, avoiding cardiac rejectio, averting premature cad
which chronic lung disease is the most common indication for bilateral lung transplant? cystic fibrosis
which condition is frequen cause of graft failure within 90 days after lung transplantation ischemia reperfusion
which of following meds are used as antirejection agents? cyclosporine, azathoiprine and mycophenolate mofetil
what conditions are considered complications of thoracic organ transplantation resp fail, bronchiolitis obliterans, infection
24 hrs after ped pt undergone lung transplan, therapist notices x-ray consitent w edema how is it best interpreted? ischmie reperfusion injury
therapist notices ped pt w lung transplant 6 days abundant lower airway secretion w out fever, abundant thick mucous, bronchorrhea
therapist notices following signs in ped pt who recently had heart transplant: decreased contractility, chf, tachy, malaise pt in rejection
while working w recent lung transplant pt therapist observes: tachy, bibasilar inspiratory crackles, increased intertitial infiltrates on chest xray, o2 destat, poor spirometry lung rejection
why does pulmonary infection rate for lung transplant appear to be higher than w other solid organ transplants? because lung is in direct contact with the external environment
which of following microorganisms is associated w increased mortality among pts w cystic fibrosis? burkholderia cepacia
months after receiving lung transplant a pt w cystic fibrosis exhibits foloowing signs and symptoms: increasing dyspnea, increasing cough w sputum, colonization pseudamonas bronchiolitis obliterans
which of following meds are associated w decreased wbc caused by bone marrow suppression? azathioprine mycophenolate mofetil
which forms of interaction tend to occur between resp pt who receives lung transplant mech vent, pulm rehab, broncho pulm hygeine

 

Respiratory Neonatal & Pediatric Care Chapter 2 Practice Questions:

 

1. How is the percentage of functional hemoglobin that is saturated with oxygen determined via pulse oximetry?

A. The sum of the amount of red and infrared absorbed by the tissue determines the Sp02
B. The ratio of the red and infrared light that reaches the photodiode signifies the Sp02
C. The percentage of infrared light that reaches the photodetector reflects the Sp02
D. The percentage of red light that lands on the photodiode represents the Sp02 (oxygen saturation as determined by pulse oximetry.

2. The therapist has applied a bandage-type pulse oximetry probe too tightly to an infant’s finger. What problem can be expected to occur in this situation?

A. The Sp02 will read erroneously low.
B. The Sp02 will read erroneously high.
C. The monitor displays a message indicating inadequate pulse.
D The monitor displays fluctuating Sp02 values between being erroneously low and high.

3. As the therapist applies a pulse oximeter finger probe to a neonate who is receiving supplemental oxygen, she notices that the Sp0 reading is 100%. What should the therapist do in this situation?

A. The therapist should reduce the fraction of inspired oxygen.
B. The therapist should switch to using a capnometer.
C. The therapist should obtain an arterial blood sample from this patient.
D. The therapist should do nothing, because the reading is accurate.

4. Why do transcutaneous oxygen tension (P0 and carbon dioxide tension (PCO values differ from Pa0 and PaCO measurements?

A. Because metabolism in the tissue consumes oxygen and produces carbon dioxide at the site of the electrode
B. Because oxygen is consumed and carbon dioxide is produced in transit from the left ventricle to the electrode site
C. Because the skin is much more permeable to oxygen than carbon dioxide
D. Because of the lag time between the cardiac output and the time the blood reaches the transcutaneous electrode site



5. While attending to a neonatal patient in the neonatal intensive care unit (NICU), the therapist notices that a transcutaneous electrode is affixed to the upper chest of the neonate. What should the therapist do at this time?

A. The therapist should relocate the electrode on the sternum as close as possible to the heart.
B. The therapist needs to move the transcutaneous electrode to the infant’s right shoulder.
C. The therapist should reposition the electrode on the neonate’s abdomen.
D. The therapist should do nothing because the transcutaneous electrode is properly placed.

6. The therapist is assessing a mechanically ventilated infant and observes that the transcutaneous electrode temperature is set between 430 C and 44° C. What action does the therapist need to take at this time?

A. The temperature range set is appropriate; therefore, no action is necessary.
B. The temperature of the transcutaneous electrode needs to be reduced to 36° C to
C. The therapist should increase the temperature range to 470 C to 48° C.
38° C.
D. The electrode needs to be repositioned and maintained at the same temperature.

7. Which of the following factors is the main physiologic factor responsible for deriving accurate transcutaneous data?

A. Ventilation—perfusion ratios
B. Peripheral perfusion
C. Minute ventilation
D. Heart rate

8. Which of the following features or characteristics apply to mainstream capnography?
I. The mainstream capnograph contains narrow tubing that can become occluded with mucus.
II. Mainstream capnography generally employs infrared spectrometers.
III. The mainstream capnograph does not add much weight to the breathing circuit.
IV. The mainstream capnograph is placed at the proximal end of the endotracheal tube.

A. I, III, and IV only
B. I, II, and III only
C. II and IV only
D. I and II only

9. How is the percentage of functional hemoglobin that is saturated with oxygen determined via pulse oximetry?

A. The percentage of red light that lands on the photodiode represents the SpO2 (oxygen saturation as determined by pulse oximetry).
B. The percentage of infrared light that reaches the photodetector reflects the SpO2.
C. The ratio of the red and infrared light that reaches the photodiode signifies the SpO2.
D. The sum of the amount of red and infrared absorbed by the tissue determines the SpO2.

Correct response: A pulse oximeter sensor has two light-emitting diodes (LEDs) that function as light sources and one photodiode that acts as a light receiver. One LED emits red light, and the other diode emits infrared light. As the light from the diodes passes through the blood and tissue, some of the light from both the red and infrared diodes is absorbed. The photodiode then measures the amount of light that passes through the body without being absorbed. By knowing the amount of light that is entering the body and the amount of light leaving the body, the amount of light absorbed is easily determined. This absorption of both the red and infrared light is used to determine the percentage of functional hemoglobin that is saturated with oxygen.

10. The therapist has applied a bandage-type pulse oximetry probe too tightly to an infant’s finger. What problem can be expected to occur in this situation?

A. The SpO2 will read erroneously low.
B. The SpO2 will read erroneously high.
C. The monitor displays a message indicating inadequate pulse.
D. The monitor displays fluctuating SpO2 values between being erroneously low and high.

Correct response: Application of the sensor is crucial to the quality of readings from the pulse oximeter. The sensor should be placed over a vascular area with the diodes and the photodiode directly opposite each other and in good contact with the skin. The sensors should be placed firmly to avoid falling off or motion artifact, but care should be taken to avoid overtightening and compromising the circulation. An artifact that obscures the pulse triggers the “loss of pulse” alarm on the monitor.

11. As the therapist applies a pulse oximeter finger probe to a neonate who is receiving supplemental oxygen, she notices that the SpO2 reading is 100%. What should the therapist do in this situation?

A. The therapist should do nothing, because the reading is accurate.
B. The therapist should obtain an arterial blood sample from this patient.
C. The therapist should switch to using a capnometer.
D. The therapist should reduce the fraction of inspired oxygen.

Correct response: Even when properly functioning, the pulse oximeter does not provide good information regarding hyperoxia in the neonatal patient. If the oximeter is reading an SaO2 (arterial oxygen saturation) of 100%, the arterial oxygen tension (PaO2) could be between 90 and 250 mm Hg. In such a situation, the therapist needs to obtain an arterial blood sample to determine the actual PaO2 of the patient. The risk in this situation is in not recognizing a dangerously high PaO2, which, if permitted to persist, can cause retinopathy of prematurity.

12. Why do transcutaneous oxygen tension (PO2) and carbon dioxide tension (PCO2) values differ from PaO2 and PaCO2 measurements?

A. Because of the lag time between the cardiac output and the time the blood reaches the transcutaneous electrode site
B. Because the skin is much more permeable to oxygen than carbon dioxide
C. Because oxygen is consumed and carbon dioxide is produced in transit from the left ventricle to the electrode site
D. Because metabolism in the tissue consumes oxygen and produces carbon dioxide at the site of the electrode.

Correct response: Transcutaneous measurements of PO2 and PCO2 are based on the fact that a heating element in the sensor elevates the temperature in the underlying tissue. Increasing the skin’s temperature increases the capillary blood flow to the tissues, making the skin more permeable to gas diffusion. Because metabolism in the tissues (through which the blood perfuses) consumes oxygen and produces carbon dioxide, transcutaneous values differ from arterial values. Usually, the PO2 is slightly lower than in the arteries, and the PCO2 is slightly higher when measured transcutaneously.

13. While attending to a neonatal patient in the neonatal intensive care unit (NICU), the therapist notices that a transcutaneous electrode is affixed to the upper chest of the neonate. What should the therapist do at this time?

A. The therapist should do nothing because the transcutaneous electrode is properly placed.
B. The therapist should reposition the electrode on the neonate’s abdomen.
C. The therapist needs to move the transcutaneous electrode to the infant’s right shoulder.
D. The therapist should relocate the electrode on the sternum as close as possible to the heart.

Correct response: A critical consideration regarding transcutaneous monitoring is the application and site selection of the sensor. The site should be a highly vascular area such as the upper chest, abdomen, and thighs, or the lower back if the patient is supine. Bony areas over the spine should be avoided. Another consideration when selecting a site is that the right side of the upper chest will give preductal oxygenation values, whereas the left side of the chest and the lower parts of the body will give postductal values.

14. The therapist is assessing a mechanically ventilated infant and observes that the transcutaneous electrode temperature is set between 43º C and 44º C. What action does the therapist need to take at this time?

A. The temperature range set is appropriate; therefore, no action is necessary.
B. The therapist should increase the temperature range to 47º C to 48º C.
C. The temperature of the transcutaneous electrode needs to be reduced to 36º C to 38º C.
D. The electrode needs to be repositioned and maintained at the same temperature.

Correct response: Selecting a sensor temperature is important to proper operation. The temperature range is usually 43º C to 44º C. Thicker skin requires a higher temperature. The fact that the sensor is heated requires changing the site routinely to prevent thermal injuries. The frequency of the site changes ranges from 3 to 4 hours. Relocating the electrode can be done sooner, that is, 2 or 3 hours, if the skin at the site has a reaction or if the sensor is operated at higher temperatures.

15. Which of the following factors is the main physiologic factor responsible for deriving accurate transcutaneous data?

A. Heart rate
B. Minute ventilation
C. Peripheral perfusion
D. Ventilation-perfusion ratios

Correct response: The main physiologic factor relating to good correlation is good peripheral blood perfusion. The skin reacts to cold, shock, and certain drugs by contracting the superficial blood vessels and by opening the larger, deeper-lying arterioles to achieve a shunting effect. In the event of exposure to cold, capillary blood flow slows or stops to reduce the loss of body heat. Shock and certain cardiopulmonary medications will dilate the blood vessels, causing the blood pressure in the body to drop. In response to this drop in blood pressure, the body will shunt blood from the skin and toward major organs. If blood flow in the capillary bed is reduced, the capillary blood rapidly becomes more or less venous, with a considerably lower PO2 and higher PCO2. Therefore, in patients with impaired peripheral blood perfusion, large deviations may occur between central PO2/PCO2 and the transcutaneous values.

16. Which of the following features or characteristics apply to mainstream capnography?
I. The mainstream capnograph contains narrow tubing that can become occluded with mucus.
II. Mainstream capnography generally employs infrared spectrometers.
III. The mainstream capnograph does not add much weight to the breathing circuit.
IV. The mainstream capnograph is placed at the proximal end of the endotracheal tube.

A. I and II only
B. II and IV only
C. I, II, and III only
D. I, III, and IV only

Correct response: Exhaled gas can be analyzed according to two methods, that is, by mainstream or sidestream capnography. Aside from other features, they differ according to how exhaled gas reaches the sample chamber. A mainstream capnograph is used with ventilated patients, and is placed at the proximal end of the endotracheal tube. This setup can be seen in Figure 11-5 in the textbook. This method generally employs infrared spectrometry. Caution must be taken because these analyzers can be a heavy addition to an infant or pediatric circuit, causing kinking or disconnecting of the endotracheal tube. Sidestream analyzers continuously aspirate a sample of gas through a small tube and into the analyzer. This method is used primarily with mass spectrometry and some infrared analyzers. It is advantageous in that it does not add much weight to the breathing circuit. However, the narrow tubing can become occluded with mucus or water, causing inaccuracies.

17. Where on the following normal capnogram is the end-tidal carbon dioxide (PetCO2) represented?

A. A
B. B
C. C
D. D

Correct response: A normal capnogram can be divided into four phases. Phase A-B is the inspiratory phase, during which the sensor detects no carbon dioxide because the gas exhaled at that time is atmospheric air from the anatomic dead space. Phase B-C is the initial expiratory phase, during which carbon dioxide tension rapidly increases as the alveoli begin to empty, and only remnants of dead space gas remain. Phase C-D is the completion of expiration as the alveoli empty (alveolar plateau) and shows a slight increase in carbon dioxide. Phase D-E is the beginning of inspiration as the waveform returns to zero because of the reentry into the lung of atmospheric air. Point D on the capnogram represents the end-tidal

18. While working in the NICU with a mechanically ventilated newborn who is being monitored for PetCO2, the therapist observes the following capnogram. What interpretation should the therapist make of this capnogram?

A. This capnogram is normal.
B. The patient is receiving about 10 cm H2O positive end-expiratory pressure.
C. The patient is rebreathing his own exhaled gas.
D. The neonate is being hyperventilated.

Correct response: Rebreathing is characterized by an elevation in the A-B phase of the capnogram with a corresponding increase in PetCO2. It indicates the rebreathing of the previously exhaled carbon dioxide. Rebreathing can be caused by using an insufficient expiratory time or an inadequate inspiratory flow.

19. The following capnogram was obtained from a newborn infant receiving mechanical ventilation. How should the therapist evaluate this capnogram?

A. Airway obstruction
B. Hypoventilation
C. Hyperventilation
D. Increased dead space ventilation

Correct response: Obstruction to the expiratory flow of gas will be noted as a change in the slope of the B-C phase of the capnogram. The B-C phase may diminish without a plateau. Obstruction can be caused by a foreign body in the upper airway, increased secretions in the airways, the patient having bronchospasms, or partial obstruction of the ventilator circuit.

20. An infant demonstrates the following capnogram while being mechanically ventilated. How should the therapist interpret this capnogram?

A. The patient has received a paralytic agent.
B. A paralytic agent is indicated for this patient because of the spontaneous breathing efforts represented by the downward deflections.
C. The patient may have developed a pneumothorax.
D. A leak has developed in the patient-ventilator system.

Correct response: A stair-stepping of the D-E phase of the capnogram, caused by unequal and incomplete emptying of the lungs, and a failure to return to baseline may suggest a pneumothorax. The capnogram depicting the possible pneumothorax is presented here.