Question 1

The therapist has been asked to measure preductal oxygen saturation.Where could the therapist place the pulse oximeter probe?

Accepted Answer

Sensor placement on right arm or head will reflect preductal values while the left arm and the lower parts of the body will reflect postductal oxygen saturation values.

Question 2

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?

Accepted Answer

The site should be a highly vascular area such as the earlobe,upper chest,abdomen,thighs,or the lower back if the patient is supine;bony areas and those with limited perfusion,such as over the spine,should be avoided.

Question 3

A therapist is monitoring a child on the mechanical ventilator who is hemodynamically stable.The PetCO₂ is 48 mm Hg.If accurate,what should be the PaCO₂?

Accepted Answer

PetCO₂ can be used as a surrogate for the arterial partial pressure of CO₂ (PaCO₂)within physiologic limits.Normally,PetCO₂ is 2-5 mmHg below PaCO₂.The reason for this is the proportion dead-space ventilation.

Question 4

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

Accepted Answer

A pulse oximeter sensor has two light-emitting diodes (LEDs)that function as light sources and a photodiode that measures the amount of light from the LEDs (see Figure 9-1 in the textbook).One LED emits red light,and the other diode emits infrared light.The sensor is placed over a translucent part of the body (finger,toe,earlobe,etc. ).As the light from the diodes passes through the blood and tissue,some of the light from both the red and the infrared diodes is absorbed by oxyhemoglobin.The photodiode then measures the amount of light that passes through the body without being absorbed.Because oxyhemoglobin (hemoglobin bound with oxygen)and deoxyhemoglobin (hemoglobin not bound with oxygen)absorb significantly different amounts of light,the proportion of oxyhemoglobin (expressed as a percentage)is determined (see Figure 9-2 in the textbook).

Question 5

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?

Accepted Answer

Correct application of the sensor is crucial to the quality of readings from the pulse oximeter.The sensors should be placed firmly to avoid falling off or motion artifact,but care should be taken to avoid overtightening and compromising local circulation.

Question 6

What is volumetric capnography able to determine?
I.Airway dead space
II.Alveolar tidal volume
III.Shunt fraction
IV.Alveolar minute volume

Accepted Answer

The concentration of CO₂ is plotted against exhaled tidal volume to determine relevant ventilation data such as airway dead space,alveolar tidal volume,and extrapolation of CO₂ elimination and alveolar minute ventilation.

Question 7

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

Accepted Answer

The normal capnogram can be divided into four phases (see Figure 9-6 in the textbook):
Phase A-B: The inspiratory phase, during which the sensor detects no carbon dioxide
Phase B-C: The initial expiratory phase, during which carbon dioxide rapidly increases as the alveoli begin to empty
Phase C-D: The completion of expiration as the alveoli empty (alveolar plateau) and show a slight increase in carbon dioxide
Phase D-E: The beginning of inspiration as the waveform returns to zero.

Question 8

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?

Accepted Answer

Rebreathing is characterized by an elevation in the A-B phase of the capnogram, with a corresponding increase in ETCO₂ . It indicates the rebreathing of previously exhaled carbon dioxide. Rebreathing can be caused by allowing an insufficient expiratory time or by inadequate inspiratory flow (see Figure 9-7 in the textbook).

Question 9

What clinical parameter is critically important to monitor when mechanical ventilation is administered?

Accepted Answer

In mechanically ventilated children,increasing intrathoracic pressure (by increasing positive end expiratory pressure,for example)can reduce venous return,resulting in decreased BP.

Question 10

The therapist is assessing a mechanically ventilated infant and observes that the transcutaneous electrode temperature is set between 41° C and 44° C.What action does the therapist need to take at this time?

Accepted Answer

Selecting a sensor temperature is important to proper operation.The temperature range is usually 41° to 44° C.Heating of the sensor requires that the site be changed on a routine basis to prevent thermal injuries.The frequency of site changes ranges from 4 to 12 hours (depending upon the device and sensor temperature)but can be reduced if necessary.

Question 11

Which of the following conditions will preclude the use of indirect calorimetry?
I.Cuffed endotracheal tubes
II.Circuit leaks
III.FiO₂ 40%
IV.HFOV

Accepted Answer

Conditions that preclude the use of indirect calorimetry include: uncuffed endotracheal tubes,cuff or ventilator circuit leaks >10-15%,FiO₂ >50%,need for high-frequency ventilation or extracorporeal membrane oxygenation,and active chest tube leakage.

Question 12

What is the purpose of indirect calorimetry?

Accepted Answer

Direct calorimetry extrapolates energy expenditure by measuring heat produced and lost from the body while indirect calorimetry combines measurements of VO₂ and VCO₂ into an equation to calculate energy expenditure.Most energy expenditure reports will contain results for VO₂,VCO₂,REE,and respiratory quotient (which is VCO₂/VO₂ and can be used to determine substrate utilization).

Question 13

The following capnogram was obtained from a newborn infant receiving mechanical ventilation.

How should the therapist evaluate this capnogram?

Accepted Answer

Obstruction of 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 (see Figure 9-8 in the textbook).

Question 14

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

Accepted Answer

Changes in perfusion can adversely affect the accuracy of transcutaneous measurements.The skin reacts to cold,shock,and certain drugs by contracting the superficial blood vessels,opening larger,deeper arterioles to achieve a shunting effect.Capillary blood flow is reduced on exposure to cold temperatures in order to reduce the loss of body heat.Shock and certain medications can also divert blood from capillaries to the central circulation.In all cases of reduced capillary perfusion,the capillary blood that is measured using a transcutaneous monitor may reflect measurements associated with venous blood,with a considerably lower PO₂ and higher PCO₂ (compared to values obtained with good capillary perfusion).If a patient has poor skin integrity,transcutaneous monitoring may also be contraindicated.

Question 15

An infant demonstrates the following capnogram while being mechanically ventilated.

How should the therapist interpret this capnogram?

Accepted Answer

A stair-stepping of the D-E phase of the capnogram,caused by unequal and incomplete emptying of the lungs,along with a failure to return to baseline,may suggest a pneumothorax (see Figure 9-10 in the textbook).

Question 16

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?

Accepted Answer

The sensitivity of pulse oximetry to detect the presence and degree of hyperoxia may be limited in the neonatal patient.If the oximeter is reading an SpO₂ of 100%,the arterial oxygen tension (PaO₂)could be between 90 and 250 mm Hg.However,many neonatal intensive care units will target an SpO₂ below a certain threshold in order to reduce the risk of retinopathy of prematurity in premature babies.

Question 17

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

Accepted Answer

Transcutaneous measurements of PO₂ and PCO₂ require a heating element,built into the sensor,which elevates the temperature in the underlying tissue.Increasing the skin's temperature increases capillary blood flow to the tissues,making it more permeable to gas diffusion.The tissue under which the sensor is placed will continue to consume oxygen and produce carbon dioxide (according to their metabolic demands).Consequently,measured values obtained with a transcutaneous monitor will differ from arterial values.Generally,the PO₂ is slightly lower than in the arteries,and the PCO₂ is slightly higher.

Question 18

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.

Accepted Answer

Gases from an exhaled breath can reach the sample chamber in one of two ways.Mainstream capnographs are used in ventilated patients,with placement at the proximal end of an endotracheal tube (see Figure 9-5 in the textbook).This method employs infrared spectrometers.Sidestream capnograph analyzers continuously aspirate a sample of gas through a small tube to the analyzer.

Quiz 9: Noninvasive Monitoring in Neonatal and Pediatric Care

The therapist has been asked to measure preductal oxygen saturation.Where could the therapist place the pulse oximeter probe?

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 therapist is monitoring a child on the mechanical ventilator who is hemodynamically stable.The PetCO₂ is 48 mm Hg.If accurate,what should be the PaCO₂?

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

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?

What is volumetric capnography able to determine? I.Airway dead space II.Alveolar tidal volume III.Shunt fraction IV.Alveolar minute volume

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

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?

What clinical parameter is critically important to monitor when mechanical ventilation is administered?

The therapist is assessing a mechanically ventilated infant and observes that the transcutaneous electrode temperature is set between 41° C and 44° C.What action does the therapist need to take at this time?

Which of the following conditions will preclude the use of indirect calorimetry? I.Cuffed endotracheal tubes II.Circuit leaks III.FiO₂ 40% IV.HFOV

What is the purpose of indirect calorimetry?

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

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

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

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?

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