Deck 10: Blood Gas Monitoring

Question 1

The purpose of an Allen test is to check blood flow in the _____ artery.1.ulnar
2)radial
3)brachial
4 posterior tibial
5)lateral plantar

A) 1,2,and 3
B) 2,3,and 4
C) 1,4,and 5
D) 3,4,and 5

Answer 1

C
An Allen test should always be done before a radial artery puncture is performed to ensure that there is collateral circulation in the ulnar artery.An Allen type of test should be performed to ensure collateral circulation in the posterior tibial and lateral plantar arteries when drawing arterial blood from the dorsal artery of the foot.

Question 2

A voltage difference of 18.7 mV is measured when a blood sample is being analyzed for pH.What is the resultant pH of the blood?
A) 7.54
B) 7.34
C) 7.14
D) 8.71
18)In a partial pressure of oxygen (PCO₂₎ electrode,carbon dioxide does which of the following?
1)It reacts with potassium chloride.2.It reacts with water to form carbonic acid. 3.It diffuses through a polyethylene membrane.4.It diffuses through a semipermeable Teflon membrane.a. 2 and 3
B) 1 and 3
C) 1 and 4
D) 2 and 4

A) 7.54
B) 7.34
C) 7.14
D) 8.71

Answer 2

D
A PCO₂ electrode is basically a pH electrode covered with a carbon dioxide-permeable Teflon or silicone (Silastic)membrane.A bicarbonate-buffered solution is held between the Teflon membrane and the pH glass electrode by a nylon spacer.CO₂ from the blood diffuses across the semipermeable Teflon membrane and reacts with the water to form carbonic acid,which dissociates into hydrogen ions and bicarbonate.

Question 3

The Henderson-Hasselbalch equation is used in acid-base analysis to relate which of the following?

A) pH to PCO₂
B) pH to bicarbonate (HCO₃‑)
C) Carbonic acid (H₂CO₃) to HCO₃‑
D) PO₂ to oxygen saturation

Answer 3

B
A modified version of the Henderson-Hasselbalch equation is used in the PCO₂ electrode to relate the pH measured to the PCO₂ of the blood.Therefore,the PCO₂ is determined as a function of the change in pH of the bicarbonate solution in the PCO₂ electrode.

Question 4

The reference half-cell of a pH analyzer is composed of:

A) silver anode.
B) platinum cathode.
C) silver-silver chloride.
D) mercury-mercurous chloride.

Question 5

If the PCO₂ of an arterial blood sample is 60 mm Hg,the expected pH is:

A) 7.20.
B) 7.30.
C) 7.50.
D) 7.60.

Question 6

Which of the following factors will cause analysis of blood gas samples to be erroneous?
1)Warming the sample
2)Low leukocyte counts
3)The presence of air bubbles in the sample
4)Icing the sample between obtaining and analyzing
5)Prolonged time delay between obtaining and analyzing a sample

A) 2 and 3
B) 2 and 4
C) 1,3,and 5
D) 1,2,4,and 5

Question 7

Which size of needle should be used to draw arterial blood from an adult?

A) 22 gauge
B) 24 gauge
C) 26 gauge
D) 28 gauge

Question 8

Which chemical reaction occurs within the Stow-Severinghaus electrode?

A) CO₂ + H₂O H₂CO₃ H⁺ + HCO₃-
B) O₂ + 2H₂O + 4e- 4OH-
C) 4Ag→ 4Ag⁺ + 4e-
D) EH⁺ = 0.0615 * pH

Question 9

Which is the correct order of steps to perform the modified Allen test?
1)Pressure is applied to both the radial and ulnar arteries.
2)The fist is opened but not fully extended.
3)Pressure on the ulnar artery is removed.
4)The hand is clenched into a tight fist
5)The palm and fingers are blanched.

A) 4,1,2,5,3
B) 4,5,1,3,2
C) 1,4,3,2,5
D) 4,2,1,3,5

Question 10

A blood sample is analyzed within a Sanz electrode.The voltage difference = 44.90 mV.What is the resultant pH of this blood?

A) 7.11
B) 7.34
C) 7.57
D) 8.18

Question 11

Hydrogen ion activity can be expressed as which of the following?

A) pH = log10[H-]
B) [H+] = log * 10
C) pH = -log10[H+]
D) pH = 1 * 10-7 mol/L

Question 12

Which of the following are the most common sites for the percutaneous sampling of arterial blood for blood gas analysis?
1)Earlobe
2)Radial artery
3)Brachial artery
4)Side of the heel

A) 1 and 2
B) 2 and 3
C) 3 and 4
D) 1 and 4

Question 13

Erroneous PCO₂ measurements can be caused by which of the following?
1)A worn electrode
2)A cracked electrode
3)Wearing out of the silver anode
4)Increased temperature of the patient
5)Dehydration of bicarbonate solution

A) 1 and 5
B) 2 and 3
C) 3 and 4
D) 1,2,and 5

Question 14

Which is the correct sequence of events when one is obtaining arterial blood from the radial artery of a patient?
1)Perform the modified Allen test.
2)Remove any air bubbles from the sample.
3)Apply direct pressure to the puncture site.
4)Clean the puncture site with a suitable antiseptic solution
5)Use a 23-gauge needle and a plastic syringe containing an anticoagulant.

A) 1,4,3,5,2
B) 4,1,5,2,3
C) 1,4,5,3,2
D) 1,5,2,4,3

Question 15

The maximum amount of blood that should be discarded from the indwelling arterial catheter of an infant is ____ mL.

A) 0.3
B) 0.5
C) 0.8
D) 1.0

Question 16

Which of the following statements is true concerning capillary blood gases?

A) They can be drawn from an earlobe.
B) They coincide with arterial blood gases.
C) They can be drawn from a peripheral artery.
D) They require the performance of an Allen test.

Question 17

Which of the following are true concerning pH?
1)A blood pH = 7.50 is alkaline.
2)A blood pH <7.40 is alkaline.
3)A blood pH >7.40 is acidotic.
4)A blood pH = 7.30 is acidotic.

A) 1 and 2
B) 2 and 3
C) 3 and 4
D) 1 and 4

Question 18

Acid-base neutrality is expressed as which of the following?
1)pH = 14
2)pH < 7.0
3)pH = 7.0
4)[H⁺] > [OH-]
5)[H⁺] = [OH-]

A) 1
B) 3 and 5
C) 2 and 4
D) 1 and 4

Question 19

A standard pH electrode includes which of the following?

A) Nylon spacer
B) Silver anode
C) Mercury bead
D) Silicon elastic membrane

Question 20

When an Allen test result is negative,blood for blood gas analysis should be drawn from which of the following sites?

A) Earlobe
B) Radial artery
C) Brachial artery
D) Side of the heel

Question 21

The Siggaard-Andersen alignment nomogram is used for which of the following?

A) Calculating pH
B) Measuring PCO₂
C) Calculating sodium (Na+), potassium (K+), chloride (Cl-), and calcium (Ca++)
D) Calculating actual and standard bicarbonate

Question 22

What type of electrode is used to measure calcium and sodium?

A) Clark
B) Ion-selective
C) Polarographic
D) Glucose-oxidase

Question 23

Normal plasma bicarbonate levels are _____ mmol/L.

A) 15 to 25
B) 22 to 26
C) 30 to 40
D) 44 to 48

Question 24

The partial pressure of oxygen in the blood is measured by which electrode?

A) Sanz
B) Severinghaus
C) Pauling
D) Clark

Question 25

Which of the following plasma electrolyte levels are outside the normal range?
1)Total calcium 7.4 mEq/L
2)Magnesium 2.0 mEq/L
3)Potassium 4.2 mEq/L
4)Chloride 115 mEq/L
5)Sodium 175 mEq/L

A) 1,4,and 5
B) 3,4,and 5
C) 2,3,and 4
D) 1

Question 26

What is the pH of the phosphate buffer solution in a Sanz electrode?

A) 6.84
B) 7.00
C) 7.32
D) 7.90

Question 27

A P₅₀ measurement refers to which of the following?

A) The amount of oxygen diffusion in fluids
B) The PO₂ when hemoglobin is 50% saturated with oxygen
C) The partial pressure of fetal hemoglobin at 50% saturation
D) The partial pressure of oxygen consumed by the oxygen electrode

Question 28

Which of the following represents the technique used to measure current changes that occur when oxygen is reduced?

A) Blood gas factor
B) Potentiometric
C) Amperometric
D) Tonometry

Question 29

The blood gas factor results from the:

A) Slow rate of oxygen diffusion in fluids.
B) Slow rate of carbon dioxide diffusion in blood.
C) Amount of carbon dioxide necessary to change the pH by 0.01.
D) Quantity of electrons that need to be added to the silver anode to reduce oxygen.

Question 30

Which reaction occurs at the platinum cathode of the Clark electrode?

A) CO₂ + H₂O H₂CO₃ H+ + HCO₃-
B) AgCl + KCl Ag₂+ Cl₂+ K
C) O₂ + 2H₂O + 4e- 4OH-
D) 4Ag → 4Ag⁺ + 4e-

Question 31

Exposure of a Clark electrode to gaseous anesthetic agents such as nitrous oxide will cause which of the following to occur?

A) The pH will increase.
B) The electrode will function normally.
C) There will be an increase in the production of peroxide ions.
D) The carbon dioxide in the blood will increase and cause an erroneous reading.

Question 32

Which of the following variables can be calculated from measured arterial blood gas values?
1)The partial pressure of oxygen at which hemoglobin is 50% saturated (P₅₀)
2)pH
3)PCO₂
4)HCO₃-
5)SaO₂

A) 1,3,and 4
B) 2,4,and 5
C) 1,4,and 5
D) 2 and 3

Question 33

Which of the following variables are measured directly by a blood gas machine?
1)pH
2)PaO₂
3)HCO₃-
4)SaO₂

A) 1 and 2
B) 2 and 3
C) 3 and 4
D) 1 and 4

Question 34

Which of the following would create the lowest P₅₀?

A) pH = 7.26
B) pH = 7.35
C) PCO₂ = 32 mm Hg
D) Temperature = 39° C

Question 35

Which of the following will decrease oxygen's affinity for hemoglobin?

A) Increased CO₂
B) Acute alkalosis
C) Methemoglobin
D) Hypothermia

Question 36

A left shift in the oxyhemoglobin dissociation curve is caused by:

A) methemoglobin.
B) acute acidosis.
C) increased temperature.
D) high 2,3-diphosphoglycerate (2,3-DPG).

Question 37

Which of the following would create the highest P₅₀?

A) pH = 7.40
B) pH = 7.50
C) PCO₂ = 40 mm Hg
D) PCO₂ = 60 mm Hg

Question 38

The PCO₂ electrode uses which of the following?

A) HCO₃- solution
B) Mercury bead
C) KCl solution
D) Silver anode

Question 39

Standard bicarbonate is calculated by use of which of the following?

A) Henderson-Hasselbalch equation
B) Two-point calibration method
C) Lambert-Beer law equation
D) Levy-Jennings chart

Question 40

Which of the following is a buffer base?

A) A metabolite solution
B) An electrolyte-specific solution
C) The solution used to perform a three-point calibration
D) Consists of hemoglobin, inorganic phosphate, and negatively charged proteins

Question 41

Absorbance or fluorescent sensors are used with which of the following?

A) Capnography
B) Photoplethysmography
C) In vitro blood gas analysis
D) In vivo blood gas analysis

Question 42

The relative transmission and/or absorption of portions of the light spectrum are the basis for which of the following?

A) Amperometry
B) Plethysmography
C) Spectrophotometry
D) Potentiometry

Question 43

CO-oximeters routinely measure which of the following?
1)Carboxyhemoglobin (HbCO)
2)Fetal hemoglobin
3)Sulfhemoglobin
4)Oxyhemoglobin (O₂Hb)
5)Methemoglobin (metHb)

A) 1 and 2
B) 1,4,and 5
C) 1,2,3,4,and 5
D) 2,3,and 5

Question 44

What type of calibration should be performed after an electrode is changed?

A) Quality control
B) Three-point
C) Two-point
D) One-point

Question 45

Which of the following statements are true concerning in vivo arterial blood gas analyzers?

A) They incorporate a polarographic electrode.
B) The operating principle is light transmission.
C) Temperature correction is unnecessary.
D) They are more accurate than in vitro blood gas analyzers.

Question 46

The gold standard for quality control for PCO₂ and PO₂ electrodes is:

A) capnography.
B) polarography.
C) tonometry.
D) anometry.

Question 47

Which device allows in vitro arterial blood gas and pH measurements in a transport vehicle?

A) CO-oximeter
B) Pulse oximeter
C) Plethysmograph
D) Point-of-care analyzer

Question 48

What type of instrument could be used to analyze pH,PO₂,PCO₂,and various electrolytes at the patient's bedside?

A) Point-of-care blood gas analyzer
B) CO-oximeter
C) Potentiometer
D) Capnograph

Question 49

A fluorescent sensor can measure which range of pH values?

A) 6.0 to 7.5
B) 6.5 to 7.5
C) 6.8 to 7.8
D) 7.0 to 8.0

Question 50

Which size of scalp vein needle should be used to draw arterial blood from an infant?

A) 22 gauge
B) 24 gauge
C) 26 gauge
D) 28 gauge

Question 51

What are the two wavelengths of light used to determine hemoglobin saturation with a pulse oximeter?

A) 550 nm and 730 nm
B) 660 nm and 940 nm
C) 730 nm and 940 nm
D) 550 nm and 840 nm

Question 52

Which of the following is true concerning the typical point-of-care blood gas analyzer?

A) It is only able to measure pH, PaCO₂, and PaO₂.
B) It measures actual hemoglobin oxygen saturation.
C) It uses silicone chips with microelectrodes.
D) It requires 1 to 2 mL of blood.

Question 53

What organizations offer proficiency testing programs?
1)The Joint Commission on Accreditation of Healthcare Organizations (JCAHO)
2)The American Association for Respiratory Care (AARC)
3)The American College of Chest Physicians (ACCP)
4)The College of American Pathologists (CAP)
5)The American Thoracic Society (ATS)

A) 4 and 5
B) 3 and 5
C) 1,2,and 3
D) 1,4,and 5

Question 54

What is responsible for the conversion of glucose to hydrogen peroxide and gluconic acid on the surface of the glucose electrode?

A) Hydrogen peroxide
B) Phosphodiesterase
C) Glucagon oxidase
D) Glucose oxidase

Question 55

Which of the following in vivo arterial blood gas values is comparable with in vitro measurements?

A) pH
B) PCO₂
C) PO₂
D) Bicarbonate

Question 56

Quality control includes which of the following?
1)Analyzing unknown samples and submitting to the sponsoring organization
2)Assessing control sample measurements against defined limits
3)Addressing problems through corrective actions
4)Identifying problems

A) 1 and 2
B) 3 and 4
C) 2,3,and 4
D) 1,2,3,and 4

Question 57

Which of the following statements is true concerning quality control of a blood gas analyzer?

A) Commercially prepared controls ensure instrument accuracy.
B) A Levy-Jennings chart is used to record quality control data.
C) Protein buildup on electrodes will not cause errors in the instrument.
D) Commercial controls are not susceptible to variations at room temperature.

Question 58

A patient with a bilirubin level of 28 mg/dL has arterial blood drawn for CO-oximetry.The respiratory therapist should expect a(n)_____ measurement.

A) Accurate O₂Hb
B) Lower-than-actual O₂Hb
C) Higher-than-actual O₂Hb
D) Higher-than-actual HbCO

Question 59

The two-point calibration for the pH electrode uses two buffers.Which of the following pH values are correct for these two buffers?
1)6.839
2)6.840
3)7.384
4)7.495

A) 1 and 3
B) 1 and 4
C) 2 and 4
D) 2 and 3

Question 60

A CO-oximeter identifies the different types of hemoglobin through the use of:

A) fiberoptics.
B) spectrophotometry.
C) optical plethysmography.
D) potentiometric measurements.

Question 61

A 38-year-old woman is currently in the emergency department and has a diagnosis of an asthma attack.The most current arterial blood gas result reveals the following: pH of 7.24; PaCO₂ of 55 mm Hg; and an HCO₃- of 27 mEq/L.The acid-base status of this patient can be interpreted as:

A) uncompensated respiratory acidosis.
B) partially compensated respiratory acidosis.
C) partially compensated metabolic alkalosis.
D) partially compensated metabolic acidosis.

Question 62

A patient on continuous pulse oximetry is receiving supplemental oxygen.Her SpO₂ has been 93% ± 2% for the past 12 hours.The pulse oximeter suddenly emits an alarm and reads 78%.A rapid assessment reveals central and peripheral cyanosis and shortness of breath.Which of the following is the appropriate immediate action?

A) Take a stat arterial blood gas reading.
B) Recalibrate the pulse oximeter.
C) Change the pulse oximeter probe.
D) Decrease the supplemental oxygen.

Question 63

Which of the following techniques allows a pulse oximeter to determine the amount of hemoglobin in a blood sample?

A) Tonometry
B) Spectrophotometry
C) Fluorescent technology
D) Optical plethysmography

Question 64

Which of the following is the correct interpretation of the following arterial blood gas results taken from a patient receiving no supplemental oxygen: pH = 7.37; PaCO₂ = 55 mm Hg; PaO₂ = 53 mm Hg; SaO₂ = 88%; and HCO₃- = 31 mEq/L?

A) Compensated metabolic alkalosis with mild hypoxemia
B) Compensated respiratory acidosis with moderate hypoxemia
C) Partially compensated respiratory acidosis with mild hypoxemia
D) Partially compensated respiratory acidosis with severe hypoxemia

Question 65

Which of the following statements is true concerning the CO-oximeter measurement of a patient with a bilirubin level greater than 20 mg/dL in whole blood?

A) The O₂Hb value will be lower than the actual O₂Hb.
B) The O₂Hb value will be higher than the actual O₂Hb.
C) The HbCO value will be higher than the actual HbCO level.
D) The bilirubin level will not affect the results of the CO-oximeter.

Question 66

Which site will provide the most accurate pulse oximetry reading in the event of low peripheral perfusion?

A) Toe
B) Thumb
C) Earlobe
D) First digit

Question 67

Measurement of oxygen saturation by a pulse oximeter can be adversely affected by which of the following?
1)Hypobilirubinemia
2)Peripheral vasodilation
3)Hypothermia
4)Dapsone

A) 1 and 2
B) 2 and 3
C) 3 and 4
D) 1 and 4

Question 68

Which of the following are important blood tests to perform on a victim of a fire?
1)Na⁺
2)PaO₂
3)O₂Hb
4)HbCO
5)Glucose

A) 1 and 2
B) 3 and 5
C) 2,3,and 4
D) 1,3,and 4

Question 69

A patient is being treated with dapsone,an antibiotic,for P.carinii infection.Which of the following ways of measuring oxygen saturation would be most appropriate?

A) In vivo blood gas monitoring
B) In vitro blood gas monitoring
C) Pulse oximetry
D) CO-oximetry

Question 70

The oxygenation status of a burn victim is most appropriately measured by which of the following?

A) CO-oximeter
B) Pulse oximeter
C) In vitro blood gas analyzer
D) In vivo blood gas monitor

Question 71

The standard transcutaneous carbon dioxide electrode is which of the following?

A) Clark
B) Levy-Jennings
C) Spectrophotometer
D) Modified Stow-Severinghaus

Question 72

Optical shunting during pulse oximetry may be caused by which of the following?

A) Dark skin pigmentation
B) Light skin pigmentation
C) Hyperbilirubinemia
D) Hyponatremia

Question 73

What are the two principles of operation for pulse oximetry?
1)Photoplethysmography
2)Tonometry
3)Spectrophotometry
4)Amperometry
5)Potentiometry

A) 1 and 3
B) 2 and 4
C) 1 and 5
D) 3 and 5

Question 74

To produce capillary vasodilatation below the surface of a transcutaneous PO₂ electrode,which of the following should be done to the electrode?

A) Icing to 0° C
B) Heating to 44° C
C) Cooling to 25° C
D) Warming to 35° C

Question 75

Which of the following cause erroneous transcutaneous oxygen (PtcO₂)readings?
1)Hypovolemia
2)Hypothermia
3)Septic shock
4)Asthma

A) 1 and 3
B) 1 and 4
C) 1,2,and 3
D) 2,3,and 4

Question 76

Which of the following statements is true concerning the operation of a transcutaneous carbon dioxide electrode?

A) PtcCO₂ readings are slightly lower than the PaCO₂ value.
B) Electrodes should be calibrated when they are repositioned.
C) Heating the transcutaneous PCO₂ (PtcCO₂) to 43°C will adversely affect its operation.
D) Before its use, the electrode should be calibrated to 20% and 40% CO₂.

Question 77

Which of the following devices should be used for noninvasive monitoring of oxygen tension of a premature newborn?

A) In vivo PO₂
B) Pulse oximetry
C) Point-of-care PO₂
D) Transcutaneous PO₂

Question 78

During the calibration of a transcutaneous electrode,the signal is found to be drifting.Which of the following is the most appropriate action to take?

A) Move the electrode to another site.
B) Increase the temperature of the electrode.
C) Clean off the silver deposit on the cathode.
D) Change the electrolyte and the sensor membrane.

Question 79

Shining a red light with a wavelength of 660 nm on a blood sample will cause which of the following?

A) HHb will absorb less light than O₂Hb.
B) O₂Hb will absorb less light than HHb.
C) MetHb will absorb less light than O₂Hb.
D) Sulfhemoglobin will absorb more light than HHb.

Question 80

Fractional hemoglobin saturation is calculated from values measured by which of the following?

A) Pulse oximeter
B) CO-oximeter
C) Clark electrode
D) Severinghaus electrode