Chapter 10 - Blood Gas Monitoring

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.

A

Capillary blood gas samples should be used to measure which of the following? 1. Partial pressure of arterial carbon dioxide (PaCO2) 2. Partial pressure of arterial oxygen (PaO2) 3. pH 4. Hemoximetry oxygen saturation (SaO2) a. 1 and 3 b. 2 and 3 c. 1 and 4 d. 1 and 2

A

Excessive nasogastric suction will cause what type of acid-base disorder? a. Acute metabolic alkalosis b. Chronic respiratory acidosis c. Uncompensated metabolic acidosis d. Uncompensated respiratory alkalosis

A

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.

A

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

A

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

A

The PCO2 electrode uses which of the following? a. HCO3−solution b. Mercury bead c. KCl solution d. Silver anode

A

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.

A

What are the two principles of operation for pulse oximetry? 1. Photoplethysmography 2. Tonometry 3. Spectrophotometry 4. Amperometry a. 1 and 3 b. 2 and 4 c. 1 and 4 d. 2 and 3A

A

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

A

What is the correct interpretation of the following arterial blood gas values: pH 7.36; PaCO2 = 65 mm Hg; and HCO3− = 35 mEq/L? a. Chronic respiratory acidosis b. Chronic metabolic alkalosis c. Acute respiratory acidosis d. Acute metabolic acidosis

A

What is the correct interpretation of the following arterial blood gas values: pH of 7.38, PaCO2 of 38 mm Hg, and HCO3− of 23 mEq/L? a. Normal b. Respiratory alkalosis c. Respiratory acidosis d. Metabolic acidosis

A

What is the pH of the phosphate buffer solution in a Sanz electrode? a. 6.84 b. 7.00 c. 7.32 d. 7.90A

A

What organizations offer proficiency testing programs? 1. The American Association for Respiratory Care (AARC) 2. The American College of Chest Physicians (ACCP) 3. The College of American Pathologists (CAP) 4. The American Thoracic Society (ATS) a. 3 and 4 b. 1 and 2 c. 1 and 3 d. 2, 3, and 4

A

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

A

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

A

Which is the correct interpretation of the following arterial blood gas values: pH 7.26; PCO2 = 64 mm Hg; PO2 = 48 mm Hg; HCO3− = 26 mEq/L; and fractional inspired oxygen (FIO2) = 0.21? a. Acute respiratory acidosis with moderate hypoxemia b. Acute metabolic acidosis with severe hypoxemia c. Acute metabolic alkalosis with severe hypoxemia d. Compensated respiratory acidosis with moderate hypoxemia

A

Which is the correct order of steps to perform the modified Allen test? 1. Pressure is applied to both the radial and the 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

A

Which of the following are electrolytes? 1. PO2 at 50% saturation (P50) 2. Na+ 3. Ca++ 4. HCO3− a. 2 and 3 b. 1, 3, and 4 c. 2 and 4 d. 2, 3, and 4

A

Which of the following arterial blood gas results could be caused by severe diarrhea? a. pH 7.15; PaCO2 = 20 mm Hg; and HCO3− = 7.4 mEq/L b. pH 7.20; PaCO2 = 65 mm Hg; and HCO3− = 26 mEq/L c. pH 7.57; PaCO2 = 22 mm Hg; and HCO3− = 20 mEq/L d. pH 7.49; PaCO2 = 49 mm Hg; and HCO3− = 38 mEq/L

A

Which of the following can cause a respiratory acidosis? 1. Diabetes mellitus 2. Neuromuscular disorder 3. Overdose of opiates 4. Restrictive pulmonary disease a. 2, 3, and 4 b. 2 and 3 c. 1 and 4 d. 1, 2, and 4

A

Which of the following in vivo arterial blood gas values is comparable with in vitro measurements? a. pH b. PCO2 c. PO2 d. Bicarbonate

A

Which of the following plasma electrolyte levels are outside the normal range? 1. Total calcium 7.4 mEq/L 2. Potassium 4.2 mEq/L 3. Chloride 115 mEq/L 4. Sodium 155 mEq/L a. 1, 3, and 4 b. 3 and 4 c. 1 and 2 d. 2

A

Which of the following statements is true concerning capillary blood gases? a. They can be drawn from the heel. b. They correlate with arterial blood gases. c. They can be drawn from a peripheral artery. d. They require the performance of an Allen test.

A

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.

A

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

A

Which of the following will cause a left shift in the oxyhemoglobin dissociation curve? a. Methemoglobin b. Acute acidosis c. Increased temperature d. High 2,3-diphosphoglycerate (2,3-DPG)

A

Which of the following will decrease oxygen's affinity for hemoglobin? a. Increased CO2 b. Acute alkalosis c. Methemoglobin d. Hypothermia

A

You are performing quality control on a machine for your hospital and the trend below is produced. What is the likely cause? a. Protein buildup on an electrode b. A tear in the electrode c. An old electrode d. Loss of the electrolyte that bathes the electrode

A

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.

B

A CO-oximeter identifies the different types of hemoglobin through the use of a. fiberoptics. b. spectrophotometry. c. optical plethysmography. d. potentiometric measurements.

B

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 PO2 consumed by the oxygen electrode

B

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

B

Acid-base neutrality is expressed as which of the following? 1. pH 14 2. pH <7.0 3. pH 7.0 4. [H+] = [OH−] a. 1 b. 3 and 4 c. 2 and 3 d. 1 and 4

B

CO-oximeters routinely measure which of the following? 1. Carboxyhemoglobin 2. Fetal hemoglobin 3. Oxyhemoglobin 4. Methemoglobin a. 1 and 2 b. 1, 3, and 4 c. 3 and 4 d. 2 and 3

B

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

B

Normal plasma bicarbonate levels are _____ mmol/L. a. 15 to 25 b. 22 to 26 c. 30 to 40 d. 44 to 48

B

Placing blood gas samples in an ice bath serves to do which of the following? a. Keep the specimen cold. b. Slow down in vitro metabolism. c. Allow the red blood cells to remain intact. d. Prevent the white blood cells from destroying the red blood cells.

B

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.

B

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

B

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

B

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

B

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

B

What type of calibration should be performed after an electrode is changed? a. Quality control b. Three-point c. Two-point d. One-point

B

What type of electrode is used to measure calcium and sodium? a. Clark b. Ion-selective c. Polarographic d. Glucose-oxidase

B

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 MULTIPLE CHOICE a. 1 and 2 b. 2 and 3 c. 3 and 4 d. 1 and 4

B

Which of the following are true if a patient has a PaO2 of 155 mm Hg? 1. The patient has mild hypoxemia. 2. The patient has an overcorrected PaO2. 3. The patient is in need of supplemental oxygen. 4. The patient is receiving supplemental oxygen therapy. a. 1 and 3 b. 2 and 4 c. 1 and 4 d. 2 and 3

B

Which of the following can cause respiratory alkalosis? 1. Encephalitis 2. Diuretic therapy 3. Renal dysfunction 4. Excessive mechanical ventilatory support a. 2 and 3 b. 1 and 4 c. 1 and 3 d. 1, 2, and 4

B

Which of the following factors will cause analysis of blood gas samples to be erroneous? 1. Warming the blood prior to analyzing a sample 2. The presence of air bubbles in the sample 3. Icing the sample between obtaining and analyzing 4. Prolonged time delay between obtaining and analyzing a sample a. 1 and 3 b. 2, 3, and 4 c. 1, 2, and 4 d. 1 and 4

B

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

B

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.

B

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.

B

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.

B

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

B

Which size of needle should be used to draw arterial blood from an adult? a. 22 gauge b. 23 gauge c. 26 gauge d. 28 gauge

B

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

C

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

C

A standard pH electrode includes which of the following? a. Nylon spacer b. Silver anode c. Mercury bead d. Silicon elastic membrane

C

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

C

After arterial blood has been drawn from a patient, which of the following should be done to the blood? a. Transported at 37°C b. Processed after 5 minutes c. Transported in an ice bath d. Placed in the freezer until processed

C

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.

C

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

C

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

C

The gold standard for quality control for PCO2 and PO2 electrodes is a. capnography. b. polarography. c. tonometry. d. anometry.

C

The purpose of an Allen test is to check blood flow in the _____ artery. 1. ulnar 2. brachial 3. posterior tibial 4. lateral plantar a. 1 and 2 b. 2, 3, and 4 c. 1, 3, and 4 d. 3 and 4

C

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

C

The respiratory system compensates for metabolic problems by changing which of the following levels? a. H2O b. HCO3− c. CO2 d. HHb

C

When a negative Allen, 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

C

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 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

C

Which of the following are important blood tests to perform on a victim of a fire? 1. Na+ 2. PaO2 3. O2Hb 4. HbCO a. 1 and 2 b. 2 and 3 c. 2, 3, and 4 d. 1, 3, and 4

C

Which of the following can cause respiratory alkalosis? a. Vomiting b. Salicylate overdose c. Hyperventilation d. Pneumothorax

C

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

C

Which of the following could adversely affect the measurement of oxygen saturation? 1. Hypobilirubinemia 2. Peripheral vasodilation 3. Hypothermia 4. Methemoglobin a. 1 and 2 b. 2 and 3 c. 3 and 4 d. 1 and 4

C

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.

C

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

C

Which of the following variables can be calculated from measured arterial blood gas values? 1. P50 2. PCO2 3. HCO3− 4. SaO2 a. 1, 2, and 3 b. 2 and 4 c. 1, 3, and 4 d. 2 and 3

C

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

C

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−

C

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

C

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

C

A 60-year-old male patient is admitted to the medical unit with a bowel obstruction causing him to vomit frequently. What is the correct interpretation of the most recent arterial blood gas values for this patient: pH 7.51; PaCO2 = 43 mm Hg; and HCO3− = 34 mEq/L? a. Respiratory acidosis b. Metabolic acidosis c. Respiratory alkalosis d. Metabolic alkalosis

D

A patient has the following acid-base status: pH 7.26; PaCO2 = 70 mm Hg; and HCO3− = 31 mEq/L. Which of the following could be the cause of his arterial blood gas status? a. Diabetes mellitus b. Salicylate intoxication c. Excess antacid ingestion d. Acute airway obstruction

D

A patient is being treated with dapsone, an antibiotic, for P. jiroveci 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

D

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

D

Approximate the corresponding saturation for a PaO2 of 80 mm Hg under normal acid-base conditions by using the oxyhemoglobin dissociation curve in the figure. a. 80% b. 85% c. 90% d. 95%

D

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.

D

Erroneous PCO2 measurements can be caused by which of the following? 1. A worn electrode 2. A cracked electrode 3. Increased temperature of the patient 4. Dehydration of bicarbonate solution a. 1 and 2 b. 2 and 3 c. 3 and 4 d. 1, 2, and 4

D

How is the oxygenation status of a burn victim best measured? a. CO-oximeter b. Pulse oximeter c. In vitro blood gas analyzer d. In vivo blood gas monitor

D

In a 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

D

Renal failure will likely cause what acid-base disorder? a. Respiratory alkalosis b. Respiratory acidosis c. Metabolic alkalosis d. Metabolic acidosis

D

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

D

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.

D

The standard transcutaneous carbon dioxide electrode is which of the following? a. Clark b. Levy-Jennings c. Spectrophotometer d. Modified Stow-Severinghaus

D

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

D

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

D

Which is the correct interpretation of the following values: pH 7.36; PaCO2 = 22 mm Hg; and HCO3− = 12 mEq/L? a. Combined alkalosis b. Combined acidosis c. Compensated respiratory alkalosis d. Compensated metabolic acidosis

D

Which of the following are considered a buffer base? a. A metabolite solution b. An electrolyte-specific solution c. The solution used to perform a three-point calibration d. Hemoglobin, inorganic phosphate, and negatively charged proteins

D

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

D

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

D

Which of the following electrodes measures the PO2 in the blood? a. Sanz b. Severinghaus c. Pauling d. Clark

D

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

D