Question 1

During a single-breath capnogram, the sharp downstroke and return to baseline that normally occurs after the end-tidal point indicates what?
A) Exhalation of mainly dead space gas
B) Inspiration of fresh respiratory gas
C) Exhalation of mixed alveolar and dead space gas
D) Exhalation of mainly alveolar gas

Accepted Answer

The sharp downstroke and return to baseline that normally occurs after the end-tidal point indicates inhalation of fresh gas with 0 CO₂.

Question 2

What is a normal end-tidal PETCO₂ range? A) 30 to 38 mm Hg B) 35 to 43 mm Hg C) 38 to 46 mm Hg D) 42 to 50 mm Hg

Accepted Answer

In healthy individuals, the PETCO₂ averages 1 to 5 mm Hg less than the PaCO₂, or between 35 and 43 mm Hg (approximately 5% to 6% CO₂).

Question 3

At the very beginning of exhalation, the PETCO₂ normally should be at what level? A) 0 mm Hg B) 15 mm Hg C) 25 mm Hg D) 40 mm Hg

Accepted Answer

Initially, the expired PCO₂ is 0 mm Hg, indicating exhalation of pure dead space gas.

Question 4

The shape of the expired CO₂ tracing of a patient is normal but instead of being zero, the baseline is elevated to approximately 12 mm Hg. Which of the following is the most likely problem? A) Patient disconnected from the system B) Obstruction of the sampling tube C) Rebreathing D) Presence of N₂O

Accepted Answer

An elevated baseline (higher than 0 mm Hg) indicates rebreathing.

Question 5

Which of the following are indications for capnography?
1) Evaluating the response to therapies affecting ventilation/perfusion ratio (  ) relationships
2) Determining the position of an artificial airway (trachea vs. esophagus)
3) Assessing a patient's readiness for weaning from ventilatory support
4) Monitoring the integrity of the ventilatory circuit and artificial airway
A)1 and 3 only
B)2, 3, and 4 only
C)1, 2, and 4 only
D)1, 2, 3, and 4

Accepted Answer

The answer of Which of the following are indications for...

Question 6

You obtain an SpO₂ reading of 90% using an oximeter with an approximate accuracy of 5%. This could indicate a PO₂ as low as what level? A) 55 mm Hg B) 60 mm Hg C) 65 mm Hg D) 70 mm Hg

Accepted Answer

However, with the accuracy of some oximeters being only ±4%, an SpO₂ reading of 90% could mean an actual SaO₂ reading as low as 86%, corresponding to a PO₂ level of 55 mm Hg or less!

Question 7

What is the most common source of error and false alarms with pulse oximetry?
A) Presence of HbCO
B) Patient motion artifact
C) Presence of vascular dyes
D) Ambient light detection

Accepted Answer

Patient motion artifact probably is the most common source of error and false alarms.

Question 8

During a single-breath capnogram, what does the occurrence of a plateau indicate?
A) Exhalation of mainly dead space gas
B) Inspiration of fresh respiratory gas
C) Exhalation of mixed alveolar and dead space gas
D) Exhalation of mainly alveolar gas

Accepted Answer

This plateau indicates exhalation of gas coming mainly from ventilated alveoli.

Question 9

A patient being monitored by capnography exhibits a sudden rise in end-tidal CO₂ levels. Which of the following are possible causes? 1) Sudden release of a tourniquet 2) Massive pulmonary embolism 3) Sudden increase in cardiac output 4) Injection of NaHCO₃ A)2 and 3 only B)1, 3, and 4 only C)2, 3, and 4 only D)1, 2, 3, and 4

Accepted Answer

A sudden rise in end-tidal CO2 can be caused by the release of a tourniquet (1), which allows CO2-rich blood to circulate, an increase in cardiac output (3), which enhances CO2 delivery to the lungs, and the injection of NaHCO3 (4), which can increase CO2 production. A massive pulmonary embolism (2) would typically decrease end-tidal CO2 due to impaired blood flow to the lungs.

Question 10

What is the measurement of CO₂ in respiratory gases called? A) Oximetry B) Capnometry C) Optometry D) Barometry

Accepted Answer

Capnometry is the measurement of CO₂ in respiratory gases.

Question 11

You obtain an SpO₂ reading of 100% on a patient receiving O₂ through a nonrebreathing mask. What range of PaO₂ levels is possible in this patient? A) 60 to 90 mm Hg B) 90 to 100 mm Hg C) 100 to 200 mm Hg D) 100 to 600 mm Hg

Accepted Answer

At the high end, oximetry data can be even less meaningful. Because of the characteristics of the oxyhemoglobin dissociation curve (see Chapter 11), a patient with an SpO₂ reading of 100% could represent a PaO₂ level anywhere between 100 and 600 mm Hg.

Question 12

What is the normal gradient between PaCO₂ and PETCO₂? A) 3 to 5 mm Hg B) 5 to 10 mm Hg C) 10 to 15 mm Hg D) 15 to 20 mm Hg

Accepted Answer

In healthy individuals, the PETCO₂ averages 3 to 5 mm Hg less than the PaCO₂, or between 35 and 43 mm Hg (approximately 5% to 6% CO₂).

Question 13

During capnography monitoring of a mechanically ventilated patient, you note that the PETCO₂ has dropped to 0 mm Hg. Which of the following is the most likely problem? A) Ventilator disconnection B) Tracheal intubation C) Increased cardiac output D) Hypoventilation

Accepted Answer

A drop in PETCO2 to 0 mm Hg indicates a problem with the delivery of carbon dioxide to the patient's airway. A ventilator disconnection is the most likely cause, as the patient is no longer receiving mechanical ventilation.

Question 14

Which of the following can cause false high readings when using a pulse oximeter?
A) Fetal hemoglobin
B) Intravascular dyes
C) Carboxyhemoglobin
D) Presence of metHb

Accepted Answer

Carboxyhemoglobin can cause false high readings on a pulse oximeter because it absorbs light at similar wavelengths as oxyhemoglobin, leading the device to overestimate oxygen saturation levels.

Question 15

What is the most common technique used to measure CO₂ in respiratory gases? A) Infrared absorption B) Mass spectroscopy C) Photoacoustics D) Raman scattering

Accepted Answer

The infrared capnometer is the most common.

Quiz 19: Analysis and Monitoring of Gas Exchange

During a single-breath capnogram, the sharp downstroke and return to baseline that normally occurs after the end-tidal point indicates what?

What is a normal end-tidal PETCO2 range?

At the very beginning of exhalation, the PETCO2 normally should be at what level?

The shape of the expired CO2 tracing of a patient is normal but instead of being zero, the baseline is elevated to approximately 12 mm Hg. Which of the following is the most likely problem?

You obtain an SpO2 reading of 90% using an oximeter with an approximate accuracy of 5%. This could indicate a PO2 as low as what level?

What is the most common source of error and false alarms with pulse oximetry?

During a single-breath capnogram, what does the occurrence of a plateau indicate?

A patient being monitored by capnography exhibits a sudden rise in end-tidal CO2 levels. Which of the following are possible causes? 1) Sudden release of a tourniquet 2) Massive pulmonary embolism 3) Sudden increase in cardiac output 4) Injection of NaHCO3

What is the measurement of CO2 in respiratory gases called?

You obtain an SpO2 reading of 100% on a patient receiving O2 through a nonrebreathing mask. What range of PaO2 levels is possible in this patient?

What is the normal gradient between PaCO2 and PETCO2?

During capnography monitoring of a mechanically ventilated patient, you note that the PETCO2 has dropped to 0 mm Hg. Which of the following is the most likely problem?

Which of the following can cause false high readings when using a pulse oximeter?

What is the most common technique used to measure CO2 in respiratory gases?

What is a normal end-tidal PETCO₂ range?

At the very beginning of exhalation, the PETCO₂ normally should be at what level?

The shape of the expired CO₂ tracing of a patient is normal but instead of being zero, the baseline is elevated to approximately 12 mm Hg. Which of the following is the most likely problem?

You obtain an SpO₂ reading of 90% using an oximeter with an approximate accuracy of 5%. This could indicate a PO₂ as low as what level?

A patient being monitored by capnography exhibits a sudden rise in end-tidal CO₂ levels. Which of the following are possible causes? 1) Sudden release of a tourniquet 2) Massive pulmonary embolism 3) Sudden increase in cardiac output 4) Injection of NaHCO₃

What is the measurement of CO₂ in respiratory gases called?

You obtain an SpO₂ reading of 100% on a patient receiving O₂ through a nonrebreathing mask. What range of PaO₂ levels is possible in this patient?

What is the normal gradient between PaCO₂ and PETCO₂?

During capnography monitoring of a mechanically ventilated patient, you note that the PETCO₂ has dropped to 0 mm Hg. Which of the following is the most likely problem?

What is the most common technique used to measure CO₂ in respiratory gases?