Question 1

While trying to use a finger probe to assess a patient's oxygenation status,the respiratory therapist finds that the pulse rate and the ECG monitor heart rate are not consistent and the oxygen saturation measured by pulse oximeter (S_pO₂)reading is blank.The patient is awake,alert,and in no obvious respiratory distress.The respiratory therapist should first take which of the following actions? 1)Change the probe site. 2)Draw an arterial blood gas. 3)Adjust the probe position on the finger. 4)Remove probe,perform a capillary refill test.

Accepted Answer

The fact that the patient is awake,alert,and in no respiratory distress decreases the likelihood that the problem is with the patient.Therefore,the first action in this case should not be to draw an arterial blood gas (ABG).In cases where the pulse oximeter cannot identify a pulsatile signal,the oxygen saturation measured by pulse oximeter (SpO₂)reading may not be present.This could be alleviated by adjusting the probe position on the finger.Absent SpO₂ readings could also be due to low perfusion states.Performing a capillary refill test on the finger being used for the probe would show whether or not the finger has adequate blood flow.If this is true,the next step would be to change the site.

Question 2

The respiratory therapist has just stopped postural drainage for a 24-year-old patient with cystic fibrosis because of shortness of breath and slight cyanosis in the "head-down" position.The respiratory therapist should recommend which of the following adjustments to therapy?

Accepted Answer

The presence of slight cyanosis and shortness of breath in the "head-down" position is indicative of hypoxemia.The respiratory therapist should administer supplemental oxygen via nasal cannula (possibly 1 to 2 L/min)and monitor the patient with a continuous pulse oximetry.Capnography is not useful in detecting hypoxemia.Using flat postural drainage positions where the head is not lower than the shoulders has not been proven to be effective.

Question 3

The area represented by the letter "Y" in the figure is which of the following?

Accepted Answer

The end-tidal carbon dioxide (EtCO₂)is represented by the very end of the wave form.The alveolar ventilation is represented by the area under the curve,which is "X." The alveolar dead space is represented by the difference between the arterial partial pressure of carbon dioxide (PaCO₂)and the EtCO₂ line,which is "Y." The airway dead space is represented by "Z."

Question 4

During which phase of a capnograph does alveolar gas containing carbon dioxide (CO₂)mix with gas from the anatomical airways and the CO₂ concentration rises?

Accepted Answer

In phase 1,the initial gas exhaled is from the conducting airways,which contain low levels of carbon dioxide (CO₂)from inspired air.During phase 2,alveolar gas containing CO₂ mixes with gas from the anatomical airways and the CO₂ concentration rises.In phase 3,the curve plateaus as alveolar gas is exhaled.In phase 4,the concentration falls to zero.

Question 5

Which of the following situations will cause an increase in the single breath carbon dioxide (CO₂)curve?

Accepted Answer

The same cause for an increase in arterial partial pressure of carbon dioxide (PaCO₂)will increase the single breath carbon dioxide curve (SBCO₂)curve.An increase in metabolic rate will increase the carbon dioxide (CO₂)production in the body.This accompanied by either no change in ventilation or a decrease in ventilation will cause the amount of CO₂ in the body to increase and thus cause the amount of CO₂exhaled to increase.The only combination that will do this is "D," increased metabolic rate and decreased ventilation.

Question 6

For a given minute ventilation,partial pressure of end-tidal carbon dioxide (PetCO₂)is a function of which of the following? 1)Metabolic rate 2)Cardiac output 3)Alveolar deadspace 4)Physiologic shunt

Accepted Answer

Changes in metabolic rate cause changes in partial pressure of end-tidal carbon dioxide (PetCO₂).For instance,fever and shivering increase the metabolism and increase the PetCO_2.A change in cardiac output will change PetCO₂ because the heart transports the blood that carries the carbon dioxide (CO₂)to the lungs for elimination.Increases in cardiac output will increase PetCO₂.A change in deadspace ventilation will also cause changes in the PetCO_2.Increasing deadspace will decrease the PetCO₂.

Question 7

The partial pressure of end-tidal carbon dioxide (PetCO₂)reading is taken at what point in the figure?

Accepted Answer

Point C shows the concentration of carbon dioxide (CO₂)at the end of the alveolar phase,just before inspiration begins.This occurs in phase 3 of the four phases of a capnogram.Point A depicts phase 1,which is the initial gas exhaled from the conducting airways.As a person exhales,the amount of CO₂in the exhaled gas increases.The amount of CO₂ exhaled levels off at point B.This coincides with phase 4 or the alveolar plateau.Point D is showing the fall in CO₂ that occurs during inspiration.

Question 8

The normal range for arterial-to-end-tidal partial pressure of carbon dioxide [P(a-et)CO₂] is which of the following?

Accepted Answer

The arterial-to-end-tidal partial pressure of carbon dioxide [P(a-et)CO₂] for tidal breathing should be approximately 4 to 6 mm Hg.

Question 9

A patient receiving mechanical ventilation is being continuously monitored for oxygen saturation measured by pulse oximeter (S_pO₂)for the last 48 hours.When initially applied,the S_pO₂ and the arterial oxygen saturation (S_aO₂),as well as the pulse on the pulse oximeter,ECG,and manual pulse,were consistent.During clinical rounds,the respiratory therapist notices that although the probe is appropriately placed and capillary refill is normal,the S_pO₂ reading is down to 90% from 95%.The most appropriate immediate action is to do which of the following?

Accepted Answer

The oxygen saturation measured by pulse oximeter (S_pO₂)has dropped from 95% to 90%.Since the SpO₂ and arterial oxygen saturation (SaO₂)previously correlated,this situation could mean that the patient is becoming hypoxemic.The probe is appropriately placed,so changing sites is not appropriate.The patient has already been checked for and has adequate circulation to the site of the probe,so moving the probe to a site with more perfusion is not appropriate.Therefore,the patient needs to have an arterial blood gas to ascertain the S_aO₂ and partial pressure of oxygen (P_aO₂).

Question 10

A patient arrives in the emergency department via ambulance following rescue from a house fire.The instrument that would be most appropriate to assist the respiratory therapist in assessing this patient's oxygenation status is which of the following?

Accepted Answer

Laboratory CO-oximeters measure four types of hemoglobin: oxyhemoglobin (O₂Hb),deoxygenated hemoglobin (HHb),carboxyhemoglobin (COHb),and methemoglobin (MetHb).This is beneficial for patients who are suffering from smoke inhalation.The CO-oximeter provides the actual O₂Hb and the COHb.Carbon monoxide produces an erroneously high oxygen saturation measured by pulse oximeter (SpO₂).Therefore,if smoke inhalation is suspected,a CO-oximeter should be used to evaluate the oxygen saturation.Capnography is the measurement of carbon dioxide concentrations in exhaled gases and is used to assess proper airway placement.Calorimetry allows the clinician to estimate energy expenditure from measurements of oxygen consumption ( 11ea68f7_d695_97a3_b0a4_c7e0d5b4c4bd_TB1877_11 O₂)and carbon dioxide production ( 11ea68f7_d695_97a4_b0a4_d38ed34edbc5_TB1877_11 CO₂).This measurement may be useful when weaning a patient from mechanical ventilation.

Question 11

A pulse oximeter differentiates oxyhemoglobin from deoxygenated hemoglobin by which of the following methods?

Accepted Answer

A pulse oximeter uses spectrophotometry to differentiate between oxyhemoglobin and deoxygenated hemoglobin.Two wavelengths of light (660 nm and 940 nm)are shined through a sample site.Oxyhemoglobin absorbs more light at 940 nm (infrared light [IR])than does deoxygenated hemoglobin.Deoxyhemoglobin absorbs more light at 660 nm.The use of cyclical changes in light transmission measured at the sampling site is the method to determine the pulse rate with a pulse oximeter.A heated polarographic electrode is used for transcutaneous partial pressure of oxygen (PtcO₂)measurements.A color sensing device is used to detect the amount of carbon dioxide in exhaled gas.

Question 12

Pulse oximetry is most useful in which of the following situations?

Accepted Answer

The oxygen status of a patient being considered for extubation needs to be assessed by an arterial blood gas,not by pulse oximetry,because not only does the patient's oxygen status need assessment,but the acid-base balance does as well.Pulse oximetry is not used as a basis for prescribing oxygen therapy in neonates.Neonatologists prefer to base oxygen therapy decisions on arterial partial pressure of oxygen (P_aO₂)rather than oxygen saturation.Pulse oximetry is useful for monitoring the oxygen status of patients undergoing chest physical therapy because it gives immediate results and is used for continuous monitoring.Pulse oximetry may not be as useful in prescribing oxygen therapy for home care patients.

Question 13

A patient in the intensive care unit is receiving mechanical ventilation,has a pulmonary artery catheter in place,and is being monitored continuously with a capnometer.The patient's arterial partial pressure of carbon dioxide (P_aCO₂)is 41 mm Hg and the partial pressure of end-tidal carbon dioxide (PetCO₂)is 36 mm Hg.There is a sudden decrease in the PetCO₂ to 18 mm Hg causing an alarm to sound.The most likely cause of this development is which of the following?

Accepted Answer

Pulmonary embolism will cause a decrease in blood flow to the lungs.This increases alveolar deadspace and leads to a decrease in the partial pressure of end-tidal carbon dioxide (PetCO₂).Hypovolemia would also cause a decrease in the PetCO₂,but it would not occur as suddenly as it did in this situation.The fact that the patient has an indwelling pulmonary artery catheter increases the risk of developing a pulmonary embolism,which often will have a quick onset.An apneic episode would have increased the PetCO₂.An increased cardiac output would increase the PetCO₂ because increases in cardiac output result in better perfusion of the alveoli and a rise in PetCO₂.

Question 14

A pulse oximeter reading will be most accurate when used with a patient in which of the following situations?

Accepted Answer

Hyperbilirubinemia does not appear to affect pulse oximetry measurements as do low perfusion states,which are caused by the use of peripheral vasoconstrictors or extracorporeal membrane oxygenation (ECMO).Carbon monoxide poisoning will lead to an overestimation of oxygen saturation measured by pulse oximeter (SpO₂).

Question 15

An arterial blood gas should be done to confirm pulse oximetry findings less than a minimum of _____________.

Accepted Answer

When a patient's oxygen saturation measured by pulse oximeter (SpO₂)is less than 80% an arterial blood gas should be drawn to confirm the patient's oxygenation status because a pulse oximeter is generally accurate for oxygen saturations greater than 80%.

Question 16

During shift report,the day shift respiratory therapist informs the night shift respiratory therapist about a freshly postoperative patient who is receiving full support via mechanical ventilation.At the time of the last patient-ventilator system check the patient had not awaken from anesthesia.During first rounds on the day shift the respiratory therapist notes the capnography shown in the figure.The most appropriate action to take would be to do which of the following?

Accepted Answer

The figure shows a patient whose capnography is demonstrating spontaneous respiratory efforts during mechanical ventilation.This corresponds to the patient waking up from anesthesia.With all else stable,the next step would be to begin the weaning process.

Question 17

The change in the single breath carbon dioxide (CO₂)curve from "A" to "B" shown in the figure may be as a result of which of the following?

Accepted Answer

The change in the figure shows an increase in phase 1 and a decrease in phase 2 of the single breath carbon dioxide curve (SBCO₂)curve.An increase in phase 1 may be caused by an increase in anatomical deadspace.This is possible as a result of increased airway obstruction or excessive positive-end-expiratory pressure (PEEP).Therefore,answers "B" and "D" cannot be correct.A decrease in phase 2 means there is a decrease in venous return or an increase in intrathoracic pressure.This could be caused by hypovolemia or an increased intrathoracic pressure as seen with increased mean airway pressures.Therefore,answer "A" cannot be correct.Answer "C" is a measure of increased intrathoracic pressure and is the correct answer.

Question 18

The capnogram in the figure is indicative of which of the following conditions?

Accepted Answer

Phase 3 becomes indistinguishable when physiological dead space increases,as in chronic obstructive pulmonary disease (COPD),and causes the capnogram to appear as it does in the figure.A cardiac arrest would lower the graph line to zero.Hyperventilation will decrease the alveolar plateau,but its shape would remain the same as a normal capnogram.A pulmonary embolism would also cause a drop in the alveolar plateau.

Question 19

During which phase of a capnogram does inhalation occur?

Accepted Answer

During inhalation the capnogram will have a zero reading because there is no exhalation of carbon dioxide (CO₂).As soon as the exhalation phase begins there is rise of the wave form.In phase 1,the initial gas exhaled is from the conducting airways,which contain low levels of CO₂ from inspired air.During phase 2,alveolar gas containing CO₂ mixes with gas from the anatomical airways and the CO₂ concentration rises.In phase 3,the curve plateaus as alveolar gas is exhaled.In phase 4,the concentration falls to zero because inspiration is occurring.

Question 20

The area under the curve of a single breath carbon dioxide curve (SBCO₂)represents which of the following?

Accepted Answer

The area under the single breath carbon dioxide curve (SBCO₂)curve represents alveolar volume.This is known as phase 3 on the SBCO₂ curve.Phase 1 is the anatomic deadspace volume.Phase 2 is a transitional phase between anatomic deadspace and alveolar volume.

Quiz 10: Assessment of Respiratory Function

The respiratory therapist has just stopped postural drainage for a 24-year-old patient with cystic fibrosis because of shortness of breath and slight cyanosis in the "head-down" position.The respiratory therapist should recommend which of the following adjustments to therapy?

The area represented by the letter "Y" in the figure is which of the following?

During which phase of a capnograph does alveolar gas containing carbon dioxide (CO₂) mix with gas from the anatomical airways and the CO₂ concentration rises?

Which of the following situations will cause an increase in the single breath carbon dioxide (CO₂) curve?

For a given minute ventilation,partial pressure of end-tidal carbon dioxide (PetCO₂) is a function of which of the following? 1) Metabolic rate 2) Cardiac output 3) Alveolar deadspace 4) Physiologic shunt

The partial pressure of end-tidal carbon dioxide (PetCO₂) reading is taken at what point in the figure?

The normal range for arterial-to-end-tidal partial pressure of carbon dioxide [P(a-et) CO₂] is which of the following?

A patient arrives in the emergency department via ambulance following rescue from a house fire.The instrument that would be most appropriate to assist the respiratory therapist in assessing this patient's oxygenation status is which of the following?

A pulse oximeter differentiates oxyhemoglobin from deoxygenated hemoglobin by which of the following methods?

Pulse oximetry is most useful in which of the following situations?

A pulse oximeter reading will be most accurate when used with a patient in which of the following situations?

An arterial blood gas should be done to confirm pulse oximetry findings less than a minimum of _____________.

The change in the single breath carbon dioxide (CO₂) curve from "A" to "B" shown in the figure may be as a result of which of the following?

The capnogram in the figure is indicative of which of the following conditions?

During which phase of a capnogram does inhalation occur?

The area under the curve of a single breath carbon dioxide curve (SBCO₂) represents which of the following?

Quiz 10: Assessment of Respiratory Function

The respiratory therapist has just stopped postural drainage for a 24-year-old patient with cystic fibrosis because of shortness of breath and slight cyanosis in the "head-down" position.The respiratory therapist should recommend which of the following adjustments to therapy?

The area represented by the letter "Y" in the figure is which of the following?

During which phase of a capnograph does alveolar gas containing carbon dioxide (CO2) mix with gas from the anatomical airways and the CO2 concentration rises?

Which of the following situations will cause an increase in the single breath carbon dioxide (CO2) curve?

For a given minute ventilation,partial pressure of end-tidal carbon dioxide (PetCO2) is a function of which of the following? 1) Metabolic rate 2) Cardiac output 3) Alveolar deadspace 4) Physiologic shunt

The partial pressure of end-tidal carbon dioxide (PetCO2) reading is taken at what point in the figure?

The normal range for arterial-to-end-tidal partial pressure of carbon dioxide [P(a-et) CO2] is which of the following?

A patient arrives in the emergency department via ambulance following rescue from a house fire.The instrument that would be most appropriate to assist the respiratory therapist in assessing this patient's oxygenation status is which of the following?

A pulse oximeter differentiates oxyhemoglobin from deoxygenated hemoglobin by which of the following methods?

Pulse oximetry is most useful in which of the following situations?

A pulse oximeter reading will be most accurate when used with a patient in which of the following situations?

An arterial blood gas should be done to confirm pulse oximetry findings less than a minimum of _____________.

The change in the single breath carbon dioxide (CO2) curve from "A" to "B" shown in the figure may be as a result of which of the following?

The capnogram in the figure is indicative of which of the following conditions?

During which phase of a capnogram does inhalation occur?

The area under the curve of a single breath carbon dioxide curve (SBCO2) represents which of the following?

During which phase of a capnograph does alveolar gas containing carbon dioxide (CO₂) mix with gas from the anatomical airways and the CO₂ concentration rises?

Which of the following situations will cause an increase in the single breath carbon dioxide (CO₂) curve?

For a given minute ventilation,partial pressure of end-tidal carbon dioxide (PetCO₂) is a function of which of the following? 1) Metabolic rate 2) Cardiac output 3) Alveolar deadspace 4) Physiologic shunt

The partial pressure of end-tidal carbon dioxide (PetCO₂) reading is taken at what point in the figure?

The normal range for arterial-to-end-tidal partial pressure of carbon dioxide [P(a-et) CO₂] is which of the following?

The change in the single breath carbon dioxide (CO₂) curve from "A" to "B" shown in the figure may be as a result of which of the following?

The area under the curve of a single breath carbon dioxide curve (SBCO₂) represents which of the following?