Ch. 20 Test, Weaning

Question 1

All of the following patients are intubated and receiving mechanical ventilation. The patient most likely to require slow liberation from mechanical ventilation is which of the following?

a. A patient who overdosed on diazepam
b. A postoperative patient who had knee surgery
c. A patient with a severe exacerbation of asthma
d. A patient with chest contusions from an accident

Answer 1

ANS: D
A large percentage of patients who need temporary mechanical ventilation do not require a gradual withdrawal process. Such patients include those receiving postoperative ventilatory support for recovery from anesthesia, treatment of uncomplicated drug overdose, and exacerbation of asthma. The patient with chest contusions from an accident has a higher risk of developing problems that will require a more gradual weaning process.

DIF: 2 REF: p. 403

Question 2

A patient is being weaned from invasive mechanical ventilation using VC-SIMV without pressure support. The respiratory therapist reviews the following data from the last few hours.

Time	SetVT Spon VT Set Rate SponRate
0630	650	  410	    8	          6
1020	650	  400	    6	          10
1600	650	  320	    4	          20
2200	650	  250	    2	          32

What should the respiratory therapist recommend for this patient?

a. Switch the mode to VC-CMV.
b. Add and titrate pressure support.
c. Extubate and place the patient on NPPV.
d. Increase the set rate to 8 breaths/min.

Answer 2

ANS: B
The data demonstrate that as the set SIMV was decreased, the patient’s spontaneous respiratory rate increased and the spontaneous tidal volume decreased. This shows that the patient’s work of breathing is excessive and most likely due to the resistance from the ventilator system, circuit, and artificial airway. Initiate pressure support and titrate the level to improve the spontaneous volume and decrease the spontaneous rate. Once the patient is stable, the pressure support may be weaned.

DIF: 3 REF: p. 404, 405

Question 3

What ends inspiration in pressure support ventilation?

a. Time
b. Flow
c. Volume
d. Pressure

Answer 3

ANS: B
Each pressure support breath is flow cycled.

DIF: 1 REF: p. 405

Question 4

At what pressure is pressure support not high enough to contribute significantly to ventilatory support but is sufficient to overcome the work imposed by the ventilator system?

a. 2 cm H2O
b. 5 cm H2O
c. 8 cm H2O
d. 10 cm H2O

Answer 4

ANS: B
When pressure support is reduced to about 5 cm H2O, the pressure level is not high enough to contribute significantly to ventilatory support. However, this level of support usually is sufficient to overcome the work imposed by the ventilator system (i.e., the resistance of the ET tube, trigger sensitivity, demand-flow capabilities, and the type of humidifier used).

DIF: 1 REF: p. 405

Question 5

Which mode of ventilation delivers the exact amount of pressure required to overcome the resistive load imposed by the ET tube for the flow measured at the time?

a. Automode
b. Volume-targeted PSV
c. Pressure support ventilation
d. Automatic tube compensation

Answer 5

ANS: D
ATC reduces the work of breathing associated with increased ET tube resistance. ATC is designed to deliver exactly the amount of pressure required to overcome the resistive load imposed by the ET tube for the flow measured at the time. In a sense, this is providing variable PSV with variable inspiratory flow compensation. Volume-targeted PSV maintains a target volume by varying the pressure support level. PSV provides an operator-selected set pressure for every spontaneous breath. The automode can switch between time-triggered mandatory breaths and patient-triggered, volume-targeted, pressure-limited breaths as long as the patient is breathing spontaneously.

DIF: 1 REF: p.406

Question 6

The mode of ventilation that maintains a minimum VE by increasing or decreasing the amount of support (VT or respiratory rate) given to the patient is ___________________.

a. volume support
b. automatic tube compensation
c. mandatory minute ventilation
d. adaptive support ventilation

Answer 6

ANS: C
In MMV the ventilator automatically increases the level of support if the patient’s spontaneous ventilation decreases, thus maintaining a consistent minimum VE. Patients who regain the ability to breathe spontaneously can increase their own VE, and the machine automatically lowers support without the clinician having to change any specific ventilator settings.

DIF: 1 REF: p. 408

Question 7

The closed loop mode used for weaning from mechanical ventilation is which of the following?

a. Pressure support ventilation
b. Adaptive support ventilation
c. Continuous positive airway pressure
d. Intermittent mandatory ventilation

Answer 7

ANS: B
ASV is a patient-centered method of closed loop mechanical ventilation that increases or decreases ventilatory support based on monitored patient parameters.

DIF: 1 REF: p. 408

Question 8

A postoperative patient, still under anesthesia, is being ventilated with VC-CMV with Automode. After 2 hours the patient is waking up and beginning to breathe spontaneously. The ventilator will respond by _____________________.

a. switching to the pressure support mode.
b. switching to the volume support mode.
c. delivering time-triggered, pressure-limited breaths.
d. ensuring minimum mandatory minute ventilation.

Answer 8

ANS: B
If a postoperative patient is still recovering from the effects of anesthesia and the ventilator operator has selected volume-controlled continuous mandatory ventilation (VC-CMV) with Automode as the operating mode, all breaths are mandatory (time triggered, volume limited, and time cycled). If the patient begins to trigger breaths, the ventilator switches to VS (patient triggered, pressure limited, and flow cycled with a volume target) and remains in this mode as long as the patient is breathing spontaneously.

DIF: 1 REF: p. 407, 408

Question 9

The ACCP/SCCM/AARC task force recommends that a search for all possible causes that may be contributing to ventilator dependence be undertaken in patients who require mechanical ventilation for longer than ______ hours.

a. 12
b. 24
c. 48
d. 72

Answer 9

ANS: B
This is the first recommendation for weaning a patient from mechanical ventilation established by the ACCP/SCCM/AARC task force.

DIF: 1 REF: p. 409

Question 10

Assess the following data obtained from the spontaneous breathing trials of four patients. Which patient is most likely to be weaned successfully at this time?

a. Spontaneous rate = 32 breaths/min, VT = 375 mL, PaO2 = 98 mm Hg, FIO2 = 0.4
b. Spontaneous rate = 15 breaths/min, VT = 450 mL, PaO2 = 87 mm Hg, FIO2 = 0.6
c. Spontaneous rate = 15 breaths/min, VT = 650 mL, PaO2 = 91 mm Hg, FIO2 = 0.28
d. Spontaneous rate = 12 breaths/min, VT = 680 mL, PaO2 = 79 mm Hg, FIO2 = 0.5

Answer 10

ANS: C
Calculate the f/VT and PaO2/FIO2 for each patient. The patient with acceptable criteria has an f/VT of 23 and a PaO2/FIO2 of 325.

DIF: 2 REF: p. 409-413, Table 20-1

Question 11

A 46-year-old male patient (IBW = 85 kg) who was injured in a motor vehicle accident has been receiving invasive mechanical ventilation for 24 hours. The patient is awake and alert and looks comfortable on these settings: VC-SIMV with pressure support of 5 cm H2O; set rate = 8 breaths/min; set VT = 500 mL; FIO2 = 0.4; PEEP = 5 cm H2O. A 10-minute spontaneous breathing trial (SBT) yields this information: f = 30 breaths/min, RSBI = 145, P0.1 = 10 cm H2O. What should the respiratory therapist suggest to the physician during patient rounds?

a. Sedate the patient and place him on VC-CMV.
b. Continue with the current ventilator settings.
c. Switch to PC-CMV with a rate of 14 breaths/min.
d. Decrease the mandatory SIMV rate to 4 breaths/min.

Answer 11

ANS: B
The RSBI is at a level that suggests the patient is not ready for weaning. An RSBI below 105 suggests that weaning is likely to be successful. The P0.1 is a measurement of the drive to breathe. The patient achieved 10 cm H2O, which indicates a high drive to breathe and suggests that weaning from mechanical ventilation is not likely to succeed. This information is a strong indicator that the patient should not begin active weaning at this time and should be continued on the original settings, because the patient was comfortable on those settings.

DIF: 3 REF: p. 409-413

Question 12

Calculate and determine the weanability of patients with this data: CD = 25 mL/cm H2O, PImax = -28 cm H2O, PaO2 = 93 mm Hg, PAO2 = 158 mm Hg, and f = 22 breaths/min.

a. 2—not weanable
b. 19—weanable
c. 32—not weanable
d. 54—weanable

Answer 12

ANS: B
Use the CROP formula: CROP  (CD PImax  [PaO2/PAO2])/f.

DIF: 2 REF: p. 413

Question 13

Which parameter is used as the primary index of the drive to breathe?

a. Airway occlusion pressure
b. CROP index
c. Maximum inspiratory pressure
d. Rapid shallow breathing index

Answer 13

ANS: A
The inspiratory drive to breathe is established by measuring the airway occlusion pressure (P0.1 [or P100]).

DIF: 1 REF: p. 412

Question 14

An SBT should not continue for longer than _____ minutes.

a. 30
b. 60
c. 120
d. 180

Answer 14

ANS: C
SBTs typically last at least 30 minutes but no longer than 120 minutes.

DIF: 1 REF: p. 413

Question 15

In which patient would continued use of an artificial airway be necessary?

a. A patient with upper airway burns and no peritubular leak
b. A patient who tests positive for a peritubular leak
c. A patient with bronchospasm and supplemental oxygen requirements
d. A patient with a strong cough who expectorates moderate amounts of sputum

Answer 15

ANS: A
A patient with upper airway burns may have upper airway inflammation that could obstruct the upper airways. The fact that the patient does not have a peritubular leak means that the airway caliber is not adequate. Extubation of this patient at this time would not be successful.

DIF: 2 REF: p. 414

Question 16

A recently extubated patient develops a partial upper airway obstruction, which causes stridor. What action can the respiratory therapist take to improve the patient’s condition?

a. Aerosolize 11.25 mg of racemic epinephrine.
b. Put a nonrebreathing mask on the patient.
c. Place the patient on NPPV.
d. Suggest the use of lorazepam (Ativan).

Answer 16

ANS: C
This patient has developed postextubation glottic edema and should be treated immediately with aerosolized racemic epinephrine. The patient also could be given steroids. A nonrebreathing mask would not address the upper airway obstruction unless the mask is powered by heliox. This would allow time for the medical treatment to take effect. Use of an antianxiety drug is not indicated in this situation, because it would decrease the patient’s drive to breathe. Putting the patient on NPPV would not address the patient’s immediate problem.

DIF: 3 REF: p. 414, 415

Question 17

A female intubated patient has been weaned from full ventilatory support to PSV 5 cm H2O, CPAP 5 cm H2O, and an FIO2 of 0.3. The patient is alert and oriented and doing well. The respiratory therapist performs a cuff leak test. The average peritubular leak is 70 mL. The respiratory therapist should recommend which of the following?

a. Maintain the patient on the current settings and redo the cuff leak test in 24 hours.
b. Increase the PSV to 10 cm H2O and maintain the CPAP and FIO2.
c. Extubate the patient and place her on a heated aerosol generator with an FIO2 of 0.4.
d. Pretreat the patient with steroids and/or racemic epinephrine before extubation.

Answer 17

ANS: D
This patient is at high risk for developing stridor after extubation. Pretreatment with either racemic epinephrine and/or steroids would help reduce this risk. No change in ventilator parameters is called for in this situation. Extubating the patient and putting her on a heated aerosol would increase the risk of upper airway inflammation because of the heat. Waiting 24 hours when the patient is ready for extubation increases the patient’s risk of ventilator-acquired pneumonia.

DIF: 3 REF: p. 414

Question 18

A patient is extubated and placed on a cool, bland aerosol with 30% oxygen. Twenty minutes postextubation, the respiratory therapist is called to assess the patient, who has shortness of breath. The respiratory therapist observes intercostal retractions, accessory muscle use, and a respiratory rate of 38 breaths/min. Stridor can be heard without a stethoscope, and the SpO2 has dropped from 97% to 85%. The patient is given an aerosolized racemic epinephrine treatment and reassessed. Accessory muscle use continues, intercostal retractions decrease slightly, and stridor is heard on auscultation. The patient’s respiratory rate is 30 breaths/min, and the SpO2 is 88%. What should the respiratory therapist recommend?

a. Reintubation and mechanical ventilation
b. Heliox therapy and steroid administration
c. Increase the FIO2 on the cool bland aerosol to 40%
d. Use a nonrebreather mask with 15 L/min oxygen

Answer 18

ANS: B
The racemic epinephrine treatment improved the patient’s clinical status, as evidenced by a decrease in intercostal retractions, decrease in respiratory rate, and increase in SpO2. The patient’s stridor now is heard only on auscultation, whereas it was audible without a stethoscope before the racemic epinephrine. Heliox therapy would reduce the patient’s WOB further and allow time for the steroids to take effect. Because the patient improved, reintubation would only increase the risk of nosocomial pneumonia and is not warranted at this time. Increasing the FIO2 may help improve the patient’s SpO2, but it does not address the patient’s upper airway obstruction. A nonrebreather mask with 15 L/min oxygen would not help relieve the patient’s upper airway obstruction.

DIF: 3 REF: p. 414, 415

Question 19

If a patient who has failed an SBT still meets the criteria for discontinuation of ventilation, an SBT should be performed every _______ hours to determine weanability.

a. 6
b. 12
c. 24
d. 36

Answer 19

ANS: C
If after failing an SBT the patient still meets the criteria for discontinuation of ventilation, another SBT should be performed every 24 hours. It is important to wait 24 hours before attempting another trial. Frequent SBTs over a single day are not helpful and can have serious consequences. Testing more frequently than every 24 hours offers no advantages.

DIF: 1 REF: p. 417

Question 20

Sixty minutes after a patient is extubated, an arterial blood gas sample is drawn; the results are: pH = 7.20, PaCO2 = 60 mm Hg, PaO2 = 55 mm Hg, SaO2 = 80%, HCO3- = 23 mEq/L with a 2 L/min nasal cannula. The patient is SOB and complaining of chest pain. His blood pressure is 92/50 mm Hg. The most likely cause of this weaning failure is which of the following?

a. Chronic obstructive pulmonary disease
b. Acute left ventricular failure
c. Ventilatory muscle weakness
d. Hypophosphatemia

Answer 20

ANS: B
Patients who do well for 30 to 60 minutes after extubation and then fail weaning because of acute respiratory acidosis, hypoxemia, hypotension, and chest pain are likely to have acute left ventricular failure. This occurs because of increased preload, which is due to the decreased pulmonary capillary compression that occurs when intrathoracic pressure is reduced as a result of being off the ventilator.
DIF: 2 REF: p. 417-419

Question 21

How long does a tracheostomy site typically take to mature?

a. 2 to 4 days
b. 4 to 6 days
c. 7 to 12 days
d. 10 to 15 days

Answer 21

ANS: C
A tracheostomy site typically requires 7 to 10 days to mature.

DIF: 1 REF: p. 422

Question 22

A patient who requires prolonged ventilatory support should not be considered permanently ventilator dependent until ________ month(s) has/have passed and all weaning attempts during that time have failed.

a. 1
b. 3
c. 6
d. 9

Answer 22

ANS: B
Unless evidence of irreversible disease exists, a patient who requires prolonged ventilatory support should not be considered permanently ventilator dependent until 3 months have passed and all weaning attempts during that time have failed.

DIF: 1 REF: p. 422

Question 23

A patient being actively weaned from mechanical ventilation currently is receiving the following ventilatory support: pressure support = 15 cm H2O, spontaneous VT = 575 mL, spontaneous rate = 14 breaths/min, spontaneous VT = 500 mL, FIO2 = 35%, PEEP = 5 cm H2O. The arterial blood gas results are: pH = 7.42, PaCO2 = 38 mm Hg, PaO2 = 94 mm Hg, SaO2 = 98%, HCO3- = 24 mEq/L. What should the respiratory therapist do next?

a. Reduce PEEP to zero.
b. Reduce the FIO2 to 30%.
c. Reduce the PS to 10 cm H2O.
d. Extubate the patient.

Answer 23

ANS: C
At this point the ABG results show no acid-base imbalance and no hypoxemia. The parameter that should be reduced is the pressure support. When pressure support is reduced to about 5 cm H2O, the pressure level is not high enough to contribute significantly to ventilatory support. Once at PS 5 mc H2O, the patient will be ready for a cuff leak test.

DIF: 3 REF: p. 405

Question 24

Which of the following would suggest that a patient is ready to be weaned from a ventilator?

a. Vital capacity (VC) of 8 mL/kg ideal body weight (IBW)
b. PaO2 or 65 mm Hg on and FIO2 of 0.6
c. Dead space-to-tidal volume ratio (VD/VT) of 0.75
d. Rapid shallow breathing index of 75 breaths/min/L

Answer 24

ANS: D
The RSBI is the most frequently studied and one of the more reliable tests for determining a patient’s weaning status. It is calculated by dividing the respiratory frequency (in breaths/min) by the VT (in L): f/VT. This measurement is taken 1 minute after disconnecting the spontaneously breathing patient from the ventilator and oxygen. Successful weaning is more likely if the RSBI is less than 105 (normal range, 60-105). Values above 105 suggest that a patient is not ready for weaning and probably will fail a weaning trial.

Question 25

A patient in the ICU who has successfully completed a 120-minute SBT requires extubation. Which of the following tests or values would indicate the potential for airway edema after extubation?

a. PImax
b. VC
c. Cuff leak test
d. Oxygen saturation measured by pulse oximeter (SpO2)

Answer 25

ANS: C
The cuff leak test is a means of testing for post-extubation airway patency. Note that to qualify for this test, the patient must no longer need ventilatory support. To perform this test, the patient is disconnected from the ventilator, the cuff is deflated, and the ET or tracheostomy tube is obstructed. A leak around the cuff (peritubular leak) during spontaneous breathing suggests that the airway caliber is adequate and successful extubation is likely. A leak of less than 110 mL (average of three values on six consecutive breaths) indicates a high risk of post-extubation stridor. Treatment with steroids or racemic epinephrine (or both) before extubation may be indicated.

Question 26

A patient with amyotrophic lateral sclerosis has a tracheostomy tube in place. He has been unable to perform an SBT successfully and has been receiving mechanical ventilation for 4 months. An appropriate recommendation for this patient might be which of the following?

1. Transfer to a long-term care facility
2. Evaluation for the use of noninvasive ventilation (NIV)
3. Termination of ventilation
4. Waiting until the primary cause of respiratory failure has been resolved
   a. 1 and 2 only
   b. 2 and 3 only
   c. 1, 2, and 3 only
   d. 1, 2, and 4 only

Answer 26

ANS: A
Unless evidence of irreversible disease exists, a patient who requires prolonged ventilatory support should not be considered permanently ventilator dependent until 3 months have passed and all weaning attempts during that time have failed. Those failing to wean may require placement in a long-term care facility.

Question 27

When weaning is unsuccessful for a patient who successfully performs an SBT, which of the following factors should be assessed?

1. Cardiac factors
2. Nutritional status and respiratory muscle strength
3. Acid-base status
4. Psychological factors
   a. 1 and 3 only
   b. 2 and 4 only
   c. 2, 3, and 4 only
   d. 1, 2, 3, and 4

Answer 27

ANS D