Cairo: Pilbeam's Mechanical Ventilation, 6th Edition

Chapter 05: Selecting the Ventilator and the Mode

WorkBook Answer Key

Key Terms Crossword Puzzle

Chapter Review Questions
1. (a) Why does the patient need ventilatory support? (Indication)
(b) Does the ventilatory problem require a special mechanical ventilation mode? (Pathology)
(c) What therapeutic goals can be achieved by using a specific ventilator? (Treatment goals)
(d) Does the patient need to be intubated, or can a mask be used? (Patient interface)
(e) Will the ventilatory support be provided in the intensive care unit, the patient’s home, or an extended-care facility? (Location)
(f) Will ventilatory support be required for a brief period or long term? (Duration)
(g) How familiar is the staff with the ventilator (or ventilators) under consideration? (Staff training)
2. D—Negative pressure ventilation
A, B, C, and E—Continuous positive airway pressure
A, E—Positive-pressure ventilation
B, C—Noninvasive positive-pressure ventilation
3. Improving oxygenation, obstructive sleep apnea
4. Bilevel positive airway pressure
5. Noninvasive positive-pressure ventilation (NIV)
6. (any five of the following) (1) chronic respiratory failure, (2) chest wall deformities, (3) neuromuscular disorders, (4) central alveolar hypoventilation, (5) COPD, (6) CF, (7) bronchiectasis, (8) ARF, (9) ARDS, (10) PNA, (11) postoperative complications, (12) asthma, (13) heart failure, (14) postextubation failure in difficult-to-wean patients, and (15) obstructive sleep apnea.
7.
Advantages
 Avoids complications associated with artificial airways
 Provides flexibility in initiating and removing mechanical ventilation
 Reduces requirements for heavy sedation
 Preserves airway defense, speech, and swallowing mechanisms
 Reduces need for invasive monitoring
Disadvantages
 Can cause gastric distention, skin pressure lesions, facial pain, dry nose, eye irritation (conjunctivitis), discomfort, claustrophobia, and poor sleep, and mask leaks can occur
8. In full ventilatory support, the ventilator provides all the energy necessary to maintain the patient’s effective alveolar ventilation. In partial ventilatory support, the patient participates in the work of breathing to help maintain effective alveolar ventilation.
9. 8 breaths/min
10. 6 breaths/min
11. Full ventilatory support allows the ventilatory muscles to rest while the machine supplies all the necessary ventilation.
12. (a) Mandatory breaths—breaths for which the ventilator controls the timing, the tidal volume, or the inspiratory pressure; (b) spontaneous breaths—the patient controls the timing and the tidal volume, the volume or pressure (or both) delivered is not set by the clinician but rather is based on patient demand and the patient’s lung characteristics; (c) assisted breaths—have characteristics of both mandatory and spontaneous breaths, all or part of the breath is generated by the ventilator, which does part of the WOB for the patient
13. It guarantees a specific volume delivery, regardless of changes in lung compliance and resistance or patient effort.
14. Peak and alveolar pressures can rise leading to alveolar overdistention when the patient’s lung conditions worsen.
15. (a) The peak inspiratory pressure rises any time airway resistance increases, such as with bronchospasm. (b) The amount of volume will remain constant, because it is the set variable.
16. Decrease, because the lung condition and airflow limitation have improved 
17. When pressure is targeted as the control variable, volume will vary with changing lung characteristics.
18. (a) It allows the clinician to set a max pressure, which reduces the risk of overdistention of the lungs. (b) The ventilator delivers a decelerating flow pattern. (c) It may be more comfortable for patients who can breathe spontaneously.
19. (a) Volume delivery varies as the patient’s lung characteristics change. (b) Clinicians are less familiar with pressure control. (c) Tidal volume and minute ventilation decrease when lung characteristics deteriorate.
20. It will decrease. 
21. (a) Continuous mandatory ventilation—either time- or patient-triggered breaths are mandatory, the patient is not generating any spontaneous breaths.(b) Intermittent mechanical ventilation—the patient receives a set number of mandatory breaths each minute but is also allowed to breathe spontaneously between mandatory breaths. (c) Continuous spontaneous ventilation—all breaths are spontaneous and are therefore patient-triggered. These spontaneous breaths may be assisted or unassisted.
22. (a) Breath type, (b) the targeted control variable, and (c) the timing of the breath delivery.
23. (a) VC-CMV, (b) PC-CMV, (c) VC-IMV, (d) PC-IMV, and (e) CSV
24. By the trigger that is used to initiate the breath. 
25. When a patient is obtunded because of drugs, cerebral malfunction, spinal cord or phrenic nerve injury, or motor nerve paralysis that makes him or her unable to produce any voluntary efforts to breathe.
26. If it is too sensitive, accidentally triggering or ventilator self-triggering can occur. If not sensitive enough, it will require too much patient effort to trigger.
27. Time triggered and patient triggered (pressure or flow) 
28. 33-50, watching the pressure manometer or the pressure-time curve, typically by increasing the inspiratory flow
29. Inspiratory time, pressure level, rate, FIO2, PEEP, and apnea settings.
30. Depends on the compliance and resistance of the patient’s lungs, patient effort, and the set pressure.
31. Decelerating ramp
32. Maximum pressure limit; +10 cm H2O; inspiration
33. PC-IRV is appropriate when a patient with very stiff lungs is not successfully ventilated with VC-CMV and PEEP or PC-CMV and PEEP.
34. IMV differs from CMV because IMV allows the patient to breathe spontaneously between mandatory breaths. In CMV, all breaths are machine breaths.
35. 
Advantages, Risks, and Disadvantages of CMV and IMV
Mode	Advantages	Risks and Disadvantages	
Volume-targeted or pressure-targeted continuous mandatory ventilation (VC-CMV or PC-CMV)	Set minimum minute ventilation () with volume-targeted breaths	Respiratory alkalosis if the number of patient-triggered breaths is high.
 may decrease with changes in compliance or airway resistance (Raw) in PC-CMV	
	Guaranteed volume or pressure with each breath	High mean airway pressure and related complications	
	May synchronize with patient efforts	Patient-ventilator asynchrony if flow or sensitivity is set incorrectly	
	Patient may establish rate.	May not be well tolerated in awake patients who are not sedated; high rates can result in auto-PEEP	
	Can provide full support in patients who are not breathing spontaneously	Muscle atrophy may result.	
Volume-targeted or pressure-targeted synchronized intermittent mandatory ventilation (VC-IMV or PC-IMV)	May lower mean airway pressure compared with CMV	IMV with pressure support ventilation (PSV) may increase mean airway pressure.	
	Variable work of breathing for patient may maintain muscle strength and reduce muscle atrophy.	Can significantly increase work of breathing for spontaneous breaths; hypercarbia and muscle fatigue can occur if rate, flow, and sensitivity are set incorrectly	
	Can be used for weaning	May increase weaning time	
	May reduce alkalosis associated with CMV	Patients may have trouble adjusting to the set mandatory rate; acute hypoventilation can occur with low rates (<6 breaths/min mandatory).	
	Full or partial support can be adjusted to meet patient’s needs.	Spontaneous work of breathing may increase excessively as set mandatory rate is reduced.	
	Sedation and paralysis are not required (unlike with CMV).	Patient-ventilator asynchrony may result if patient actively breathes during a mandatory breath when the set rate is low; rapid, shallow breathing may occur during spontaneous periods.	
36. When the goal is to have the patient breathe spontaneously without receiving a mandatory breath with every effort.
37. (a) Spontaneous breathing, (b) CPAP, and (c) PSV
38. An SBT is used to evaluate a patient’s readiness for discontinuation from mechanical ventilation. It reduces support and allows the patient to breathe spontaneously for a brief time while his or her vital signs and physical appearance are monitored and evaluated.
39. The patient must have a consistent and reliable spontaneous respiratory pattern.
40. Inspiratory pressure, CPAP, flow-cycle criteria, sensitivity; rate, inspiratory flow, and inspiratory time
41. In PSV, the tidal volume is determined by the pressure gradient, lung compliance, airway resistance, and patient effort.
42. A leak in the circuit will cause a ventilator in PSV to time cycle, because the inspiratory time would reach the maximum inspiratory time setting.
43. The time required for the ventilator to rise to the set pressure at the beginning of inspiration
44. Flow
45. Any condition associated with increase airway resistance such as COPD, asthma.
46. An inspiratory pressure and an expiratory positive airway pressure
47. Patient coughing or forcible exhalation will cause a ventilator to pressure cycle 
48. The size of the patient (infant, child, and adult)
49. Pressure augmentation (PAug) is a dual-control mode that provides pressure-limited ventilation with volume delivery targeted for every breath. (Another term that is used to describe this mode is volume-assured pressure support (VAPS). VAPS is the term used to describe this mode on the Bird 8400st (CareFusion, Viasys Corp, San Diego, Calif.).
Each breath in PAug is patient triggered and pressure targeted, such as a pressure-supported breath. However, PAug guarantees that at least the volume set on the control panel is delivered for each breath. 
50. If the set volume is achieved prior to flow cycling, the breath is volume cycled.
51. If the set volume is not reached before flow drops to the set level, the ventilator maintains the flow at its set value until the volume is delivered (volume cycled).
52. The patient can receive more volume than is set in PAug if the patient’s inspiratory flow demand is high enough to prevent maintenance of the set pressure level. This causes the ventilator to provide additional flow to the patient.
53. PCRV is patient or time triggered, pressure limited (volume targeted), and time cycled.
54.
Ventilator	Pressure-regulated volume control name	
Carefusion Avea	PRVC	
Covidien PB 840 	AC/VC+	
Hamilton G5 and G3	Adaptive pressure ventilation 	
Dräger Evita XL and V500	CMV autoflow	
Servoi	PRVC	
55. The ventilator will not allow the pressure to rise higher than 5 cm H2O below the upper pressure limit setting. Therefore, at 35 cm H2O, the alarm will activate.
56. Patient triggered (pressure or flow triggered), pressure limited (volume targeted), and flow cycled.
57. With PRVC, inspiration can be either time triggered or patient triggered. In VS, inspiration is only patient triggered. A PRVC breath is time cycled, whereas a VS breath is usually flow cycled (it may pressure cycle if pressure rises too high or time cycle if the inspiratory time is extended for some reason).
58. Mandatory minute ventilation (MMV), also called minimum minute ventilation and augmented minute ventilation, is used primarily for weaning patients from the ventilator. It allows the operator to set a minimum minute ventilation, which usually is 70-90% of  the patient’s current . The ventilator provides whatever part of the minute ventilation that the patient is unable to accomplish by increasing the breathing rate or by increasing the preset pressure. The ventilator monitors the patient’s spontaneous breathing and provides additional ventilatory support if the patient does not achieve the set . If a patient increases the level of his or her spontaneous ventilation, the ventilator reduces its amount of support.
59. In MVV, the high rate alarm and the low VT alarm must be set to protect against rapid, shallow breathing by the patient.
60. Airway pressure-release ventilation (APRV)
61. Time constant
62. Stiff lungs
63. Pressure, flow, and volume delivery
64. In PAV, (a) the amount of pressure produced by the ventilator depends on the patient’s demand for inspiratory flow and volume and (b) the amplification setting selected by the clinician.
65. The advantage of PAV is the ability to track changes in patient effort. Disadvantages are that PAV provides only for assisted ventilation; it cannot compensate for system leaks, and it may be more difficult for the patient to trigger in the presence of auto-PEEP.
Critical Thinking Questions
1. The patient’s use of accessory muscles and the presence of diaphoresis are manifestations of acute respiratory distress. Patient-ventilator asynchrony can also be a sign of acute respiratory distress. The use of the accessory muscles and the diaphoresis show that the patient is working to breathe. However, there are no assisted breaths. This situation could be caused by an improper sensitivity setting. If the setting is too insensitive, the patient will have inspiratory efforts but will be unable to trigger assisted breaths from the ventilator. Make sure the sensitivity is set so that the patient is able to trigger the ventilator without auto-triggering.
2. When a patient’s ventilatory drive is increased during use of VC-CMV, the patient’s assist rate will increase. Since every breath will be a machine breath at the set volume, this can easily lead to a decreased PaCO2 or respiratory alkalosis. Identification of the source of the increased drive (i.e., fever, sepsis, etc.) and correction of this are the best ways to control the respiratory alkalosis. However, since this may take some time, sedatives, paralytic agents, or switching to SIMV with similar settings may be tried.
3. Central sleep apnea occurs when the brain fails to send the appropriate signals to the breathing muscles to initiate breathing. It is characterized by apneic events during sleep with no associated ventilatory effort. The apnea will cause hypoxemia and hypercapnia. Since bi-level positive airway pressure creates a pressure gradient between EPAP and IPAP, air is pushed into the lungs. Therefore, bi-level PAP would “breathe” for the patient during periods of apnea. 
4.
Answer	Rationale	
d. VC-CMV (1)—Intubated with quadriplegia from a spinal cord injury	Patient will most likely be unable to breathe without full ventilatory support.	
e. PC-CMV with PEEP (2)—Intubated with acute respiratory distress syndrome	With ARDS it is important to guard against increasing peak pressures due to stiff lungs.	
a. Nasal mask CPAP (3)—Obstructive sleep apnea at home	This will keep the upper airways open so that the patient can breathe spontaneously.	
b. CPAP through ventilator (4)—Intubated with spontaneous breathing with ARDS	This will improve oxygenation while allowing the patient to be monitored. Patient would also benefit from pressure support.	
c. Pressure support (5)—Intubated with consistent spontaneous respiratory pattern	This will help the patient to overcome the resistance due to the endotracheal tube, ventilator circuit, and demand valve system while allowing the patient to be monitored.	
a. Nasal mask CPAP (6)—Nonintubated, spontaneously breathing with refractory hypoxemia	This will improve oxygenation without having to intubate the patient. This, hopefully, will avoid intubation. 	
d. VC-CMV (7)—Intubated with drug overdose	Patient will require full ventilatory support until the effects of the drugs wear off.	
Case Studies
Case Study 1

1. The ventilator is set to deliver PC-SIMV.
2. The inspiratory time is 1 second.
3. The expiratory time is 3.0 seconds.

Case Study 2

1. Full ventilatory support to ensure adequate ventilation.
2. PC-SIMV with pressure support and PEEP. Pressure control may be necessary to guard against high inspiratory pressures. Pressure support to overcome the airway resistance caused by the small ET tube and ventilator circuit and PEEP for the refractory hypoxemia. If peak pressures are not an issue, VC-SIMV with pressure support and PEEP may be used.

Case Study 3

1. The scalar represents pressure support ventilation (PSV).
2. The problem is pressure overshoot at the beginning of inspiration.
3. To correct this problem, slow down the rise time.
NBRC-Style Questions
1. B
2. C
3. A
4. C
5. A
6. C
7. B
8. D
9. B
10. D