Cairo: Pilbeam's Mechanical Ventilation, 6th Edition

Chapter 07: Final Considerations in Ventilator Setup

WorkBook Answer Key

Key Terms CROSSWORD Puzzle

Chapter Review Questions
1. 60-100 mm Hg
2. A nasal cannula at 2 L/min is approximately equivalent to approximately 28% oxygen. The ventilator FIO2, therefore, should be 28%.
3. Desired FIO2 = PaO2 (desired) × [FIO2 (known) ÷ PaO2 (known)]
Desired FIO2 = 90 mm Hg × (0.5 ÷ 60 mm Hg)
Desired FIO2 = 90 × 0.00833 = 0.75 or 75%
4. >92%
5. 10-20 minutes after placement on a ventilator.
6. (a) Absorption atelectasis, (b) oxygen toxicity, and (c) intrapulmonary shunting
7. Flow triggering is faster for two reasons: (1) The exhalation valve does not close, so no time is taken up there; and (2) there is already flow in the system when the patient begins to breathe; this provides immediate flow to the patient.
8. Auto-PEEP makes pressure triggering more difficult, because the patient must breathe through the amount of auto-PEEP plus the sensitivity setting to trigger the breath. For example, if the auto-PEEP is +8 cm H2O and the sensitivity setting is –1 cm H2O, the patient would have to create –9 cm H2O to trigger a breath.
9. Isothermic saturation boundary, fourth to fifth generation of subsegmental bronchi
10. At least 30 mg H2O/L, 31-35° C
11. A closed system (a) maintains a steadier temperature and (b) reduces the risk of contamination, because the ventilator circuit does not have to be opened to refill the humidifier.
12. A ventilator circuit that does not have heated wires is exposed to the cooler temperatures of the room, which subsequently cools down heated gas as it travels toward the patient. The cooler the gas, the less water it can hold; therefore, condensation forms in the tubing.
13. 10-14 mg/L cm H2O
14. 22-34 mg/L cm H2O
15. Resistance to flow will increase, causing auto-PEEP and increased work of breathing.
16. The HME should be removed to avoid increasing resistance from the collection of the aerosol within the HME. A circuit adapter that selectively bypasses the HME can be used during aerosol treatments. This is desirable to avoid breaking the circuit and increasing the risk of VAPS.
17. The metered dose inhaler (MDI) with spacer should be placed within the inspiratory limb of the circuit. The HME needs to be removed during the treatment. It should be kept in mind, however, that circuit disconnection increases the risk of circuit contamination. An alternate approach is to use an MDI with an MDI adapter placed between the HME and the endotracheal tube (ET). If a spacer is used with the MDI on the inspiratory line, the HME must still be removed. Another solution is to use a circuit adapter that does not require the HME to be removed during aerosol treatments.
18. (any of the following) Thick, copious, or bloody secretions; exhaled VT <70% of inhaled VT; body temperature <32° C; spontaneous minute ventilation >10 L/min; during aerosol treatments; when VT is small and would be compromised by the HME dead space; and with a large VT
19. Level 1—immediately life-threatening; level 2—potentially life-threatening; and level 3—non-life-threatening but a potential source of patient harm.
20. Level 2	Heater/humidifier malfunction
21. Level 1	Timing failure
22. Level 2 	Autocycling
23. Level 3	Intrinsic PEEP
24. Level 1	Excessive gas delivery to patient
25. Level 2	Inappropriate PEEP/CPAP
26. Level 1	Exhalation valve failure
27. Level 2	I:E ratio inappropriate
28. Level 1	Electrical power failure
29. Level 3	Changes in lung characteristics
30. Level 2	Circuit leak
31. Level 1	No gas delivery to patient
32. Level 1	Electrical power failure
33. Level 2	Circuit partially obstructed
34. Level 2	Inappropriate oxygen level
35. Level 3	Changes in ventilatory drive
36. Low-pressure alarm, 20 cm H2O; high-pressure alarm, 40 cm H2O; and low-PEEP/CPAP, 3 cm H2O
37. 20 seconds or 2 × TCT + 1 is a good estimate.
38. Both sigh maneuvers and lung recruitment strategies attempt to reverse atelectasis; in fact, sighs may be used as a lung recruitment strategy while using lung-protective ventilation (especially with VT <7 mL/kg) in patients who have ARDS.
39. (any of the following) Before and after suctioning, before and after bronchoscopy, during an extubation procedure, during chest physiotherapy, during ventilation with VT <7 mL/kg, and as a recruitment maneuver in some patient with ARDS
40. (a) Check ventilator and circuit function for leaks; (b) fill humidifier with sterile water and set appropriate temperature or place an HME inline; (c) place a temperature/monitoring device near patient connector when heated humidifier is used; (d) check FIO2; (e) adjust alarms; (f) make sure ECG is connected to the patient; (g) ensure emergency airway equipment is available; (h) provide suction equipment; (i) attach a volume monitoring device and oxygen analyzer if not available on the ventilator; and (j) keep a manual resuscitator (and mask) with the ventilator.
41. (a) Prepare the patient, (b) establish and airway interface, (c) manually ventilate the patient, (d) ensure that the patient’s cardiovascular status is stable, (e) meet his or her ventilatory needs, and (f) treat the underlying cause of the respiratory failure.
42. Modes: VC-CMV, VC-SIMV or PC-CMV, PC-SIMV, and spontaneous CPAP/PSV
Tidal volume range:	100-2000 mL
Respiratory rate range:	1-60 breaths/min
Pressure range:	0-100 cm H2O
PEEP/CPAP range:	0-30 cm H2O
Flow rate range:	10-180 L/min
Flow waveforms:	constant and descending
FIO2:	21-100%
Diagnostic measurements:	Inflation hold (to measure Cstat) and expiratory pause (to measure auto-PEEP)
Alarms:	Apnea, power failure, gas source failure, low-pressure limit, high-pressure limit, high frequency, decreased tidal volume, and high and low minute ventilation
43. COPD patients have increased airway resistance and may also have increased lung compliance.
44. A respiratory infection superimposed on their chronic disease (acute-on-chronic respiratory failure).
45. (any of the following) Air trapping, nosocomial infections, barotrauma and volutrauma, cardiac problems, aspiration, and weaning difficulties
46. BiPAP
47. Orotracheal
48. 
Parameter	Preferred Setting or Range	
Tidal volume	6-8 mL/kg	
Rate	8-16 breaths/min	
Inspiratory time	0.6-1.2 second	
Flow rate	>60-100 L/min	
Flow waveform	Descending ramp	
PEEP	≤5 cm H2O (or about 50% of PEEPI)	
FIO2	Maintain PaO2 at 55-75 mm Hg with FIO2 <0.5	
49. The alteration of blood flow through the thorax and heart as a result of dramatic intrapleural pressure changes during inspiration and expiration in a patient with acute severe asthma.
50. (a) Increased airway resistance and (b) air trapping
51. <30 cm H2O despite the high PIP
52.
Parameter	Preferred Setting or Range	
Tidal volume	6-8 mL/kg	
Rate	8-16 breaths/min	
Inspiratory time	≤1 second	
Flow rate	80-100 L/min 	
Flow waveform	Descending flow waveform	
PEEP	About 80% of intrinsic PEEP	
FIO2	An FIO2 as needed to achieve a PaO2 from 60-100 mm Hg (usually FIO2 ≥ 0.5)	
53. Hyperresonance
54. (any of the following) Myasthenia gravis, amyotrophic lateral sclerosis, muscular dystrophy, polio or postpolio, Guillain-Barré, tetanus, cervical spinal cord injury, and botulism
55. Progressive respiratory muscle weakness leads to problems coughing and clearing secretions and eventually to ventilatory failure. Also, a weak gag reflex may lead to aspiration.
56.
Parameter	Preferred Setting or Range	
Tidal volume	6-8 mL/kg	
Rate	8-16 breaths/min	
Inspiratory time	About 1 second	
Flow rate	>60 L/min	
Flow waveform	Constant or descending ramp	
PEEP	5 cm H2O	
FIO2	0.21	
57. Trauma to the head from falls, automobile accidents, and blows to the head, as well as post-craniotomy, cerebral vascular accident, and post-resuscitation hypoxemia.
58. Cerebral perfusion pressure (CPP) = Mean arterial pressure (MAP) – Intracranial pressure (ICP); MAP = 90-95 mm Hg, ICP <10 mm Hg; therefore, normal CPP is 80-85 mm Hg.
59. CPP <60 mm Hg
60. Iatrogenic hyperventilation should be used only temporarily for increased ICP; it is accomplished by maintaining the PaCO2 level between 25 and 30 mm Hg and gradually allowing it to return to normal levels in 24-48 hours.
61.
Parameter	Preferred Setting or Range	
Tidal volume	6 -8 mL/kg while maintaining Palv < 30 cm H2O	
Rate	15-20 breaths/min	
Inspiratory time	1 second (avoid PEEPI)	
Flow rate	>60 L/min	
Flow waveform	Descending or constant 	
PEEP	0-5 cm H2O (use PEEP to avoid severe hypoxemia and measure ICP, keep ICP ≤ 10 mm Hg)	
FIO2	1.0 initially; titrate PaO2 to 70-100 mm Hg	
62.
 History of precipitating condition that occurs within 1 week of a known clinical insult
 Diffuse bilateral alveolar infiltrates on chest radiograph (or computed tomography scan) not fully explained by effusions, lobar/lung collapse, or nodules.
 Pulmonary edema that is not fully explained by cardiac failure or fluid overload. Objective assessment to verify if no risk factor is present
 Reduced CL (<40 mL/cm H2O)
 Refractory hypoxemia (Reduced partial pressure of arterial oxygen [PaO2]/fractional inspired oxygen concentration [FIO2])
 Mild ≤ 200 mm Hg PaO2/FIO2 ≤ 300 mm Hg with 5 cm H2O PEEP
 Moderate <100 mm Hg ≤ 200 mm Hg with 5 cm H2O PEEP
 Severe ≤ 100 mm Hg with 5 cm H2O PEEP)
63. (any of the following) Sepsis, aspiration of gastric contents, thoracic and nonthoracic trauma, heroin or other drug overdose, massive blood transfusions, fat emboli, smoke or chemical inhalation injury, burns, pancreatitis, near-drowning, interstitial viral pneumonitis, disseminated intravascular coagulation, oxygen toxicity, and prolonged cardiopulmonary bypass
64. The open lung approach involves using PEEP levels equal to or exceeding the inflection point on a pressure-volume curve. This helps to prevent opening and closing of small airways and alveoli, which may cause shear stress.
65.
Parameter	Preferred Setting or Range	
Tidal volume	4-6 mL/kg (while maintaining Pplateau ≤ 30 cm H2O)	
Rate	15-25 breaths/min	
Inspiratory time	<1 second	
Flow rate	>60 L/min	
Flow waveform	Descending	
PEEP	High levels >15 cm H2O	
FIO2	Start at 1.0; use PEEPE to keep FIO2 at safe levels	
66. pH = 7.20-7.40; PaCO2 = 40-80 mm Hg; and PaO2 = 60-100 mm Hg
67. Refractory hypoxemia is identified with a low PaO2 on a high FIO2 (PaO2/FIO2 ≤ 200)
68. Diffuse alveolar infiltrates
69. CL < 30 mL/cm H2O
70. >20%
71. <15-18 mm Hg
72. (a) Acute myocardial infarction, (b) hypertension, (c) rapid heart rates with inadequate filling time, (d) valvular heart disease, and (e) fluid overload
73.
Parameter	Preferred Setting or Range	
Tidal volume	6-8 mL/kg	
Rate	≥10 breaths/min	
Inspiratory time	1-1.5 seconds	
Flow rate	≥60 L/min	
Flow waveform	Descending or constant	
PEEP	5-10 cm H2O	
FIO2	Start at 1.0, then titrate to SpO2 >90-92%	
74. Noninvasive mask CPAP or NPPV by mask.
Critical Thinking Questions
1. A deep breath or a sigh is a part of our normal breathing pattern and usually occurs in nonintubated individuals every 6 minutes. A ventilator sigh is usually set at 1½ to 2 times the set tidal volume. Sighs are beneficial before and after suctioning of intubated patients and also before and after bronchoscopy. However, sighs may cause overdistention when used with larger tidal volumes and with CPAP. Recently, sighs have become part of lung recruitment strategies during the ventilation of patients with ARDS.
2. Upon arrival at the ED, a patient would most likely present with tachycardia and hypertension. The patient would be using accessory muscles during inspiration and possibly expiration. There would be increased resonance on percussion, bilateral inspiratory and expiratory wheezes, and prolonged expiration. Arterial blood gases at that time would show acute alveolar hyperventilation with hypoxemia. If the patient is unresponsive to aggressive bronchodilator therapy and corticosteroids, the episode may progress, and the arterial blood gases would reveal a PaCO2 of 40 mm Hg or higher and a normal to acidotic pH. Hypoxemia would be moderate to severe with supplemental oxygen. At this point, the patient would be exhausted, breath sounds and chest movement would decrease, and life-threatening arrhythmias may develop. The patient should be intubated before respiratory arrest occurs.
3. PSV may not be appropriate for use with patients with COPD because PSV is flow cycled at set percentages of the patient’s inspiratory flow rate. This can lead to longer inspirations than the patient can tolerate. Patients with COPD need to have shortened inspiratory times to allow for longer expiratory times. The patient’s active breathing pattern may increase work of breathing, cause dyssynchrony with the ventilator and PEEPI. PSV may be used with patients with COPD if the ventilator allows for adjustments in the expiratory flow cycle percentage. Higher flow cycle percentages begin expiration earlier, allowing the patient enough time to exhale all the volume.
4. A patient with increased airway resistance requires more time for exhalation. Inadequate expiratory time in these patients leads to air trapping and PEEPI.
Case Studies
Case Study 1

1. Noninvasive mask CPAP would be appropriate at this time. It may improve oxygenation, reduce the PaCO2, reduce the work of breathing, and reduce myocardial work. This would allow time for pharmacological treatment to become effective.
2. The most appropriate mode would be either VC-CMV or PC-CMV. This patient’s BSA is 2.42 m2, which requires a minute ventilation of 9.7 L/min. The patient’s IBW is 84 kg. The guideline for VC-CMV ventilation of patients with CHF recommends moderate tidal volumes of 6-8 mL/kg IBW. This puts the patient’s tidal volume in the range of 504-672 mL. Dividing the minute ventilation by the tidal volume used provides the respiratory rate needed. If 0.6 L is used for the tidal volume, the respiratory rate needed to produce a minute volume of 9.7 L/min is 16 breaths/min.

Case Study 2

1. The patient has hypercapnic respiratory failure. This is most likely due to the closed head injury.
2. The patient has an acute respiratory acidosis.
3. PC-CMV or VC-CMV would be most appropriate.
4. The BSA for this patient is 1.94 m2, making her minute ventilation 6.8 L/min. The tidal volume range for closed head injury is 6-8 mL/kg IBW. The patient’s IBW is 66 kg. The tidal volume range should be 396-528 mL. Set the flow rate to keep TI at 1 second or less. PEEP needs to be kept to a minimum because of the potential to increase ICP.

Case Study 3

1. The ABG results show that the patient is tiring. Acute asthmatic episodes cause the patient to hyperventilate at first. This continues until the episode either clears or the patient becomes tired. As the patient tires, the PaCO2 rises back to the normal range. Meanwhile, the patient becomes hypoxemic. This patient demonstrates an acute respiratory acidosis with moderate hypoxemia (the low pH is too low to be caused by the PaCO2; it is most likely due to lactic acidosis).
2. This patient requires intubation. The patient has already been receiving continuous nebulization of a bronchodilator and oxygen therapy. Despite this, she demonstrates fatigue and impending respiratory failure.
3. Full ventilatory support with either VC-CMV or PC-CMV. It may be easier to keep pressure under control with PC-CMV.
4. Keep the set PIP <30 cm H2O; target tidal volumes to 6-8 mL/kg IBW (366-488 mL) at a rate 8-16 breaths/min; keep TI <1 second; descending ramp; and use PEEPE only to offset auto-PEEP.

Case Study 4

1. Acute-on-chronic respiratory failure with moderate hypoxemia or partially compensated respiratory acidosis with moderate hypoxemia.
2. This patient should be tried on BiPAP with a mask first to try to avoid intubation. However, if the patient’s secretions cannot be mobilized, the patient may require intubation and mechanical ventilation.
3. VC-CMV or PC-CMV could be used. With VC-CMV, the tidal volume should be between 6 and 8 mL/kg mL. Using a volume of 600 mL would require a ventilator frequency of 14 breaths/min. The flow rate should be set so that the inspiratory time is between 0.6 and 1.2 seconds. PEEP should be set lower than 5 cm H2O.
NBRC-Style Questions
1. A
2. C
3. D
4. A
5. A
6. B
7. C
8. B
9. B
10. A