Cairo: Pilbeam's Mechanical Ventilation, 6th Edition

Chapter 19: Basic Concepts of Noninvasive Positive-Pressure Ventilation

WorkBook Answer Key

Key Terms Crossword Puzzle

Chapter Review Questions
1. NIV is the delivery of mechanical ventilation to the lungs using techniques that do not require an endotracheal airway.
2. The three basic methods of applying noninvasive ventilation are (a) negative-pressure ventilation, (b) abdominal displacement ventilation, and (c) positive-pressure ventilation.
3. Negative-pressure ventilators operate by intermittently applying negative pressure to the entire body region below the neck or to the upper region of the chest. This negative pressure is transmitted across the chest wall, into the pleural space, and finally into the alveolar space. The result is an increase in transpulmonary pressure, which causes air to enter the lungs. Exhalation is passive and depends on the elastic recoil of the lungs and chest wall.
4. (a) Iron lung and (b) chest cuirass
5. Avoidance of intubation
6. The avoidance of intubation and invasive ventilation is the primary goal of NIV in the acute care setting.
7. (any of the following) Decreases need for intubation; decreases incidence of nosocomial pneumonia; decreases length of ICU stay; decreases length of hospital stay; decreases mortality; preserves airway defenses; improves patient comfort; and decreases need for sedation
8. (any of the following) Alleviates symptoms of chronic hypoventilation; improves duration and quality of sleep; improves functional capacity; and prolongs survival
9. NIV in ARF improves gas exchange by resting the respiratory muscles and increasing alveolar ventilation.
10. Using NIV via face mask for ARF from COPD significantly reduces the need for intubation, decreases the duration of mechanical ventilation, decreases the length of stay in the ICU, decreases complications, and reduces the mortality rate.
11. Shorter ICU and hospital stays
12. CPAP (10-12 cm H2O); if the patient remains hypercapnic and dyspneic with CPAP, a trial of NIV by mask using PSV plus PEEP has proved effective for the treatment of cardiogenic pulmonary edema.
13. (a) Chronic hypoventilation, (b) nocturnal desaturation, (c) respiratory muscle fatigue, and (d) poor sleep quality.
14. (a) Fatigue, (b) morning headache, (c) daytime hypersomnolence, (d) cognitive dysfunction, and (e) dyspnea.
15. 4-6 hours
16. Nocturnal or intermittent daytime NIV shows improvement in daytime gas exchange and respiratory muscle strength and also alleviates symptoms of hypoventilation in patients with neuromuscular disorders.
17. Patients with chronic stable COPD may benefit from NIV if they have severe daytime CO2 retention (CO2 ≥52 mm Hg) and nocturnal hypoventilation despite the administration of nocturnal oxygen therapy.
18. Do not be unrealistic with your answer because the role of NIV in the treatment of advanced CF has not been precisely defined. In general, NIV increases VT, reduces diaphragmatic activity, and improves oxygenation. Intermittent use of NIV could help support Jane while she awaits lung transplantation.
19. OSA that does not respond to CPAP is an indication for NIV.
20. You can explain to her that decreasing the number of days a patient spends receiving invasive mechanical ventilation decreases the risk of infection and other complications, lowers the mortality rate, and reduces health care costs.
21. NIV may provide relief from severe dyspnea and preserve patient comfort. It may also reverse the acute process in disorders such as COPD or pulmonary edema and enable the patient to live longer.
22. (any five of the following) (a) Acute exacerbation of COPD, (b) acute asthma, (c) hypoxemic respiratory failure, (d) community-acquired pneumonia, (e) cardiogenic pulmonary edema, (f) immunocompromised patients, (g) postoperative patients, (h) postextubation (weaning), and (i) do not intubate
23. Tachypnea (respiratory rate >24 breaths/min), use of accessory muscles, and paradoxical breathing; physiological criteria for NIV include a PaCO2 >45 mm Hg, a pH <7.35, or a PaO2/FIO2 <200.
24. No. The following are all exclusion criteria for NIV: (1) respiratory arrest or the need for immediate intubation; (2) hemodynamic instability; (3) inability to protect the airway (impaired cough or swallowing); (4) excessive secretions; (5) agitation and confusion; (6) facial deformities or conditions that prevent a good mask fit; (7) uncooperative or unmotivated patient; and (8) brain injury with unstable respiratory drive.
25. The potential reversibility of the disease process is the final consideration for NIV.
26. PaCO2 >55 mm Hg; PaCO2 50-54 mm Hg with an SpO2 <88% for 5 consecutive minutes; PaCO2 50-54 mm Hg with recurrent hospitalizations for hypercapnic respiratory failure (more than two hospitalizations within 12 months).
27. PTVs have a single-circuit gas delivery system that uses an intentional leak port for patient exhalation instead of a true exhalation valve.
28. These ventilators are flow and time triggered, pressure limited, and flow and time cycled.
29. IPAP and EPAP
30. IPAP, 2-30 cm H2O, and EPAP, 2-20 cm H2O.
31. CPAP, PSV (assist mode; IPAP/EPAP), and spontaneous/timed (S/T).
32. The patient’s delivered tidal volume depends on the gradient between the IPAP level and the EPAP level, the inspiratory time, patient inspiratory effort, and the patient’s lung characteristics.
33. The source for unintentional leaks is around the patient interface (e.g., mask).
34. Flow triggering is made easier by the PTV’s ability to compensate for leaks.
35. AVAPS devices automatically adapt pressure support to match a patient’s ventilatory needs by delivering an average tidal volume (VT range = 200-1500 mL) based on the patient’s condition.
36. AVAPS may be useful in the treatment of patients with COPD, neuromuscular diseases, obesity hypoventilation, and chronic hypoventilation.
37. (a) The oxygen flow rate; (b) the type of leak port in the system; (c) the site where oxygen is bled into the circuit; and (d) the IPAP and EPAP.
38. Use an oxygen blender.
39. An EPAP level of 4 cm H2O or higher keeps the continuous gas flow high enough to prevent CO2 rebreathing.
40. Advantages of using an acute care ventilator for NIV are availability of additional ventilatory support options and alarms, a precise FIO2, and more monitoring features than are available on portable pressure-targeted ventilators. A disadvantage is the inability of some machines to compensate for leaks. Leaks at the patient interface interfere with the triggering and cycling function and may result in patient-ventilator asynchrony and increased WOB.
41. The patient would be most comfortable in the PC-CMV mode during NIV, because cycling to exhalation would be a function of time rather than flow. This may provide better synchronization with the ventilator and less patient respiratory effort.
42. Using heated humidity can significantly reduce drying of the nasal mucosa that may lead to nasal congestion and increased nasal resistance. Mucosal drying also leads to patient discomfort and noncompliance.
43. A heated passover-type humidifier should be used. Heated bubble humidifiers and heat-moisture exchangers increase airway resistance in the ventilator circuit and may also interfere with patient triggering.
44. The nasal mask is easier to fit and secure to the patient’s face. Also, it is better tolerated by patients who are claustrophobic. The nasal mask allows the patient to cough and clear secretions and to speak and possibly eat; in addition, there is less mechanical dead space, which reduces the potential for rebreathing of CO2.
45. (a) Air leaks and (b) skin irritations.
46. Concerns with the use of face masks with NIV include (1) the risk of aspiration of vomit; (2) asphyxia if the ventilator malfunctions; (3) increased dead space, leading to CO2 retention; (4) inability of the patient to eat, communicate, cough, or expectorate secretions; and (5) claustrophobia.
47. Approximately 250 mL
48. The patient should be sitting upright.
49. Attach the interface and circuit to the ventilator. Turn on the ventilator and adjust it initially to low-pressure settings. Hold or allow the patient to hold the mask gently to the face until the patient becomes comfortable with it. Encourage the patient in proper breathing technique. Monitor oxygen (O2) saturation; adjust the fractional inspired oxygen (FIO2) to maintain O2 saturation above 90%. Secure the mask to the patient. Do not make the straps too tight. Titrate the IPAP and EPAP to achieve patient comfort, adequate exhaled tidal volume, and synchrony with the ventilator. Do not allow peak pressures to exceed 20 cm H2O. Check for leaks and adjust the straps if necessary. Monitor the respiratory rate, heart rate, level of dyspnea, O2 saturation, minute ventilation, and exhaled tidal volume. Obtain blood gas values within 1 hour.
50. Clinical indicators that demonstrate improved patient comfort include a decrease in the respiratory rate, a reduction in inspiratory muscle activity, and synchronization with the ventilator.
51. When the patient is not comfortable with NIV, corrective measures include refitting or changing the mask to reduce air leaks, encouraging and coaching the patient in the proper breathing pattern, or adjusting the ventilator settings.
52. 5-7 mL/kg or greater; volume is manipulated by increasing the difference between the IPAP and EPAP. This is usually accomplished by increasing the IPAP.
53. The pH and PaCO2 continue to worsen or show no improvement and are accompanied by respiratory distress, declining level of consciousness, hemodynamic instability, or diminishing oxygenation.
54. Type of aerosol generator (SVN or MDI), position of the leak port, synchronization of MDI actuation with inspiration, IPAP and EPAP levels, and presence or absence of a humidifier in the circuit.
55. Air leaks in the mask or circuit cause continuous flow in the circuit to increase, which may increase aerosol loss. The volume of the mask itself increases the potential for a larger portion of the aerosol dose to deposit on the patient’s face or in the eyes. For this reason, it is recommended that aerosols not be delivered when a total face mask or helmet is used to administer NIV.
56. The straps may be too tight because the mask is too large. The mask should be refitted or resized and changed to a different style (e.g., nasal pillows, nasal seal, and nasal gel mask). Forehead spacers and/or wound care dressing should be applied to alleviate pressure on the nasal bridge.
57. It is a common occurrence that may be diminished with the administration of simethicone agents.
58. (a) Aspiration pneumonia, (b) mucous plugging, (c) hypoxemia, (d) hypotension, and (e) respiratory arrest.
59. Increasing periods of time off the NIV or reducing IPAP gradually to a minimum level, allowing the patient to assume more of the WOB.
Critical Thinking Questions
1. When IPAP and EPAP are equal, or set at the same setting, the ventilator does not deliver a timed or spontaneously triggered breath. The pressure remains constant in the circuit at the set pressure, supplying CPAP.
2. Drying of the nasal mucosa can be prevented with use of a heated humidifier; improper interfaces that allow leakage can be avoided by ensuring that the mask is not too large; and skin irritation from tight straps may be prevented by minimizing headgear tension as much as possible and using forehead spacers.
3. Portable pressure-targeted ventilators use a leak port for patient exhalation instead of a true exhalation valve. The leak port allows a continuous flow of gas through it to help maintain pressure levels and flush exhaled gases from the circuit. If this port and the oxygen bleed-in are located in the same area, the oxygen bled into the circuit is lost through the leak port. Therefore, to achieve the highest oxygen concentrations, the leak port and oxygen bleed-in must be as far apart as possible (e.g., leak port in the circuit and oxygen bled into the patient mask).
Case Studies
Case Study 1

1. Yes, the patient is demonstrating signs of moderate to severe dyspnea, as evidenced by a respiratory rate >24 (28 breaths/min) and accessory muscle use with a PaCO2 >45 (49 mm Hg), pH <7.35 (7.31), and PaO2/FIO2 <200 (53 ÷ approximately 0.7 = 76).
2. NIV beginning with IPAP/EPAP 10/5 cm H2O to start via nasal mask if tolerated by patient. Bleed in oxygen to titrate SpO2 to 90-92%. Titrate the IPAP until VT is at least 5-7 mL/kg.
3. This patient is demonstrating criteria for the termination of NIV. The patient should be intubated and placed on invasive mechanical ventilation.

Case Study 2

1. (1) Acute hypercapnic respiratory failure superimposed on chronic respiratory failure—indicated by the arterial blood gas results; (2) bronchospasm—evidenced by the wheezing; (3) hypoxemia—evidenced by the arterial blood gas results and the presence of cyanosis; (4) retained secretions—evidenced by the productive sputum; and (5) upper respiratory tract infection—evidenced by the elevated WBC and green, purulent sputum.
2. Aerosolized albuterol 2.5 mg and ipratropium bromide 0.5 mg, air entrainment mask with 24% oxygen (or 28%), repeat arterial blood gas evaluations (intravenous antibiotics and a sputum culture and sensitivity).
3. Noninvasive positive-pressure ventilation.
NBRC-Style Questions
1. A
2. B
3. B
4. C
5. D
6. A
7. D
8. A
9. C
10. C