Cairo: Pilbeam's Mechanical Ventilation, 6th Edition

Chapter 04: Establishing the Need for Mechanical Ventilation

WorkBook Answer Key

Key Terms Crossword Puzzle

Chapter Review Questions
1. To maintain homeostasis.
2. (a) Support or manipulate pulmonary gas exchange: alveolar ventilation—achieve eucapnic ventilation or allow permissive hypercapnia and alveolar oxygenation—maintain adequate oxygen delivery; (b) increase lung volumes: prevent or treat atelectasis with adequate end-inspiratory lung inflation and restore and maintain an adequate FRC; and (c) reduce work of breathing.
3. (a) Reverse acute respiratory failure, (b) reverse respiratory distress, (c) reverse hypoxemia, (d) prevent or reverse atelectasis and maintain FRC, (e) reverse respiratory muscle fatigue, (f) permit sedation and/or paralysis, (g) reduce systemic or myocardial oxygen consumption, and (h) minimize associated complications and reduce mortality.
4. (a) Tachypnea; (b) nasal flaring; (c) diaphoresis; (d) accessory muscle use; (e) retractions of suprasternal, supraclavicular, and intercostal spaces; (f) paradoxical or abnormal movement of the thorax and abdomen; (g) abnormal breath sounds; (h) tachycardia; (i) arrhythmia; and (j) hypotension.
5. Acute respiratory failure (ARF)
6. (a) A PaO2 below the predicted normal range for the patient’s age under ambient conditions, (b) a PaCO2 greater than 50 mm Hg and rising, and (c) a falling pH of 7.25 or lower.
7. (a) An acute life-threatening or vital organ-threatening tissue hypoxia. Hypoxemic respiratory failure is a result of severe ventilation/perfusion mismatching. It can also occur with diffusion defects, right-to-left shunting, alveolar hypoventilation, aging, and inadequate inspired oxygen. (b) Acute hypercapnic respiratory failure, or acute ventilatory failure, occurs when a person cannot achieve adequate ventilation to maintain a normal PaCO2. Disorders that can lead to this are central nervous system disorders, neuromuscular disorders, or disorders that increase the work of breathing.
8. Oxygen and PEEP/CPAP
9. Respiratory muscles, thoracic cage, and nerves and nerve centers that control ventilation.
10. (a) Brain or brainstem lesions, such as stroke, head or neck trauma, cerebral hemorrhage, or spinal cord injury; (b) depressant drugs; (c) hypothyroidism; (d) central sleep apnea; and (e) inappropriate oxygen therapy.
11. (any of the following) (1) Myasthenia gravis, (2) Guillain-Barré syndrome, (3) poliomyelitis, (4) muscular dystrophy, (5) amyotrophic lateral sclerosis, (6) tetanus, and (7) botulism.
12. Flail chest, rib fracture, kyphoscoliosis, and obesity
13. Asthma, emphysema, chronic bronchitis, croup, acute epiglottitis, and acute bronchitis
14. Level of consciousness, presence of cyanosis and/or diaphoresis, respiratory rate, heart rate, blood pressure, SpO2, and temperature
15.
HYPOXEMIA	
	Mild to Moderate	Severe	
Respiratory findings	Tachypnea
Dyspnea
Paleness	Tachypnea
Dyspnea
Cyanosis	
Cardiovascular findings	Tachycardia
Mild hypertension
Peripheral vasoconstriction	Tachycardia (eventually bradycardia, arrhythmias)
Hypertension (eventually hypotension)	
Neurologic findings	Restlessness
Disorientation
Headaches
Lethargy	Somnolence
Confusion
Delirium
Blurred vision
Tunnel vision
Loss of coordination
Impaired judgment
Slowed reaction time
Manic-depressive activity
Loss of consciousness
Coma	
HYPERCAPNIA	
	Mild to Moderate	Severe	
Respiratory findings	Tachypnea
Dyspnea	Tachypnea (eventually bradypnea)	
Cardiovascular findings	Tachycardia
Hypertension
Vasodilation	Tachycardia
Hypertension (eventually hypotension)	
Neurologic findings	Headaches
Drowsiness
Dizziness
Confusion	Hallucinations
Hypomania
Convulsions
Loss of consciousness (eventually coma)	
Signs	Sweating
Skin redness		
16. (a) Use of supplemental oxygen therapy, (b) maintenance of a patent airway, and (c) continuous monitoring of oxygenation and ventilatory status with pulse oximetry and ABGs.
17. (a) Cheyne-Stokes breathing and (b) Biot’s breathing
18. Every 2-4 hours
19. (a) Vital capacity equal to or less than 10-15 mL/kg and (b) a maximum inspiratory pressure between 0 and 20 cm H2O.
20. Respiratory muscle fatigue
21. (a) Tachypnea, (b) increased depth of respiration, and (c) paradoxical breathing
22. 50 to 100 cm H2O
23. Negative inspiratory force (NIF)
24. 20
25. 65-75 mL/kg
26. 10 L/min
27. FEV1, less than 10 mL/kg
28. Peak expiratory flow rate, less than 75-100 L/min
29. PaCO2
30. 0.3, 0.4, and greater than 0.6
31. (a) Pulmonary thromboemboli, (b) pulmonary vascular injury, and (c) regional hypoperfusion
32.
Measurement	Normal Range	Critical Value	
P(Aa)O2	2-30 mm Hg on room air	Greater than 450 mm Hg on supplemental oxygen	
PaO2/PAO2	0.75-0.95	Less than 0.15	
PaO2/FIO2	475	Less than 200	
33. Intubate and mechanically ventilate the patient.
34. PaO2 and SpO2
35. The following blood gas results:
Criteria	Normal Values	Critical Value	
Ventilation*	
pH	7.35-7.45	<7.25	
Arterial partial pressure of carbon dioxide (PaCO2) (mm Hg)	35-45	>55 and rising	
Dead space to tidal volume ratio (VD/VT)	0.3-0.4	>0.6	
Oxygenation†	
Arterial partial pressure of oxygen (PaO2) (mm Hg)	80-100	<70 (on O2 >0.6)	
Alveolar-to-arterial oxygen difference P(Aa)O2 (mm Hg)	3-30	>450 (on O2)	
Ratio of arterial to alveolar PO2 (PaO2/PAO2)	0.75	<0.15	
PaO2/FIO2	475	<200	
36. Intubation is contraindicated when it is contrary to the patient’s wishes, medically pointless, or futile.
37. (a) Respiratory rate >25 breaths/min, (b) moderate to severe acidosis (pH 7.25-7.30 and PaCO2 45-60 mm Hg), and (c) moderate to severe dyspnea with the use of accessory muscles and paradoxical breathing pattern
38. Or (any of the following) (1) Respiratory arrest, (2) cardiac arrest, (3) non-respiratory organ failure, (4) upper airway obstruction, (5) inability to protect the airway and/or high risk of aspiration, (6) inability to clear secretions, and (7) facial/head surgery or trauma.
39. This patient is hypoxemic with a non-rebreather mask, and is unable to move an adequate amount of air. The pink, frothy sputum is an indicator of pulmonary edema, and the hypotension is due to cardiogenic shock. This is a medical emergency, and the patient requires intubation, mechanical ventilation, and PEEP.
40. Oxygen therapy would be most appropriate for this patient. If the patient wishes further intervention, arterial blood gas evaluations and other diagnostic tests may be performed.
41. Aggressive bronchodilator therapy (continuous), corticosteroids, oxygen therapy, and close monitoring of this patient are required. If the bronchospasm does not respond to aggressive therapy, intubation and mechanical ventilation may be necessary.
42. This patient requires oxygen and bronchodilator therapy. The patient’s PaCO2 reveals that he is able to move air and therefore does not require mechanical ventilation at this time.
43. This patient is developing acute respiratory failure and meets some of the criteria for mechanical ventilatory support (pH, 7.21; PaCO2 >55 and rising PaO2; FIO2 <200). This patient should be intubated, and mechanical ventilatory support should be started. This patient’s head trauma makes NPPV an absolute contraindication.
44. CaO2 = [Hb × 1.34 × SaO2] + [PaO2 × 0.003]
= [12 × 1.34 × 0.91] + [59 × 0.003]
= 14.63 + 0.18
= 14.81 vol%
45. CaO2 = [Hb × 1.34 × SaO2] + [PaO2 × 0.003]
= [8 × 1.34 × 0.9] + [58 × 0.003]
= 9.65 + 0.17
= 9.82 vol%
46. CaO2 = [Hb × 1.34 × SaO2] + [PaO2 × 0.003]
= [17 × 1.34 × 0.79] + [48 × 0.003]
= 18.00 + 0.14
= 18.14 vol%
47. PAO2 = [FIO2 (Pb  PH2O)]  [PaCO2/R] = [0.7 (760  47)]  [48/0.8]
= [0.7 × 713]  60 = 499  60 = 439 mm Hg
PaO2 = 50 mm Hg
PAO2  PaO2 = 439  50 = 389 mm Hg
48. PaO2/PAO2 = 50 mm Hg/439 mm Hg = 0.11
Of the oxygen available to the alveolus, only 11% is getting into the artery. Yes, 0.11 is a critical value.
49. PaO2/FIO2 = 50 mm Hg/0.70 = 71.43. Yes, this is a critical value; it indicates the need for mechanical ventilatory support.
50. PAO2 = [FIO2 (Pb  PH2O)]  [PaCO2/R] = [0.21 (760  47)]  [55/0.8]
PAO2 = 150  69 = 81 mm Hg; PAO2  PaO2 = 81  51 = 30 mm Hg. This value is within the normal range.
51. PaO2/PAO2 = 51 mm Hg/81 mm Hg = 0.63. This is not a critical value.
52. PaO2/FIO2 = 51/0.21 = 243. This is not a critical value.
Critical Thinking Questions
1. A rapid physical assessment of a trauma patient should include, but is not limited to checking for a patent airway, respirations, chest auscultation, patient appearance, pulse, blood pressure, temperature, SpO2, chest inspection, chest palpation, chest percussion, and patient sensorium.
2. The diagnostic evaluations that should be done to assess the need for mechanical ventilation include arterial blood gases, chest X-ray, and pulse oximetry.
3. The patient would be very anxious looking, flushed and sweating, in a tripod position (i.e., leaning forward braced on elbows or hands), using accessory muscles, and cyanotic or pale.
4. The patient requiring oxygen therapy only presents with hypoxic respiratory failure, as evidenced by a PaO2 below the predicted normal for the patient’s age. This patient will have a normal PaCO2. A patient requiring mechanical ventilation will have both hypoxic respiratory failure and hypercapnic respiratory failure.
Case Studies
Case Study 1

1. Hypoxemia is likely the cause of the patient’s tachycardia. Anxiety may also be a contributing factor.
2. The patient’s PaO2 of 48 mm Hg on 40% oxygen and the PaO2/FIO2 value of 120 are critical. However, both the P(Aa)O2 and PaO2/PAO2 are outside the normal range but not at critical levels.
3. This patient is presenting with an acute asthma episode. At the onset of an asthma episode, the patient hyperventilates. A normal PaCO2 in this situation indicates a severe episode (stage III) and impending respiratory failure.
4. Continuous bronchodilator therapy would be appropriate. Additional medications could include magnesium sulfate and steroids. However, if little or no improvement is seen, ventilatory support will be necessary.

Case Study 2

1. The patient’s oxygenation status is not at a critical level. The alveolar-arterial oxygen gradient is wider than normal, 42.5 mm Hg, but not critical. The arterial/alveolar PO2, at 0.59, is lower than normal but also not critical. The PaO2/FIO2 is lower than normal but not critical.
2. The patient’s pH and PaCO2 are both within normal limits. The patient is not weak enough to require mechanical ventilatory intervention at this time.
3. The patient should be closely monitored for acute ventilatory failure by measuring the maximum inspiratory pressure and/or vital capacity and also by evaluating the arterial blood gases for PaCO2 changes. Medical treatment of myasthenia gravis includes an anticholinesterase medication. The patient may benefit from low-flow oxygen, about 2 L/min by nasal cannula.

Case Study 3

1. The alveolar-arterial oxygen gradient is increased (315 mm Hg) but not critical. However, the PaO2 (41 mm Hg), the PaO2/PAO2 (0.13), and the PaO2/FIO2 (68) indicate severe hypoxemic respiratory failure.
2. The PaCO2 is markedly elevated, and the pH is very low. This is an indication that the patient is in acute ventilatory failure.
3. This patient requires intubation, based on the deteriorating arterial blood gas values.
NBRC-Style Questions
1. D
2. C
3. D
4. D
5. C
6. C
7. C
8. B
9. B
10. A