Respiratory failure is a term that refers to inadequate gas exchange. It means that the patient has an inability to take in enough oxygen or remove enough carbon dioxide from the body.
It’s a clinical problem that all respiratory therapists and medical professionals must be able to identify and treat. This guide covers the basics of respiratory failure and contains helpful practice questions on this topic. So, if you’re ready, let’s get into it.
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What is Respiratory Failure?
Respiratory failure is a term characterized by the inability of the lungs to perform oxygenation or ventilation. During a breathing cycle, the body takes in oxygen while removing carbon dioxide.
This process is known as gas exchange.
However, if not enough oxygen taken into the body, or if not enough carbon dioxide is removed, this results in respiratory failure and can lead to serious medical conditions.
Types of Respiratory Failure
Respiratory failure is caused by either a lack of oxygen or by the accumulation of too much carbon dioxide. This means that there are two primary types:
- Hypoxemic respiratory failure
- Hypercapnic respiratory failure
Hypoxemic respiratory failure (type I) describes a lack of oxygenation where there is a PaO2 of less than 60 mmHg in arterial blood.
Hypercapnic respiratory failure (type 2) describes an acidotic state in which there is a PaCO2 greater than 50 mmHg in arterial blood.
What is Acute Hypoxemic Respiratory Failure?
Acute hypoxemic respiratory failure is a state in which there are severely decreased oxygenation levels that occur over a relatively short period of time. It’s one of the most common reasons that patients are admitted to the intensive care unit (ICU).
The causes of acute hypoxemic respiratory failure include the following:
- Bacterial infection
- Viral pneumonia
- Airway obstruction
- Pulmonary embolism
- Pulmonary edema
- Acute Respiratory Distress Syndrome (ARDS)
Keep in mind that there may be other causes of this condition. These are just a few of the most common examples.
Respiratory Failure Practice Questions:
1. How is acute respiratory failure identified?
By a PaO2 less than 60 mm Hg or PaCO2 greater than 50 mm Hg, or both, in otherwise healthy individuals at sea level.
2. Hypoxemic respiratory failure is most commonly due to what?
V/Q mismatch, shunt, or hypoventilation.
3. Hypercapnic respiratory failure, also known as ventilatory failure, results from what?
Decreased ventilatory drive, neurologic disease, or increased work of breathing.
4. Chronic respiratory failure may manifest with hypercapnia and evidence of what?
A compensatory metabolic alkalosis (chronic ventilatory failure) or with polycythemia reflecting chronic hypoxemia.
5. The clinical status of the patient is the most important factor determining the need for what?
6. Excessive work of breathing is the most common cause of what?
Respiratory muscle fatigue.
7. The beneficial role of NIV in the acute setting has been best established in acute exacerbations of what?
COPD and in cardiogenic pulmonary edema.
8. Increased FiO2 and PEEP are the main therapies for what?
9. What is the goal of therapy in hypercapnic respiratory failure?
Normalize the pH.
10. A control variable is the primary variable that the ventilator manipulates to cause inspiration. What are the three variables in the equation of motion that a ventilator can control?
Pressure, Volume, and Flow.
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11. What are three goals of Noninvasive Positive Pressure Ventilation?
(1) Avoid intubation, (2) Decrease the incidence of ventilator-associated pneumonia, and (3) Improve gas exchange.
12. What are the main therapies to treat severe hypoxemia?
Increased FIO2 and PEEP.
13. What is the main goal of therapy when treating (acute ventilatory failure) hypercapnic respiratory failure?
To bring the pH values back to normal.
14. What is the most important factor to consider when determining whether or not a patient needs ventilatory support?
The clinical status of the patient.
15. During invasive ventilatory support on a patient with obstructive lung disease, what tidal volumes, respiratory rates, and flow rates should you set to avoid dynamic hyperinflation?
Lower tidal volumes (6 to 8 ml/kg), moderate respiratory rates, and high inspiratory flow rates (70 to 100 L/min.) are best to avoid dynamic hyperinflation.
16. When transporting a mechanically ventilated patient what device must you always bring with you?
You must always have a manually powered bag-valve mask.
17. What are the two different power sources for a ventilator?
Either electrical energy or compressed gas.
18. What does the output control valve on a mechanical ventilator regulate?
The output control valve regulates the flow of gas to the patient.
19. Most current evidence indicates that NPPV should be the standard of care for managing patients with what respiratory diseases?
Patients with a COPD exacerbation and acute cardiogenic pulmonary edema.
20. What is the selection criteria for NPPV in the care of patients with acute respiratory failure?
Two or more of the following should be present: Use of accessory muscles, Paradoxical breathing, Respiratory rate greater than or equal to 25 breaths/minute, Dyspnea, PaC02 greater than 45 mm Hg with PH less than 7.35, Pa02/FIO2 ratio less than 200.
21. Before NPPV is considered for patients with restrictive thoracic disorders, what symptoms must be present?
22. Absence of breath sounds on one side of the chest may reveal what?
Collapse, infection, edema, or effusion as potential causes of the VQ mismatch
23. What is a description of Acute Hypercapnic Failure?
The pH decreases 0.08 for every 10 mm Hg increase in PaCO2.
24. How does hypoventilation differ from other causes of Acute Hypoxemic Respiratory Failure?
Manifesting with a normal alveolar to arterial PO2 difference.
25. Hypercapnic Respiratory Failure is also known as what?
Ventilatory Failure. It is the inability to maintain the normal removal of CO2 from the tissue, and may be indicated by a PaCO2 greater than 50 mm Hg in an otherwise healthy individual.
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26. What is Hypercapnic Respiratory Failure?
An elevated PaCO2, creating an uncompensated respiratory acidosis.
27. Hypercapnic Respiratory Failure is also known as what?
Pump failure or ventilatory failure.
28. An MIP of what usually indicates adequate respiratory muscle strength to continue spontaneous breathing?
An MIP of -30 cm H2O.
29. What is Noninvasive Ventilation (NIV)?
Mechanical ventilation without endotracheal intubation of tracheotomy, usually via a form-fitting mask.
30. A physiologic shunt leads to hypoxemia when?
When the alveoli collapse or when they are filled with fluid or exudate.
31. What is Respiratory Failure?
The inability to maintain either the normal delivery of oxygen to the tissues or the normal removal of carbon dioxide from the tissues and often results from an imbalance between respiratory workload and ventilatory strength of endurance.
32. Respiratory Failure is defined as what?
Arterial partial pressure of oxygen (PaO₂) less than 60 mm Hg, or Alveolar partial pressure of carbon dioxide (PaCO₂) greater than 50 mm Hg.
33. What is respiratory muscle weakness?
The decreased capacity of a rested muscle to generate force and decreased endurance.
34. Respiratory muscle weakness occurs most commonly in patients with?
Neuromuscular disease, COPD, Kyphoscoliosis, and Obesity.
35. Severe hypoxemia can lead to?
Significant central nervous system dysfunction, ranging from irritability to confusion, to coma.
36. Shunting can be diagnosed by?
Using 100% oxygen breathing techniques, Contrast-enhanced echocardiography, Macroaggregated albumin scanning, and Pulmonary Angiography.
37. A shunt is differentiated from a V/Q mismatch by?
The lack of increase in PO2 as FiO2 is increased.
38. What is Venous Admixture?
A decrease in mixed venous oxygen increases the gradient by which oxygen needs to be stepped up as it passes through the lungs.
39. What are the causes of V/Q mismatch?
Obstructive Lung diseases, Bronchospasm, Mucous Plugging, Inflammation, Premature airway closure that signal asthmatic or emphysematous exacerbations, Infection, Heart Failure, Inhalation injury may lead to partially collapsed or fluid-filled alveoli.
40. What are the most commonly used tests to assess respiratory muscle strength at the bedside?
Maximum inspiratory pressure (MIP), Maximum expiratory pressure (MEP), Forced Vital Capacity, and Maximum voluntary ventilation (MVV).
41. What are the primary causes of hypoxemia?
Ventilation/Perfusion mismatch, Shunt, Alveolar hypoventilation, Diffusion impairment, Perfusion/diffusion impairment, Decreased inspired oxygen, Venous admixture.
42. What are the three main causes of Hypoxemic Respiratory Failure?
Hypoventilation, V/Q mismatch, and Shunt.
43. What causes hypercapnic respiratory failure due to a decreased ventilatory drive?
Drug overdose or sedation, Bilateral carotid endarterectomy with incidental resection of the carotid bodies, Brainstem lesions, Disease of the CNS such as multiple sclerosis or Parkinson’s, Hypothyroidism, Morbid obesity (obesity hypoventilation), Sleep apnea, Metabolic Alkalosis, Malnutrition, Sleep deprivation, Metabolic encephalopathy, Elevated ICP.
44. What diseases are associated with Hypercapnic respiratory failure?
COPD, Asthma, Upper airway obstruction, Obesity hypoventilation, Pneumothorax, Severe burns, Chest wall disorders (kyphoscoliosis), and Ankylosing spondylitis.
45. What diseases cause muscle weakness/fatigue?
Guillain Barre Syndrome, Myasthenia gravis, COPD, Kyphoscoliosis, and Obesity.
46. What is a Shunt?
An extreme version of V/Q mismatch in which there is no ventilation to match perfusion.
47. What is the clinical presentation of a patient with a V/Q mismatch?
Hypoxemia commonly manifests with dyspnea, tachycardia, and tachypnea, use of accessory muscles, nasal flaring, lower extremity edema, peripheral or central cyanosis
48. What is the most common cause of hypoxemia?
49. What is the term for Respiratory Failure due to inadequate ventilation?
Hypercapnic Respiratory Failure.
50. What is the treatment for decreased inspired oxygen?
51. What are some causes of Hypoxemia?
Ventilation/perfusion mismatch, shunt, alveolar hypoventilation, diffusion impairment, perfusion/diffusion impairment, decreased inspired oxygen, and venous admixture.
52. Hypercapnic respiratory failure is also known as ventilatory failure, and this results from what?
Neurologic disease, decreased ventilatory drive, and increased work of breathing.
53. What is hypoxemic respiratory failure?
The inability to maintain normal oxygenation in the arterial blood (i.e. oxygen is too low).
54. In what disease states have NIV been shown to be beneficial in the acute setting?
Acute exacerbation of COPD, and Carcinogenic edema.
55. What are the main therapies used for severe hypoxemia?
Increased FiO2 and PEEP.
56. What are the most common reasons for Hypoxemic Respiratory Failure?
V/Q mismatch, shunt, and hypoventilation.
57. What is a typical ABG result for a patient in acute respiratory failure due to V/Q mismatch or shunt?
A pH of 7.45, PaCO2 of 33 mmHg, and a PaO2 of 40 mmHg.
58. What is the goal of therapy in hypercapnic respiratory failure?
To normalize the patient’s pH.
59. What is the most common cause of respiratory muscle fatigue?
Excessive work of breathing
60. What is the most important factor determining the need for ventilatory support?
The clinical status of the patient.
61. What will chronic respiratory failure manifest from?
Hypercapnia, evidence of compensatory metabolic alkalosis, and polycythemia reflecting chronic hypoxemia.
62. What is work of breathing?
The amount of force needed to move a given volume into the lung with a relaxed chest wall; mathematically, work is the integral of pressure times volume (the physiologic cost of increased dead space and resistance).
63. What is type I respiratory failure?
It refers to hypoxemic respiratory failure where the PaO2 is less than 60 mmHg.
64. What is type II respiratory failure?
It refers to hypercapnic respiratory failure where the PaCO2 is greater than 50 mmHg.
65. What is the goal of treating hypercapnic respiratory failure?
The goal is to normalize the pH.
Respiratory failure is an extremely important topic for medical professionals. This is especially true for respiratory therapists. RT’s must be able to recognize and provide care for patients with hypoxemia and/or ventilatory inadequacies.
Hopefully, this guide can help you learn the basics of this topic.
If you enjoyed this information, we have a similar guide on ventilation and oxygenation that I think you would find useful. Thanks for reading and, as always, breathe easy, my friend.
John Landry, BS, RRT
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
- Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020.
- Chang, David. Clinical Application of Mechanical Ventilation. 4th ed., Cengage Learning, 2013.
- Rrt, Cairo J. PhD. Pilbeam’s Mechanical Ventilation: Physiological and Clinical Applications. 7th ed., Mosby, 2019.