Respiratory Failure: Overview and Practice Questions (2025)

Respiratory failure is a serious and potentially life-threatening condition where the lungs are unable to perform their essential function of exchanging oxygen and carbon dioxide. This dysfunction can lead to dangerously low oxygen levels in the blood, excessive carbon dioxide buildup, or both.

Respiratory failure can develop suddenly (acute) or gradually over time (chronic), and its causes range from lung diseases like COPD and pneumonia to conditions affecting the respiratory muscles or nervous system.

Understanding the types, causes, and treatment options for respiratory failure is crucial for managing this condition and improving patient outcomes.

What is Respiratory Failure?

Respiratory failure occurs when the respiratory system is unable to maintain adequate gas exchange, leading to insufficient oxygen levels in the blood (hypoxemia) or excessive carbon dioxide levels (hypercapnia).

It can be acute, developing rapidly, or chronic, occurring over time. There are two main types of respiratory failure:

• Type 1 (Hypoxemic Respiratory Failure): This is characterized by low oxygen levels in the blood (PaO₂ < 60 mm Hg) with normal or low levels of carbon dioxide. It is often caused by conditions that affect oxygenation, such as acute respiratory distress syndrome (ARDS), pneumonia, pulmonary embolism, and pulmonary edema.
• Type 2 (Hypercapnic Respiratory Failure): In this type, carbon dioxide levels in the blood are elevated (PaCO₂ > 50 mm Hg), often due to inadequate ventilation. This can occur from chronic obstructive pulmonary disease (COPD), neuromuscular diseases, respiratory muscle fatigue, and central nervous system depression.

Some common causes of respiratory failure can include lung diseases, airway obstructions, trauma, or neurological conditions.

The treatment focuses on addressing the underlying cause and may involve oxygen therapy, mechanical ventilation, or medications. If left untreated, respiratory failure can lead to life-threatening complications.

Causes of Respiratory Failure

Respiratory failure can result from a wide range of conditions that impair the lungs’ ability to exchange oxygen and carbon dioxide.

These causes can be grouped into issues affecting the lungs, airways, or the muscles and nervous system that control breathing.

Some of the most common causes include:

Lung Diseases

• Chronic Obstructive Pulmonary Disease (COPD): A progressive lung disease, including emphysema and chronic bronchitis, that damages the airways and restricts airflow, leading to inadequate gas exchange.
• Pneumonia: Infection of the lungs causing inflammation and fluid buildup, impairing oxygen exchange.
• Pulmonary Embolism: A blood clot that blocks the pulmonary arteries, reducing blood flow to the lungs and hindering oxygenation.
• Acute Respiratory Distress Syndrome (ARDS): A severe form of lung injury characterized by inflammation and fluid in the alveoli, which impairs oxygen absorption.

Airway Obstruction

• Asthma: A chronic condition that causes airway narrowing and obstruction, making it difficult to move air in and out of the lungs.
• Foreign Body Aspiration: When a foreign object gets lodged in the airway, it can block airflow, leading to respiratory failure if not promptly treated.
• Tumors or Growths: Cancerous or benign masses in the airways can obstruct airflow and cause respiratory failure.

Neuromuscular Disorders

• Amyotrophic Lateral Sclerosis (ALS): A neurodegenerative disease that weakens the respiratory muscles, preventing proper ventilation.
• Myasthenia Gravis: An autoimmune disease that causes muscle weakness, including those required for breathing.
• Guillain-Barré Syndrome: A condition that affects the peripheral nerves and can lead to respiratory muscle paralysis.

Chest Trauma

• Rib Fractures or Chest Wall Injuries: Trauma to the chest can restrict lung expansion and impair ventilation.
• Pneumothorax: A collapsed lung, often caused by chest trauma or underlying lung disease, leads to insufficient ventilation.

Central Nervous System Disorders

• Stroke: Damage to the brain can affect the respiratory centers that regulate breathing.
• Drug Overdose: Narcotics, sedatives, and other drugs can depress the central nervous system, leading to hypoventilation and respiratory failure.
• Head Injury: Trauma to the brain can impair the respiratory centers and lead to inadequate breathing.

Note: By recognizing and addressing these underlying causes, healthcare providers can tailor treatment to manage respiratory failure and prevent further complications.

Treatment for Respiratory Failure

The treatment for respiratory failure focuses on addressing the underlying cause of the condition and restoring adequate oxygenation and ventilation.

Depending on whether the failure is acute or chronic, as well as the severity, different interventions may be necessary.

Here are the key treatment options for respiratory failure:

Oxygen Therapy

• Supplemental Oxygen: This is often the first line of treatment for hypoxemic respiratory failure (Type 1). Administered through nasal cannulas, face masks, or high-flow devices, oxygen therapy helps to raise oxygen levels in the blood.
• Noninvasive Positive Pressure Ventilation (NIPPV): Devices such as continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) deliver oxygen and support ventilation without the need for intubation. This is often used for patients with COPD or those in mild to moderate respiratory distress.

Mechanical Ventilation

• Invasive Ventilation: For more severe cases of respiratory failure, especially when non-invasive methods are insufficient, mechanical ventilation is required. A tube is inserted into the patient’s airway (intubation) to support breathing by delivering oxygen and removing carbon dioxide. This approach is common in ICU settings for patients with ARDS, severe pneumonia, or trauma.
• Ventilator Settings: The ventilator settings are adjusted based on the patient’s condition, such as using low tidal volumes for ARDS to protect the lungs from ventilator-induced injury.

Medications

• Bronchodilators: For patients with obstructive lung diseases like COPD or asthma, bronchodilators are prescribed to relax the airway muscles and improve airflow.
• Steroids: Corticosteroids reduce inflammation in the lungs, which can help treat respiratory failure caused by conditions like pneumonia, COPD, or asthma exacerbations.
• Antibiotics: If the respiratory failure is due to an infection like pneumonia, antibiotics are used to target the underlying bacterial cause.
• Diuretics: In cases of pulmonary edema or heart failure, diuretics help remove excess fluid from the lungs, improving breathing and gas exchange.

Addressing the Underlying Cause

• Treating Infections: If a respiratory infection is causing the failure, antibiotics or antiviral medications will be given.
• Blood Thinners: In the case of a pulmonary embolism, anticoagulants (blood thinners) are administered to dissolve or prevent blood clots.
• Surgery or Procedures: In some cases, surgery may be needed to remove tumors, repair damaged lung tissue, or manage trauma that is causing respiratory failure.

Supportive Care

• Positioning: In cases of ARDS or severe hypoxemia, prone positioning (lying face down) can improve oxygenation by redistributing airflow in the lungs.
• Fluids and Nutritional Support: Proper hydration and nutrition are important for recovery. Intravenous fluids or enteral feeding may be necessary in patients who are critically ill.

Long-Term Care for Chronic Respiratory Failure

• Home Oxygen Therapy: Patients with chronic respiratory failure, such as those with COPD, may require long-term oxygen therapy at home to maintain adequate blood oxygen levels.
• Pulmonary Rehabilitation: A structured rehabilitation program that includes exercise, education, and breathing techniques can improve lung function and overall quality of life for patients with chronic respiratory conditions.

Note: The choice of treatment depends on the cause, type, and severity of respiratory failure. In severe cases, early intervention and appropriate management are critical to preventing complications and improving patient outcomes.

Respiratory Failure Practice Questions

1. How is acute respiratory failure identified?
By a PaO2 less than 60 mmHg or PaCO2 greater than 50 mmHg, or both, in otherwise healthy individuals at sea level.

2. Hypoxemic respiratory failure most commonly occurs 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. 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.

5. The clinical status of a patient is the most important factor determining the need for what?
Ventilatory support

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 cardiogenic pulmonary edema

8. Increased FiO2 and PEEP are the primary ways to treat what?
Severe hypoxemia

9. What is the goal of therapy for hypercapnic respiratory failure?
Normalize the pH

10. What are the three variables in the equation of motion that a ventilator can control?
Pressure, volume, and flow

11. What are the 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 ways to treat severe hypoxemia?
Increased the FiO2 and PEEP

13. What is the main goal of therapy when treating acute ventilatory failure?
Bring the pH value 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 of a patient with an obstructive lung disease, what tidal volume, respiratory rate, and flow rate should you set to avoid dynamic hyperinflation?
For these patients, 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?
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?
COPD 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, PaCO2 greater than 45 mmHg with hH less than 7.35, PaO2/FiO2 ratio less than 200.

21. Before NPPV is considered for patients with restrictive thoracic disorders, what symptom must be present?
Nocturnal hypoventilation

22. What is the goal of treating hypercapnic respiratory failure?
The goal is to normalize the pH.

23. What is a description of acute hypercapnic failure?
The pH decreases by 0.08 for every 10 mmHg increase in PaCO2.

24. What is hypercapnic respiratory failure?
The inability to maintain the normal removal of CO2 from the tissues, and is characterized by a PaCO2 greater than 50 mmHg in an otherwise healthy individual.

25. Hypercapnic respiratory failure is also known as what?
Ventilatory failure

26. What is type I respiratory failure?
It refers to hypoxemic respiratory failure where the PaO2 is less than 60 mmHg.

27. What is type II respiratory failure?
It refers to hypercapnic respiratory failure where the PaCO2 is greater than 50 mmHg.

28. An MIP of what usually indicates adequate respiratory muscle strength to continue spontaneous breathing?
-30 cmH2O

29. What is noninvasive ventilation (NIV)?
Mechanical ventilation without endotracheal intubation or tracheotomy; usually via a form-fitting mask.

30. When does a physiologic shunt lead to hypoxemia?
When the alveoli collapse or when they are filled with fluid or exudate.

31. What is the definition of 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; often results from an imbalance between respiratory workload and ventilatory strength of endurance.

32. What are the PaO2 and PaCO2 during respiratory failure?
Arterial partial pressure of oxygen (PaO2) less than 60 mmHg; Alveolar partial pressure of carbon dioxide (PaCO2) greater than 50 mmHg.

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 what?
Significant central nervous system dysfunction, ranging from irritability to confusion, to coma.

36. Shunting can be diagnosed by?
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 an of increase in PaO2 as the 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, mucus plugging, inflammation, premature airway closure that signals asthmatic or emphysematous exacerbations, infection, heart failure, or an inhalation injury that 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 (FVC), 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, and 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, or 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, tachypnea, use of accessory muscles, nasal flaring, lower extremity edema, and peripheral or central cyanosis.

48. What is the most common cause of hypoxemia?
V/Q mismatch

49. What type of respiratory failure is due to inadequate ventilation?
Hypercapnic respiratory failure

50. What is the treatment for decreased inspired oxygen?
Supplemental oxygen

51. What are the 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 results from what?
Neurologic disease, decreased ventilatory drive, or increased work of breathing.

53. What is work of breathing?
The amount of force needed to move a given volume into the lungs with a relaxed chest wall.

54. What disease states may benefit from NIV in an acute setting?
Acute exacerbation of COPD and carcinogenic edema

55. How is respiratory failure diagnosed?
Respiratory failure is diagnosed through clinical assessment and blood gas analysis to measure oxygen and carbon dioxide levels. Imaging tests like chest X-rays or CT scans help identify underlying conditions, while spirometry evaluates lung function.

56. What are the most common causes of 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?
pH 7.45, PaCO2 33 mmHg, and PaO2 40 mmHg

58. How is respiratory failure related to gas exchange?
Respiratory failure arises when the lungs can’t exchange gases properly, usually due to lung conditions like pneumonia, COPD, ARDS, or neuromuscular disorders affecting breathing mechanics.

59. What is the most common cause of respiratory muscle fatigue?
Excessive work of breathing

60. What will chronic respiratory failure manifest from?
Hypercapnia, evidence of compensatory metabolic alkalosis, and polycythemia.

Final Thoughts

Respiratory failure is a critical condition that requires prompt diagnosis and treatment to prevent serious health complications.

Whether it arises acutely or becomes a chronic issue, addressing the underlying cause and providing the appropriate respiratory support is key to managing the condition.

With advances in medical interventions such as oxygen therapy, non-invasive ventilation, and mechanical ventilation, many patients with respiratory failure can experience improved outcomes and quality of life.

Early recognition and comprehensive care are essential in mitigating the risks associated with this life-threatening disorder.