Respiratory Failure: Overview and Practice Questions (2024)

Respiratory failure is a critical condition marked by the inability of the respiratory system to fulfill its primary function of gas exchange, leading to inadequate oxygenation or carbon dioxide elimination.

This condition can manifest due to chronic illnesses like chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS) or acute events like trauma.

This article delves into the mechanisms, classifications, causes, and management strategies of respiratory failure, shedding light on the importance of prompt diagnosis and intervention.

What is Respiratory Failure?

Respiratory failure occurs when the respiratory system fails in oxygenation or carbon dioxide elimination, affecting the levels of oxygen or carbon dioxide in the blood. It can be caused by conditions like COPD or pneumonia. In acute cases, it demands immediate medical attention as it can be life-threatening, requiring support like mechanical ventilation.

Types of Respiratory Failure

Respiratory failure can be categorized primarily into two types:

1. Hypoxemic respiratory failure (Type I)
2. Hypercapnic respiratory failure (Type II)

Hypoxemic Respiratory Failure 

This occurs due to impaired oxygenation, with PaO2 (partial pressure of oxygen in arterial blood) less than 60 mmHg while breathing room air.

Causes can include conditions that affect gas exchange within the lungs, such as pneumonia, pulmonary embolism, or acute respiratory distress syndrome (ARDS).

Hypercapnic Respiratory Failure

This is characterized by inadequate alveolar ventilation, leading to PaCO2 (partial pressure of carbon dioxide in arterial blood) of more than 45 mmHg.

Chronic obstructive pulmonary disease (COPD), severe asthma, and neuromuscular disorders are typical conditions leading to Type II respiratory failure.

Note: Respiratory failure can also be classified as acute, chronic, or acute on chronic based on the onset and duration of the condition. In acute respiratory failure, there is a rapid onset of symptoms, often requiring immediate medical attention, whereas chronic respiratory failure develops over time and is typically associated with underlying chronic conditions. Acute on chronic respiratory failure occurs when an acute event exacerbates an existing chronic respiratory condition.

Treatment for Respiratory Failure

Treatment for respiratory failure is often multifaceted, involving both supportive care and addressing the underlying cause.

Here’s a general overview of the treatment strategies:

• Oxygen Therapy: Supplemental oxygen is administered to correct hypoxemia, and it’s the primary treatment for Type 1 respiratory failure.
• Ventilatory Support: Noninvasive ventilation (NIV) like continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) can be used, particularly in Type 2 respiratory failure. Invasive mechanical ventilation is employed in severe cases or when noninvasive measures fail.
• Medication: Bronchodilators and anti-inflammatory medications can aid in conditions like asthma and COPD. Antibiotics are administered when an infection is the underlying cause. Diuretics may be used to remove excess fluid in cases of heart failure causing respiratory failure.
• Addressing Underlying Cause: Treating the underlying condition causing respiratory failure is crucial, whether it’s an infection, a pulmonary embolism, or a neuromuscular disorder.
• Extracorporeal Membrane Oxygenation (ECMO): In extreme cases, especially when mechanical ventilation is insufficient, ECMO may be utilized to oxygenate the blood externally.
• Pulmonary Rehabilitation: In chronic cases, pulmonary rehabilitation can be helpful to improve lung function, manage symptoms, and enhance the quality of life.
• Lifestyle Modifications: Smoking cessation, maintaining a healthy lifestyle, and avoiding respiratory irritants are essential in managing and preventing further deterioration in cases of respiratory failure.
• Fluid Management: Appropriate fluid management is crucial to prevent fluid overload, particularly in cases with concomitant heart failure.

Note: Treatment must be promptly initiated and tailored according to the type and cause of respiratory failure, the severity of the condition, and the patient’s overall clinical status and comorbidities.

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 severe medical condition where compromised respiratory function leads to insufficient oxygen levels or inadequate carbon dioxide elimination from the blood.

Early detection and appropriate intervention are crucial to manage the underlying causes effectively and prevent further complications.

The management of respiratory failure is multifaceted, involving pharmacological interventions, mechanical ventilation, and in severe cases, extracorporeal membrane oxygenation (ECMO) to support affected individuals, emphasizing the critical nature of understanding and addressing this life-threatening condition.