The document discusses acute respiratory failure, defined as insufficient oxygen and elevated carbon dioxide levels in the blood, and describes its two main types: hypoxemic respiratory failure characterized by low oxygen levels, and hypercapnic respiratory failure characterized by high carbon dioxide levels. It examines the causes, clinical features, diagnosis, and treatment of each type of acute respiratory failure.

1. Acute
respiratory
failure
JEGANNATH A S
GROUP 65

3. Introduction
The body depends on the coordinated functioning of the central nervous
system, pulmonary system, heart, and vascular system to achieve effective
respiration. Respiratory failure arises when one or more of these systems or
organs fail to maintain optimal functioning. If respiratory failure occurs rapidly,
such that compensatory mechanisms cannot accommodate, or if these
compensatory mechanisms are overwhelmed, acute respiratory failure
develops.

4. Definition
Acute respiratory failure (or ARF) is a condition characterized by insufficient
oxygen levels (PaO2 < 60 mmHg) and/or elevated carbon dioxide levels (PaCO2 >
50 mmHg) in the blood, indicating impaired gas exchange in the lungs and an
inability to adequately support the body's respiratory requirements.

5. ARF is classified as:
HYPOXEMIC RESPIRATORY FAILURE
•PaO2 < 60 mmHg
•PaCO2 Normal or Low
•PA-aO2 Increased
HYPERCAPNIC RESPIRATORY
FAILURE
•Pao2 decreased
•PaCO2 > 50 mmHg
•PA-aO2 Normal
•PH decreased

6. Hypoxemic Respiratory Failure
•Definition: Hypoxemic respiratory failure is a subtype of acute respiratory
failure characterized by inadequate oxygenation of the blood.
•Key Indicator: Low levels of oxygen (PaO2) in arterial blood, typically
defined as PaO2 less than 60 mmHg.
•Impaired Gas Exchange: The condition is marked by the failure of the
lungs to efficiently transfer oxygen from the air into the bloodstream.

7. Etiology and Pathophysiology
1.Decreased O2 Delivery:
•Mechanisms:
•Reduced FIO2 due to Increased Altitudes
2.Hypoventilation:
•Mechanisms:
• CNS depression: Drugs (opiates, sedatives), medical conditions (strokes, brain tumors)
• Neuromuscular disorders: ALS, spinal cord injury, Guillain-Barre, myasthenia gravis
• Chest wall or pleural issues: Ankylosing Spondylitis, pleural effusions, pneumothorax,
obesity
• Airway obstruction: Asthma, COPD, foreign body aspiration

8. Etiology and Pathophysiology
3.V/Q Mismatch:
•Mechanisms:
• Ventilation-perfusion mismatch: Airflow (V) doesn't reach areas with blood flow (Q), or
vice versa.
• Dead space ventilation: Ventilation to areas without blood flow (e.g., collapsed alveoli).
• Shunting within the lung: Blood flow bypassing alveoli (e.g., pneumonia, emboli).
4.Shunt
•Types:
• Intracardiac: Blood flows directly from right to left side of heart without going through
lungs (congenital heart defects).
• Intrapulmonary: Blood bypasses alveoli within the lungs (pulmonary emboli, ARDS,
pneumonia with abscesses)

9. Etiology and Pathophysiology
5.Decreased Diffusion
Mechanism:
Oxygen can't easily cross from air sacs to the bloodstream due to:
•Thickened alveolar walls (scarring, protein buildup)
•Fluid in air sacs (edema, ARDS)
•Less membrane surface area (emphysema, lung collapse)
•Abnormal blood flow in capillaries (shunts, clots)

10. Clinical Manifestations
1. Dyspnea (Shortness of Breath)
2. Cyanosis
3. Tachypnea
4. Confusion or Altered Mental Status
5. Fatigue
6. Tachycardia
7. Use of Accessory Muscles

11. Diagnosis of Hypoxemic RF
1.Hypoventilation:
•Diagnosis:
• History and physical examination: Look for signs of respiratory distress,
decreased breath sounds.
• Chest X-ray: May reveal abnormalities like pneumonia or pleural effusions.
• ABG: Shows elevated CO2 levels and potentially low O2 levels.
• Pulmonary function tests: Measure lung function and identify airway obstruction.

12. Diagnosis of Hypoxemic RF
2.V/Q Mismatch
•Diagnosis:
• History and physical examination: Look for signs of respiratory distress and
underlying lung conditions.
• Chest X-ray and CT scan: May show abnormalities like pneumonia or emboli.
• ABG: May show low O2 levels and potentially elevated CO2 levels.
• V/Q scan: Helps identify areas of ventilation-perfusion mismatch.

13. Diagnosis of Hypoxemic RF
3.Shunt
•Diagnosis:
• History and physical examination: Look for signs of right heart strain or
pulmonary embolism.
• Chest X-ray and CT scan: May show enlarged heart or evidence of lung
abnormalities.
• Echocardiogram: To assess heart structure and function.
• V/Q scan: Helps identify areas of perfusion without ventilation (indicative of shunt).

14. Diagnosis of Hypoxemic RF
4.Decreased Diffusion
•History and physical exam: Look for signs of respiratory distress, abnormal
breath sounds, and underlying lung conditions.
•Chest X-ray and CT scan: May show evidence of lung disease, fluid accumulation, or
structural abnormalities.
•Arterial blood gas (ABG): Shows low oxygen levels (PaO2) and potentially normal or
slightly elevated carbon dioxide levels (PaCO2).
•Pulmonary function tests: Can assess gas exchange efficiency and identify
ventilation-perfusion mismatch.

15. Treatment
1.Hypoventilation:
•Address the underlying cause: Reverse drug effects, manage neurological disorders, treat
chest wall or airway issues.
•Non-invasive ventilation (BiPAP) or mechanical ventilation may be needed in severe cases.
2. V/Q Mismatch:
•Address the underlying cause: Antibiotics for pneumonia, anticoagulation for emboli,
ventilation support for ARDS, bronchodilators for COPD.
•Oxygen therapy to improve oxygenation.
•Mechanical ventilation may be needed in severe cases.

16. Treatment
3.Shunt
•Depends on the type and cause of
shunt.
•Surgery for congenital heart defects.
•Anticoagulation for pulmonary emboli.
•Antibiotics for pneumonia with
abscesses.
•Mechanical ventilation for ARDS.
4.Decreased Diffusion
•Address the underlying cause:
• Treat lung disease with
medications or surgery
• Manage fluid accumulation with
diuretics or other therapies
• Anticoagulation for pulmonary
emboli
• Oxygen therapy to improve
oxygenation
• Mechanical ventilation may be
needed in severe cases

17. Hypercapnic Respiratory Failure:
•Definition:
• Medical condition marked by elevated carbon dioxide (hypercapnia) and often
concurrent low oxygen levels (hypoxemia) in the blood.
•Key Indicators:
• Elevated levels of carbon dioxide (PaCO2) in arterial blood (typically >50 mmHg).
• Often accompanied by low levels of oxygen (PaO2), contributing to hypoxemia.
•Underlying Causes:
• Impaired ventilatory function or inadequate respiratory muscle activity.
• Commonly associated with chronic conditions like COPD exacerbation,
neuromuscular diseases (e.g., myasthenia gravis), or chest wall disorders.

18. Etiology and pathophysiology
•Hypoventilation: This is the most common cause of hypercapnic respiratory
failure and occurs when the body is not taking in enough breaths or the breaths
are not deep enough. This can be due to a variety of reasons, including:
• CNS depression: This can be caused by medications like opioids, sedatives, or
anesthesia, or by conditions like stroke, brain tumors, or metabolic imbalances.
• Neuromuscular disorders: These disorders affect the nerves or muscles that control
breathing, such as ALS, Guillain-Barre syndrome, or myasthenia gravis.
• Chest wall or pleural disease: Conditions that restrict the movement of the chest wall
or lungs, such as Ankylosing Spondylitis, pleural effusions, or pneumothorax, can
make it difficult to take deep breaths.
• Obesity: Severe obesity can restrict the movement of the diaphragm and make it
difficult to breathe deeply.
• Airway obstruction: Blockage of the upper or lower airways can make it difficult to get
enough air into the lungs.

19. Clinical Features
•Respiratory:
• Tachypnea: Increased breathing rate, often in an attempt to compensate for the lack of
oxygen.
• Shallow breaths: Patients may take shallow breaths due to fatigue or muscle weakness.
• Apnea: In severe cases, patients may stop breathing altogether for short periods.
• Wheezing: This may be present if there is also an underlying airway obstruction.
• Crackles: These are abnormal sounds heard during lung auscultation, which can indicate
fluid in the lungs.
•Neurological:
• Confusion: Patients may be confused or disoriented due to the buildup of carbon
dioxide in the blood.
• Somnolence: Patients may feel drowsy or sleepy.
• Headache: This is a common symptom of hypercapnia.
• Coma: In severe cases, patients may lapse into a coma.

20. Diagnosis
1. ABG
2. Chest X-ray
3. Pulmonary Function Tests (PFTs)
4. Neuromuscular Studies
5. Capnography
6. Continuous Oxygen Saturation Monitoring

21. Treatments
Bronchodilators
Oxygen Therapy
Non-Invasive Ventilation (NIV): BiPAP and CPAP
Corticosteroids
Mechanical Ventilation