RESPIRATORY FAILURE

Acute & Chronic Respiratory Failure

Complete Adult Health Nursing Notes + Clinical Management + NORCET MCQ Practice

1. Introduction

Respiratory failure is a serious clinical condition in which the respiratory system fails to maintain adequate oxygenation and/or adequate removal of carbon dioxide.

It can result from problems involving the airways, lungs, respiratory muscles, chest wall, central nervous system, or combinations of these conditions.

NORCET Focus: Respiratory failure is primarily identified by abnormal PaO₂ and/or PaCO₂, together with the clinical condition of the patient.

2. Definition

Respiratory failure is a condition in which the respiratory system is unable to maintain adequate gas exchange, resulting in inadequate oxygenation, inadequate carbon dioxide elimination, or both.

Common ABG Concept:

Hypoxemic respiratory failure: PaO₂ is typically <60 mmHg on room air.

Hypercapnic respiratory failure: PaCO₂ is typically >50 mmHg with acidemia in acute respiratory failure.

These values are useful examination thresholds, but clinical interpretation should consider the patient's baseline condition, oxygen therapy, chronicity, and overall clinical picture.

3. Types of Respiratory Failure

Type	Main Problem	Typical ABG Pattern	Examples
Type I Hypoxemic	Failure of oxygenation	Low PaO₂; PaCO₂ normal or low	Pneumonia, pulmonary edema, ARDS, pulmonary embolism
Type II Hypercapnic	Failure of ventilation	High PaCO₂; acute cases usually have low pH	COPD exacerbation, severe asthma, neuromuscular weakness
Type III	Perioperative/atelectatic respiratory failure	Variable	Postoperative atelectasis, reduced functional residual capacity
Type IV	Shock-related respiratory failure	Variable	Shock states with respiratory muscle hypoperfusion/fatigue

Exam Focus: The two most important classic categories are Type I hypoxemic and Type II hypercapnic respiratory failure.

4. Type I Respiratory Failure — Hypoxemic

Type I respiratory failure is primarily a failure of oxygenation. The PaO₂ is reduced, while PaCO₂ may be normal or decreased, especially when the patient is initially hyperventilating.

Common Causes

Pneumonia
ARDS
Pulmonary edema
Pulmonary embolism
Atelectasis
Severe interstitial lung disease
Severe alveolar filling disorders

Pathophysiology

Lung Injury

→

V/Q Mismatch
or Shunt

→

Reduced O₂ Transfer

→

Hypoxemia

5. Type II Respiratory Failure — Hypercapnic

Type II respiratory failure occurs when alveolar ventilation is inadequate, resulting in carbon dioxide retention.

Key Concept:
Hypoventilation → CO₂ retention → increased PaCO₂.

Common Causes

Acute exacerbation of COPD
Severe asthma
Central nervous system depression
Opioid or sedative overdose
Neuromuscular disorders
Spinal cord injury
Guillain-Barré syndrome
Myasthenia gravis crisis
Severe chest-wall disorders
Respiratory muscle fatigue

ABG Pattern

Increased PaCO₂
Acute cases: decreased pH due to respiratory acidosis
Chronic cases: renal bicarbonate retention may partially compensate

Important: A rising PaCO₂ in a tiring patient can be a warning sign of worsening ventilatory failure, particularly when the patient was previously hyperventilating.

6. Acute vs Chronic Respiratory Failure

Feature	Acute	Chronic
Onset	Sudden or rapid	Gradual or persistent
Renal compensation	Limited	More developed
pH in hypercapnia	Usually significantly decreased	May be closer to normal because of compensation
Example	Acute opioid overdose	Advanced COPD with chronic CO₂ retention

ABG Trick: In chronic respiratory acidosis, the kidneys retain bicarbonate over time, so the pH is usually less abnormal than in acute respiratory acidosis.

7. Causes of Respiratory Failure

A. Airway Disorders

Foreign-body obstruction
Severe asthma
Upper-airway obstruction
Severe airway edema
Mucus plugging

B. Lung Disorders

Pneumonia
ARDS
Pulmonary edema
Pulmonary embolism
Pneumothorax
Severe COPD
Interstitial lung disease

C. Neurological Causes

Stroke
Brainstem injury
Spinal cord injury
Guillain-Barré syndrome
Myasthenia gravis

D. Drug-Related Causes

Opioid overdose
Sedative overdose
Other central respiratory depressants

E. Chest Wall / Muscle Causes

Severe kyphoscoliosis
Chest trauma
Respiratory muscle weakness
Severe obesity-related ventilatory impairment

8. Pathophysiology

Primary Disease

→

Impaired Ventilation
and/or Oxygenation

→

↓ PaO₂
and/or ↑ PaCO₂

→

Cellular Hypoxia

→

Organ Dysfunction

Hypoxemia

Hypoxemia occurs when oxygen transfer from the lungs to the blood is inadequate. Important mechanisms include ventilation-perfusion mismatch, shunt, diffusion impairment and low inspired oxygen.

Hypercapnia

Hypercapnia primarily results from inadequate alveolar ventilation. When carbon dioxide production exceeds effective elimination, PaCO₂ rises.

9. Clinical Manifestations

Early Signs

Tachypnea
Dyspnea
Restlessness
Anxiety
Tachycardia
Increased work of breathing
Use of accessory muscles
Low oxygen saturation

Progressive / Severe Signs

Cyanosis
Confusion
Altered level of consciousness
Severe fatigue
Bradypnea in impending ventilatory failure
Paradoxical breathing
Hypotension
Cardiac dysrhythmias
Respiratory arrest

Critical Warning: A patient who initially has severe respiratory distress and later becomes drowsy, quieter or develops a slowing respiratory rate may be deteriorating, not improving.

10. Diagnostic Evaluation

1. Arterial Blood Gas — ABG

ABG is one of the most important investigations in suspected respiratory failure.

Parameter	What It Tells Us
PaO₂	Oxygenation
PaCO₂	Ventilation / carbon dioxide removal
pH	Acid-base status
HCO₃⁻	Metabolic/renal compensation
SaO₂	Arterial oxygen saturation

2. Pulse Oximetry

Provides continuous non-invasive estimation of oxygen saturation.
Useful for monitoring trends.
Does not measure PaCO₂ directly.

3. Chest X-ray

May identify pneumonia.
May show pulmonary edema.
May show atelectasis or pneumothorax.

4. ECG

Helps identify cardiac causes, dysrhythmias and effects of severe hypoxemia.

5. Additional Tests

CT chest when indicated
Blood cultures when infection is suspected
CBC
Electrolytes
Renal and liver function tests
Cardiac investigations when indicated
Pulmonary function testing in stable chronic conditions, when appropriate

11. ABG Patterns — High Yield

Condition	PaO₂	PaCO₂	pH
Type I Respiratory Failure	↓	Normal / ↓	Variable
Acute Type II	↓	↑	↓
Chronic Type II	Often ↓	↑	Near normal or mildly ↓ due to compensation

Remember:

Type I = Oxygen problem
↓ PaO₂

Type II = Ventilation problem
↑ PaCO₂

12. Management of Respiratory Failure

Step 1: Immediate Assessment — ABC

Assess airway patency.
Assess breathing.
Assess circulation.
Monitor oxygen saturation.
Obtain ABG when indicated.
Identify and treat the underlying cause.

Step 2: Oxygen Therapy

Administer supplemental oxygen according to clinical need.
Monitor response using clinical assessment and SpO₂.
Use controlled oxygen strategies when appropriate, especially in patients at risk of hypercapnic respiratory failure.

COPD / CO₂ Retention Point: In patients at risk of hypercapnic respiratory failure, oxygen should be carefully titrated according to the prescribed target range and clinical assessment rather than automatically giving uncontrolled high-concentration oxygen.

Step 3: Treat the Cause

Antibiotics when bacterial infection is suspected and indicated.
Bronchodilators for bronchospasm.
Diuretics when fluid overload/pulmonary edema is present and clinically appropriate.
Antidotes for specific drug overdoses.
Anticoagulation for appropriate thromboembolic disease.
Relief of airway obstruction.

Step 4: Non-Invasive Ventilation

Non-invasive ventilation provides ventilatory support without an endotracheal tube.

CPAP: primarily provides continuous positive airway pressure.
BiPAP/NIV: provides different inspiratory and expiratory pressure support and can improve ventilation in selected patients.

Step 5: Invasive Mechanical Ventilation

Endotracheal intubation and mechanical ventilation may be required when respiratory failure is severe or non-invasive support is unsuccessful or inappropriate.

13. Indications for Endotracheal Intubation & Mechanical Ventilation

Inability to protect the airway
Severe or worsening hypoxemia
Severe hypercapnia with acidemia
Respiratory arrest
Severe respiratory muscle fatigue
Persistent altered consciousness affecting airway safety
Failure or contraindication of non-invasive ventilation
Severe work of breathing despite initial treatment

Clinical Priority: The decision to intubate is based on the overall clinical condition, airway protection, gas exchange, work of breathing and response to treatment— not on a single ABG number alone.

14. Non-Invasive Ventilation — CPAP vs BiPAP

Feature	CPAP	BiPAP / NIV
Pressure	One continuous pressure	Different inspiratory and expiratory pressures
Main effect	Alveolar recruitment / oxygenation support	Ventilatory assistance + oxygenation support
Useful in	Selected hypoxemic conditions and sleep-related disorders	Selected hypercapnic respiratory failure, especially COPD exacerbation

NIV should be used only when the patient is an appropriate candidate and can protect the airway, cooperate and tolerate the interface.

15. Nursing Management of Respiratory Failure

A. Airway

Assess airway patency.
Position the patient appropriately.
Clear secretions when clinically indicated.
Prepare for advanced airway management if deterioration occurs.

B. Breathing

Monitor respiratory rate.
Assess depth and pattern.
Assess work of breathing.
Monitor accessory muscle use.
Assess breath sounds.
Monitor SpO₂ continuously when indicated.

C. ABG Monitoring

Review PaO₂.
Review PaCO₂.
Assess pH.
Evaluate bicarbonate for compensation.
Report worsening gas exchange promptly.

D. Positioning

Position to maximize ventilation and comfort.
Elevate the head of bed when appropriate.
Use individualized positioning according to the cause of respiratory failure.

E. Oxygen Therapy

Administer prescribed oxygen.
Ensure correct device placement.
Monitor response.
Monitor for deterioration despite oxygen therapy.

F. Mechanical Ventilation

Monitor ventilator settings and alarms.
Assess patient-ventilator synchrony.
Maintain airway security.
Provide oral care.
Follow infection-prevention protocols.

G. Nutrition & Hydration

Assess nutritional status.
Monitor fluid balance.
Provide enteral nutrition when appropriate.
Monitor aspiration risk.

H. Psychological Support

Reduce anxiety.
Explain procedures.
Provide reassurance.
Use communication aids for ventilated patients.

16. Nursing Priorities — ABC Approach

A
Airway

→

B
Breathing

→

C
Circulation

→

ABG + Monitoring

→

Treat Cause

Priority: If the patient has an immediately threatened airway or severe respiratory compromise, stabilize the patient first while the underlying cause is being investigated.

17. Complications

Severe tissue hypoxia
Altered consciousness
Cardiac dysrhythmias
Cardiac arrest
Respiratory arrest
Multi-organ dysfunction
Hemodynamic instability
Ventilator-associated pneumonia
Barotrauma
Ventilator-induced lung injury
Muscle weakness
Death

18. Prevention

Early treatment of respiratory infections.
Smoking cessation.
Good control of chronic respiratory diseases.
Vaccination according to recommended schedules.
Aspiration precautions in high-risk patients.
Safe medication use.
Early mobilization when appropriate.
Effective postoperative pulmonary care.
Appropriate airway and ventilator care.

19. NORCET High-Yield Points

Type I = Hypoxemic respiratory failure.
Type I usually has low PaO₂ with PaCO₂ normal or low.
Type II = Hypercapnic respiratory failure.
Type II is characterized by elevated PaCO₂.
Acute hypercapnic respiratory failure usually causes respiratory acidemia.
Chronic CO₂ retention produces renal bicarbonate compensation.
COPD exacerbation is a common cause of Type II respiratory failure.
Pneumonia, ARDS and pulmonary edema commonly produce Type I respiratory failure.
ABG is an important investigation for respiratory failure.
Pulse oximetry measures oxygen saturation but does not directly measure PaCO₂.
A rising PaCO₂ with worsening mental status may indicate ventilatory failure.
Severe work of breathing and inability to protect the airway may require intubation.
NIV is useful in selected patients who can protect their airway and tolerate the interface.
BiPAP provides inspiratory and expiratory pressure support and can improve ventilation.
CPAP provides continuous positive airway pressure.

20. Quick Revision Table

Question	Answer
What is respiratory failure?	Failure of adequate oxygenation and/or ventilation.
Type I?	Hypoxemic respiratory failure.
Type II?	Hypercapnic respiratory failure.
Type I key ABG	Low PaO₂.
Type II key ABG	High PaCO₂.
Common Type II cause	Acute COPD exacerbation.
Common Type I causes	Pneumonia, ARDS, pulmonary edema, PE.
Important investigation	ABG.
Non-invasive support	CPAP / BiPAP depending on clinical indication.
Advanced support	Endotracheal intubation and mechanical ventilation when indicated.

21. Easy Memory Tricks

Type I = "O₂ Problem"

I = Inadequate Oxygen

Main problem → ↓ PaO₂

Type II = "CO₂ Problem"

II = Increased CO₂

Main problem → ↑ PaCO₂

ABG Memory:

PaO₂ → Oxygenation
PaCO₂ → Ventilation
pH → Acid-base status
HCO₃⁻ → Metabolic/renal component