ARDS

Acute Respiratory Distress Syndrome

Complete Nursing Notes + Clinical Management + NORCET MCQ Practice

1. Introduction

Acute Respiratory Distress Syndrome (ARDS) is a severe, life-threatening form of acute respiratory failure caused by widespread inflammation and increased permeability of the alveolar-capillary membrane.

The major consequence is accumulation of fluid in the lungs, loss of functional alveoli, severe impairment of gas exchange, and refractory hypoxemia.

NORCET Focus: ARDS is a form of non-cardiogenic pulmonary edema. The primary problem is increased pulmonary capillary permeability, not left ventricular failure.

2. Definition

ARDS is an acute inflammatory lung injury characterized by increased pulmonary vascular permeability, bilateral pulmonary opacities, impaired oxygenation, and respiratory failure that is not primarily explained by cardiogenic pulmonary edema or fluid overload.

Easy Definition:
ARDS = Acute inflammatory lung injury → alveolar-capillary damage → pulmonary edema → alveolar collapse → severe hypoxemia.

3. Key Features of ARDS

Acute onset Diffuse lung injury Bilateral opacities Severe hypoxemia Low lung compliance Non-cardiogenic pulmonary edema

Acute respiratory distress
Rapidly worsening oxygenation
Diffuse alveolar injury
Increased alveolar-capillary permeability
Protein-rich fluid enters alveoli
Reduced surfactant activity
Alveolar collapse
Ventilation-perfusion mismatch
Intrapulmonary shunting
Reduced lung compliance

4. Causes of ARDS

A. Direct Lung Injury

Severe pneumonia
Aspiration of gastric contents
Inhalation injury
Smoke inhalation
Pulmonary contusion
Near drowning
Viral respiratory infections

B. Indirect/Systemic Causes

Sepsis — one of the most important causes
Septic shock
Severe trauma
Major surgery
Acute pancreatitis
Massive blood transfusion
Severe burns
Shock
Drug toxicity/overdose
Severe systemic inflammatory conditions

Exam Point: Always remember Sepsis + Pneumonia + Aspiration as important clinical triggers of ARDS.

5. Risk Factors

Category	Examples
Infection	Sepsis, severe pneumonia
Aspiration	Vomiting, aspiration of gastric contents
Trauma	Major trauma, pulmonary contusion
Pancreatic disease	Acute pancreatitis
Transfusion	Massive transfusion, transfusion-related lung injury
Burns	Severe burns and inhalation injury
Shock	Septic, hypovolemic or other severe shock states

6. Pathophysiology of ARDS

Trigger
Sepsis / Pneumonia / Aspiration

→

Inflammatory Response

→

Alveolar-Capillary Injury

→

Pulmonary Edema

→

Alveolar Collapse

→

Severe Hypoxemia

Step 1: Inflammatory Trigger

A severe systemic or pulmonary insult activates inflammatory cells and mediators.

Step 2: Alveolar-Capillary Membrane Damage

The pulmonary capillary endothelium and alveolar epithelium become injured. This increases permeability.

Step 3: Fluid Leakage

Protein-rich fluid leaks from pulmonary capillaries into the interstitial tissue and alveolar spaces.

Step 4: Surfactant Dysfunction

Injury and inflammation interfere with surfactant function. This promotes alveolar collapse.

Step 5: Reduced Compliance

The lungs become stiff and difficult to ventilate.

Step 6: V/Q Mismatch and Shunting

Blood continues to pass through poorly ventilated or collapsed alveoli, producing severe oxygenation impairment.

Key Concept: In severe ARDS, increasing oxygen concentration alone may not adequately correct hypoxemia because of significant intrapulmonary shunting.

7. Phases of ARDS

1. Exudative Phase

Usually early phase.
Increased alveolar-capillary permeability.
Protein-rich fluid enters alveoli.
Pulmonary edema develops.
Severe hypoxemia may occur.
Hyaline membrane formation may develop.

2. Proliferative Phase

Begins during recovery or ongoing injury.
Type II pneumocytes proliferate.
Repair of alveolar epithelium begins.
Lung mechanics may gradually improve.

3. Fibrotic Phase

May occur in prolonged severe disease.
Interstitial fibrosis may develop.
Lung compliance becomes markedly reduced.
Prolonged ventilator dependence may occur.

8. Clinical Manifestations

Respiratory Manifestations

Severe dyspnea
Tachypnea
Increased work of breathing
Use of accessory muscles
Hypoxemia
Low oxygen saturation
Cyanosis may occur in severe cases
Crackles may be present
Progressive respiratory failure

Cardiovascular Manifestations

Tachycardia
Hypotension in severe disease
Reduced cardiac output may occur
Right ventricular strain may develop

Neurological Manifestations

Anxiety
Restlessness
Confusion
Altered level of consciousness due to hypoxemia

Clinical Clue: A patient with sepsis who develops rapidly increasing oxygen requirements, bilateral lung opacities and severe hypoxemia should raise suspicion for ARDS.

9. Diagnosis and Berlin Definition

ARDS is diagnosed using clinical assessment, oxygenation measurements, imaging and exclusion of alternative explanations.

Criterion	Key Point
Timing	Within 1 week of a known clinical insult or new/worsening respiratory symptoms.
Chest Imaging	Bilateral opacities not fully explained by effusions, lobar collapse or nodules.
Origin of edema	Respiratory failure not fully explained by cardiac failure or fluid overload.
Oxygenation	PaO₂/FiO₂ ≤300 mmHg with minimum PEEP/CPAP of about 5 cm H₂O.

ARDS Severity

Severity	PaO₂/FiO₂	PEEP
Mild	201–300	≥5 cm H₂O
Moderate	101–200	≥5 cm H₂O
Severe	≤100	≥5 cm H₂O

Exam Point: Lower PaO₂/FiO₂ ratio = more severe oxygenation impairment.

10. Investigations

1. Arterial Blood Gas (ABG)

PaO₂ is often decreased.
Hypoxemia is a major feature.
Early respiratory alkalosis may occur due to tachypnea.
Severe fatigue may lead to respiratory acidosis.
PaO₂/FiO₂ ratio is important for assessing oxygenation.

2. Chest X-ray

Bilateral diffuse or patchy pulmonary opacities.
Findings may resemble pulmonary edema.

3. CT Chest

May demonstrate diffuse lung injury and dependent atelectatic changes.
Not always required for diagnosis.

4. Pulse Oximetry

Continuous SpO₂ monitoring is often required in critically ill patients.

5. Echocardiography

May help evaluate cardiac function.
Useful when cardiogenic pulmonary edema is an alternative diagnosis.

6. Laboratory Tests

CBC
Electrolytes
Renal and liver function tests
Blood cultures when infection is suspected
Inflammatory markers according to clinical situation

11. ARDS vs Cardiogenic Pulmonary Edema

Feature	ARDS	Cardiogenic Pulmonary Edema
Main mechanism	Increased alveolar-capillary permeability	Increased hydrostatic pressure
Primary problem	Lung injury	Cardiac dysfunction
Cardiac failure	Not the primary cause	Usually present
Edema type	Non-cardiogenic	Cardiogenic
PCWP	Classically not elevated because of left heart failure	May be elevated
Common causes	Sepsis, pneumonia, aspiration	Left ventricular failure, acute MI

Remember:
ARDS = permeability problem
Cardiogenic pulmonary edema = hydrostatic pressure problem

12. Medical Management of ARDS

1. Treat the Underlying Cause

Early recognition and treatment of sepsis.
Appropriate antimicrobial therapy when bacterial infection is suspected.
Treatment of aspiration, trauma, pancreatitis or other precipitating conditions.

2. Oxygen Therapy

Supplemental oxygen is provided according to oxygenation status.
Escalation may include high-flow oxygen or non-invasive support in selected patients.
Patients with severe respiratory failure may require invasive mechanical ventilation.

3. Lung-Protective Mechanical Ventilation

Lung-protective ventilation is a cornerstone of management for mechanically ventilated patients with ARDS.

Use lower tidal volumes based on predicted body weight.
A commonly taught target is approximately 6 mL/kg predicted body weight, adjusted according to clinical response and protocol.
Plateau pressure is generally targeted at less than 30 cm H₂O.
PEEP is used to prevent alveolar collapse.

NORCET High-Yield: In ARDS, avoid ventilator-induced lung injury by using lung-protective ventilation.

4. PEEP

Positive end-expiratory pressure helps keep alveoli open at the end of expiration and may improve oxygenation.

5. Prone Positioning

Prone positioning is an important intervention for selected patients with moderate-to-severe ARDS and significant hypoxemia.

Key Point: Proning can improve ventilation-perfusion matching and oxygenation by recruiting dependent lung regions and reducing regional overdistension.

6. Conservative Fluid Strategy

When appropriate, avoiding unnecessary positive fluid balance can help reduce pulmonary edema and may facilitate lung recovery.

7. Neuromuscular Blockade

Short-term neuromuscular blockade may be considered in selected patients when severe ventilator dyssynchrony or other clinical indications exist.

8. Extracorporeal Support

ECMO may be considered in selected patients with severe refractory respiratory failure despite optimal conventional therapy.

13. Prone Positioning in ARDS

Prone positioning means placing the patient on the abdomen rather than the usual supine position.

Benefits

Improves ventilation-perfusion matching.
May improve oxygenation.
Promotes recruitment of dependent lung regions.
May reduce ventilator-induced lung injury when appropriately performed.

Nursing Responsibilities During Proning

Assess airway security before turning.
Check endotracheal tube position and fixation.
Coordinate turning with the multidisciplinary team.
Protect eyes from pressure and injury.
Assess pressure points.
Protect skin.
Monitor oxygen saturation and hemodynamic status.
Ensure all lines, tubes and drains remain secure.
Provide regular repositioning and skin assessment according to protocol.

14. Nursing Management of ARDS

A. Airway and Breathing

Assess airway patency.
Monitor respiratory rate and pattern.
Assess work of breathing.
Monitor SpO₂ continuously when indicated.
Assess breath sounds.
Administer oxygen as prescribed.
Prepare for advanced airway management when respiratory failure worsens.

B. Mechanical Ventilation

Monitor ventilator settings and alarms.
Assess patient-ventilator synchrony.
Monitor airway pressures.
Check endotracheal tube security.
Perform oral care according to ICU protocol.
Use appropriate infection-prevention measures.

C. Oxygenation Monitoring

Monitor SpO₂ trends rather than relying on a single value.
Review ABG results.
Observe for increasing oxygen requirement.
Report worsening hypoxemia immediately.

D. Hemodynamic Monitoring

Monitor blood pressure.
Monitor heart rate and rhythm.
Assess peripheral perfusion.
Monitor urine output.
Observe for signs of shock.

E. Fluid Management

Maintain accurate intake-output charting.
Daily weight may be monitored when appropriate.
Assess for edema.
Administer IV fluids and diuretics only according to the clinical plan.

F. Nutrition

Assess nutritional requirements.
Enteral nutrition is generally preferred when the gastrointestinal tract is functional and there is no contraindication.
Monitor tolerance.

G. Infection Prevention

Strict hand hygiene.
Maintain aseptic technique.
Provide appropriate oral care.
Monitor for ventilator-associated complications.
Collect specimens as ordered.

H. Psychological Support

Explain procedures whenever possible.
Reduce anxiety.
Communicate with ventilated patients using appropriate methods.
Support family members.

15. Nursing Care of a Mechanically Ventilated ARDS Patient

Area	Nursing Action
Airway	Maintain airway patency and secure ETT.
Ventilator	Check settings, alarms and patient-ventilator synchrony.
Oxygenation	Monitor SpO₂ and ABG trends.
Secretions	Assess and suction when clinically indicated using appropriate technique.
Pressure injury	Perform regular skin assessment and repositioning.
VAP prevention	Follow institutional ventilator-associated pneumonia prevention bundle.
Nutrition	Monitor enteral feeding and aspiration precautions as appropriate.
Mobility	Provide appropriate mobilization according to stability and ICU protocol.

16. Complications of ARDS

Severe hypoxemic respiratory failure
Respiratory arrest
Multiorgan dysfunction
Septic shock
Barotrauma
Ventilator-induced lung injury
Ventilator-associated pneumonia
Deep vein thrombosis
Pressure injuries
Muscle weakness
Delirium
Prolonged mechanical ventilation
Pulmonary fibrosis in some prolonged cases
Death

17. Prevention of ARDS

Early recognition and treatment of sepsis.
Prevention of aspiration.
Appropriate infection prevention.
Safe blood transfusion practices.
Early treatment of pneumonia.
Appropriate fluid management in critically ill patients.
Use lung-protective ventilation when mechanical ventilation is required.
Prevention of ventilator-associated complications.

18. NORCET High-Yield Points

ARDS is an acute inflammatory lung injury.
ARDS causes non-cardiogenic pulmonary edema.
Sepsis is an important cause of ARDS.
Pneumonia and aspiration are major direct lung insults.
ARDS causes severe hypoxemia.
PaO₂/FiO₂ ratio is used to assess oxygenation severity.
Lower PaO₂/FiO₂ = greater severity.
ARDS is associated with decreased lung compliance.
PEEP helps maintain alveolar recruitment.
Lung-protective ventilation is essential.
Tidal volume is based on predicted body weight, not actual body weight.
Plateau pressure is generally kept below 30 cm H₂O.
Prone positioning is important for selected severe ARDS patients.
Conservative fluid management may be beneficial when appropriate.
ECMO may be considered for selected refractory severe cases.

19. Quick Revision

Question	Answer
Full form	Acute Respiratory Distress Syndrome
Main pathology	Diffuse inflammatory alveolar-capillary injury
Type of edema	Non-cardiogenic pulmonary edema
Important causes	Sepsis, pneumonia, aspiration, trauma, pancreatitis
Major clinical problem	Severe hypoxemia
Important measurement	PaO₂/FiO₂ ratio
Ventilation strategy	Lung-protective ventilation
Important ventilator parameter	PEEP
Positioning strategy	Prone positioning in selected moderate-to-severe cases
Severe refractory respiratory failure	Consider ECMO in selected patients

20. Easy Memory Trick

ARDS = "AIR"

A → Alveolar-capillary injury

I → Inflammation

R → Reduced oxygenation

S → Stiff lungs

Management Memory:
O-P-V-F-C

O → Oxygenation support
P → Prone positioning
V → Ventilation: lung protective
F → Fluid strategy
C → Cause treatment

ARDS — Clinical MCQ Practice Test

25 Questions • One by One • 30 Minutes

30:00

Important Note

These notes are prepared for educational and nursing examination purposes. Clinical management should always follow current institutional protocols, physician/critical-care team recommendations and evidence-based guidelines.

ARDS (Acute Respiratory Distress Syndrome): Complete Nursing Notes, Phases & NORCET MCQs