Guide — Respiratory

ARDS Fundamentals for Nurses

Acute Respiratory Distress Syndrome is a life-threatening form of acute hypoxic respiratory failure characterized by diffuse alveolar damage, refractory hypoxemia, and bilateral pulmonary infiltrates. It requires mechanical ventilation and meticulous nursing care.

12 min read · Respiratory

Educational use only. ARDS management requires an ICU team including intensivists, respiratory therapists, and critical care nurses. This guide supports learning and NCLEX preparation — it does not replace clinical training or institutional protocols. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.

Definition and Pathophysiology

ARDS is caused by direct or indirect lung injury that triggers a massive inflammatory response. The sequence:

1Insult (pneumonia, sepsis, trauma, aspiration) → inflammatory cascade

2Inflammatory mediators damage the alveolar-capillary membrane

3Increased capillary permeability → protein-rich fluid floods alveoli (non-cardiogenic pulmonary edema)

4Surfactant disruption → alveolar collapse (atelectasis) at end-expiration

5Refractory hypoxemia — V/Q mismatch and shunt → SpO₂ does not respond to supplemental O₂ alone

Common Causes

Direct Lung Injury

Pneumonia (bacterial, viral, fungal)
Aspiration of gastric contents
Pulmonary contusion (chest trauma)
Inhalation injury (smoke, chemical)
Near-drowning

Indirect Lung Injury

Sepsis (most common cause overall)
Severe trauma / multiple injuries
Pancreatitis
Massive blood transfusion (TRALI)
Cardiopulmonary bypass

Berlin Criteria Overview

The 2012 Berlin Definition classifies ARDS by the PaO₂/FiO₂ (P/F) ratio while on PEEP ≥5 cmH₂O. Diagnosis requires all four criteria:

TimingWithin 1 week of a known insult or new/worsening respiratory symptoms

Chest imagingBilateral opacities on CXR or CT — not fully explained by effusions, atelectasis, or nodules

Origin of edemaRespiratory failure not fully explained by cardiac failure or fluid overload (rule out cardiogenic pulmonary edema)

Oxygenation (P/F ratio)Mild: 200–300 mmHg | Moderate: 100–200 mmHg | Severe: <100 mmHg

P/F Ratio = PaO₂ ÷ FiO₂. Example: PaO₂ 80 mmHg on FiO₂ 0.6 (60%) → P/F ratio = 80/0.6 = 133 (moderate ARDS).

Clinical Manifestations

System	Finding
Respiratory	Severe dyspnea; tachypnea; refractory hypoxemia (SpO₂ fails to improve with supplemental O₂); bilateral crackles; increased work of breathing with accessory muscle use
Oxygenation	P/F ratio <300 mmHg; refractory hypoxemia requiring mechanical ventilation
Cardiovascular	Tachycardia; hypotension (from sepsis or high PEEP reducing venous return)
Imaging	Bilateral diffuse infiltrates ('white-out' or 'ground-glass' opacities) on CXR and CT
Mental status	Anxiety, agitation from hypoxia; altered LOC in severe hypoxemia
ABG	Initially: resp. alkalosis (hyperventilation trying to compensate). Later: respiratory acidosis as fatigue develops. Low PaO₂ throughout.

Ventilator Considerations in ARDS

ARDS lungs are heterogeneous — some regions are collapsed (atelectatic), some flooded, and some relatively normal. Mechanical ventilation must protect the healthy regions while recruiting the collapsed ones.

Lung-Protective Ventilation (ARDSNet)Tidal volume 6 mL/kg of ideal body weight (low Vt). Plateau pressure target <30 cmH₂O. Higher PEEP tables to match FiO₂ requirements and maintain alveolar recruitment. Permissive hypercapnia is tolerated — pH >7.20 acceptable to avoid high pressures.

PEEP StrategyHigher PEEP (up to 15–20 cmH₂O in severe ARDS) recruits collapsed alveoli and prevents end-expiratory deatelectasis. However, high PEEP can overdistend healthy lung regions (barotrauma) and reduce cardiac output — monitor BP and perfusion.

FiO₂ TitrationGoal SpO₂ 88–95%. Use the lowest FiO₂ that achieves the target. High FiO₂ (>60%) for prolonged periods causes oxygen toxicity — PEEP recruitment should allow FiO₂ reduction over time.

Prone PositioningPlacing ARDS patients prone for 16+ hours/day improves oxygenation by redistributing perfusion to better-ventilated lung regions. Shown to reduce mortality in moderate-severe ARDS. Requires careful ETT management, pressure injury prevention, and team coordination.

Neuromuscular BlockadeCisatracurium (48 hours) is used in moderate-severe ARDS to eliminate patient-ventilator dyssynchrony, reduce oxygen consumption, and prevent breathing effort-induced lung injury. Nursing: maintain analgesia and sedation; assess train-of-four (TOF) per protocol; prevent complications of immobility.

Nursing Priorities

Oxygenation monitoringContinuous SpO₂, frequent ABGs, P/F ratio trending

Ventilator managementVerify settings match orders; monitor PIP and plateau; respond to alarms; report plateau >30 cmH₂O

Hemodynamic monitoringPEEP decreases venous return; monitor BP, HR, and perfusion indicators with PEEP changes

VAP prevention bundleHOB 30–45°, oral care q4h, hand hygiene, closed suction system, daily SBT readiness review

Prone positioning managementCoordinate team; secure ETT before turning; protect pressure points (face, sternum, knees); maintain tube patency

Fluid managementConservative fluid strategy is preferred after initial resuscitation — monitor intake/output and daily weights

Nutrition supportEnteral feeding within 24–48h when hemodynamically stable; prone position does not preclude enteral feeds

Skin and pressure injury preventionReposition q2h minimum; protect bony prominences; extra vigilance during prone positioning

NCLEX Pearls

›ARDS hallmark: bilateral infiltrates + refractory hypoxemia (SpO₂ does not improve with supplemental O₂ alone) + non-cardiogenic cause.
›P/F ratio < 300 = ARDS. < 200 = moderate. < 100 = severe.
›Tidal volume 6 mL/kg IBW (not actual weight) is the lung-protective target in ARDS.
›PEEP improves oxygenation by preventing alveolar collapse at end-expiration but decreases cardiac output by reducing venous return.
›Prone positioning for 16+ hours/day reduces mortality in moderate-severe ARDS — requires coordinated team turn.
›The most common cause of ARDS is sepsis — treat the underlying cause while supporting the lungs.
›Permissive hypercapnia is intentionally allowed in ARDS to avoid dangerously high airway pressures.

Related Resources

Mechanical Ventilation BasicsFiO₂, PEEP, tidal volume, RR — key settings and nursing monitoring

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Respiratory Failure ReferenceType I vs Type II — causes, ABG patterns, and nursing implications

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Respiratory Failure Comparison ChartType I vs Type II oxygenation, CO₂, and causes side by side

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Ventilator Troubleshooting for NursesHigh/low pressure alarms, DOPE mnemonic, step-by-step response

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Sepsis Recognition and ManagementSepsis-3, septic shock, nursing priorities — ARDS trigger

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Standards & sources

Fact-checked Jun 21, 2026

This page is written to align with American Association for Respiratory Care (AARC) · GOLD (COPD) / ATS / CHEST. It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →