ARDS Nursing Guide | GCC ICU Reference

Berlin Definition (2012) — ARDS Classifier

All four criteria must be met. Use the interactive tool below.

1. Timing: within 1 week of clinical insult or new/worsening respiratory symptoms? 2. Chest imaging: bilateral opacities (not explained by effusion, collapse, or nodules)? 3. Origin: not fully explained by cardiac failure or fluid overload? 4. Oxygenation: P/F ratio on PEEP ≥ 5 cmH₂O?

P/F Ratio Calculator

PaO₂ (mmHg) ÷ FiO₂ (decimal)

PaO₂ (mmHg) — from ABG FiO₂ (0.21 – 1.0)

SpO₂/FiO₂ Calculator

Use when no ABG is available

SpO₂ (%) FiO₂ (0.21 – 1.0)

ARDS Severity — Quick Reference

MILD P/F 200–300 | S/F 235–315 | PEEP ≥ 5 cmH₂O

MODERATE P/F 100–200 | S/F 148–235 | PEEP ≥ 5 cmH₂O

SEVERE P/F < 100 | S/F < 148 | PEEP ≥ 5 cmH₂O

Common ARDS Causes in the GCC

Pulmonary (Direct)

Pneumonia — CAP, COVID-19, MERS-CoV
Aspiration of gastric contents
Inhalation injury (smoke, chemicals)
Near-drowning (pools & sea — GCC-specific)

Extra-pulmonary (Indirect)

Sepsis — most common overall cause
TRALI (blood transfusion-related)
Acute pancreatitis
Major trauma, burns
Road traffic accidents (very common in GCC)
MERS-CoV outbreaks (Saudi Arabia, UAE)

Pathophysiology — Disease Phases

Exudative Phase — Day 0 to 7 Diffuse alveolar damage, protein-rich oedema floods alveoli, hyaline membrane formation, neutrophil influx, refractory hypoxaemia. Onset of bilateral infiltrates on imaging.

Fibroproliferative Phase — Day 7 to 21 Type II pneumocyte proliferation, early fibrosis, organisation of exudate. Reduced compliance, worsening dead-space ventilation. High ventilator pressures often required.

Resolution or Fibrosis — Day 21+ Majority recover lung function over weeks to months. ~20% progress to fibrosis with persistent restrictive defect. Survivors may have long-term cognitive and physical impairment (PICS).

ARDSNet / ARMA Trial Evidence: Tidal volume 6 mL/kg IBW reduces 28-day mortality versus 12 mL/kg IBW (31.0% vs 39.8%). Plateau pressure ≤ 30 cmH₂O is mandatory.

Lung-Protective Ventilation Parameters

Parameter	Target	Notes
Tidal Volume (VT)	6 mL/kg IBW	Use ideal body weight — not actual weight
Plateau Pressure	≤ 30 cmH₂O	Inspiratory hold manoeuvre (0.5–1 s)
Driving Pressure	≤ 15 cmH₂O	Plateau − PEEP; independent mortality predictor
PEEP	8–16 cmH₂O	Titrate per PEEP/FiO₂ table below
FiO₂	Titrate	Target SpO₂ 88–95%; avoid hyperoxia
Respiratory Rate	20–35 /min	Maintain pH > 7.20 (permissive hypercapnia OK)
SpO₂ Target	88–95%	Do NOT target > 97% — hyperoxia is harmful
PaCO₂ Tolerance	50–70 mmHg	Acceptable if pH > 7.20; contraindicated if raised ICP

IBW Calculator (ARDSNet)

IBW determines safe tidal volume

Height (cm) Sex

Driving Pressure Calculator

Plateau Pressure − PEEP

Plateau Pressure (cmH₂O) PEEP (cmH₂O)

PEEP / FiO₂ Table (ARDSNet)

Lower PEEP strategy — titrate to achieve SpO₂ 88–95%

FiO₂	0.3	0.4	0.4	0.5	0.5	0.6	0.7	0.7	0.8	0.9	1.0
PEEP	5	5	8	8	10	10	10	12	14	14–16	18–24

Higher PEEP strategy used in moderate-severe ARDS at discretion of intensivist.

Ventilator Alarm Management

High Pressure Alarm

Secretions / ETT obstruction — suction
Biting on ETT — deepen sedation, bite block
Bronchospasm — salbutamol nebs
Pneumothorax — urgent CXR, auscultate
Right mainstem intubation — reposition ETT
Patient-ventilator dyssynchrony

Low Pressure / High RR Alarm

Low pressure: circuit disconnection, cuff leak
ETT cuff deflation — check and inflate
High RR: pain, anxiety — assess CPOT/NRS
High RR: hypoxia, fever — treat cause
Inadequate sedation / analgesia

Permissive Hypercapnia: Accept PaCO₂ 50–70 mmHg if pH > 7.20. Do NOT increase tidal volume to correct CO₂ — volutrauma risk. Contraindicated in raised intracranial pressure (ICP), severe pulmonary hypertension, or haemodynamic instability.

Prone Positioning

Indications

P/F ratio < 150 (moderate–severe ARDS)
Initiate early: within 36 hours of ARDS onset
Duration: minimum 16 hours/day
Continue until P/F consistently > 150

Benefits (PROSEVA Trial)

28-day mortality: 16% prone vs 32.8% supine
Improves V/Q matching — recruits dependent alveoli
Reduces ventral overdistension
More homogeneous stress distribution

Team Required

Minimum 5 people: 1 at head (airway lead), 2 on each side. Designate a team leader before starting.

Contraindications

Unstable spinal fracture
Open chest / recent sternotomy (<15 days)
Elevated ICP
Haemodynamic instability not responding to vasopressors
Pregnancy (relative)
Facial trauma / recent facial surgery

Prone Complications & Supination Criteria

Complications

Facial and periorbital oedema — common
ETT displacement / accidental extubation
Pressure injuries: face, chest, ASIS, knees
Haemodynamic instability during turn
Brachial plexus stretch injury
Increased secretions / mucus plugging
Corneal abrasion / eye pressure injury

Supination Criteria

All three required:

P/F > 150 in supine position
PEEP ≤ 10 cmH₂O
FiO₂ ≤ 0.60

Maintained for at least 4 hours in supine before considering cessation.

Neuromuscular Blockade (NMB)

Indication & Agent

Severe ARDS: P/F < 150
First 48 hours only (ACURASYS trial)
Agent: Cisatracurium infusion (Hofmann elimination — safe in organ failure)
Dose: 37.5 mg bolus then 15–37.5 mg/hr infusion
Indication: refractory dyssynchrony despite deep sedation

TOF Monitoring

Train-of-Four (TOF) monitoring every 4h:
Target: 1–2 twitches out of 4
0 twitches → reduce/stop infusion
3–4 twitches → inadequate block, increase dose
Place electrode over ulnar nerve (wrist)

Eyes must be taped closed; regular eye care essential. Avoid NMB beyond 48h — ICU-acquired weakness risk.

Inhaled Nitric Oxide (iNO)

Selective pulmonary vasodilator
Improves V/Q matching and oxygenation transiently
Used as a bridge therapy (not mortality benefit proven)
Dose: 5–40 ppm; monitor MetHb levels
Risk: rebound hypoxaemia on weaning — taper slowly over hours

ECMO (Extracorporeal Membrane Oxygenation)

Indication: P/F < 50–80 refractory to all measures
VV-ECMO (veno-venous) for pure respiratory failure
Allows ultra-lung-protective ventilation during ECMO
GCC ECMO centres:
- Cleveland Clinic Abu Dhabi (UAE)
- Hamad Medical Corporation, Doha (Qatar)
- KFSH&RC, Riyadh (Saudi Arabia)

Sedation & Analgesia in ARDS

Analgesia-first approach: Treat pain before adding sedation. Under-treated pain drives tachycardia, tachypnoea, and patient-ventilator dyssynchrony.

Analgesics

Fentanyl infusion — preferred; rapid titration
Morphine — effective but caution in renal failure (morphine-6-glucuronide accumulation)
Multimodal: paracetamol IV, ketamine as adjunct
Use CPOT or BPS to guide dosing (non-verbal patients)

Sedatives

Propofol — rapid on/off; risk PRIS at >5 mg/kg/hr >48h (check TG, CK, pH)
Midazolam — longer-acting; accumulates; consider in haemodynamic instability
Dexmedetomidine — light sedation, analgesia-sparing; reduces delirium; no respiratory depression

RASS Target Guide

RASS Score	Description	Target in ARDS
0	Alert and calm	Post-ARDS / weaning phase
-1	Drowsy	Mild ARDS / SBT phase
-2	Light sedation	Standard ARDS target
-3	Moderate sedation	Prone positioning / NMB
-4	Deep sedation	Only during proning procedure itself
-5	Unarousable	Avoid — associated with worse outcomes

Ventilator Weaning Readiness

Weaning criteria must all be met before SBT attempt.

Parameter	Readiness Threshold
P/F ratio	> 200 mmHg
PEEP	≤ 8 cmH₂O
FiO₂	≤ 0.4–0.5
RSBI (f/VT)	< 105 breaths/min/L
Cough	Adequate spontaneous cough
GCS	≥ 8 or following commands
Haemodynamics	Stable; vasopressors weaning or off
Cause of ARDS	Resolving — CXR improving

RSBI = RR ÷ tidal volume (L). Measure during 2-minute T-piece or low-pressure support trial. RSBI < 80 = very likely success.

Ventilator-Associated Pneumonia (VAP)

Diagnosis

New fever (>38.3°C) or hypothermia
Purulent tracheal secretions (change in character)
New or worsening bilateral infiltrate on CXR
Positive quantitative BAL / tracheal aspirate culture
Onset > 48h after intubation

VAP Prevention Bundle

Head of bed 30–45°
Daily SAT + SBT assessment
Oral care with chlorhexidine 0.12% every 4–6h
Subglottic suctioning ETT (if available)
ETT cuff pressure 20–30 cmH₂O (25 optimal)
Hand hygiene before all airway interventions
Closed suction system preferred

Pneumothorax (Barotrauma)

Tension pneumothorax = EMERGENCY
Do NOT wait for CXR if haemodynamically compromised.

Recognition

Sudden acute deterioration
High peak & plateau pressures
Reduced / absent air entry unilaterally
Tracheal deviation (late sign)
Hypotension, tachycardia, desaturation
Distended neck veins (JVP raised)

Management

Needle decompression immediately: 2nd ICS, MCL
Followed by chest drain insertion
Reduce PEEP and tidal volume urgently
Call senior/intensivist stat

ICU-Acquired Weakness (ICUAW)

Affects up to 50% of mechanically ventilated ICU patients
Risk factors: prolonged NMB use, corticosteroids, hyperglycaemia, immobility, sepsis
Prevention: early mobilisation & physiotherapy
Avoid NMB beyond 48h unless absolutely essential
Avoid prolonged deep sedation (RASS ≤ -3)
Tight glycaemic control (target 6–10 mmol/L)
Passive & active range of motion from day 1

Right Heart Failure & Renal Failure

RV Failure from High PEEP

High PEEP → increased RV afterload
Monitor: CVP, tricuspid regurgitation (echo), signs of RV dilatation
If RV failure suspected: reduce PEEP cautiously
Prone positioning may unload RV

AKI in ARDS

AKI in up to 40% of ARDS patients
Fluid balance critical — neither overload nor depleted
Avoid nephrotoxins: aminoglycosides, NSAIDs, iodinated contrast
CRRT if severe AKI or fluid overload

Quick Reference Summary

6 mL/kgTidal Volume (IBW)

≤ 30Plateau Pressure (cmH₂O)

≤ 15Driving Pressure (cmH₂O)

< 150Prone P/F Threshold

≥ 16hProne Duration/Day

88–95%SpO₂ Target

> 7.20Minimum pH

48hMax NMB Duration

10-Question MCQ Quiz

Test your ARDS knowledge. Click an option to see if it is correct.

1. According to the Berlin Definition, what is the minimum PEEP required for oxygenation classification in ARDS?

A. PEEP ≥ 3 cmH₂O

B. PEEP ≥ 5 cmH₂O

C. PEEP ≥ 8 cmH₂O

D. Any PEEP level

The Berlin Definition specifies that P/F ratio must be measured on PEEP ≥ 5 cmH₂O to ensure that the degree of oxygenation impairment is not simply due to absent PEEP support.

2. What tidal volume does ARDSNet recommend for lung-protective ventilation?

A. 8 mL/kg actual body weight

B. 10 mL/kg ideal body weight

C. 6 mL/kg ideal body weight

D. 4 mL/kg actual body weight

The ARMA trial demonstrated that 6 mL/kg IBW significantly reduces 28-day mortality compared to 12 mL/kg IBW. Actual body weight is never used — obese patients would receive dangerously high volumes.

3. A patient has PaO₂ 65 mmHg on FiO₂ 0.8. What is the P/F ratio and ARDS severity?

A. P/F 97 — Mild ARDS

B. P/F 81 — Severe ARDS

C. P/F 81 — Moderate ARDS

D. P/F 130 — Moderate ARDS

P/F = 65 ÷ 0.8 = 81.25. P/F < 100 = Severe ARDS by Berlin criteria. This patient requires urgent consideration of prone positioning and NMB.

4. The PROSEVA trial showed prone positioning reduces 28-day mortality when P/F is below:

A. P/F < 200

B. P/F < 100

C. P/F < 150

D. P/F < 80

PROSEVA enrolled patients with P/F < 150 on PEEP ≥ 5 and FiO₂ ≥ 0.6. Prone positioning for ≥ 16h/day reduced 28-day mortality from 32.8% to 16.0% (p < 0.001).

5. What is the target SpO₂ range in ARDS to avoid both hypoxia AND hyperoxia?

A. 95–100%

B. 88–95%

C. 85–90%

D. 92–98%

SpO₂ 88–95% is the recommended target. Targeting >96% causes hyperoxia which is independently associated with increased ICU mortality (oxygen free radical tissue damage). Values <88% risk end-organ hypoxic injury.

6. Which drug is preferred for NMB infusion in severe ARDS and why?

A. Vecuronium — long-acting, cheaper

B. Rocuronium — fastest onset

C. Cisatracurium — Hofmann elimination, safe in organ failure

D. Suxamethonium — depolarising agent

Cisatracurium undergoes spontaneous Hofmann elimination (non-organ-dependent). This makes it safe in patients with renal and hepatic failure common in ARDS. ACURASYS trial used cisatracurium for the first 48 hours.

7. The maximum safe driving pressure in lung-protective ventilation is:

A. 20 cmH₂O

B. 10 cmH₂O

C. 15 cmH₂O

D. 25 cmH₂O

Driving pressure (plateau pressure − PEEP) ≤ 15 cmH₂O is the target. Amato et al. (NEJM 2015) demonstrated driving pressure is the strongest predictor of ARDS survival, even after adjusting for tidal volume and PEEP.

8. A VAP prevention bundle in ARDS includes all EXCEPT:

A. Head of bed at 30–45°

B. Daily spontaneous awakening trial

C. Routine antibiotic prophylaxis

D. Oral care with chlorhexidine

Routine antibiotic prophylaxis is NOT recommended in VAP prevention — it promotes drug-resistant organisms. The bundle includes: HOB 30-45°, oral care, SAT, SBT, subglottic suctioning ETT, and cuff pressure maintenance.

9. How many staff members are the minimum required for safe prone positioning?

A. 2 people

B. 3 people

C. 4 people

D. 5 people minimum

A minimum of 5 people is required: one designated at the head (airway protection lead), two on each side of the bed. A team leader must be designated. Fewer staff increases risk of ETT displacement and patient harm.

10. Permissive hypercapnia in ARDS is acceptable when PaCO₂ is elevated, provided:

A. pH > 7.35

B. pH > 7.20

C. pH > 7.10

D. Any pH is acceptable

pH > 7.20 is the threshold for permissive hypercapnia. PaCO₂ of 50–70 mmHg is often accepted to maintain safe tidal volumes. Contraindications: raised ICP, severe pulmonary hypertension, significant haemodynamic instability.