EM Command Center / Resuscitation & Critical Care • 3 min read • 5 sections

Mechanical Ventilation & ARDS Management

Comprehensive emergency medicine and critical care guide to mechanical ventilation. Covers initial vent mode selection, the ARDSNet low-tidal-volume protocol, driving pressure optimization, severe obstructive ventilation strategies to prevent dynamic hyperinflation (auto-PEEP), and the DOPE/DOPES ventilator troubleshooting algorithm.

Resuscitation Quick Ribbon (First 2 Minutes)

High-Acuity

Standard initial settings:Volume Control (VC) or PRVC; Tidal Volume 6-8 mL/kg Predicted Body Weight (PBW); RR 14-18 bpm; PEEP 5 cmH2O; FiO2 100% (titrate to SpO2 92-96%).

ARDSNet protocol:Tidal volume 4-6 mL/kg PBW; Plateau pressure (Pplat) < 30 cmH2O; titrate PEEP/FiO2 table.

Obstructive physiology (Asthma/COPD):TV 6-8 mL/kg PBW; RR 8-12 bpm; I:E ratio 1:4 to 1:5; peak flow 70-80 L/min; permissive hypercapnia (target pH > 7.15-7.20).

Sudden vent alarm / deterioration:Disconnect from ventilator IMMEDIATELY and bag manually on 100% O2 -> perform DOPE troubleshooting.

Bottom-Line Clinical Pearl

In severe asthma/COPD intubation, prioritize exhalation time over normal PaCO2: accept permissive hypercapnia, use low respiratory rates (8-12 bpm), high inspiratory flow rates (70-80 L/min), and low I:E ratios (1:4 or 1:5) to prevent auto-PEEP and obstructive cardiac arrest.

1. Predicted Body Weight (PBW) & Initial Setting Formula

Lungs do not grow larger with adipose tissue. Tidal volume MUST ALWAYS be calculated from Predicted Body Weight (PBW), never actual weight:

Gender	Predicted Body Weight (PBW) Formula	Example: 5 ft 10 in (70 inches) Person
Male	50 + 2.3 [Height in inches - 60] (or 50 + 0.91 [Height in cm - 152.4])	PBW = 50 + 2.3 * 10 = 73 kg -> 6 mL/kg = 440 mL TV
Female	45.5 + 2.3 [Height in inches - 60] (or 45.5 + 0.91 [Height in cm - 152.4])	PBW = 45.5 + 2.3 * 10 = 68.5 kg -> 6 mL/kg = 410 mL TV

2. ARDS Definition & ARDSNet Lung-Protective Strategy

The Berlin Definition classifies ARDS within 7 days of known clinical insult with bilateral opacities on chest radiograph/CT not fully explained by heart failure or fluid overload, categorized by PaO2/FiO2 ratio (with PEEP >= 5 cmH2O):

Severity Category	PaO2 / FiO2 Ratio (P/F Ratio)	Evidence-Based Intervention Strategy
Mild ARDS	201 - 300 mmHg (with PEEP >= 5)	Low TV (6 mL/kg PBW); titrate PEEP according to ARDSNet lower PEEP table; SpO2 target 88-95%.
Moderate ARDS	101 - 200 mmHg (with PEEP >= 5)	Reduce TV to 4-6 mL/kg PBW; keep Plateau Pressure (Pplat) <= 30 cmH2O; higher PEEP titration.
Severe ARDS	<= 100 mmHg (with PEEP >= 5)	Early neuromuscular blockade (cisatracurium for 48h); early prone positioning (> 16 hrs/day, PROSEVA trial); evaluate for VV-ECMO.

Practice Recommendation

Plateau Pressure vs. Peak Pressure: Peak inspiratory pressure (PIP) reflects airway resistance + lung compliance. Plateau pressure (measured via inspiratory pause) reflects true alveolar compliance. Elevated PIP with normal Pplat (< 30) = airway resistance (bronchospasm, mucous plug, biting tube). Elevated PIP AND elevated Pplat (> 30) = decreased compliance (ARDS, tension pneumothorax, pulmonary edema, mainstem intubation, abdominal compartment syndrome).

3. Obstructive Lung Disease (Asthma & COPD) Ventilator Strategies

In patients with severe bronchospasm, the paramount emergency goal is preventing dynamic hyperinflation (stacking breaths, auto-PEEP) and hemodynamic collapse:

Low Respiratory Rate: Set RR to 8-12 breaths/minute to allow sufficient expiratory time.
High Inspiratory Flow Rate: Set peak flow to 70-80 L/min (shortens inspiration and maximizes expiratory time).
Inspiratory to Expiratory (I:E) Ratio: Prolong to 1:4 or 1:5.
Permissive Hypercapnia: Tolerate elevated PaCO2 (60-90 mmHg) provided arterial pH remains >= 7.15-7.20. Normalizing PaCO2 in severe asthma causes fatal hyperinflation.
Check Auto-PEEP: Perform an end-expiratory pause. If auto-PEEP > 10 cmH2O, reduce RR or TV immediately.

4. Troubleshooting the Crashing Ventilator Patient: The DOPE Protocol

When a ventilated patient acutely deteriorates, becomes hypotensive, or triggers high-pressure alarms:

Mnemonic Component	Pathology to Rule Out	Emergency Action & Management
D - Dislodgement	Endotracheal tube dislodged into pharynx or right mainstem bronchus	Check depth at teeth; confirm with capnography and bilateral breath sounds; adjust or re-intubate.
O - Obstruction	Mucus plug, blood clot, patient biting tube, kinking of circuit	Pass suction catheter down ETT; insert bite block; replace inline filter/tubing.
P - Pneumothorax	Tension pneumothorax from barotrauma or central line attempt	Bedside lung ultrasound for absent lung sliding; emergent 5th ICS finger thoracostomy / chest tube.
E - Equipment Failure	Ventilator malfunction, O2 source disconnection, valve failure	DISCONNECT PATIENT FROM VENTILATOR IMMEDIATELY and bag manually with BVM on 100% O2.
S - Stacking (Breath Stacking / Auto-PEEP)	Incomplete exhalation causing elevated intrathoracic pressure and decreased venous return	DISCONNECT ETT from ventilator circuit; manually compress chest to expel trapped air; listen for prolonged whoosh of air; reconnect at lower RR.

5. Attending Extubation Readiness & Disposition

ICU Admission: All mechanically ventilated patients require immediate placement in a medical, surgical, or neurovascular ICU.
Sedation Management: Maintain light sedation targeting RASS -1 to -2 with propofol or dexmedetomidine; avoid benzodiazepines when possible to reduce delirium and ventilator days.
Spontaneous Breathing Trial (SBT): Rapid Shallow Breathing Index (RSBI = RR / TV in liters) < 105 predicts successful weaning when underlying pathology has resolved.

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