How do I set up and initiate mechanical ventilation in an adult patient, including confirming identity, indication, contraindications (e.g., severe facial trauma, untreated pneumothorax, raised intracranial pressure), reviewing respiratory disease history, comorbidities such as chronic obstructive pulmonary disease and heart failure, medications and allergies, and selecting initial ventilator settings (tidal volume 6–8 mL/kg predicted body weight, respiratory rate 12–16 breaths/min, FiO₂ 100 %, PEEP 5 cm H₂O)?

Initial Ventilator Setup for Adult Mechanical Ventilation

Set initial tidal volume at 6 mL/kg predicted body weight (not actual weight), respiratory rate 12-16 breaths/min, FiO₂ 100%, and PEEP 5 cm H₂O, while ensuring plateau pressure remains below 30 cm H₂O. 1

Pre-Intubation Assessment

Before initiating mechanical ventilation, confirm the following critical elements:

• Patient identity and informed consent (or emergency exception) 1
• Clear indication for intubation: apnea, impending respiratory arrest, inability to protect airway, refractory hypoxemia (PaO₂ <60 mmHg despite high-flow oxygen), respiratory rate >35 breaths/min, or vital capacity <15 mL/kg 1, 2
• Absolute contraindications to exclude: untreated pneumothorax (must be drained first), severe facial trauma preventing mask seal, recent upper airway surgery, or fixed upper airway obstruction 1, 3

Essential History Elements

Document these specific factors that alter ventilator management:

• COPD or chronic hypercapnia: These patients require target SpO₂ 88-92% (not 94-98%) and may need lower minute ventilation to avoid respiratory alkalosis 1
• Heart failure: Requires judicious fluid management and may benefit from higher PEEP 1
• Raised intracranial pressure: Avoid hyperventilation in first 24 hours; maintain normocapnia (PaCO₂ 40-45 mmHg) 1, 4
• Prior episodes of hypercapnic respiratory failure requiring NIV: Start with lower oxygen targets 1

Initial Ventilator Settings

Mode Selection

• Start with volume-controlled assist-control (CMV) for complete ventilatory support immediately after intubation 1
• Pressure-controlled ventilation is equally acceptable if you are experienced with it 1

Tidal Volume Calculation

Calculate predicted body weight (PBW) first—never use actual body weight:

• Men: PBW (kg) = 50 + 2.3 × (height in inches - 60) 1
• Women: PBW (kg) = 45.5 + 2.3 × (height in inches - 60) 1
• Set tidal volume at 6 mL/kg PBW (range 6-8 mL/kg acceptable, but start at 6 mL/kg) 1, 5
• Document tidal volume as mL/kg PBW in the medical record 5

Respiratory Rate

• Set initial rate at 12-16 breaths/min for adults (adjust based on minute ventilation needs) 1
• For patients with COPD or obstructive disease, use lower rates (10-15 breaths/min) with prolonged I:E ratio (1:4 or 1:5) to prevent auto-PEEP 6

FiO₂ (Fraction of Inspired Oxygen)

• Start at 100% (FiO₂ 1.0) immediately after intubation 1, 7
• Rapidly titrate down to maintain SpO₂ 94-98% in most patients 1
• Exception for COPD/chronic hypercapnia: Target SpO₂ 88-92% and start with 24-28% Venturi equivalent 1
• Obtain arterial blood gas within 30-60 minutes to guide further adjustments 1

PEEP (Positive End-Expiratory Pressure)

• Set initial PEEP at 5 cm H₂O for most patients 1
• PEEP prevents alveolar collapse and improves oxygenation in acute lung injury 1
• Monitor for auto-PEEP, especially in COPD patients—adjust trigger settings to prevent ventilator auto-triggering with chest compressions if applicable 1

Pressure Limits

• Ensure plateau pressure <30 cm H₂O by performing an inspiratory pause (0.3-0.5 seconds) 1, 7, 6
• If plateau pressure exceeds 30 cm H₂O, reduce tidal volume further (even below 6 mL/kg PBW) and accept permissive hypercapnia 1
• Monitor driving pressure (plateau pressure minus PEEP) as it may better predict outcomes than tidal volume alone 6

Immediate Post-Intubation Management

Confirm Tube Placement

• Assess proper endotracheal tube placement and securement immediately 5
• Confirm bilateral breath sounds and chest rise 1
• Obtain chest radiograph to verify tube position 1

Cuff Management

• Measure cuff pressure with manometer and maintain at appropriate level (typically 20-30 cm H₂O) 5
• Continuous cuff pressure monitoring is not recommended to prevent VAP 5

Ventilator Circuit

• Use HEPA filter in the circuit to maintain closed system and reduce aerosolization risk 1
• Ensure circuit continuity to prevent unplanned disconnections 1
• Assess humidification device appropriateness for invasive mechanical ventilation 5

Critical Monitoring Parameters

First Hour Assessment

• Obtain arterial blood gas at 30-60 minutes after initiating ventilation 1
• Assess plateau pressure to ensure lung-protective settings 5
• Document tidal volume as mL/kg PBW 5
• Measure auto-PEEP especially in obstructive lung disease 5
• Monitor SpO₂ continuously for at least 24 hours 3

Adjust Based on Blood Gas Results

If pH and PCO₂ are normal:

• Increase target SpO₂ to 94-98% (unless COPD/prior hypercapnia) 1
• Recheck blood gases at 30-60 minutes to ensure no rising PCO₂ or falling pH 1

If hypercapnia develops (PCO₂ >45 mmHg with pH <7.35):

• Do not hyperventilate—this worsens cerebral perfusion and hemodynamic stability 1
• Accept permissive hypercapnia if plateau pressure is at limit 1
• Consider bicarbonate infusion only for severe acidosis 1

If hypocapnia occurs (PCO₂ <35 mmHg):

• Reduce minute ventilation by decreasing respiratory rate or tidal volume 6
• Maintain lung-protective parameters (tidal volume 6 mL/kg PBW, plateau pressure <30 cm H₂O) 6

Common Pitfalls to Avoid

Dangerous Errors

• Never use actual body weight for tidal volume calculation—this causes ventilator-induced lung injury in overweight patients 1
• Never hyperventilate routinely—this reduces cerebral blood flow and worsens hemodynamics in shock states 1
• Never target SpO₂ >92% in COPD patients with prior hypercapnia until blood gases confirm safety 1
• Never exceed plateau pressure of 30 cm H₂O—reduce tidal volume instead 1, 7

Monitoring Failures

• Do not skip the 30-60 minute blood gas recheck—even if initial PCO₂ was normal, hypercapnia can develop 1
• Do not forget to adjust trigger settings in patients with high respiratory drive to prevent auto-triggering 1
• Do not use excessive PEEP in cirrhosis or vasodilated states (<10 cm H₂O) as this compromises venous return 6

Special Population Errors

• In raised intracranial pressure: avoid hyperventilation in first 24 hours—maintain normocapnia (PaCO₂ 40-45 mmHg) 1, 4
• In COPD: do not use high minute ventilation—this causes auto-PEEP and hemodynamic compromise 1, 6
• In cardiac arrest patients already intubated: leave on ventilator with HEPA filter rather than disconnecting 1

Ongoing Ventilator Adjustments

Oxygenation Management

• Titrate FiO₂ to maintain target SpO₂ (94-98% for most, 88-92% for COPD) 1
• Increase PEEP before increasing FiO₂ if hypoxemia persists 1
• Consider prone positioning if 65% of patients with ARDS respond with improved oxygenation 1

Ventilation Management

• Maintain normocapnia (PaCO₂ 40-45 mmHg or ETCO₂ 35-40 mmHg) in most patients 1
• Accept permissive hypercapnia if needed to maintain plateau pressure <30 cm H₂O 1
• Adjust respiratory rate rather than tidal volume when changing minute ventilation 6

Skin and Interface Assessment

• Assess skin surrounding endotracheal tube regularly to prevent pressure injury 5
• Provide oral hygiene (tooth brushing and oral antiseptic) at least twice daily to prevent VAP 1
• Position patient semi-recumbent (30-45 degrees) to prevent aspiration 1