What are the recommended mechanical ventilation (Mechvent) settings?

Recommended Mechanical Ventilation Settings

For adult patients requiring mechanical ventilation, use tidal volumes of 4-8 ml/kg predicted body weight with plateau pressure maintained below 30 cmH₂O, PEEP starting at 5 cmH₂O, and initial FiO₂ of 0.4 titrated to SpO₂ 88-95%. 1, 2

Initial Core Settings for Adults

Tidal Volume and Pressure Limits

• Set tidal volume at 4-8 ml/kg predicted body weight (PBW), with 6 ml/kg being the most protective target 1, 2, 3
• Calculate PBW using: Males = 50 + 0.91[height (cm) - 152.4] kg; Females = 45.5 + 0.91[height (cm) - 152.4] kg 1, 2
• Maintain plateau pressure strictly below 30 cmH₂O to prevent ventilator-induced lung injury 1, 2
• Monitor driving pressure (plateau pressure minus PEEP) as it may predict outcomes better than tidal volume or plateau pressure alone 1, 2

PEEP and Oxygenation

• Start with PEEP of 5 cmH₂O—zero PEEP is not recommended 1, 2
• Set initial FiO₂ to 0.4 after intubation, then titrate to the lowest concentration achieving SpO₂ 88-95% 1, 2

Ventilation Targets

• Target PaCO₂ 35-45 mmHg or PETCO₂ 35-40 mmHg 2
• Use standard inspiratory-to-expiratory (I:E) ratio of 1:2 for most patients 2
• Set inspiratory time at 30-40% of the total respiratory cycle 2

Disease-Specific Adjustments

ARDS Patients

• Use lower tidal volumes (4-8 ml/kg PBW) with plateau pressure <30 cmH₂O 1, 2, 3
• For moderate-to-severe ARDS (PaO₂/FiO₂ <200 mmHg), consider higher PEEP strategy (>12 cmH₂O) 1, 2
• For mild ARDS (PaO₂/FiO₂ 200-300 mmHg), consider lower PEEP strategy (<10 cmH₂O) 2
• The landmark ARMA trial demonstrated that 6 ml/kg PBW reduced mortality from 39.8% to 31.0% compared to traditional 12 ml/kg volumes 3

Obstructive Airway Disease

• Use tidal volumes of 6-8 ml/kg PBW 1, 2
• Set respiratory rate at 10-15 breaths per minute to allow adequate expiratory time 1, 2
• Use shorter inspiratory time with I:E ratio of 1:2 or 1:3 to prevent air trapping 2
• Avoid hyperventilation as it causes auto-PEEP and hemodynamic compromise 2

Liver Disease/Cirrhosis

• Use lung-protective ventilation with low tidal volumes (6 ml/kg PBW) and plateau pressure <30 cmH₂O 1, 2
• Consider low PEEP strategy (<10 cmH₂O) for mild ARDS in cirrhotic patients 2
• Monitor closely for hemodynamic effects as high PEEP impedes venous return and exacerbates hypotension in vasodilated states 2

Pediatric Settings (Critically Ill Children)

For Children with Obstructive Disease (e.g., Asthma)

• Use pressure-controlled ventilation with peak inspiratory pressure ≤30 cmH₂O 4, 5
• Set PEEP at 5-8 cmH₂O; add additional PEEP when air-trapping is present to facilitate triggering 4, 5
• Target tidal volume ≤10 ml/kg ideal body weight 4, 5
• Use lower respiratory rates with longer expiratory times (I:E ratio 1:3 or greater) to prevent air trapping 4, 5
• Target SpO₂ ≤97% 4, 5
• Accept permissive hypercapnia with pH target >7.20 rather than normal PCO₂ 4, 5

General Pediatric Monitoring

• Measure end-tidal CO₂ and SpO₂ in all ventilated children 4
• For moderate-to-severe disease, measure arterial PO₂, pH, lactate, and central venous saturation 4
• Monitor peak inspiratory pressure, plateau pressure, mean airway pressure, and PEEP 4
• Observe pressure-time and flow-time scalars to assess mechanics 4

Pediatric Oxygenation Targets

• For healthy lungs: SpO₂ ≥95% when breathing room air 4
• For any disease condition: keep SpO₂ ≤97% 4
• For pediatric ARDS (PARDS): SpO₂ 92-97% when PEEP <10 cmH₂O and 88-92% when PEEP ≥10 cmH₂O 4

Critical Monitoring Parameters

Essential Measurements

• Monitor dynamic compliance, driving pressure, and plateau pressure in all patients 1, 2
• Assess patient-ventilator synchrony continuously 1, 2
• Monitor ventilation (PaCO₂, PETCO₂) 2
• Track changes in respiratory mechanics and gas exchange 1

Common Pitfalls to Avoid

• Do not use traditional high tidal volumes (10-15 ml/kg) as they increase mortality 3, 6
• Avoid hyperventilation with hypocapnia—it causes cerebral vasoconstriction and worsens brain ischemia 2
• Do not use excessive PEEP in hemodynamically unstable patients 2
• In obstructive disease, avoid delayed recognition of auto-PEEP 2
• Never assume dialed volumes equal delivered volumes—continuously verify actual tidal volumes being delivered 7

Supportive Measures

Standard Care

• Use humidification in all ventilated patients 4, 5
• Maintain head of bed elevated 30-45° 4, 5
• Use cuffed endotracheal tubes with cuff pressure ≤20 cmH₂O 4, 5
• Minimize dead space by limiting added circuit components 4
• Use double-limb circuits for invasive ventilation 4

Weaning Strategy

• Start weaning as soon as possible 4
• Perform daily extubation readiness testing 4
• Consider non-invasive ventilation in neuromuscular patients 4
• Use T-tube trials to assess true patient work of breathing without pressure support 8

When to Consider Advanced Interventions

• Consider recruitment maneuvers when atelectasis is evident, particularly during rapid compliance changes 1, 2
• Adjust settings based on changes in respiratory mechanics and gas exchange 1