Levels of support on ventilator and ventilator settings
Reading File
Finding Sources
Finding Sources
Searching PubMed
"Mechanical Ventilation"[MeSH Terms] AND settings
Searching the Web
mechanical ventilation initial settings tidal volume respiratory rate PEEP FiO2 guideline
Reading File
Reading File
Reading File
Reading File
Finding Sources
Finding Sources
Levels of ventilatory support
Ventilatory support ranges from no positive-pressure ventilation to full control of every breath.
| Level | Typical modality/mode | Patient effort required | Main use |
|---|---|---|---|
| 1. Supplemental oxygen | Nasal cannula, face mask, Venturi, non-rebreather | Yes | Hypoxemia without ventilatory failure |
| 2. High-flow nasal cannula (HFNC) | Heated humidified high-flow oxygen | Yes | Hypoxemic respiratory failure with preserved ventilatory drive |
| 3. Non-invasive ventilation (NIV) | CPAP or BiPAP through mask | Yes, except backup breaths in some modes | COPD exacerbation with hypercapnia, cardiogenic pulmonary edema, selected patients |
| 4. Partial invasive support | Pressure support ventilation (PSV), SIMV + PS | Yes | Weaning and spontaneous breathing with assistance |
| 5. Full invasive support | Assist-control volume control (VC-A/C) or pressure control (PC-A/C) | No, or minimal | Apnea, paralysis, severe respiratory failure, shock, severe work of breathing |
1. CPAP
- Delivers one continuous pressure throughout inspiration and expiration.
- Improves oxygenation by recruiting alveoli.
- No added inspiratory pressure support, so it does not directly increase tidal volume or reduce CO2 substantially.
- Common initial setting: CPAP/PEEP 5-10 cm H2O, titrated to oxygenation and tolerance.
2. BiPAP or bilevel NIV
- IPAP: inspiratory positive airway pressure.
- EPAP: expiratory positive airway pressure, physiologically similar to PEEP.
- Pressure support = IPAP - EPAP.
- Increasing IPAP increases tidal volume and minute ventilation, therefore usually lowers PaCO2.
- Increasing EPAP improves oxygenation and counteracts alveolar collapse.
Typical starting point: IPAP 10 cm H2O, EPAP 5 cm H2O, then increase by 1-2 cm H2O based on work of breathing, respiratory rate, oxygenation, ventilation, leaks, and comfort. IPAP above about 20 cm H2O may increase discomfort and gastric insufflation risk.
Source: ROSEN's Emergency Medicine, Mechanical Ventilation of the Intubated Patient.
Source: ROSEN's Emergency Medicine, Mechanical Ventilation of the Intubated Patient.
3. Invasive partial-support modes
Pressure support ventilation (PSV)
- Patient triggers each breath.
- Ventilator provides a set pressure above PEEP.
- Used when the patient has adequate respiratory drive, especially during weaning.
- Common weaning trial settings: PS 5-8 cm H2O, PEEP 5-8 cm H2O, low FiO2 as tolerated.
SIMV
- Delivers a set number of mandatory breaths, while allowing spontaneous breaths between them.
- Spontaneous breaths may receive pressure support.
- Less commonly preferred as a primary weaning strategy than daily spontaneous-breathing trials with PSV or T-piece.
4. Full-support modes
Volume assist-control (VC-A/C)
- Set tidal volume is delivered with each mandatory or patient-triggered breath.
- Airway pressure varies according to lung compliance and airway resistance.
- Main settings: tidal volume, respiratory rate, flow, inspiratory time/I:E ratio, FiO2, and PEEP.
Pressure-control assist-control (PC-A/C)
- A set inspiratory pressure is delivered for a set inspiratory time.
- Tidal volume varies with compliance, resistance, and patient effort.
- Useful when limiting inspiratory pressure is a priority, but tidal volume must be watched closely.
For an apneic or paralyzed intubated patient, assist-control is generally used initially.
Source: ROSEN's Emergency Medicine, Mechanical Ventilation of the Intubated Patient.
Source: ROSEN's Emergency Medicine, Mechanical Ventilation of the Intubated Patient.
Main ventilator settings and what they control
| Setting | Primary effect | How to adjust |
|---|---|---|
| FiO2 | Oxygenation | Increase for hypoxemia; reduce promptly once adequate saturation is achieved to limit oxygen toxicity |
| PEEP | Oxygenation and alveolar recruitment | Increase for persistent hypoxemia/atelectasis; watch for hypotension, overdistension, and barotrauma |
| Tidal volume (VT) | Ventilation and lung stretch | Set by predicted/ideal body weight, not actual body weight |
| Respiratory rate (RR) | Minute ventilation and PaCO2 | Increase to lower PaCO2, but allow adequate expiration in obstructive disease |
| Pressure support | Work of breathing, VT, PaCO2 in spontaneous modes | Increase if inadequate VT or excessive work of breathing |
| Inspiratory pressure | VT in pressure-control modes | Increase cautiously while monitoring exhaled VT and pressures |
| I:E ratio / inspiratory time | Expiratory time and air trapping | Longer expiration is needed in asthma/COPD |
| Trigger sensitivity | Patient-ventilator synchrony | Too insensitive causes missed triggers; too sensitive can cause auto-triggering |
| Flow rate / waveform | Inspiratory flow and synchrony | Higher flow shortens inspiratory time and lengthens expiration |
Key relationships
- Minute ventilation = tidal volume × respiratory rate.
- Increasing minute ventilation usually lowers PaCO2.
- Oxygenation is primarily adjusted through FiO2 and PEEP.
- Ventilation/CO2 clearance is primarily adjusted through VT, RR, and pressure support.
- Raising RR in asthma or COPD can worsen dynamic hyperinflation because it shortens expiratory time.
Typical adult initial invasive ventilator settings
For a newly intubated adult without a special lung strategy:
- Mode: Volume A/C or Pressure A/C
- VT: 6-8 mL/kg predicted/ideal body weight
- RR: 12-14/min, then adjust for pH and PaCO2
- FiO2: initially 1.0 (100%) in emergency intubation, then rapidly titrate down
- PEEP: 5 cm H2O initially
- I:E ratio: about 1:2
- Plateau pressure target: generally keep ≤30 cm H2O
- SpO2 target: often 88-94% initially in the emergency setting, individualized to the clinical context
These settings must be reassessed clinically and with capnography, ventilator waveforms, pressures, and blood gas testing, commonly about 15-20 minutes after starting or materially changing settings. StatPearls review and ROSEN's Emergency Medicine, Mechanical Ventilation of the Intubated Patient support this approach.
Condition-specific starting strategy
| Clinical situation | VT | RR / expiratory time | PEEP | Special point |
|---|---|---|---|---|
| ARDS | 4-6 mL/kg predicted body weight | Adjust RR to maintain acceptable pH | Use a protocolized PEEP-FiO2 approach | Keep plateau pressure ≤30 cm H2O; permissive hypercapnia may be accepted |
| COPD/asthma | 6-8 mL/kg PBW | Lower RR, usually 8-12/min; long expiration, often I:E 1:3 to 1:5 | Low external PEEP initially, individualized | Prevent auto-PEEP and dynamic hyperinflation; accept some hypercapnia if pH acceptable |
| Severe metabolic acidosis | 6-8 mL/kg PBW | Often needs high RR to match pre-intubation minute ventilation | Usually 5 cm H2O initially | Avoid a post-intubation fall in minute ventilation and severe acidemia |
| Cardiogenic pulmonary edema | 6-8 mL/kg PBW if intubated | Standard | Often higher PEEP if tolerated | NIV, especially CPAP/BiPAP, may avoid intubation in suitable patients |
| Brain injury | 6-8 mL/kg PBW | Adjust toward normal PaCO2 unless temporary hyperventilation is specifically indicated | Lowest PEEP compatible with oxygenation | Routine prolonged hyperventilation is avoided |
| Postoperative uncomplicated patient | 6-8 mL/kg PBW | 10-14/min | 5 cm H2O | Titrate rapidly toward spontaneous support and extubation readiness |
PBW/IBW matters: tidal volume should not be calculated from actual body weight, especially in obesity. It is based mainly on height and sex.
Safety checks after setting the ventilator
- Confirm tube position and bilateral chest movement.
- Check exhaled tidal volume and minute ventilation.
- Monitor SpO2 and continuous capnography.
- Obtain an ABG when indicated after initiation or major changes.
- Measure plateau pressure in passive patients.
- Check for auto-PEEP, especially in asthma/COPD.
- Watch hemodynamics after raising PEEP or mean airway pressure.
- Reduce FiO2 to the lowest level that achieves the oxygenation target.
- Reassess sedation, analgesia, dyssynchrony, and readiness for spontaneous breathing daily.
Ventilator adjustment is not a fixed recipe. It must be matched to the cause of respiratory failure, patient effort, blood gases, mechanics, and hemodynamics.
This is a shared conversation. Sign in to Orris to start your own chat.