Chart — Respiratory
Ventilator Modes Comparison Chart
A side-by-side comparison of the five major ventilator modes — AC, SIMV, Pressure Support, CPAP, and BiPAP — organized by patient effort, advantages, and limitations for clinical and NCLEX use.
Educational use only. Ventilator mode selection requires provider and respiratory therapy orders. Nurses monitor and respond to alarms but do not adjust modes independently. This chart supports learning and NCLEX preparation. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
Mode Comparison
| Mode | Patient Effort | Advantages | Limitations |
|---|---|---|---|
| AC (Assist Control) | Minimal — ventilator delivers full support for every breath | Full respiratory muscle rest; reliable minute ventilation; prevents fatigue; appropriate for hemodynamically unstable or apneic patients | Auto-PEEP risk if patient over-breathes; respiratory alkalosis; no respiratory muscle conditioning; dyssynchrony if patient breathes faster than set RR |
| SIMV | Partial — mandatory breaths are supported; spontaneous breaths between are unsupported (unless PS added) | Maintains some respiratory muscle activity; allows gradual weaning by reducing mandatory rate; backup rate guarantees minimum ventilation | Spontaneous unsupported breaths cause fatigue; dyssynchrony possible; generally slower weaning compared to PSV-based SBTs |
| Pressure Support (PSV) | High — patient triggers and determines rate for every breath; ventilator only augments pressure | Preserves respiratory muscle function; improves patient-ventilator synchrony; preferred mode for spontaneous breathing trials (SBTs); reduces sedation needs | No mandatory backup rate (apnea alarm only); not for apneic or hemodynamically unstable patients; tidal volume varies with patient effort and lung compliance |
| CPAP | Full — patient does all the work of breathing; ventilator only maintains positive pressure | Maintains alveolar recruitment and oxygenation; evaluates extubation readiness; non-invasive option for OSA and select cardiogenic pulmonary edema | No ventilatory assistance (CO₂ removal is entirely patient-driven); no backup breaths; requires cooperative and hemodynamically stable patient; rapid fatigue if patient not ready |
| BiPAP (Non-Invasive) | Assisted — less than spontaneous breathing, more than AC mode; patient triggers breaths assisted by IPAP pressure | Non-invasive (avoids intubation); assists ventilation (CO₂ removal) and oxygenation; first-line for COPD exacerbation with acidosis; optional backup rate available | Requires patient cooperation and mask tolerance; aspiration risk in altered LOC; air leak around mask reduces effectiveness; failure may lead to delayed intubation |
Support Features at a Glance
| Mode | Backup Rate | CO₂ Removal | Invasive? | Weaning Role |
|---|---|---|---|---|
| AC | Yes | Controlled | Yes (ETT) | Initial support; not a weaning mode |
| SIMV | Yes | Guaranteed (mandatory breaths) | Yes (ETT) | Gradual RR reduction |
| PSV | Apnea alarm only | Patient-driven | Yes (ETT) | Primary SBT mode |
| CPAP | None | Patient only | Yes (ETT) or non-invasive | Pre-extubation assessment |
| BiPAP | Optional | Via IPAP−EPAP | No (mask) | Avoids intubation; not a weaning mode per se |
Clinical Selection Guide
| Clinical Scenario | Typical Mode Choice |
|---|---|
| Acute respiratory failure, apneic, hemodynamically unstable | AC — full support, backup rate, reliable minute ventilation |
| ARDS initial management | AC with lung-protective settings (Vt 6 mL/kg IBW, PEEP per FiO₂ table) |
| Weaning — gradual spontaneous breathing increase | SIMV with decreasing mandatory rate (or PSV-based SBT) |
| Spontaneous breathing trial (SBT) for extubation readiness | PSV 5–8 cmH₂O + PEEP 5 — preferred SBT method |
| Pre-extubation assessment | CPAP — tests patient ability to breathe without pressure support |
| COPD exacerbation with acute respiratory acidosis | BiPAP (non-invasive) — first-line before intubation |
NCLEX Pearls
- ›AC = full support for every breath. Minimal patient work. Used for acute respiratory failure.
- ›PSV = patient triggers every breath; ventilator only adds pressure boost. No backup rate.
- ›CPAP = positive pressure maintained throughout; patient breathes entirely independently.
- ›BiPAP is non-invasive; first-line for COPD exacerbation with acute CO₂ retention and acidosis.
- ›SBT (Spontaneous Breathing Trial) = low PSV + PEEP 5; assesses extubation readiness.
- ›Patient-ventilator dyssynchrony = patient and ventilator out of sync → increased work of breathing, agitation, worsened oxygenation → notify RT.
Related Resources
Ventilator Modes ReferenceAC, SIMV, PSV, CPAP, BiPAP — detailed descriptions and nursing notes
Open →Mechanical Ventilation BasicsPurpose, indications, FiO₂, PEEP, tidal volume, RR — key settings
Open →Ventilator Troubleshooting for NursesAlarm types, DOPE mnemonic, and step-by-step response guide
Open →Standards & sources
Fact-checked Jun 21, 2026This page is written to align with AARC / ACCP Ventilator Guidelines. It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →