Ventilation modes: Difference between revisions

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==Background==
*Ventilation modes define the pattern of breath delivery by a [[Mechanical ventilation (main)|mechanical ventilator]]
*Understanding modes is critical for optimizing oxygenation and ventilation while minimizing [[Ventilator associated lung injury|ventilator-associated lung injury]]
*Mode selection is determined by the clinical scenario, degree of [[Respiratory failure|respiratory failure]], and patient effort
*All modes control some combination of volume, pressure, and flow during the respiratory cycle
*The variable that is set (controlled) determines the mode category; the other variable becomes dependent
===Key Terminology===
*'''Tidal volume (TV)''': volume of gas delivered per breath
*'''Peak inspiratory pressure (PIP)''': maximum airway pressure during inspiration
*'''Plateau pressure (Pplat)''': pressure measured during an inspiratory hold; reflects alveolar pressure
**Goal Pplat < 30 cmH2O to minimize [[Ventilator associated lung injury|barotrauma]]<ref>The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342(18):1301-1308.</ref>
*'''Driving pressure''': Pplat minus PEEP; values < 14 cmH2O associated with improved survival<ref>Amato MB, Meade MO, Slutsky AS, et al. Driving pressure and survival in the acute respiratory distress syndrome. N Engl J Med. 2015;372(8):747-755.</ref>
*'''PEEP''': positive end-expiratory pressure; prevents alveolar collapse and improves oxygenation
*'''FiO2''': fraction of inspired oxygen
*'''I:E ratio''': ratio of inspiratory to expiratory time
*'''Trigger''': mechanism by which patient initiates a breath (flow or pressure)
*'''Cycle''': mechanism by which inspiration ends and expiration begins
===Volume Control vs. Pressure Control===
*'''Volume-controlled modes''': TV is set; airway pressure is variable
**Guarantees minute ventilation
**PIP varies with changes in compliance and resistance
*'''Pressure-controlled modes''': inspiratory pressure is set; TV is variable
**Limits peak airway pressures
**TV varies with compliance and resistance changes
**Decelerating flow pattern may improve gas distribution
==Modes==
==Modes==
===Assist Control (AC)===
 
*Preset rate and TV
===Volume Assist Control (AC)===
*Pt able to trigger additional breaths (full assisted tidal volume)
*'''The recommended default mode for ED ventilation'''<ref name="weingart">Weingart SD. Managing Initial Mechanical Ventilation in the Emergency Department. Ann Emerg Med. 2016;68:614-617.</ref>
*Spontaneous breathing (above rate) is not allowed
*Prevents patient fatigue by offering full respiratory support with every breath
*Beneficial for patients requiring a high minute-ventilation (reduces oxygen consumption and CO2 production of the respiratory muscles)
*The safety and ease of this mode typically outweighs the theoretical benefits of other modes<ref name="weingart"/>
*May worsen obstructive airway disease by air trapping or breath stacking
*Preset rate and TV; every breath (mandatory and triggered) delivers the full set tidal volume
*Set: RR, FiO2, PEEP, TV, I:E ratio
*Patient able to trigger additional breaths above set rate (each delivers full assisted tidal volume)
*Beneficial for patients requiring a high minute ventilation (reduces O2 consumption and CO2 production of the respiratory muscles)
*May worsen [[Asthma|obstructive airway disease]] by air trapping or breath stacking
**Consider deep [[Sedation|sedation]] ± [[Neuromuscular blockade|paralysis]] if breath stacking occurs
*Set: RR, FiO2, PEEP, TV, I:E ratio (or inspiratory flow rate)
*ED Pearl: Start with lung protective settings (TV 6-8 mL/kg [[Ideal body weight estimation|ideal body weight]], RR 16-18, PEEP 5, FiO2 100% and wean)<ref>Brower RG, et al. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342(18):1301-1308.</ref>
 
===Pressure Assist Control (Pressure Control Ventilation, PCV)===
*Set inspiratory pressure, PEEP, RR, and inspiratory time
*Every breath (mandatory and triggered) delivers gas at the set pressure
*TV varies based on lung compliance and airway resistance
*Decelerating flow pattern may improve gas distribution and comfort
*Useful when high peak pressures are problematic (e.g., bronchopleural fistula, subcutaneous emphysema)
*Limitation: TV not guaranteed; must closely monitor for hypoventilation if compliance changes
*Set: inspiratory pressure, PEEP, RR, I-time, FiO2


===Synchronous Intermittent Mandatory Ventilation (SIMV)===
===Synchronous Intermittent Mandatory Ventilation (SIMV)===
*Senses not to give with breathing if present, extra breaths of pt's TV
*Preset mandatory breaths delivered in coordination with the patient's respiratory effort
*Preset breaths in coordination with the respiratory effort
*Spontaneous breathing allowed between mandatory breaths
*Spontaneous breathing allowed between breaths
**Spontaneous breaths receive only whatever pressure support is additionally set (not full TV)
*Synchronization attempts to limit the barotrauma by not delivering a breath when already maximally inhaled (vs. IMV)
*Synchronization attempts to limit barotrauma by not delivering a breath when already maximally inhaled (vs. older IMV)
*For each additional breath triggered by pt, vent delivers variable TV depending on pt effort and condition of lung
*Because of need for patient effort, ''not recommended for tired or [[Sepsis|septic]] patients''
*Because of need for pt effort, not recommended for tired or septic pt
*Historically believed to ease [[Weaning mechanical ventilation|weaning]] but has ''not'' demonstrated superiority over AC for weaning<ref>Esteban A, Frutos F, Tobin MJ, et al. A comparison of four methods of weaning patients from mechanical ventilation. N Engl J Med. 1995;332(6):345-350.</ref>
*Set: RR, FiO2, PEEP, TV, I:E ratio
*For the paralyzed patient, there is no difference in minute ventilation or airway pressures between AC and SIMV
*Set: RR, FiO2, PEEP, TV, I:E ratio, PS (for spontaneous breaths)


^For the paralyzed patient, there is no difference in minute-ventilation or airway pressures between A/C and SIMV
===Pressure Support Ventilation (PSV)===
 
*Patient-triggered, pressure-limited, flow-cycled mode
===Pressure Support (PS)===
*Level of pressure set (not TV) to augment each spontaneous effort
*Controls via pressure, good if pressures getting too high
*Limits barotrauma and decreases the work of breathing in the spontaneously breathing patient
*Limits barotrauma and decreases the work of breathing in the spontaneously breathing patient
*Level of pressure set (not TV) to assist spontaneous efforts
*Breath terminates when inspiratory flow drops below a threshold (typically 25% of peak flow)
*Most ventilators allow back-up respiratory rate (in case of apnea)
*Most ventilators allow a back-up respiratory rate (apnea backup) in case of apnea
*Mode of choice in patients whose respiratory failure is not severe and who have an adequate respiratory drive (improved patient comfort, reduced cardiovascular effects, reduced risk of barotrauma, and improved distribution of gas)
*Mode of choice in patients whose [[Respiratory failure|respiratory failure]] is not severe and who have adequate respiratory drive
*Set: RR, FiO2, PEEP, PS, I:E ratio
**Improved patient comfort, reduced cardiovascular effects, reduced risk of barotrauma, improved gas distribution<ref>MacIntyre NR. Respiratory function during pressure support ventilation. Chest. 1986;89(5):677-683.</ref>
*Commonly used during [[Weaning mechanical ventilation|weaning]] and spontaneous breathing trials
*'''Limitation:''' TV not guaranteed; should not be used in patients with unreliable respiratory drive
*'''Set:''' PS level, FiO2, PEEP (RR is patient-determined)


===Pressure Regulated Volume Control (PRVC)===
===Pressure Regulated Volume Control (PRVC)===
*Provides constant pressure through inspiration with decelerating inspiratory flow pattern
*Dual-control mode that combines features of volume and pressure control
*Ventilator adjusts pressure breath to breath based on patient’s airway resistance and compliance
*Provides pressure-limited breaths with a decelerating flow pattern
*Benefits: minimum PIP, guaranteed tidal volume, patient can trigger more breaths, improved oxygenation, breath by breath changes
*Ventilator adjusts inspiratory pressure breath-to-breath to achieve a target tidal volume based on measured compliance
*Not recommended for asthma or COPD
*Benefits: minimum PIP, guaranteed tidal volume, patient can trigger additional breaths, breath-by-breath adaptation
*Set: FiO2, RR, TV, upper pressure limit, I:E ratio, PEEP
*'''Not recommended for [[Asthma|asthma]] or [[COPD]]''' (auto-PEEP may cause the ventilator to inappropriately lower pressure support)
*'''Set:''' FiO2, RR, TV (target), upper pressure limit, I:E ratio, PEEP


===CPAP===
===Airway Pressure Release Ventilation (APRV)===
*Needs spont breathing pt
''Main article: [[Airway pressure release ventilation]]''
*Not for fatiguing pt
*Pressure-controlled, time-cycled mode with inverse I:E ratio
*Set: FiO2, PEEP, back up RR
*Sustained high constant pressure (P<sub>high</sub>) for alveolar recruitment with brief intermittent releases (T<sub>low</sub>) for ventilation
*Allows unrestricted spontaneous breathing at both pressure levels
*"Open lung" ventilation strategy used as rescue therapy in severe [[Acute respiratory distress syndrome|ARDS]]
*''Cannot be used with [[Neuromuscular blockade|paralysis]]'' (requires spontaneous breathing for full benefit)
*Main limitation is hypercarbia/[[Respiratory acidosis|respiratory acidosis]] due to short release times
*Set:P<sub>high</sub>, P<sub>low</sub>, T<sub>high</sub>, T<sub>low</sub>, FiO2


===CPAP (Continuous Positive Airway Pressure)===
*Provides constant positive pressure throughout the respiratory cycle to a '''spontaneously breathing''' patient
*Equivalent to PEEP without additional inspiratory support
*Recruits collapsed alveoli, improves oxygenation, reduces work of breathing
*Not appropriate for fatiguing patients or those with inadequate respiratory drive
*Invasive CPAP is used during [[Weaning mechanical ventilation|weaning]]/spontaneous breathing trials
*Noninvasive CPAP - see [[Noninvasive ventilation]]
*'''Set:''' FiO2, PEEP (CPAP level), back-up RR (if available)


===Control Mode===
===Control Mode (CMV)===
* only in OR
*Ventilator initiates and controls every breath; no patient triggering allowed
* machine initiates and delivers breath
*Fixed rate and TV
* fixed rate and TV
*Primarily used in the OR setting
*Requires patient to be fully [[Sedation|sedated]] or [[Neuromuscular blockade|paralyzed]]
*Not used in the ED
 
===High Frequency Oscillatory Ventilation (HFOV)===
*Delivers very small tidal volumes at extremely high respiratory rates (3-15 Hz)
*Maintains near-constant airway pressure (mean airway pressure) with minimal tidal excursion
*Historically considered a rescue mode for refractory [[Acute respiratory distress syndrome|ARDS]]
*'''OSCILLATE and OSCAR trials showed no mortality benefit and possible harm; largely abandoned'''<ref>Ferguson ND, Cook DJ, Guyatt GH, et al. High-frequency oscillation in early acute respiratory distress syndrome. N Engl J Med. 2013;368(9):795-805.</ref><ref>Young D, Lamb SE, Shah S, et al. High-frequency oscillation for acute respiratory distress syndrome. N Engl J Med. 2013;368(9):806-813.</ref>
 
==ED-Specific Considerations==
 
===Mode Selection by Clinical Scenario===
{| class="wikitable"
|-
! Clinical Scenario !! Recommended Mode !! Key Settings
|-
| Default / undifferentiated || Volume AC || TV 6-8 mL/kg IBW, RR 16-18, PEEP 5
|-
| [[Acute respiratory distress syndrome|ARDS]] || Volume AC (lung protective) || TV 6 mL/kg IBW, Pplat <30, PEEP per ARDSnet table
|-
| [[Asthma]] / [[COPD]] || Volume AC || TV 6-8 mL/kg IBW, RR 10, I:E 1:4-1:5, PEEP 0-5
|-
| Severe [[Metabolic acidosis]] || Volume AC || TV 6-8 mL/kg IBW, high RR (match pre-intubation minute ventilation)
|-
| [[Acute respiratory distress syndrome|Refractory ARDS]] || [[Airway pressure release ventilation|APRV]] || P<sub>high</sub> ≤ 35, T<sub>high</sub> 4.5-6s, T<sub>low</sub> 0.5-0.8s
|-
| [[Weaning mechanical ventilation|Weaning trial]] || PSV or CPAP || PS 5-8, PEEP 5, FiO2 ≤0.4
|}
 
===Common Pitfalls===
*Forgetting to use [[Ideal body weight estimation|ideal body weight]] for tidal volume calculation (obese patients are at high risk for volutrauma)
*Not matching pre-intubation minute ventilation in patients with severe [[Metabolic acidosis]] (e.g., [[Diabetic ketoacidosis|DKA]], severe [[Sepsis|sepsis]])
**Can cause cardiovascular collapse from worsening acidosis post-intubation<ref>Weingart SD, Levitan RM. Preoxygenation and prevention of desaturation during emergency airway management. Ann Emerg Med. 2012;59(3):165-175.e1.</ref>
*Inadequate [[Sedation|sedation]] leading to ventilator dyssynchrony and breath stacking
*Using SIMV when patient cannot reliably generate adequate spontaneous breaths
*Not reassessing ventilator settings after initial setup (check plateau pressure within 30 minutes)


==See Also==
==See Also==
{{Mechanical ventilation pages}}
{{Mechanical ventilation pages}}
*[[EBQ:ARDSnet]]
*[[EBQ:ARDSnet]]
==External Links==
*[https://emcrit.org/wp-content/uploads/2010/05/Managing-Initial-Vent-ED.pdf EMCrit: Managing Initial Mechanical Ventilation in the ED]
*[https://www.ardsnet.org/ ARDSnet]
==References==
<references/>


[[Category:Critical Care]]
[[Category:Critical Care]]
[[Category:Pulm]]
[[Category:Pulmonary]]

Latest revision as of 21:59, 25 March 2026

Background

  • Ventilation modes define the pattern of breath delivery by a mechanical ventilator
  • Understanding modes is critical for optimizing oxygenation and ventilation while minimizing ventilator-associated lung injury
  • Mode selection is determined by the clinical scenario, degree of respiratory failure, and patient effort
  • All modes control some combination of volume, pressure, and flow during the respiratory cycle
  • The variable that is set (controlled) determines the mode category; the other variable becomes dependent

Key Terminology

  • Tidal volume (TV): volume of gas delivered per breath
  • Peak inspiratory pressure (PIP): maximum airway pressure during inspiration
  • Plateau pressure (Pplat): pressure measured during an inspiratory hold; reflects alveolar pressure
  • Driving pressure: Pplat minus PEEP; values < 14 cmH2O associated with improved survival[2]
  • PEEP: positive end-expiratory pressure; prevents alveolar collapse and improves oxygenation
  • FiO2: fraction of inspired oxygen
  • I:E ratio: ratio of inspiratory to expiratory time
  • Trigger: mechanism by which patient initiates a breath (flow or pressure)
  • Cycle: mechanism by which inspiration ends and expiration begins

Volume Control vs. Pressure Control

  • Volume-controlled modes: TV is set; airway pressure is variable
    • Guarantees minute ventilation
    • PIP varies with changes in compliance and resistance
  • Pressure-controlled modes: inspiratory pressure is set; TV is variable
    • Limits peak airway pressures
    • TV varies with compliance and resistance changes
    • Decelerating flow pattern may improve gas distribution

Modes

Volume Assist Control (AC)

  • The recommended default mode for ED ventilation[3]
  • Prevents patient fatigue by offering full respiratory support with every breath
  • The safety and ease of this mode typically outweighs the theoretical benefits of other modes[3]
  • Preset rate and TV; every breath (mandatory and triggered) delivers the full set tidal volume
  • Patient able to trigger additional breaths above set rate (each delivers full assisted tidal volume)
  • Beneficial for patients requiring a high minute ventilation (reduces O2 consumption and CO2 production of the respiratory muscles)
  • May worsen obstructive airway disease by air trapping or breath stacking
  • Set: RR, FiO2, PEEP, TV, I:E ratio (or inspiratory flow rate)
  • ED Pearl: Start with lung protective settings (TV 6-8 mL/kg ideal body weight, RR 16-18, PEEP 5, FiO2 100% and wean)[4]

Pressure Assist Control (Pressure Control Ventilation, PCV)

  • Set inspiratory pressure, PEEP, RR, and inspiratory time
  • Every breath (mandatory and triggered) delivers gas at the set pressure
  • TV varies based on lung compliance and airway resistance
  • Decelerating flow pattern may improve gas distribution and comfort
  • Useful when high peak pressures are problematic (e.g., bronchopleural fistula, subcutaneous emphysema)
  • Limitation: TV not guaranteed; must closely monitor for hypoventilation if compliance changes
  • Set: inspiratory pressure, PEEP, RR, I-time, FiO2

Synchronous Intermittent Mandatory Ventilation (SIMV)

  • Preset mandatory breaths delivered in coordination with the patient's respiratory effort
  • Spontaneous breathing allowed between mandatory breaths
    • Spontaneous breaths receive only whatever pressure support is additionally set (not full TV)
  • Synchronization attempts to limit barotrauma by not delivering a breath when already maximally inhaled (vs. older IMV)
  • Because of need for patient effort, not recommended for tired or septic patients
  • Historically believed to ease weaning but has not demonstrated superiority over AC for weaning[5]
  • For the paralyzed patient, there is no difference in minute ventilation or airway pressures between AC and SIMV
  • Set: RR, FiO2, PEEP, TV, I:E ratio, PS (for spontaneous breaths)

Pressure Support Ventilation (PSV)

  • Patient-triggered, pressure-limited, flow-cycled mode
  • Level of pressure set (not TV) to augment each spontaneous effort
  • Limits barotrauma and decreases the work of breathing in the spontaneously breathing patient
  • Breath terminates when inspiratory flow drops below a threshold (typically 25% of peak flow)
  • Most ventilators allow a back-up respiratory rate (apnea backup) in case of apnea
  • Mode of choice in patients whose respiratory failure is not severe and who have adequate respiratory drive
    • Improved patient comfort, reduced cardiovascular effects, reduced risk of barotrauma, improved gas distribution[6]
  • Commonly used during weaning and spontaneous breathing trials
  • Limitation: TV not guaranteed; should not be used in patients with unreliable respiratory drive
  • Set: PS level, FiO2, PEEP (RR is patient-determined)

Pressure Regulated Volume Control (PRVC)

  • Dual-control mode that combines features of volume and pressure control
  • Provides pressure-limited breaths with a decelerating flow pattern
  • Ventilator adjusts inspiratory pressure breath-to-breath to achieve a target tidal volume based on measured compliance
  • Benefits: minimum PIP, guaranteed tidal volume, patient can trigger additional breaths, breath-by-breath adaptation
  • Not recommended for asthma or COPD (auto-PEEP may cause the ventilator to inappropriately lower pressure support)
  • Set: FiO2, RR, TV (target), upper pressure limit, I:E ratio, PEEP

Airway Pressure Release Ventilation (APRV)

Main article: Airway pressure release ventilation

  • Pressure-controlled, time-cycled mode with inverse I:E ratio
  • Sustained high constant pressure (Phigh) for alveolar recruitment with brief intermittent releases (Tlow) for ventilation
  • Allows unrestricted spontaneous breathing at both pressure levels
  • "Open lung" ventilation strategy used as rescue therapy in severe ARDS
  • Cannot be used with paralysis (requires spontaneous breathing for full benefit)
  • Main limitation is hypercarbia/respiratory acidosis due to short release times
  • Set:Phigh, Plow, Thigh, Tlow, FiO2

CPAP (Continuous Positive Airway Pressure)

  • Provides constant positive pressure throughout the respiratory cycle to a spontaneously breathing patient
  • Equivalent to PEEP without additional inspiratory support
  • Recruits collapsed alveoli, improves oxygenation, reduces work of breathing
  • Not appropriate for fatiguing patients or those with inadequate respiratory drive
  • Invasive CPAP is used during weaning/spontaneous breathing trials
  • Noninvasive CPAP - see Noninvasive ventilation
  • Set: FiO2, PEEP (CPAP level), back-up RR (if available)

Control Mode (CMV)

  • Ventilator initiates and controls every breath; no patient triggering allowed
  • Fixed rate and TV
  • Primarily used in the OR setting
  • Requires patient to be fully sedated or paralyzed
  • Not used in the ED

High Frequency Oscillatory Ventilation (HFOV)

  • Delivers very small tidal volumes at extremely high respiratory rates (3-15 Hz)
  • Maintains near-constant airway pressure (mean airway pressure) with minimal tidal excursion
  • Historically considered a rescue mode for refractory ARDS
  • OSCILLATE and OSCAR trials showed no mortality benefit and possible harm; largely abandoned[7][8]

ED-Specific Considerations

Mode Selection by Clinical Scenario

Clinical Scenario Recommended Mode Key Settings
Default / undifferentiated Volume AC TV 6-8 mL/kg IBW, RR 16-18, PEEP 5
ARDS Volume AC (lung protective) TV 6 mL/kg IBW, Pplat <30, PEEP per ARDSnet table
Asthma / COPD Volume AC TV 6-8 mL/kg IBW, RR 10, I:E 1:4-1:5, PEEP 0-5
Severe Metabolic acidosis Volume AC TV 6-8 mL/kg IBW, high RR (match pre-intubation minute ventilation)
Refractory ARDS APRV Phigh ≤ 35, Thigh 4.5-6s, Tlow 0.5-0.8s
Weaning trial PSV or CPAP PS 5-8, PEEP 5, FiO2 ≤0.4

Common Pitfalls

  • Forgetting to use ideal body weight for tidal volume calculation (obese patients are at high risk for volutrauma)
  • Not matching pre-intubation minute ventilation in patients with severe Metabolic acidosis (e.g., DKA, severe sepsis)
    • Can cause cardiovascular collapse from worsening acidosis post-intubation[9]
  • Inadequate sedation leading to ventilator dyssynchrony and breath stacking
  • Using SIMV when patient cannot reliably generate adequate spontaneous breaths
  • Not reassessing ventilator settings after initial setup (check plateau pressure within 30 minutes)

See Also

Mechanical Ventilation Pages

External Links

References

  1. ↑ The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342(18):1301-1308.
  2. ↑ Amato MB, Meade MO, Slutsky AS, et al. Driving pressure and survival in the acute respiratory distress syndrome. N Engl J Med. 2015;372(8):747-755.
  3. ↑ 3.0 3.1 Weingart SD. Managing Initial Mechanical Ventilation in the Emergency Department. Ann Emerg Med. 2016;68:614-617.
  4. ↑ Brower RG, et al. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342(18):1301-1308.
  5. ↑ Esteban A, Frutos F, Tobin MJ, et al. A comparison of four methods of weaning patients from mechanical ventilation. N Engl J Med. 1995;332(6):345-350.
  6. ↑ MacIntyre NR. Respiratory function during pressure support ventilation. Chest. 1986;89(5):677-683.
  7. ↑ Ferguson ND, Cook DJ, Guyatt GH, et al. High-frequency oscillation in early acute respiratory distress syndrome. N Engl J Med. 2013;368(9):795-805.
  8. ↑ Young D, Lamb SE, Shah S, et al. High-frequency oscillation for acute respiratory distress syndrome. N Engl J Med. 2013;368(9):806-813.
  9. ↑ Weingart SD, Levitan RM. Preoxygenation and prevention of desaturation during emergency airway management. Ann Emerg Med. 2012;59(3):165-175.e1.
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