Mechanical Ventilation: Pressure Modes (Respiratory Therapy)

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ALERT

Ventilator failure or accidental disconnection can be catastrophic in patients undergoing neuromuscular blockade.

Patients on mechanical ventilation are at high risk for complications, like pneumonia, sepsis, acute respiratory distress syndrome (ARDS), and ventilator-induced lung injury (VILI), from volutrauma, barotrauma, or atelectrauma.

OVERVIEW

Pressure control ventilation (PCV) delivers breaths triggered by time or patient effort, and time ends the breath. A preset inspiratory pressure (IP) and inspiratory time (TI) keep the airway pressure constant regardless of changes in resistance or compliance. Tidal volume (VT) varies based on driving pressure, TI, patient effort, positive end-expiratory pressure (PEEP), and changes in compliance or resistance. Some ventilators combine the benefits of pressure and volume by using additional settings that may offer a volume guarantee or limit setting for more lung protection. Setting options, terminology, and abbreviations vary by ventilator brand.

Primary modes used include assist control (AC), which delivers breaths with fixed settings while allowing extra spontaneous breaths with the same settings; synchronized intermittent mandatory ventilation (SIMV), which delivers breaths with fixed settings and allows spontaneous breaths in between; pressure support ventilation (PSV), a spontaneous mode where breaths are triggered and ended by the patient; and SIMV/pressure support (PS), which delivers breaths with fixed settings and allows spontaneous breaths in between, augmented by pressure.

Sensitivity settings determine how easily a patient can trigger spontaneous breaths, using pressure-trigger or flow-trigger mechanisms. Lower cm H₂O or L/min settings increase sensitivity, making it easier for the patient to breathe spontaneously. Flow-trigger mechanisms are used to reduce spontaneous breathing effort, while pressure-trigger mechanisms are used to fix breath auto-cycling. Sensitivity must be adjusted for each patient to avoid auto-cycling or increased work of breathing.

Peak inspiratory pressure (PIP) is the highest pressure during inspiration. Plateau pressure (Pplat) is the pressure at end-inspiration when gas flow stops. Mean airway pressure (MAP) is the average pressure over the respiratory cycle. Exhaled VT will change when the patient’s condition changes. Decreased compliance stiffens the lungs, making it necessary to increase the IP or TI to maintain exhaled VT and gas exchange. Changes in the TI affect the I:E ratio and should be monitored to avoid an unintentional inverse ratio. Lung protective strategies, such as VT (6 to 8 mL/kg)^{undefined#ref1">1,3} for predicted body weight (PBW) (Table 1), IP ≤ 30 cm H₂O,^1,3 and PEEP,¹ are used to reduce the risk of VILI. PEEP is used to improve or maintain lung volume and improve oxygenation. Auto-PEEP is air trapped in the lungs that cannot be fully exhaled. Auto-PEEP can happen when the exhalation time is not long enough or when lung elasticity and resistance in the airways worsens. A patient-ventilator assessment at regular intervals allows adjustments to ventilator settings for safety, comfort, and synchrony, aiming for mechanical ventilator liberation.¹

SUPPLIES

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EDUCATION

• Give developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, preferred learning style, and overall neurologic and psychosocial state.
• Explain the need for mechanical ventilation or setting changes and the alarms to the patient and family.
• Encourage questions and answer them as they arise.

ASSESSMENT AND PREPARATION

Assessment

1. Assess the need for mechanical ventilation or change in ventilator support.²
   1. Apnea
   2. Acute ventilatory failure
   3. Impending ventilatory failure
   4. Severe oxygenation problems (refractory hypoxemia)
2. Assess the patient’s hemodynamic and cardiorespiratory systems.
3. Determine if the patient or family has health literacy needs or requires tools or assistance to effectively communicate. Be sure these needs can be met without compromising safety.
4. Review the patient’s and family’s previous experience and knowledge of mechanical ventilation and understanding of the care to be provided.

Preparation

1. Gather equipment, including a ventilator with PCV and PSV or equivalent option, circuit, humidification device, filters (if needed), manual resuscitation bag, and closed suction device.
2. Before initiating the mechanical ventilator, check the microprocessor or ventilation system. Perform a short self-test as appropriate.
   1. Verify compliance of the ventilator circuit with the humidification device and filters (if needed).
   2. Document the completed ventilation system test. Include pass or fail, date, initials or signature, and credentials.
3. Verify the practitioner’s order for the initiation of mechanical ventilation or mode of ventilation change.

PROCEDURE

Pressure Control Ventilation (PCV)

1. Clean hands and put on appropriate personal protective equipment (PPE) based on the risk of exposure to body fluids or infection precautions.
2. Verify the correct patient using two identifiers.
3. Explain the procedure and ensure that the patient agrees to treatment.
4. Select PCV and the mode choice, such as AC, SIMV, or SIMV/PS.

   Setting options, terminology, and abbreviations may be brand specific based on trademarked mechanical ventilator specifications.

5. Set the IP. Begin with 15 to 20 cm H₂O pressure above PEEP. Adjust to obtain exhaled VT of 6 to 8 mL/kg PBW (Table 1).^2,3

   PIP should not exceed 30 cm H₂O to minimize the risk of VILI.²

6. Set the desired minimum respiratory rate starting at 12 to 14 breaths/min.^2,3

   The patient may breathe above the set respiratory rate.

7. Set the TI. Begin at 0.6 to 1.0 seconds.^2,3 Adjust to ensure flow meets or exceeds patient demand.

   Changes in the TI affect the I:E ratio, so monitor it to avoid I:E ratio less than 1:2.³

8. Set the PEEP.
   1. Begin with 5 cm H₂O.
   2. Monitor for auto-PEEP.^2,3

      PEEP is titrated up to improve oxygenation, lung function, or lung compliance.

      Increasing I:E ratio or expiratory time may decrease auto-PEEP.

9. Set the trigger sensitivity.
   1. For pressure-trigger, start at –0.05 to –1.5 cm H₂O pressure.^2,3
   2. For flow-trigger, start at 1 to 2 L/min below baseline flow.^2,3

      Adjust to minimize patient effort and auto-cycling. The lower the number, the easier it is for the patient to trigger the breath.

10. Set pressure rise time or slope while observing the pressure-time curve waveform.

    Adjust to minimize pressure overshoot or spike at the beginning of inspiration, but ensure it rises quickly to meet the patient’s breathing needs.

11. Set the fraction of inspired oxygen (FIO₂).
12. If using SIMV, set the PS level.
    1. Begin with 12 to 15 cm H₂O above PEEP.²
    2. Adjust to obtain a spontaneous exhaled VT of 6 to 8 mL/kg PBW (Table 1).²
    3. Set additional parameters available for patient comfort and patient-ventilator synchrony, such as slope, rise time, or flow cycle threshold.
13. Ensure that all ventilator alarms are on and set appropriately for the patient’s individual ventilator settings.
14. Discard supplies, remove PPE, and clean hands.
15. Document the procedure in the patient’s record.

Pressure Support Ventilation (PSV)

1. Clean hands and don gloves. Don additional PPE based on the risk of exposure to bodily fluids or infection precautions.
2. Verify the correct patient using two identifiers.
3. Explain the procedure and ensure that the patient agrees to treatment.
4. Select spontaneous mode.
5. Set the PS level. Begin with 12 to 15 cm H₂O above PEEP.² Adjust to obtain a spontaneous exhaled VT of 4 to 8 mL/kg PBW and maintain gas exchange (Table 1).^2,3

   Rationale: An increase in the PS increases the spontaneous VT.

6. Set the PEEP level. Begin with 5 cm H₂O.²

   PIP should not exceed 30 cm H₂O to minimize the risk of VILI.²

7. Set the trigger sensitivity.
   1. For pressure-trigger, start at –0.05 to –1.5 cm H₂O pressure.^2,3
   2. For flow-trigger, start at 1 to 2 L/min below baseline flow.^2,3

      Adjust to minimize patient effort and auto-cycling. The lower the number, the easier it is for the patient to trigger the breath.

8. Set pressure rise time or slope while observing the pressure-time curve waveform.

   Adjust to ensure pressure rises quickly enough to meet the patient’s spontaneous inspiratory demand.

9. Set the FIO₂.
10. Ensure that the ventilator alarms are on and set appropriately for the patient’s individual ventilator settings.
11. Discard supplies, remove PPE, and clean hands.
12. Document the procedure in the patient’s record.

MONITORING AND CARE

1. Regularly perform a check of ventilator settings, alarms, and measured parameters.
2. Maintain the humidification device and circuit temperature (if applicable) to avoid excessive condensation in the ventilator circuit.
3. Assess the patient’s overall level of comfort and patient-ventilator synchrony.
4. To minimize alveolar derecruitment, consider using a closed suction device to minimize the number of times the patient is disconnected from the ventilator.

EXPECTED OUTCOMES

• Improved oxygenation
• Improved ventilation
• Patient-ventilator synchrony and comfort
• Minimized ventilator-induced lung injury
• Liberation from mechanical ventilation

UNEXPECTED OUTCOMES

• Alveolar overdistention
• Increased work of breathing
• Worsening oxygenation
• Worsening ventilation
• Ventilator-associated event (VAE)
• Hemodynamic compromise

DOCUMENTATION

• Ventilator settings
  • Mode of ventilation
  • Set IP
  • Set respiratory rate
  • Set TI or set I:E
  • Set PEEP
  • Set trigger sensitivity
  • Set FIO₂
  • Set PS, if applicable
  • Slope, rise time, flow cycle, if applicable
• Monitored settings
  • Exhaled VT (mandatory breath)
  • Exhaled VT (spontaneous breath)
  • Minute volume (total)
  • Minute volume (spontaneous)
  • Respiratory rate (total)
  • PIP
  • MAP
  • I:E ratio
  • Auto-PEEP
• Education
• Patient’s tolerance
• Unexpected outcomes and related interventions

REFERENCES

1. Goodfellow, L.T. and others. (2024). AARC clinical practice guideline: Patient-ventilator assessment. Respiratory Care, 69(8), 1042-1054. doi:10.4187/respcare.12007
2. Shelledy, D.C., Peters, J.I. (2020). Chapter 6: Ventilator initiation. In D.C. Shelledy, J.I. Peters (Eds.), Mechanical ventilation (3rd ed., pp. 311-366). Burlington, MA: Jones & Bartlett Learning.
3. Vines, D.L. (2025). Chapter 49: Initiating and adjusting invasive ventilatory support. In J.K. Stoller and others (Eds.), Egan’s fundamentals of respiratory care (13th ed., pp. 1071-1103). St. Louis: Elsevier.

ADDITIONAL READINGS

Gallagher, J.J. (2024). Procedure 27: Invasive mechanical ventilation (through an artificial airway): Volume and pressure modes. In K.L. Johnson (Ed.), AACN procedure manual for progressive and critical care (8th ed., pp. 233-253). St. Louis: Elsevier.

Clinical Review: Jennifer Elenbaas, MA, BS, RRT, AE-C

Published: April 2025