APPENDIX B: VENTILATOR MODES AND SETTINGS

Volume-targeted Modes

- Volume Assist/Control (V-AC), Assist Control (AC) or Volume Control Ventilation (VCV): Delivers a preset number of mandatory breaths per minute (control part). The patient can take their own breaths in addition to mandatory breaths, with each spontaneous breath receiving the full preset tidal volume (assist part). Airway pressures can vary during delivery. 1-3
- Volume Synchronized Intermittent Mandatory Ventilation (V-SIMV) combines mandatory breaths and supported breaths. “synchronized” means it will adjust the delivery of breaths with the patient’s effort. “Intermittent” means that not all breaths are supported. The ventilator delivers a preset number of mandatory breaths per minute. Any breath taken over the set RR will not receive the set tidal volume and is solely based on the patient’s lung compliance and effort. Newer models offer PS with patient triggered breaths.

Pressure-targeted Modes

- Pressure Support Ventilation (PSV) supports every patient breath with a preset amount of pressure support. No mandatory breaths are given, so the patient must be spontaneously breathing.
- Pressure Assist control (P-AC), or Pressure Control Ventilation (PCV) delivers a set number of mandatory pressure-controlled breaths, in which the patient receives a fixed pressure during a preset inspiratory time. Any breaths over the set rate will be pressure controlled with the same amount of pressure. The delivered tidal volume will be based on the amount of pressure applied, the lung compliance and airway resistance of the patient.

Adaptive Support Ventilation (ASV)

ASV provides intelligent ventilation mode that continuously adjusts respiratory rate, tidal volume, and inspiratory time depending on the patient’s lung mechanics and effort. This is similar to “Auto-Flow” or other like settings on different brands of ventilators. Currently only available on the Hamilton-T1.

Continuous Positive Airway Pressure (CPAP)

CPAP Is a type of positive airway pressure, where the air flow is introduced into the airways to maintain a continuous pressure to constantly stent the airways open, in people who are breathing spontaneously.1 CPAP provides constant pressure above that of the atmospheric pressure. Delivered via the upper respiratory tract.

Pressure Regulated Volume Control (PRVC) Ventilation

PRVC ventilation is designed for invasive mechanical ventilation and combines volume and pressure strategies. PRVC delivers a pressure-controlled and tidal volume (VT)–targeted breath using a decelerating flow waveform pattern that allows unrestricted spontaneous breathing with or without pressure support (PS). 2 (may be Impact 731 only). ***

BL (bilevel)

The BL ventilator provides two pressure settings to assist patients breathing spontaneously: a higher inhalation pressure (IPAP) and a lower exhalation pressure (EPAP).NOTE: This feature is only available on the Zoll. ***

***See Acute Respiratory Failure CPG for more detail on advanced ventilator modes/settings.

VENTILATOR ADJUSTABLE SETTINGS

Tidal volume (VT )

The volume of gas, exchanged during a breath and commonly expressed in milliliters. VT is generally set between 4-8ml/kg IBW, to prevent lung over distension and barotrauma.4-8

Ideal IBW

The weight at which tidal volume is calculated against instead of using actual weight. This enables patients to be ventilated in a lung-protective strategy. A quick reference chart can be found in Appendix C. IBW can be calculated manually as follows:

- Male: {(Height in inches-60) x 2.2} +50 (e.g. 72in-60= 12; 12 x 2.2 = 26.4; 26.4 + 50 = IBW of 76.4 kg)
- Female: {(Height in inches-60) x 2.2} +45 (e.g. 65in-60= 5; 5 x 2.2 = 11; 11 + 45 = IBW of 56 kg)

Minute Ventilation (VE)

The average volume of gas entering, or leaving, the lungs per minute, commonly expressed in liters per minute. Also called minute volume. Minute ventilation is the product of VT and RR (respiratory rate). Normal VE is 5 – 10 L/min. 4-8

I:E Ratio

See I:E definition. I:E might need to be adjusted for physiology that requires extended exhalation time. 4-8 For example: Asthma patient may require an I:E of 1:3, 1:4, or 1:5 to allow for more exhalation time.

Flow Rate

Is the velocity at which gas is delivered to the patient, expressed in liters per minute. When the flow rate is set higher, the speed of gas delivery is faster and inspiratory time is shorter. 4-8

Peak Inspiratory Pressure (PIP)

Represents the total pressure that is required to deliver the VT and depends upon various airway resistance, lung compliance, and chest wall factors. It is expressed in centimeters of water (cm H2O).

Sensitivity or trigger sensitivity

Trigger sensitivity Is the effort, or negative pressure, required by the patient to trigger a machine breath, commonly set so that minimal effort (-1 to -2 cm H2O) triggers a breath.1,3 This is usually seen with assist modes of ventilator operation.

Pressure alarms

Pressure alarms ensure that providers are alerted to pressures that fall outside of appropriate ranges and have potential to harm the patient via barotrauma (over-pressure) or under-ventilation (circuit disconnect or under-pressure). Pressures will be determined by placing the patient on the vent for ~1-2 minutes and determining intrinsic peak inspiratory pressure. (Labeled as PEAK on 754 Ventilator (top right); Labeled as peak on Hamilton T1 ventilator (top left); Labeled as PIP on ZOLL EMV+ (731) (right center). Standard alarm settings should be: Need to measure a peak pressure 5 min after setting initial settings.

- High pressure alarm: 10 cmH2O above peak airway pressure.
- Low pressure alarm: 5 cmH2O below peak airway pressure.

References

1. Grossbach I, Chlan L., Tracy MF. Overview of mechanical ventilatory support and management of patient-and ventilator-related responses. Critical care nurse, 2011. 31(3), 30-44.
2. The National Heart, Lung, and Blood Institute. How the Lungs Work Video. Nov 10, 2020 https://www.youtube.com/watch?v=C0mYCssvYpE
3. Wilcox SR, Richards JB, Fisher DF, et al. Initial mechanical ventilator settings and lung protective ventilation in the ED. The American journal of emergency medicine, 2016. 34(8), 1446-1451.
4. Mora Carpio AL, Mora JI. Ventilator Management. [Updated 2023 Mar 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
5. Maddry JK, Ng PC, et al. Impact of prehospital airway management on combat mortality. The American journal of emergency medicine, 2018. 36(6), 1032-1035.
6. Shah AA, Kettle PB, Niven AS. Ventilator management: a practical approach to respiratory failure in combat casualties. In Front Line Surgery, 2017. 631-646.
7. Wilcox SR, Saia MS, Waden H, et al. Mechanical ventilation in critical care transport. Air Medical Journal, 2016. 35(3), 161-165.
8. Hollott J, Stokoe A, Vallance S, et al. Advanced ventilation and monitoring during helicopter hoist extraction of an intubated patient. Air Medical Journal, Nov 2020. 39(6), 512-515.