Mechanical ventilation choosing amongst ventilator modes
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Syed Hassan A. Kazmi BSc, MD [2]
Overview
Choice of ventilator mode depends upon the clinical condition of the patient. Choice of ventilator mode can be tailored to achieve specific goals of management and set to achieve spontaneous breathing, volume-targeted ventilation, pressure-targeted ventilation, or some combination. In some conditions, for example in case of spontaneously breathing patient, the patient set the respiratory rate and generates their desired flow rate. Different modes of ventilation include pressure support ventilation (PSV), continued mandatory ventilation (CMV) or assis control mode (AC), synchronous intermittent mandatory ventilation (SIMV), proportional assist ventilation (PAV), dual control mode, high frequency ventilation, pressure and volume targeted modes.
Choosing Amongst Ventilator Modes
Choice of ventilator mode depends upon the clinical condition of the patient. Choice of ventilator mode can be tailored to achieve specific goals of management and set to achieve spontaneous breathing, volume-targeted ventilation, pressure-targeted ventilation, or some combination. In some conditions, for example in case of spontaneously breathing patient, the patient set the respiratory rate and generates their desired flow rate.[1][2][3] The following are the various ventilator modes and their features:
Pressure support ventilation (PSV)
- This mode supports patient initiated breaths with a set inspiratory pressure and positive end expiratory pressure (PEEP)
- Mode of partial ventilatory support because there is no set rate
- The clinician sets the FiO 2 and PEEP. The patient sets the respiratory rate and generates their desired flow rate.
- After the optimal flow is achieved, the applied pressure can be turned off.
- The volume given depends upon the patient's effort and lung/chest wall compliance
- There is no minimal rate
Continued mandatory ventilation (CMV) or assist control (AC)
- Ventilator delivers a minimum number of supported breaths
- Mode of fully assisted ventilatory support
- Additional patient initiated breaths trigger fully assisted vent breaths. There fore, vent-triggered breaths identical to patient triggered breaths
- May be pressure targeted or volume targeted
- If patient develops tachypnea, may lead to respiratory alkalosis, breath stacking and auto PEEP
Synchronous intermittent mandatory ventilation (SIMV)
- Ventilator develops a minimum number of supported breaths
- Tidal volume of additional breaths is determined by the patients effort
- This strategy also supplies inspiratory pressure during spontaneous breaths (similar to pressure support ventilation)
- May be used to wean off patient after extubation (maybe combined with pressure support ventilation- PSV)
Proportional assist ventilation (PAV)
- Delivers variable pressure to achieve targeted percentage of work of breathing
Dual control modes
- Combination of volume and pressure targeted ventilation
- Use a closed loop ventilator logic
- Automatically alter control variables, either breath-to-breath or within a breath, to ensure a minimum tidal volume or minute-ventilation
High frequency ventilation
- Helps to achieve optimum gas exchange when using high respiratory rates (RR) with tidal volumes (Vt) lesser than the antomical dead space
- Used in neonatal respiratory failure
- May be used in cases of acute lung injury (ALI) or acute respiratory distress syndrome (ARDS)
Volume targeted modes
- Both assist control (AC) and syncronous intermittent support ventilation (SIMV) can be volume controlled
- Ventilator delivers a set tidal volume (Vt)
- Pressures depend on lung compliance
Advantages
- Safe in cases of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS)
- Ideal initial ventilator setting
- Easy to measure mechanics (PIP, Pplat, airway resistance, compliance)
Pressure targeted modes
- Ventilator delivers a fixed inspiratory pressure regardless of Vt
- Vt depends on lung/chest wall compliance
Advantages
- May increase patient comfort (PSV) requiring less sedation
Proportional assist ventilation plus and proportional pressure support
References
- ↑ "Treatment of severe cardiogenic pulmonary edema with continuous positive airway pressure delivered by face mask. - PubMed - NCBI".
- ↑ "How is mechanical ventilation employed in the intensive care unit? An international utilization review. - PubMed - NCBI".
- ↑ "Characteristics and outcomes in adult patients receiving mechanical ventilation: a 28-day international study. - PubMed - NCBI".