Modes of Ventilator
1. Basic modes of Ventilator
2. Newer modes of Ventilator
A. Basic modes of Ventilator
1. Volume controlled Ventilator (VCV)
Also called volume-controlled or volume-cycled ventilation
Volume control favours the control of ventilation.
Set volume, pressure variable.
Better control of Ventilation than oxygenation.
VCV requires the clinician to set the peak flow rate, flow pattern, tidal volume, respiratory rate, positive end-expiratory pressure (applied PEEP, also known as extrinsic PEEP), and fraction of inspired oxygen (FiO2).
Used in used in anesthesia mode.
Patient is fully sedated in this mode so it provide rest to respiratory muscle.
Ventilator delivers the preset tidal volume (TV) with constant flow during the preset inspiratory time at preset respiratory rate.
2. Assist/control mode (A/C)
Common method.
AC ventilation is a volume-cycled mode of ventilation. It works by setting a fixed tidal volume (VT) that the ventilator will deliver at set intervals of time or when the patient initiates a breath.
Useful for patients with asthma or chronic obstructive pulmonary disease.
Assist control mode allow patient to initiate ventilator delivered breath although tidal volume is controlled by ventilator.
Any respiratory attamp by patient triggered a ventilator breath.
This mode will not allow the patient take intermittent spontaneous breaths.
3. Pressure-controlled ventilation (PCV)
Pressure control favours the control of oxygenation.
Set pressure, volume variable.
Better control of oxygenation than Ventilation.
The PCV mode is used for mandatory pressure control ventilation with fixed pressure levels. This mode is used on patients who have no spontaneous respiration.
4. Synchronized intermittent mandatory Ventilation (SIMV)
In SIMV, ventilator delivers mandatory breaths during a spontaneous inspiratory effort.
It allows spontaneous breath of any tidal volume in between tha mandatory breaths.
This ventilator mode will provide a set number of breaths at a fixed tidal volume, but a patient can trigger a spontaneous breath with the volume determined by patient effort.
SIMV is type of volume control mode of ventilation. With this mode, the ventilator will deliver a mandatory (set) number of breaths with a set volume while at the same time allowing spontaneous breaths.
If SIMV has dual control mode with pressure support then spontaneous breath is pressure supported which reduces the work of breathing during spontaneous breathing and hastens weaning.
With this mode, the ventilator will deliver a mandatory (set) number of breaths with a set volume while at the same time allowing spontaneous breaths.
5. Continuous positive airway pressure (CPAP)
Non invasive mode of ventilation via nasal or face mask.
Types of positive airway pressure. CPAP delivers constant pressure in both cycle of respiration in a spontaneous breathing patient.
CPAP delivers the same amount of pressure at all times.
Used for common treatment for obstructive sleep Apnea and eliminate snoring.
6. Bilevel positive airway pressure (BiPAP)
Non invasive mode of ventilation via nasal or face mask.
Two level positive airway pressure.
Type of Positive Airway pressure.
BiPap has two different pressure level.
1. Inspiratory positive airway pressure (IPAP)
2. Expiratory positive airway pressure (EPAP)
Higher pressure when breathing in and lower pressure in breathing out.
BiPAP delivers higher air pressure when you breathe in.
CPAP machines are primarily used to treat Obstructive Sleep Apnea (OSA) while BiPAP machines are used to treat Central Sleep Apnea, Complex Sleep Apnea, or COPD.
7. Pressure support ventilation (PSV)
Pressure support ventilation (PSV) is a mode of positive pressure mechanical ventilation and is a spontaneous mode of ventilation.
The patient initiate every breath and ventilator delivers support with preset pressure value.
With support from the ventilator, the patient also regulates their own respiratory rate and tidal volume.
In Pressure Support, the set inspiratory pressure support level is kept constant.
If there is a change in the mechanical properties of the lung/thorax and patient effort, the delivered tidal volume will be affected then regulate the pressure support level to obtain desired ventilation.
This mode helps in overcome resistance of breathing during weaning.
Pressure support ventilation is a common ventilator setting for both invasive and non-invasive ventilation.
B. Newer modes of Ventilator
1. Pressure regulated volume control (PRVC)
PRVC is combines pressure and volume controlled ventilation.
Pressure-regulated volume control (PRVC) is a mode of ventilation in which the ventilator attempts to achieve set tidal volume at lowest possible airway pressure.
Used to treat acute respiratory distress syndrome (ARDS), meet lung protective strategy.
PRVC is considered an advanced dual-control or adaptive mode because the ventilator uses both volume and pressure to automatically adjust to the patient’s ventilatory needs breath by breath.
Ventilator monitor each breath and compare delivered tidal volume with set tidal volume.
If delivered volume is low it increases respiratory pressure on next breath.
2. Airway pressure release Ventilation (APRV)
APRV uses longer inspiratory times; this results in increased mean airway pressures, which aim to improve oxygenation.
APRV is open-lung mode of invasive mechanical ventilation mode, in which spontaneous breathing is encouraged.
Long period constitute the inspiratory phase and short period constitute the expiratory phase resulting I:E ratio (7-9): 1
APRV mode allows the breath spontaneously during any point mandatory breath.
The tidal volume will vary according to lung dynamics and pressure gradient.
3. Inverse ratio Ventilation (IRV)
Pressure control ventilation is used in IRV with the I:E ratio of 2:1 - 4:1
IRV improves oxygenation by reducing alveolar dead space ventilation and intrapulmonary shunting.
4. Biphasic positive airway pressure (BiPAP)
Also known as PeV+.
In biphasic positive airway pressure spontaneous ventilation could be achieved at any point in the mechanical ventilation cycle (inspiration and expiration).
5. Liquid Ventilator
It is a technique where perfluorocarbons are used as oxygen delivery agents.
The solubility of oxygen and carbon dioxide is 20 times higher in PFC's (perfluorocarbon).
Types of liquid Ventilation
The two main types of LV delivery techniques are:
1. Total (or tidal) liquid ventilation (TLV)
2. Partial liquid ventilation (PLV)
Used in treatment of bronchopulmonary, improves pulmonary function, gas exchange, and prevent lung injury.
6. High frequency ventilator
In high frequency ventilation, ventilator delivers small tidal volumes of high respiratory rates (>60 breaths/minutes).
High-frequency ventilation is a type of mechanical ventilation which utilizes a respiratory rate greater than three times the normal value.and very small tidal volumes.
High frequency ventilation reduce the ventilator-associated lung injury, especially in ARDS and acute lung injury patient.
7. Closed loop ventilator
It changes the ventilatory parameters according to patient's breathing pattern.
It alters the mandatory breaths and pressure support level according to the feedback, the ventilator gets from lung dynamics of patient.
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