Volume controlled continuous mandatory ventilation
Encyclopedia
Volume controlled continuous mandatory ventilation — (VC-CMV) is a mode of mechanical ventilation where breaths are delivered based on set variables. The patient may initate breaths by attempting to breathe. Once a breath is initated, either by the patient or by the ventilator the set tidal volume
is delivered.
is a mode of ventilation where breaths are delivered based on set variables. The patient may initate breaths by attempting to breathe. Once a breath is initated, either by the patient or by the ventilator the set tidal volume
is delivered. Assist Control is also called Volume Control or Assist Control Volume Control (AC/VC).
This mode was created out of the need for patient-initiation in breaths. Fundamentally, AC is controlled mechanical ventilation (CMV) with a sensitivity for patient breathing. The use of CMV in the original version required the patient be completely unconscious, either pharmacokinetically or otherwise in a coma
. With the addition of breath sensitivity, that requirement is relaxed but if the patient is actively breathing synchronization may be required in a mode such as pressure controlled intermittent mandatory ventilation or volume controlled intermittent mandatory ventilation.
The variables required in VC-CMV are: tidal volume (VT), respiratory rate (f), flow rate and trigger sensitivity (for sensing patient effort). Additional variables like peak-end expiratory pressure (PEEP) and pressure support (PS) may be added for additional support.
Limit — Limits in VC-CMV may be set and pressure based. The ventilator will attempt to deliver the set tidal volume utilizing whatever pressure is required to reach its setting. A pressure limit may be added to limit damage to the lungs (barotrauma
).
Cycle — Expiration cycling can be set by time or the pressure limit. Once the Ti (inspiratory time) is reached, or a pressure limit is reached the ventilator will cycle into expiratory mode and allow passive exhalation until another breath is triggered.
. Nomenclature of mechanical ventilation
has become more standardized and these terms are no longer preferred but still may be seen in older research there are many different names that historically were used to reference CMV but now reference Assist Control. Names such as: volume control ventilation, and volume cycled ventilation in modern usage refer to the Assist Control mode.
Tidal volume
Tidal volume is the lung volume representing the normal volume of air displaced between normal inspiration and expiration when extra effort is not applied.Typical values are around 500ml or 7ml/kg bodyweight.-Mechanical Ventilation:...
is delivered.
Volume controlled continuous mandatory ventilation
VC-CMV — Most commonly referred to as assist control (AC) though not preferredNomenclature of mechanical ventilation
Many terms are used in mechanical ventilation, some are specific to brand, model, trademark and mode of mechanical ventilation. There is a standardized nomenclature of mechanical ventilation that is specific about nomenclature related to modes, but not settings and variables.-Volume Controlled...
is a mode of ventilation where breaths are delivered based on set variables. The patient may initate breaths by attempting to breathe. Once a breath is initated, either by the patient or by the ventilator the set tidal volume
Tidal volume
Tidal volume is the lung volume representing the normal volume of air displaced between normal inspiration and expiration when extra effort is not applied.Typical values are around 500ml or 7ml/kg bodyweight.-Mechanical Ventilation:...
is delivered. Assist Control is also called Volume Control or Assist Control Volume Control (AC/VC).
This mode was created out of the need for patient-initiation in breaths. Fundamentally, AC is controlled mechanical ventilation (CMV) with a sensitivity for patient breathing. The use of CMV in the original version required the patient be completely unconscious, either pharmacokinetically or otherwise in a coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
. With the addition of breath sensitivity, that requirement is relaxed but if the patient is actively breathing synchronization may be required in a mode such as pressure controlled intermittent mandatory ventilation or volume controlled intermittent mandatory ventilation.
The variables required in VC-CMV are: tidal volume (VT), respiratory rate (f), flow rate and trigger sensitivity (for sensing patient effort). Additional variables like peak-end expiratory pressure (PEEP) and pressure support (PS) may be added for additional support.
Expected outcomes and considerations
Assist Control is associated with profound diaphragm muscle dysfunction and atrophy. AC is no longer the preferred mode of mechanical ventilation.Trigger, limit, cycle
Trigger — Breath initiation is based on time or patient initiation. Time is set by respiratory rate (Vf or RR) and patient initiation is sensed by a flow, volume or pressure trigger and a full ventilator breath (the set tidal volume) is given.Limit — Limits in VC-CMV may be set and pressure based. The ventilator will attempt to deliver the set tidal volume utilizing whatever pressure is required to reach its setting. A pressure limit may be added to limit damage to the lungs (barotrauma
Barotrauma
Barotrauma is physical damage to body tissues caused by a difference in pressure between an air space inside or beside the body and the surrounding fluid...
).
Cycle — Expiration cycling can be set by time or the pressure limit. Once the Ti (inspiratory time) is reached, or a pressure limit is reached the ventilator will cycle into expiratory mode and allow passive exhalation until another breath is triggered.
Terms no longer accepted
Many terms have been developed to describe the same modes of mechanical ventilationModes of mechanical ventilation
Modes of mechanical ventilation are one of the most important aspects of the usage of mechanical ventilation. The mode refers to the method of inspiratory support. Mode selection is generally based on clinician familiarity and institutional preferences since there is a paucity of evidence...
. Nomenclature of mechanical ventilation
Nomenclature of mechanical ventilation
Many terms are used in mechanical ventilation, some are specific to brand, model, trademark and mode of mechanical ventilation. There is a standardized nomenclature of mechanical ventilation that is specific about nomenclature related to modes, but not settings and variables.-Volume Controlled...
has become more standardized and these terms are no longer preferred but still may be seen in older research there are many different names that historically were used to reference CMV but now reference Assist Control. Names such as: volume control ventilation, and volume cycled ventilation in modern usage refer to the Assist Control mode.
- Assist/control
- A/C
- CMV
- Volume assist/control
- Volume control
- Volume limited ventilation
- Volume controlled ventilation
- Controlled ventilation
- Volume targeted ventilation
See also
- Modes of mechanical ventilationModes of mechanical ventilationModes of mechanical ventilation are one of the most important aspects of the usage of mechanical ventilation. The mode refers to the method of inspiratory support. Mode selection is generally based on clinician familiarity and institutional preferences since there is a paucity of evidence...
- Volume controlled intermittent mandatory ventilation
- Pressure controlled continuous mandatory ventilationPressure controlled continuous mandatory ventilationPressure Controlled Continuous Mandatory Ventilation is any mode of mechanical ventilation with preset inspiratory pressure and inspiratory time. Every breath is mandatory .-Pressure control:...
- Pressure controlled intermittent mandatory ventilation
- Continuous spontaneous ventilationContinuous spontaneous ventilationContinuous spontaneous ventilation is any mode of mechanical ventilation where every breath is spontaneous .Some of these include:* Bilevel positive airway pressure* Continuous positive airway pressure...