CMV Mode Workshop

Objectives: Know the difference between controlled ventilation and assist/control Controlled variables: PC-CMV vs VC-CMV Phase variables: trigger/limit/cycle Know the breath types Know the breath sequence Settings and adjustment Indications, advantages and disadvantages

Continuous Mandatory Ventilation All breaths are mandatory and can be volume or pressure targeted Controlled Ventilation – when mandatory breaths are time triggered Assist/Control Ventilation – when mandatory breaths are either time triggered or patient triggered

Mandatory Modes of Ventilation CMV Control Trigger Limit Target Cycle Pressure Or Volume Time Pressure or Volume Time or Volume Time Triggered Time Cycled Ventilation

Controlled Ventilation: Breath Types All breaths are mandatory breaths Ventilator determines the start time (time triggered) Ventilator delivers the set control (volume or pressure target) Te ventilator ends the breath (time- or volume-cycled)

Controlled Ventilation: Breath Sequence All breaths are mandatory breaths

Controlled Ventilation: Indications Appropriate when a patient can make no effort to breathe or when ventilation must be completely controlled Drugs Cerebral malfunctions Spinal cord injury Phrenic nerve injury Motor nerve paralysis

Controlled Ventilation: Indications In other types of patients, controlled ventilation is difficult to use unless the patient is sedated or paralyzed with medications Seizure activity Tetanic contractions Inverses I:E ratio ventilation Patient is fighting (bucking) the ventilator Crushed chest injury – stabilizes the chest Complete rest for the patient

Controlled Ventilation: Settings Adequate alarms must be set to safeguard the patient E.g., disconnection Sensitivity should be set so that when the patient begins to respond, they can receive gas flow from the patient Do not lock the patient out of the ventilator!

Control Mode (Pressure-Targeted Ventilation) Set PC Level Time Cycling Pressure (cm H2O) Flow (L/m) Volume (mL) Time (sec) Time Triggered, Pressure Limited, Time Cycled Ventilation

Control Mode (Volume-Targeted Ventilation) Time Cycling Pressure (cm H2O) Dependent on CL & Raw Flow (L/m) Preset VT Volume Cycling Volume (mL) Time (sec) Time Triggered, Flow Limited, Volume Cycled Ventilation

Pressure Or Volume-Targeted Ventilation Advantages Disadvantages Decreases the work of breathing (WOB) Helps maintain a normal PaCO2 Not able to assist the ventilator

Hybrid Modes of Ventilation A/C Control Trigger Limit Target Cycle Pressure Or Volume Time Patient Pressure or Volume Time or Volume Time or PatientTriggered Time Cycled Ventilation

Assist/Control Ventilation A time or patient triggered CMV mode in which the operator sets a minimum rate, sensitivity level, type of breath (volume or pressure) The patient can trigger breaths at a faster rate than the set minimum, but only the set volume or pressure is delivered with each breath

Volume Controlled-CMV Time or patient triggered, volume targeted, volume cycled ventilation Graphic (VC-CMV) Time-triggered, constant flow, volume-targeted ventilation

Volume Controlled-CMV Time or patient triggered, volume targeted, volume cycled ventilation Graphic (VC-CMV) Time-triggered, descending-flow, volume-targeted ventilation

Pressure Controlled-CMV PC – CMV (AKA – Pressure control ventilation - PCV) Time or patient triggered, pressure targeted (limited), time cycled ventilation The operator set the length of inspiration (Ti), the pressure level, and the backup rate of ventilation VT is based on the compliance and resistance of the patient’s lungs, patient effort, and the set pressure

Pressure Controlled-CMV Airway pressure is limited, which may help guard against barotrauma or volume-associated lung injury Maximum inspiratory pressure set at 30 – 35 cm H2O Especially helpful in patients with ALI and ARDS Allows application of extended inspiratory time, which may benefit patients with severe oxygenation problems Usually reserved for patient who have poor results with a conventional ventilation strategy of volume ventilation

Assisted Mode (Volume-Targeted Ventilation) Time Cycling Pressure (cm H2O) Preset peak Flow Flow (L/m) Volume (mL) Time (sec) Patient Triggered, Flow limited, Volume Cycled Ventilation

Assisted Mode (Pressure-Targeted Ventilation) Set PC Level Time Cycling Pressure (cm H2O) Flow (L/m) Volume (mL) Time (sec) Patient Triggered, Pressure Limited, Time Cycled Ventilation

Assist/Control Ventilation Indications Patients requiring full ventilatory support Patients with stable respiratory drive Advantages Decreases the work of breathing (WOB) Allows patients to regulate respiratory rate Helps maintain a normal PaCO2 Complications Alveolar hyperventilation

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