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 VentilationCMV 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) Time Cycling Set PC Level 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 Not able to assist the ventilator • Decreases the work of breathing (WOB) • Helps maintain a normal PaCO2
Hybrid Modes of VentilationA/C 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) Time Cycling Set PC Level 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
Thank You
