Principles of Mechanical Ventilation

1. Principles of Mechanical Ventilation RET 2284L Module 2.0 Set Up/Check of a Volume Ventilator

2. Set Up/Check of a Volume Ventilator • Ventilator Circuit Assembly

3. Set Up/Check of a Volume Ventilator • OVP – Operational Verification Procedure • Usually an automated self-test • Usually includes a system-leak test to check the integrity of the ventilator circuit, humidifier and related equipment • Done before placing a patient on the ventilator for the first time and before reconnecting the patient to a ventilator if the circuit has been changed or disassembled for any reason • Must be documented

4. Set Up/Check of a Volume Ventilator • Circuit Compressible Volume Loss • Determination of Circuit Compressible Volume Loss • Set VT to 100-200 and PEEP to zero • Set inspiratory pause at 2 seconds • Select a minimum flow rate and maximum pressure limit • Occlude Y-connection and initiate a mechanical breath • Record the exhaled volume (ml) and peak inspiratory pressure (cm H2O) • Divide exhaled volume by PIP (V/PIP) = circuit compression factor • Multiply compression factor by the patient’s PIP (PIP minus PEEP if PEEP is used) Example Circuit compression factor = 150 ml / 50 cm H2O = 3 ml/cm H2O Circuit compression volume = 3 ml/cm H2O x (60 cm H2O PIP – 10 cm H2O PEEP) 3 ml/cm H2O x 50 cm H2O = 150 ml (circuit volume Loss)

5. Set Up/Check of a Volume Ventilator • Circuit Compressible Volume Loss • The amount of volume lost can be added to the VT setting to ensure that the patient is receiving the desired tidal volume Example: A patient’s estimated VT is 400 ml. Her peak pressure reading during inspiration is 30 cm H2O and circuit compression factor is 2.9 mL/cm H2O. What is the actual VT delivery to the patient? How should you set the desired VT? Volume lost = 2.9 mL/cm H2O x 30 cm h2O = 87 ml; actual volume received by the patient = 400 – 87 mL = 313 mL. To compensate, increase set VT to about 487 mL to deliver the 400 mL desired.