Ventilator modes

What are the 3 breath types in ventilation?

Mandatory, Assisted, Spontaneous

What are the control variables in mechanical ventilation?

Volume, Pressure, Time

What are the main breath sequences in mode classification?

CMV (Controlled), IMV/SIMV (Intermittent), CSV (Spontaneous)

What is the control variable in Volume Control Ventilation (VCV)?

Volume (flow and volume are fixed)

How does pressure behave in VCV?

Varies depending on compliance and resistance

What is an advantage of Volume Control Ventilation (VCV)?

Guaranteed VT, good ABG control, synchronizes with patient if sensitivity is set

What is a disadvantage of Volume Control Ventilation (VCV)?

Risk of high pressures → barotrauma, fixed flow may not meet patient demand, risk of respiratory alkalosis or auto-PEEP

What settings are entered in Volume Control (VC)?

Rate, VT, Flow, PEEP, FiO2, Sensitivity, Optional: Inspiratory pause

How is TI calculated in VCV?

TI = VT / Flow

What is the control variable in Pressure Control Ventilation (PCV)?

Pressure

How does VT behave in PCV?

VT varies depending on compliance (C) and resistance (R)

What waveform is seen with Pressure Control Ventilation (PCV)?

Square pressure waveform

What is an advantage of PCV?

Lower risk of barotrauma, better distribution of ventilation, can improve oxygenation, precise control of Pplat and MAP

What is a disadvantage of Pressure Control Ventilation (PCV)?

VT is not guaranteed, ABG may vary

What settings are entered in Pressure Control (PC)?

PC level (ΔP or PIP), Rate, TI, PEEP, FiO2, Sensitivity

How do you calculate ΔP and PIP in PCV?

ΔP = PIP – PEEP, PIP = ΔP + PEEP

What factors affect VT in PC?

Lung compliance, Airway resistance, Inspiratory time, Patient effort

What kind of breaths are delivered in Pressure Support Ventilation (PSV)?

Patient-triggered, pressure-limited, flow-cycled breaths

What is PSV typically used for?

Weaning, reducing WOB, patients with spontaneous drive

What are the key settings in PSV?

PS level, PEEP, FiO2, Sensitivity, Rise Time

What is the cycle variable in PSV?

Flow (typically ends when flow drops to 25% of peak)

What is a disadvantage of Pressure Support Ventilation (PSV)?

No backup rate, not ideal for patients without reliable drive

What is Volume Support (VS)?

A spontaneous mode that auto-adjusts PS level to reach a target VT

What are the advantages of Volume Support (VS)?

VT guaranteed over several breaths, self-weaning mode, adjusts support based on patient effort

What is a disadvantage of Volume Support (VS)?

No backup rate, only available in CSV mode, apnea alarms are critical

What are the trigger, limit, and cycle for Volume Support (VS)?

Trigger: Patient, Limit: Pressure-limited, volume-targeted, Cycle: Flow

What is SIMV?

Synchronized Intermittent Mandatory Ventilation — allows for mandatory, assisted, and spontaneous breaths

What is IMV?

Intermittent Mandatory Ventilation — mandatory breaths occur at intervals, not synchronized

What is A/C (CMV)?

Assist-Control (CMV): every breath is mandatory or assisted; all breaths receive full support

What is CPAP?

Continuous Positive Airway Pressure — baseline pressure only, no added support

What is PSV in Continuous Spontaneous Ventilation (CSV)?

Pressure Support Ventilation — adds PS to spontaneous breaths