In a volume-controlled mode of ventilation, the inspiratory flow waveform is rectangular (as the machine delivers a steady flow of gas, waiting for the target volume to be achieved).

What is volume control mode in ventilation?

The SIMV mode is used for volume control ventilation with a fixed mandatory minute volume. The patient can breathe spontaneously between the mandatory mechanical breaths and thereby increase the minute volume. During spontaneous respiration, the mandatory mechanical breath is synchronized with the patient's breathing.

How does the pressure waveform differ between volume and pressure control ventilation?

Because pressure is not controlled or regulated in any way, the pressure waveform takes a parabolic sloping shape as the lungs distend during a breath. The pressure waveform is highly variable during volume control ventilation, changing shape depending on lung compliance and airway resistance.