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Tidewater Community College
Virginia Beach Campus
Respiratory Care Program

Inspiratory flow wave form choices

The modern ventilator has selectable waveforms, usually rectangular often referred to as square, sine wave, ascending ramp, and descending ramp. On the Galileo ventilator the descending ramp wave form is further broken down into complete or total descending and 50 percent descending. The practitioner can change waveforms simply pressing a button. Which wave form to choose is a clinical decision.

Each wave form has basic things in common, a beginning point (where inspiratory flow is just starting) a high point or peak (where inspiratory flow has its highest velocity) and end point (where inspiratory flow ceases).

The inspiratory flow waveform is always viewed as a scalar quantity with inspiratory flow in liters/minute represented on the Y axis and inspiratory time in seconds represented on the X axis.

When viewing the total descending ramp, take note of the fact that the beginning point where inspiratory flow is just starting and peak inspiratory flow occur almost simultaneously. Then the flow slopes downward in a linear fashion. The linear degrading slope angle is maintained from peak inspiration, until end point is reached when inspiratory flow rate reaches zero.