Monday, June 29, 2009

Waveform of the week: Inspiratory time too short

Inappropriate termination during breath delivery may be the result of an inspiratory time which is too short for the patients inspiratory time constant, when utilizing PC-CMV or PC-IMV.

The above image demonstrates a I-time set too short as evidence of the inspiratory flow waveform not fully decelerating to baseline (shown by red the arrow).

Ideally the operator should titrate I-time to allow for full deceleration of the inspiratory flow waveform. When flow is allowed to fully decelerated, alveolar recruitment, alveolar ventilation, & mean airway pressure is maximized.

The below video clip shows the titration of I-time to allow for a fully decelerating flow waveform, observe the increase in Vt even when the pressure, compliance, & resistance remains constant.