The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

AN INCREASE IN END EXPIRATORY LUNG VOLUME DUE TO TIDAL RECRUITMENT CAN BE SIGNIFICANT IN INJURED LUNGS

Chris Carter M.D., Alexander Adams RRT, John Hotchkiss M.D., Mary Stone RRT, John Marini M.D., Regions Hospital, St. Paul, MN

Background: End expiratory lung volume (EELV) status during mechanical ventilation is dependent on the underlying FRC (at ZEEP), applied PEEP, autoPEEP if present and tidal recruitment. Tidal recruitment (TR) is defined as an increase in EELV - above the EELV predicted by PEEP alone - resulting from the current ventilatory strategy. TR may be dependent on the status of the lungs, PEEP, I:E, frequency, and/or tidal volume. Our goal was to detect and measure an effect of lung injury, tidal excursion and the PEEP setting on TR in a model of lung injury.

Methods: In an oleic acid lung injury model, pressure-volume (P-V) curves and TR determinations were made before and after injury in 5 pigs (wt.ยป 22 kg.). P-V curves were generated by the super syringe method. TR was measured by disconnecting the ventilator and tracking the drop in lung volume by inductance plethysmography for 30 seconds after disconnection. TR was measured under 8 conditions in each animal at PEEP = 0, 5, 10, 15 cmH2O, PCV excursions of 10 cmH2O (low excursion) and 30 cmH2O (high excursion), f = 10/min and I:E=1:2. AutoPEEP was not detected.

Results: TR was present preinjury but was significantly greater post injury (p<.01). A PCV of 30 cmH2O resulted in greater TR than PCV of 10 cmH2O (p=.0005, see figure). There was also an association between PEEP and TR, pre and post injury, as tested by ANOVA (p<.01).

Conclusions: TR was significant in this model of lung injury and may be of importance during ventilation of injured lungs in ALI/ARDS. Injury presence, tidal excursion and PEEP were important in generating TR but related factors not evaluated in this study such as frequency, I:E, or inspiratory flow profile may be of equal or greater importance. (See Original for Figure)

You are here: RCJournal.com » Past OPEN FORUM Abstracts » 2000 Abstracts » AN INCREASE IN END EXPIRATORY LUNG VOLUME DUE TO TIDAL RECRUITMENT CAN BE SIGNIFICANT IN INJURED LUNGS