The Science Journal of the American Association for Respiratory Care

1995 OPEN FORUM Abstracts

EFFECTS OF VOLUME CONTROL (VC) VERSUS PRESSURE VENTILATION ON PATIENTS WITH HYPOXEMIC RESPIRATORY FAILURE.

Jamie Vaccaro, RRT, John Steinbach, BS, Mark Lund, BS, Amy Orons BA, Dori Miller, the Respiratory Care Staff, Herbert Patrick, MD; Department of Respiratory Care, Thomas Jefferson University Hospital, Philadelphia, PA.

Introduction: At our institution, patients meeting criteria for hypoxemic respiratory failure, a FIO2 > 60% or a PaO2/FIO2, were eligible for a study examining the effects of VC vs. pressure ventilation on pulmonary mechanics, oxygenation, ventilation, and cardiac parameters using the Bear 1000 ventilator (Allied Healthcare, Inc., Riverside, CA). The modes of pressure ventilation were Pressure Augment (PA) Maximum (PAM) without and with inspiratory pause (IP). PA provides pressure support breaths with a breath-by-breath minimum Vt guarantee; PAM is the PA sufficient to insure the Vt without evoking the guarantee. We hypothesized that PAM ± IP would mimic pressure control ventilation without being labor intensive.

Methods: Each patient was initially ventilated in VC using decelerating flow for 4-6 hours and then was switched to PAM with identical RR, Vt, FIO2, and PEEP settings. If the FIO2 remained > 60%, IP was added until either auto-PEEP was detected or the I:E ratio = 1:1; the RR, Vt, FIO2, and PEEP settings were again retained for another 4-6 hour interval. Data were analyzed in pairs corrected for the duration of VC vs. PAM and Pre- (PAM + IP) vs, PAM + IP,

Results: We prospectively studied 21 patients from November 1994 to April 1995. Data shown are mean ± SEM with pɘ.05 ANOVA, *VC vs, PAM and [filled diamond]Pre (PAM + IP) vs, PAM + IP:

Mode x 6 hoursVC PAM

n21 21

PaO2/FIO2 85.0 ± 5.097.9 ± 6.4

PIP 47.1 ± 1.643.4 ± 2.4

MAP 18.0 ± 1.416.7 ± .98

PIFR actual 95.1 ± 2.597.3 ± 4.7

Vt actual 755 ± 23 863 ± 25*

Ve actual15.3 ± .8216.1 ± .86

I:E 1:3.6 ± .25 1:3.5 ± .21

Qs/Qt 0.39 ± .030.39 ± .03

Vd/Vt 0.65 ± .200.66 ± .02

CO 7.6 ± .58 7.4 ± .48

Pre (PAM+IP) PAM + IP

16 16

81.0 ± 5.2 94.8 ± 9.1

46.5 ± 2.3 45.7 ± 2.1

16.8 ± .83 20.8 ± 1.1[filled diamond]

106.0 ± 5.0103.8 ± 4.0

826 ± 24869 ± 32

13.9 ± .70 15.3 ± .69

1:3.5 ± .221:2.6 ± .20[filled diamond]

0.36 ± .04 0.35 ± .04

0.64 ± .03 0.60 ± .05

8.2 ± .78 7.9 ± .62

Sixteen patients (76%) required PAM + IP as the FIO2 remained > 60%; there were clinical delays from the end of PAM to the initiation of PAM + IP ranging from 0.5 to 216 hours (average 27 hours); auto-PEEP was not detected in any mode. Conclusion: Both PAM vs. VC and PAM + IP vs. pre (PAM + IP) appear to improve oxygenation without compromising cardiac parameters. PAM ± IP are alternatives to VC in patients with hypoxemic respiratory failure; the presence of a breath-by-breath Vt guarantee should encourage PAM usage.

OF-95-122

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