The Science Journal of the American Association for Respiratory Care

1998 OPEN FORUM Abstracts

SYNCHRONIZED PARTIAL LIQUID VENTILATION IMPROVES GAS EXCHANGE AND DECREASES BREATHING EFFORT.

Patricia A. Meyers RRT, EM Bendel-Stenzel MD, DR Bing RRT, JE Connett PhD, MC Mammel MD. Infant Pulmonary Research Center, Children's Hospital-St. Paul, Minnesota and Depts. Of Pediatrics and Biostatistics. University of Minnesota, Minneapolis, MN.

Introduction: Does mode of assisted ventilation affect breathing effort and gas exchange during partial liquid ventilation (PLV) in an animal model of neonatal RDS? We compared IMV, SIMV, and A/C modes during PLV with perflubron (Liquivent(r), Alliance Pharmaceuticals) in surfactant depleted, spontaneously breathing newborn piglets.

Method: Ten piglets (1.19±0.04 kg) were sedated, but not paralyzed, and ventilated using a volume target of 15cc/kg (Drager Babylog(r)). We induced lung injury, defined as PaO2 < 100 torr at FiO2 1.0 and lung compliance reduction by > 30%, with repeated saline lavage. We randomized the piglets to sequential 30 minute periods of either IMV>SIMV>A/C, or A/C>SIMV>IMV, during PLV. Respiratory rate (RR) and minute ventilation (Ve) were determined as 1 minute moving averages. For each breath, we measured tidal volume (Vt), mean airway pressure (MAP), and esophageal pressure-time- rate index (PE[cdot]RR). PE*RR, an estimate of nonventilator breathing effort, is defined as the area below baseline of the esophageal pressure time curve x RR (Novametrix VenTrak(r)). A continuous intra-arterial monitor (Diametrics Paratrend7(r)) recorded blood gases every 30 seconds; we calculated a/A with period means. We assessed Vt variability using the coefficient of variation (V of Vt, SD/ mean x 100). Data were analyzed using paired t-tests with Bonferroni correction; Wilcoxon rank-sum test for nonparametric data.

Results: Breathing effort, estimated by PE[cdot]RR, was significantly lower with A/C than SIMV during PLV (A/C vs IMV, p=0.06). a/A was significantly better with A/C than either IMV or SIMV. Ve and MAP increased during A/C. RR was significantly less in AC vs SIMV, and trended lower in A/C vs IMV (p=0.07). Vt was always more consistent during A/C.

Mode a/A Ve MAP RR

IMV 0.27±0.11 0.78±0.11 6.8±0.3 112±16

SIMV 0.26±0.02 0.75±0.13 6.7±0.3 114±16

A/C 0.35±0.03* 0.98±0.13* 10.7±0.7* 77±10**

Mode PE[cdot]RR V of Vt

IMV 49.7±13 54±10%

SIMV 46.8±10.9 72±12%

A/C 13.7±5.1** 11±2%*

*p < 0.05 A/C vs IMV, SIMV; **p < 0.05 A/C vs SIMV.

Conclusion: In spontaneously breathing animals, fully-synchronized PLV using A/C mode required the least breathing effort, increased Ve and a/A at the lowest RR and least variable Vt. These data suggest physiologic benefit from A/C during PLV in nonparalyzed subject.

The 44th International Respiratory Congress Abstracts-On-Disk®, November 7 - 10, 1998, Atlanta, Georgia.

You are here: RCJournal.com » Past OPEN FORUM Abstracts » 1998 Abstracts » SYNCHRONIZED PARTIAL LIQUID VENTILATION IMPROVES GAS EXCHANGE AND DECREASES BREATHING EFFORT.