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Partial liquid ventilation: a comparison using conventional and high-frequency techniques in an animal model of acute
K M Smith1, D R Bing, P A Meyers
1Infant Pulmonary Research Center, Children's Health Care-St. Paul, School of Public Health, University of Minnesota, Minneapolis, USA.
Objective:
To test the hypothesis that high-frequency ventilation (HFV), when compared with conventional techniques, enhances respiratory gas exchange during partial liquid ventilation (PLV).
Design:
A four-period crossover design.
Setting:
Animal research laboratory of Children's Health Care-St. Paul.
Subjects:
Thirty-two newborn piglets, weighing 1.40 +/- 0.39 kg.
Interventions:
Animals were divided into four groups of eight animals: a) PLV with high-frequency jet ventilation; b) PLV with jet ventilation using a background intermittent mandatory ventilation (IMV) rate; c) PLV with high-frequency oscillation; or d) PLV with high-frequency flow interruption using a background IMV rate. After anesthesia, paralysis, and tracheotomy, a normal saline wash procedure produced lung injury. Perfluorocarbon was then instilled via the endotracheal tube in an amount estimated to represent functional residual capacity. Animals received randomly either PLV using conventional techniques or PLV using the selected HFV technique as initial treatment. Then, animals were crossed over to the alternative treatment at equal mean airway pressure, as measured at the endotracheal tube tip. This sequence was repeated for a total of four crossover periods, such that all animals were treated twice with PLV using conventional techniques and twice with PLV using HFV.
Measurements And Main Results:
We measured airway pressures at the endotracheal tube tip, aortic and central venous blood pressures, arterial blood gases, and respiratory system mechanics at baseline, after induction of lung injury, and at specified intervals throughout the experiment. Measurements were made before and 15 mins after crossovers, then ventilators were adjusted to normalize gas exchange. Measurements were again made 30 mins later, at the end of the treatment period. All types of PLV provided adequate gas exchange. Only PLV using jet ventilation with IMV produced gas exchange equal to that seen during PLV using conventional techniques at equivalent mean airway pressure. By the end of the treatment periods, only PLV using high-frequency oscillation continued to require higher airway pressure than PLV using conventional techniques for equivalent gas exchange.
Conclusions:
Gas exchange was not enhanced during PLV-HFV. Application of HFV with PLV provides no clear acute physiologic advantages to PLV using more conventional techniques.