Kendra M. Smith

Prolonged partial liquid ventilation using conventional and high-frequency ventilatory techniques: gas exchange and lung pathology in an animal model of respiratory distress syndrome.

OBJECTIVE To evaluate the effect of prolonged partial liquid ventilation with perflubron (partial liquid ventilation), using conventional and high-frequency ventilatory techniques, on gas exchange, hemodynamics, and lung pathology in an animal model of lung injury. DESIGN Prospective, randomized, controlled study. SETTING Animal laboratory of the Infant Pulmonary Research Center, Childrens Health Care-St. Paul. SUBJECTS Thirty-six newborn piglets. INTERVENTIONS We studied newborn piglets with lung injury induced by saline lavage. Animals were randomized into one of five treatment groups: a) conventional gas ventilation (n = 8); b) partial liquid ventilation with conventional ventilation (n = 7); c) partial liquid ventilation with high-frequency jet ventilation (n = 7); d) partial liquid ventilation with high-frequency oscillation (n = 7); and e) partial liquid ventilation with high-frequency flow interruption (n = 7). After induction of lung injury, all partial liquid ventilation animals received intratracheal perflubron to approximate functional residual capacity. After 30 mins of stabilization, animals randomized to high-frequency ventilation were changed to their respective high-frequency modes. Hemodynamics and blood gases were measured before and after lung injury, after perflubron administration, and then every 4 hrs for 20 hrs. Histopathologic evaluation was carried out using semiquantitative scoring and computer-assisted morphometric analysis on pulmonary tissue from animals surviving at least 16 hrs. MEASUREMENTS AND MAIN RESULTS All animals developed acidosis and hypoxemia after lung injury. Oxygenation significantly (p < .001) improved after perflubron administration in all partial liquid ventilation groups. After 4 hrs, oxygenation was similar in all ventilator groups. The partial liquid ventilation-jet ventilation group had the highest pH; intergroup differences were seen at 16 and 20 hrs (p < .05). The partial liquid ventilation-oscillation group required higher mean airway pressure; intergroup differences were significant at 4 and 8 hrs (p < .05). Aortic pressures, central venous pressures, and heart rates were not different at any time point. Survival rate was significantly lower in the partial liquid ventilation-flow interruption group (p < .05). All partial liquid ventilation-treated animals had less lung injury compared with gas-ventilated animals by both histologic and morphometric analysis (p < .05). The lower lobes of all partial liquid ventilation-treated animals demonstrated less damage than the upper lobes, although scores reached significance (p < .05) only in the partial liquid ventilation-conventional ventilation animals. CONCLUSIONS In this animal model, partial liquid ventilation using conventional or high-frequency ventilation provided rapid and sustained improvements in oxygenation without adverse hemodynamic consequences. Animals treated with partial liquid ventilation-flow interruption had a significantly decreased survival rate vs. animals treated with the other studied techniques. Histopathologic and morphometric analysis showed significantly less injury in the lower lobes of lungs from animals treated with partial liquid ventilation. High-frequency ventilation techniques did not further improve pathologic outcome.

Partial liquid ventilation : A comparison using conventional and high-frequency techniques in an animal model of acute respiratory failure

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 Childrens 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.

Perfluorocarbon priming and surfactant: physiologic and pathologic effects.

OBJECTIVE To test the hypothesis that perfluorocarbon (PFC) priming before surfactant administration improves gas exchange and lung compliance, and also decreases lung injury, more than surfactant alone. DESIGN Prospective, randomized animal study. SETTING Animal research laboratory of Childrens Hospital of St. Paul. SUBJECTS Thirty-two newborn piglets, weighing 1.55 +/- 0.18 kg. INTERVENTIONS We studied four groups of eight animals randomized after anesthesia, paralysis, tracheostomy, and establishment of lung injury using saline washout to receive one of the following treatments: a) surfactant alone (n = 8); b) priming with the PFC perflubron alone (n = 8); c) priming with perflubron followed by surfactant (n = 8); and d) no treatment (control; n = 8). Perflubron priming was achieved by instilling perflubron via the endotracheal tube in an amount estimated to represent the functional residual capacity, ventilating the animal for 30 mins, and then removing perflubron by suctioning. After all treatments were given, animals were mechanically ventilated for 4 hrs. MEASUREMENTS AND MAIN RESULTS We evaluated oxygenation, airway pressures, respiratory system compliance, and hemodynamics at baseline, after induction of lung injury, and at 30-min intervals for 4 hrs. Histopathologic evaluation was carried out using a semiquantitative scoring system and by computer-assisted morphometric analysis. After all treatments, animals had decreased oxygenation indices (p < .001) and increased respiratory system compliance (p < .05). Animals in PFC groups had similar physiologic responses to treatments as animals treated with surfactant only; both the PFC-treated groups and the surfactant-treated animals required lower mean airway pressures throughout the experiment (p < .001) and had higher pH levels at 90 and 120 mins (p < .05) compared with the control group. Pathologic analysis demonstrated decreased lung injury in surfactant-treated animals compared with animals treated with PFC or the controls (p < .02). CONCLUSIONS Priming the lung with PFC neither improved the physiologic effects of exogenous surfactant nor improved lung pathology in this animal model.

Lower respiratory rates without decreases in oxygen consumption during neonatal synchronized intermittent mandatory ventilation

Objective: We tested the hypothesis that synchronization to patient effort during intermittent mandatory ventilation (SIMV), when compared to conventional unsynchronized intermittent mandatory ventilation (IMV), will decrease energy

PARTIAL LIQUID VENTILATION VS GAS VENTILATION: HISTOLOGIC DIFFERENCES USING HIGH FREQUENCY AND CONVENTIONAL TECHNIQUES. † 2083

PARTIAL LIQUID VENTILATION VS GAS VENTILATION: HISTOLOGIC DIFFERENCES USING HIGH FREQUENCY AND CONVENTIONAL TECHNIQUES. † 2083

High Frequency Oscillatory and Conventional Ventilation, Exogenous Surfactant, and Partial Liquid Ventilation: Physiologic Effects of Prolonged Treatment in an Animal Lung Injury Model

High Frequency Oscillatory and Conventional Ventilation, Exogenous Surfactant, and Partial Liquid Ventilation: Physiologic Effects of Prolonged Treatment in an Animal Lung Injury Model

High Frequency Oscillatory and Conventional Ventilation, Exogenous Surfactant, and Partial Liquid Ventilation: Effect of Prolonged Treatment on Lung Pathology in an Animal Lung Injury Model

High Frequency Oscillatory and Conventional Ventilation, Exogenous Surfactant, and Partial Liquid Ventilation: Effect of Prolonged Treatment on Lung Pathology in an Animal Lung Injury Model

Exogenous Surfactant during Partial Liquid Ventilation: Lung Pathology.† 1550

Surfactant (surf, Survanta®) followed by partial liquid ventilation(PLV) with perflubron (LiquiVent®) improves lung mechanics and oxygenation more than S only, PLV only, or PLV followed by S (Peds Res 1996:39;343A). Histologic and morphometric analysis was performed on slides from the upper anterior and lower posterior lobes of 32 newborn piglets (1.7±0.8 kg) with saline lavage-induced lung injury (PaO2<60 torr, FiO2 1.0) after randomization into 4 groups and treatment for 2 hours with: 1) surf only (S; n=8); 2) PLV only (PLV; n=8); 3) PLV followed by surf (PLV-S; n=8 and 4) surf followed by PLV (S-PLV; n=8). Ventilators were adjusted to maintain tidal volume of 15 cc/kg; FiO2 was 1.0. Histologic variables (alveolar, interstitial inflammation; alveolar, interstitial hemorrhage; edema; atelectasis; necrosis) were scored on a 0-4 point scale (no injury = 0, injury in 25% of field = 1, injury in 50% of field = 2, injury in 75% of field = 3, and injury throughout field = 4). Morphometric analysis on trichrome-stained slides analyzed total cellular to air space, expressed as percent tissue area (% tissue area =[cellular area/total area] × 100). Kruskal-Wallis, Wilcoxin, and paired t-tests with Bonferroni correction (p<0.05) were used to assess differences. Table

Partial Liquid Ventilation Using High Frequency Oscillation: Effects of Changes in Frequency on Gas Exchange. † 1593

Partial Liquid Ventilation Using High Frequency Oscillation: Effects of Changes in Frequency on Gas Exchange. † 1593

PARTIAL LIQUID VENTILATION AND SURFACTANT: INTERACTION AND ADMINISTRATION ORDER EFFECTS. † 2040

PARTIAL LIQUID VENTILATION AND SURFACTANT: INTERACTION AND ADMINISTRATION ORDER EFFECTS. † 2040