Ellen M. Bendel-Stenzel

Surfactant and partial liquid ventilation via conventional and high-frequency techniques in an animal model of respiratory distress syndrome.

Objective To compare the physiologic and pathologic effects of conventional ventilation (CV) and high-frequency ventilation (HFV) during partial liquid ventilation (PLV) with perflubron after surfactant treatment with the results of HFV plus surfactant in an animal lung-injury model created by saline lavage. We also studied the dose effects of perflubron during HFV. Design Randomized experimental study. Setting Research animal laboratory. Subjects A total of 32 newborn piglets. Interventions After lung injury was induced, the animals were randomized to one of four groups: a) CV + surfactant + perflubron to functional residual capacity (FRC); b) HFV + surfactant + perflubron to FRC; c) HFV + surfactant + 10 mL/kg perflubron; and d) HFV + surfactant. All then received intratracheal surfactant. After 30 mins, perflubron was administered to the PLV groups. The animals underwent ventilation for 20 hrs. Measurements and Main Results Arterial blood gases and hemodynamic variables were continuously monitored. Pulmonary histologic and morphometric analyses were performed after death or euthanasia at 20 hrs. All animals had sustained improvements in arterial/alveolar oxygen ratios, and no differences were observed among groups. All HFV groups required higher mean airway pressures to maintain oxygenation (p < .05). Hemodynamics did not differ among groups. Pathologic analysis demonstrated decreased lung injury in both cranial-dorsal (nondependent) and caudal-ventral (dependent) lobes of all animals treated with PLV when compared with those treated with HFV + surfactant (p < .05). Conclusions After surfactant treatment, physiologic support over 20 hrs was similar during HFV with or without perflubron and CV with perflubron. All PLV modalities improved lung pathologic factors uniformly to a greater degree than did HFV + surfactant. A lower treatment volume of perflubron during HFV produced physiologic and pathologic results similar to those produced by perflubron with respect to FRC during either CV or HFV.

Volume Targeted Patient Triggered Ventilation: Decreased Subject Effort and Improved Efficiency in an Animal Model of Respiratory Distress Syndrome|[dagger]| 1611

We hypothesized that a fully-synchronized patient triggered mode of ventilation, assist-control (A/C), would reduce subject effort when compared to IMV and SIMV. Ten newborn piglets (1.9±0.40 kg) with saline lavage-induced lung injury (PaO2<100 torr at FiO2 1.0) were randomized to sequential 30 minute periods of IMVSIMVAC (n=5), or ACSIMVIMV (n=5) using time-cycled, pressure limited, volume targeted (15 mL/kg) ventilation (Drager Babylog®). Respiratory rate(RR) and minute ventilation (Ve) were determined as 1 minute moving averages every 15 seconds; tidal volume (Vt), mean airway pressure (MAP), and an esophageal pressure-time index (PE·RR) to estimate subject, not mechanical, work of breathing were determined for all breaths. PE·RR was defined as the area below baseline of the esophageal pressure-time curve× RR, and was recorded using a computer-assisted lung mechanics analyzer(VenTrak®). Blood gases were recorded every 30 seconds using an in-line continuous blood gas analyzer (Paratrend 7®); a/A was calculated. Vt variation was assessed using the coefficient of variation (V; SD/mean × 100). Data analysis used paired t-tests with Bonferroni correction. Wilcoxon rank-sum test was used for nonparametric data.Results: Subject work, estimated by PE·RR, was significantly lower with A/C. Statistically significant differences in A/C vs IMV and SIMV included higher pH, lower RR, and increased Ve and MAP. No differences in a/A were seen. Vt was always less variable during A/C. Conclusion: Fully-synchronized A/C ventilation produced the highest Ve and pH, and the most consistent Vt, with the lowest subject effort as estimated by PE·RR. This data suggests A/C is more efficient during spontaneous respiration than either IMV or SIMV, as it provides improved gas exchange with less inspiratory effort, Table

Positive End-Expiratory Pressure during Partial Liquid Ventilation: Impact on Lung Volume Recruitment and Gas Exchange

Positive End-Expiratory Pressure during Partial Liquid Ventilation: Impact on Lung Volume Recruitment and Gas Exchange

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

Synchronized Partial Liquid Ventilation: Improved Gas Exchange and Decreased Subject Effort in an Animal Model of Respiratory Distress Syndrome|[dagger]| 1610

We hypothesized that during partial liquid ventilation (PLV) with perflubron in spontaneously breathing lung injured animals, a fully-synchronized mode of ventilation, assist-control (A/C), would reduce subject effort when compared to IMV and SIMV. Ten newborn piglets(1.19±0.40 kg) with saline lavage-induced lung injury (PaO2<100 torr at FiO2 1.0) were randomized to sequential 30 minute periods of PLV during IMVSIMVA/C, or A/CSIMVIMV. Piglets were ventilated using time-cycled, pressure limited, volume targeted (15 cc/kg) ventilation(Drager Babylog®). Respiratory rate (RR) and minute ventilation (Ve) were determined as 1 minute moving averages every 15 seconds; tidal volume(Vt), mean airway presure (MAP), and an esophageal pressure-time index(PE·RR) to estimate subject, not mechanical, work of breathing were determined for all breaths. PE·RR was defined as the area below baseline of the esophageal pressure-time curve × RR, and was recorded using a computer-assisted lung mechanics analyzer (VenTrak®). Blood gases were recorded every 30 seconds using an in-line continuous blood gas analyzer(Paratrend 7®); a/A was calculated. Vt variation was assessed using the coefficient of variation (V; SD/mean × 100). Data analysis used paired t-tests with Bonferroni correction. Wilcoxon rank-sum test was used for nonparametric data. Results: Subject work, estimated by PE·RR, was significantly lower with A/C vs SIMV during PLV (A/C vs IMV, p=0.06). pH was higher and a/A was significantly improved using A/C. 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.Conclusion: In spontaneously breathing animals, fully-synchronized PLV using A/C, which required the least patient effort, increased pH, Ve, and a/A at the lowest RR and least variable Vt. These data suggest substantial physiologic benefit from A/C during PLV in nonparalyzed subjects. Perflubron provided by Alliance Pharmaceutical Corp./Hoechst Marion Roussel. VenTrak provided by Novametrix Medical Systems. Babylog provided by Drager Inc. Table

Dynamics of Spontaneous Breathing during Partial Liquid Ventilation. |[dagger]| 1466

We tested the hypothesis that partial liquid ventilation (PLV) with perflubron (LiquiVent®) in spontaneously breathing (SB) animals would increase respiratory rate (RR), minute ventilation (Ve), and work of breathing when compared to animals treated with gas ventilation (GV). We studied 8 newborn piglets after sedation with ketamine, intubation, and placement of catheters and an esophageal balloon. CPAP was initially used, then animals were randomized to sequentially receive different modes of ventilation during GV (Drager Babylog): IMV-SIMV-AC, or AC-SIMV-IMV. We then instilled perflubron to FRC and repeated the sequence during PLV. Animals returned to CPAP during PLV at the end of the experiment. Each treatment lasted 30 minutes. Ventilator rate during IMV and SIMV, and backup rate during AC, was 10/minute. RR, Ve, and pressure- time product (PTP=ΔPes·Ti, by flow) were measured for all spontaneous and triggered breaths. Standardized PTP•RR is an index of work of breathing. Blood gases were measured and OI calculated every 15 minutes. Reported values are means for the treatment periods. Data analysis used paired t-tests (p<0.05).Table