The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

SURFACTANT ADMINISTRATION IN PIGLETS TREATED WITH BUBBLE NASAL CONTINUOUS POSITIVE AIRWAY PRESSURE OR SYNCHRONIZED INTERMITTENT MECHANICAL VENTILATION: PHYSIOLOGY AND INJURY

Patricia A. Meyers, RRT, JL Nold, MD, CT Worwa, RRT, RH Goertz, BS, G Schauer, MD & MC Mammel, MD.Children's Hospitals & Clinics of MN Minnesota, St. Paul, MN.

Background: Nasal continuous positive airway pressure (NCPAP) is often used instead of intubation and mechanical ventilation for respiratory distress syndrome. No studies have evaluated effects of surfactant on inflammatory markers in spontaneously breathing NCPAP-treated animals.

Objective: We hypothesized animals treated with bubble (B)NCPAP following surfactant (+S) would have decreased inflammatory markers and lung injury compared to those treated with synchronized intermittent mechanical ventilation following S (SIMV+S) or BNCPAP without S (-S).

Design/Methods: We compared BNCPAP+S, SIMV+S, and BNCPAP-S in spontaneously breathing piglets with lavage-induced lung injury (PaO2 of 80-100 mmHg in FIO2 1.0). Animals were randomized to BNCPAP 5cmH2O, or to surfactant treatment followed by SIMV or BNCPAP. SIMV settings: PEEP 5, rate 20, VT 8ml/kg. O2 was adjusted for PaO2 of 80-100mmHg. Physiologic parameters were continuously monitored. After 4 hours, bronchoalveolar lavage (BAL) samples were collected for neutrophil count and H2O2, and lungs were fixed for histopathologic scoring and morphometric analysis. Data were analyzed using repeated measures ANOVA or ANOVA.

Results: No physiologic differences were noted. BAL fluid from BNCPAP-S piglets contained more neutrophils with more H2O2 than that from the SIMV+S group (p≤ 0.05; 0.01) or the CPAP+S group (p≤ 0.17; 0.03). Morphometric analysis showed more total open alveolar airspace in non-dependent regions in the BNCPAP+S vs BNCPAP-S group (p≤ 0.01) and the SIMV+S vs BNCPAP-S groups (p≤ 0.09). Conversely, dependent regions showed more total open alveolar airspace in the BNCPAP-S group compared to BNCPAP+S or SIMV+S (p≤ 0.05 and 0.01). Histopathologic scores revealed less microscopic inflammation in BNCPAP-S pigs (p≤ .002).

Conclusions: In this model, piglets treated with S prior to initiation of either BNCPAP or SIMV had lower biochemical indicators of acute lung injury 4 hours post lung injury. However, S treated pigs exhibited more microscopic lung injury. Open airspaces in non-dependent regions of the lung were greater in S treated pigs, with the converse being true in the dependent areas of the lung. Surfactant, not ventilation style, appears most important.

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