M F Krause1, T Hoehn. 1. Children's Hospital, Albert Ludwigs University, Freiburg, Germany. krause@kkl200.ukl.uni-freiburg.de
Abstract
BACKGROUND: In the past, the rabbit model of repeated airway lavage has been extensively used to induce a decrease in lung volume accompanied by impairment in lung mechanics and gas exchange. OBJECTIVES: The rationale of our study was to investigate the influence of different end-expiratory pressure (EEP) levels (0.4-4.2 cm H2O) on changes in functional residual capacity (FRC) and the efficacy of lavages administered. METHODS: Forty-five rabbits were subjected to 2-8 lavages with 20 ml/kg warm normal saline until arterial/alveolar oxygen tension (a/A ratio) had decreased to </=0. 12. RESULTS: FRC and dynamic compliance of the respiratory system (Crs) decreased significantly (both p < 0.001; from 19.1 +/- 4.2 to 10.5 +/- 5.6 ml/kg and from 1.17 +/- 0.27 to 0.47 +/- 0.10 ml/cm H2O, respectively, means +/- SD). The decrease in FRC was significantly influenced by EEP (-28.6 +/- 15.8% at EEP = 1 cm H2O vs. -58.7 +/- 12.9% at EEP = 3 cm H2O, p < 0.0001). There was a significant correlation between the number of lavages and EEP (p < 0.01), indicating that successive lavages at higher EEP became ineffective in lowering FRC compared to those at lower EEP. CONCLUSIONS: We conclude that the EEP levels used in this model are of critical importance for the prediction of a decrease in lung volume (FRC) and the efficacy of lavages.
BACKGROUND: In the past, the rabbit model of repeated airway lavage has been extensively used to induce a decrease in lung volume accompanied by impairment in lung mechanics and gas exchange. OBJECTIVES: The rationale of our study was to investigate the influence of different end-expiratory pressure (EEP) levels (0.4-4.2 cm H2O) on changes in functional residual capacity (FRC) and the efficacy of lavages administered. METHODS: Forty-five rabbits were subjected to 2-8 lavages with 20 ml/kg warm normal saline until arterial/alveolar oxygen tension (a/A ratio) had decreased to </=0. 12. RESULTS: FRC and dynamic compliance of the respiratory system (Crs) decreased significantly (both p < 0.001; from 19.1 +/- 4.2 to 10.5 +/- 5.6 ml/kg and from 1.17 +/- 0.27 to 0.47 +/- 0.10 ml/cm H2O, respectively, means +/- SD). The decrease in FRC was significantly influenced by EEP (-28.6 +/- 15.8% at EEP = 1 cm H2O vs. -58.7 +/- 12.9% at EEP = 3 cm H2O, p < 0.0001). There was a significant correlation between the number of lavages and EEP (p < 0.01), indicating that successive lavages at higher EEP became ineffective in lowering FRC compared to those at lower EEP. CONCLUSIONS: We conclude that the EEP levels used in this model are of critical importance for the prediction of a decrease in lung volume (FRC) and the efficacy of lavages.
Authors: Tobias Ankermann; Tina Wiemann; Anja Reisner; Marzenna Orlowska-Volk; Heike Köhler; Martin F Krause Journal: Intensive Care Med Date: 2004-10-20 Impact factor: 17.440